Power Amp Repair
 

I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Power Amp Repair
 

Haaky wrote:
I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.



You could check for cracked solder joints. Audio amps though,
particularly the higher power variety, can become real money pits for
the inexperienced to work on. Output transistors are often expensive,
and they'll pop in the blink of an eye as you've found, if any fault
remains when you switch it on.

Power Amp Repair
 

"Haaky" wrote in message
oups.com...

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Post the schematic on abse.

Power Amp Repair
 

You could check for cracked solder joints. Audio amps though,
particularly the higher power variety, can become real money pits for
the inexperienced to work on. Output transistors are often expensive,
and they'll pop in the blink of an eye as you've found, if any fault
remains when you switch it on.

I'll definitely check for any cracked soldier joints. I figure i paid
175 for the amp. I just put another 140 into fixing it
that's probably all i'm gonna put into it.

I'll probably end up buying a new Power Amp, Keep this one and use it
as a backup or use it to experiment with.

I'm wondering if it's something in the power supply?. It's seems like
it's getting a surge of power when i turn it on. Not all the time just
on occasion.
I changed speaker wires and changed out the cables going from the
mixer into the amp. Just incase there was a short somewhere.

All i get from the repair shop is "maybe you have a short in the
speaker wire" or "try plugging it into another outlet"

I'm not impressed with the service of the repair shop. I mean if the
guy new what he was doing. I would think he would have tried to find
what caused the output to blow. And not just replace the output. There
has to be something else wrong somewhere in there.

And it's not like i was in a hurry to get the amp back. I was willing
to let them keep it for as long as they needed. I guess there to busy
to do a good job:)

Power Amp Repair
 

On Feb 3, 11:47 pm, "Homer J Simpson" wrote:
"Haaky" wrote in message

oups.com...

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Post the schematic on abse.

What's abse??

Power Amp Repair
 

On 3 Feb 2007 21:02:03 -0800, "Haaky" wrote:

On Feb 3, 11:47 pm, "Homer J Simpson" wrote:
"Haaky" wrote in message

oups.com...

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Post the schematic on abse.

What's abse??

alt.binaries.schematic.electronics

Power Amp Repair
 

On Feb 3, 9:59 pm, "Haaky" wrote:
I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.


I would probably start by troubleshooting the things external to the
amp given the description you gave.
Things like frayed speaker wires, damaged speaker coils, overdriven
inputs, etc all could be causing the repeat failures of the amp.

Power Amp Repair
 

What's abse??

alt.binaries.schematic.electronics

Correction : electronic

Power Amp Repair
 

I would probably start by troubleshooting the things external to the
amp given the description you gave.
Things like frayed speaker wires, damaged speaker coils, overdriven
inputs, etc all could be causing the repeat failures of the amp.

Checked and replace the speaker wires. Had the wedge monitors and
speaker wires hooked up to another amp with no problems.

Damaged speaker coils? Didn't check them. How would i check them?

Overdriven inputs?. Was thinking about that. The only inputs going to
the amp are from the mixing board.

Power Amp Repair
 

Haaky wrote:

I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Did the repair shop fit the correct replacement part ? Did they re-adjust the
bias current ? There are simply so many possibilities.

The fact that it's 'gone' several times suggests some other underlying problem
though as others have mentioned.

Does it run hot when idling for example ? When it originally popped was it
running hot ? Excessive heat is death for output devices.


Graham

Power Amp Repair
 

Haaky wrote:

I'm wondering if it's something in the power supply?

Pretty unlikely.

It's seems like it's getting a surge of power when i turn it on. Not all the
time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

Graham

Power Amp Repair
 

Haaky wrote:

"Homer J Simpson" wrote:
"Haaky" wrote in message

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Post the schematic on abse.

What's abse??

alt.binaries.schematics.electronics where you can post 'binary files' -
attachments in other words.

Google groups don't have binary groups though.

Cogeco appears to have news.cogeco.ca though - that's a 'proper' news server.

Graham

Power Amp Repair
 

Haaky wrote:


I would probably start by troubleshooting the things external to the
amp given the description you gave.
Things like frayed speaker wires, damaged speaker coils, overdriven
inputs, etc all could be causing the repeat failures of the amp.

Checked and replace the speaker wires. Had the wedge monitors and
speaker wires hooked up to another amp with no problems.

Damaged speaker coils? Didn't check them. How would i check them?

You'll tend to know if they're damaged !


Overdriven inputs?. Was thinking about that. The only inputs going to
the amp are from the mixing board.

Was it running loud ? Decent pro gear is protected against overheating etc but
consumer ( and 'prosumer' ) products usually aren't.

From the appearance of it and the price I'd guess it's an 'also-ran' Chinese amp
and I wouldn't expect it to be that durable.

OK, American Audio is a DJ brand. DJ brands are normally total crap.

A Behringer EP1500 would be a far better choice btw.

Graham

Power Amp Repair
 

Did the repair shop fit the correct replacement part ? Did they re-adjust the
bias current ? There are simply so many possibilities.

The fact that it's 'gone' several times suggests some other underlying problem
though as others have mentioned.

Does it run hot when idling for example ? When it originally popped was it
running hot ? Excessive heat is death for output devices.

Graham

The first time they fixed it, apperently they didn't use the correct
part cause it did the same thing as soon as i got it home.
The second time they fixed it, it appears to be the proper part,
number match etc.
Have no idea if they re-adjusted the bias current or not. I would
think they should. But i would bet they didn't

It doesn't run hot now. But when it blew the first time. It seemed to
be to hot, actually very hot

Maybe it's my imagination but it doesn't seem to be as loud as it was
before. Maybe i'm just used to the other amps now.
I was using my Marshal and Fender amps while the power am was in the
shop.

Power Amp Repair
 

On Feb 4, 1:06 am, Eeyore
wrote:
Haaky wrote:
I'm wondering if it's something in the power supply?

Pretty unlikely.

It's seems like it's getting a surge of power when i turn it on. Not all the
time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

Graham

So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.

Power Amp Repair
 

Haaky wrote:
On Feb 4, 1:06 am, Eeyore
wrote:

Haaky wrote:

I'm wondering if it's something in the power supply?

Pretty unlikely.


It's seems like it's getting a surge of power when i turn it on. Not all the
time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

Graham


So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.


Cut your losses, buy a real amp.

If its a POS before it was fixed, its still a POS amp.
The only way i fix a fry out is to replace ALL the output devices.
Not just the shorted ones. Yes, it cost more. But there is no way to
guarantee the other devices where not damaged and will soon fail.

Bob

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----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Power Amp Repair
 

On Feb 4, 1:21 am, Eeyore
wrote:
Haaky wrote:

I would probably start by troubleshooting the things external to the
amp given the description you gave.
Things like frayed speaker wires, damaged speaker coils, overdriven
inputs, etc all could be causing the repeat failures of the amp.

Checked and replace the speaker wires. Had the wedge monitors and
speaker wires hooked up to another amp with no problems.

Damaged speaker coils? Didn't check them. How would i check them?

You'll tend to know if they're damaged !

Overdriven inputs?. Was thinking about that. The only inputs going to
the amp are from the mixing board.

Was it running loud ? Decent pro gear is protected against overheating etc but
consumer ( and 'prosumer' ) products usually aren't.

From the appearance of it and the price I'd guess it's an 'also-ran' Chinese amp
and I wouldn't expect it to be that durable.

OK, American Audio is a DJ brand. DJ brands are normally total crap.

A Behringer EP1500 would be a far better choice btw.

Graham

That's the funny part. It wasn't running loud at all when it went. Had
it turned almost off while one of the guitar players was tuning up.
This amp is suppose to have overheating and surge protection circuits
build into it. I'm just wondering if it could be that.
Behringer EP1500 is pretty good eh?. I'll have to look into it. I was
looking at the Crown brands i think the 402 or the 602

It's definitely gonna be replaced with a new unit hopefully very soon.
This little amp has given it's all for me. I'm not about to chuck it:)
It's actually a pretty good sounding amp. Problem is once something
goes on it, you can be that that's just the start. It's usually
followed by other thing going too.

Power Amp Repair
 

"Eeyore" wrote in message
...


Haaky wrote:

I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Did the repair shop fit the correct replacement part ? Did they re-adjust
the
bias current ? There are simply so many possibilities.

The fact that it's 'gone' several times suggests some other underlying
problem
though as others have mentioned.

Does it run hot when idling for example ? When it originally popped was it
running hot ? Excessive heat is death for output devices.


Graham


Just a couple of 'simples'. Are you fitting a fuse that is the correct
*type* as well as rating ? Most gear of this kind will require " T " rated
types, otherwise unexplained intermittent failure at switch on is the
symptom you will get. Also, how is the fuse blowing ? Vapourised and
blackened, blob in the middle of melted wire ends, or wire just broken ?
This will give you a big clue as to what is causing the failure. What is the
purpose of the fuse. Is it the line power fuse ? Are there other fuses
either on the secondary windings of the tranny, or downstream of the bridge
? Also, Have you considered calling the manufacturers ? Often, they can be a
lot more helpful than you might imagine. If you are not an electronics
repair shop, just wing it, and tell them that you are. Sound confident and
just say " This is Bloggs Disco and HiFi Repairs in Vancouver. I'm looking
for some technical assistance with an XYZ 400. Can I speak with someone in
your service department please ? " Worth a try, and at least you will get a
proper opinion. It might be something as simple as the bias needing setting,
as someone else in the thread suggested.

Arfa

Power Amp Repair
 

On Feb 4, 10:37 am, Bob Urz wrote:
Haaky wrote:
On Feb 4, 1:06 am, Eeyore
wrote:

Haaky wrote:

I'm wondering if it's something in the power supply?

Pretty unlikely.

It's seems like it's getting a surge of power when i turn it on. Not all the
time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

Graham

So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.

Cut your losses, buy a real amp.

If its a POS before it was fixed, its still a POS amp.
The only way i fix a fry out is to replace ALL the output devices.
Not just the shorted ones. Yes, it cost more. But there is no way to
guarantee the other devices where not damaged and will soon fail.

Bob


That's exactly what i would have done if i would have fixed it myself.
Everything that i read said that your better off replacing all the
outputs
Cause whos to say one of the other outputs might not be a little
flaky. And if it goes, they charge me to replace it because it wasn't
work done already by the repair shop.
That's a scam. I would have rather paid a extra and had them replace
them all. But when it went the second time it was the same output that
they had replaced.

The amp is gonna be replaced with a new unit as soon as i can decide
on what to buy. Maybe i'll just use this one for the vocals

Power Amp Repair
 

On Feb 4, 10:40 am, "Arfa Daily" wrote:
"Eeyore" wrote in message

...



Haaky wrote:

I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Did the repair shop fit the correct replacement part ? Did they re-adjust
the
bias current ? There are simply so many possibilities.

The fact that it's 'gone' several times suggests some other underlying
problem
though as others have mentioned.

Does it run hot when idling for example ? When it originally popped was it
running hot ? Excessive heat is death for output devices.

Graham

Just a couple of 'simples'. Are you fitting a fuse that is the correct
*type* as well as rating ? Most gear of this kind will require " T " rated
types, otherwise unexplained intermittent failure at switch on is the
symptom you will get. Also, how is the fuse blowing ? Vapourised and
blackened, blob in the middle of melted wire ends, or wire just broken ?
This will give you a big clue as to what is causing the failure. What is the
purpose of the fuse. Is it the line power fuse ? Are there other fuses
either on the secondary windings of the tranny, or downstream of the bridge
? Also, Have you considered calling the manufacturers ? Often, they can be a
lot more helpful than you might imagine. If you are not an electronics
repair shop, just wing it, and tell them that you are. Sound confident and
just say " This is Bloggs Disco and HiFi Repairs in Vancouver. I'm looking
for some technical assistance with an XYZ 400. Can I speak with someone in
your service department please ? " Worth a try, and at least you will get a
proper opinion. It might be something as simple as the bias needing setting,
as someone else in the thread suggested.

Arfa

When it went the first time. The fuses where black, really black.
I replaced the fuse with the exact same fuse that came out of it. But
i have no idea if that first fuse was even the proper one.
The guy i bought it from might not have replaced it with the proper
type of fuse.
On the back of the unit it says the fuse type is 250v T 7A
The fuse that was in it was a 250v don't know if it was a "T" or not
6.3A

When the fuse blows now. It's not blackened it just looks like the
metal thread is snapped.

I'm guessing it's the line fuse. There's only 1 there and it's
connected to the power switch and AC cord. In series i guess.

I emailed American Audio, explained what was going on. They just send
me the schematics of the unit. I think that all i asked for.

I figured posting here is a good idea. Get some fresh perspective and
some things i would never have thought of.
I noticed when i got the amp back from the repair shop. He marked on
the heat sink the letters C A A C over top of each pair of i'm
guessing that these are the outputs?

When i got the amp back after the first repair. The first set of "A"
where different color than the rest and different than what was in
there before it went in.
When i got it back the second time those different color ones were
gone and the ones that are in there look like the rest.

I see there are markings on them 2 are C2837 then there are 2 A1186
then 2 more A1186 and then 2 more C2837 screwed onto the heat sink.

It's actually very educational researching and trying to diagnose the
problem. And i'm not affraid to get in there and get my hands dirty
and doing the repairs myself.

Power Amp Repair
 

Haaky wrote:

On Feb 4, 1:06 am, Eeyore
wrote:

Haaky wrote:

I'm wondering if it's something in the power supply?

Pretty unlikely.


It's seems like it's getting a surge of power when i turn it on. Not all the
time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

Graham


So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.

sounds like a bad bridge or caps.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Power Amp Repair
 

Haaky wrote:

On Feb 4, 1:21 am, Eeyore
wrote:

Haaky wrote:


I would probably start by troubleshooting the things external to the
amp given the description you gave.
Things like frayed speaker wires, damaged speaker coils, overdriven
inputs, etc all could be causing the repeat failures of the amp.

Checked and replace the speaker wires. Had the wedge monitors and
speaker wires hooked up to another amp with no problems.

Damaged speaker coils? Didn't check them. How would i check them?

You'll tend to know if they're damaged !


Overdriven inputs?. Was thinking about that. The only inputs going to
the amp are from the mixing board.

Was it running loud ? Decent pro gear is protected against overheating etc but
consumer ( and 'prosumer' ) products usually aren't.

From the appearance of it and the price I'd guess it's an 'also-ran' Chinese amp
and I wouldn't expect it to be that durable.

OK, American Audio is a DJ brand. DJ brands are normally total crap.

A Behringer EP1500 would be a far better choice btw.

Graham


That's the funny part. It wasn't running loud at all when it went. Had
it turned almost off while one of the guitar players was tuning up.
This amp is suppose to have overheating and surge protection circuits
build into it. I'm just wondering if it could be that.
Behringer EP1500 is pretty good eh?. I'll have to look into it. I was
looking at the Crown brands i think the 402 or the 602

It's definitely gonna be replaced with a new unit hopefully very soon.
This little amp has given it's all for me. I'm not about to chuck it:)
It's actually a pretty good sounding amp. Problem is once something
goes on it, you can be that that's just the start. It's usually
followed by other thing going too.


are you using a Slow blow fuse?


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Power Amp Repair
 

Haaky wrote:

On Feb 4, 10:40 am, "Arfa Daily" wrote:

"Eeyore" wrote in message

...




Haaky wrote:

I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Did the repair shop fit the correct replacement part ? Did they re-adjust
the
bias current ? There are simply so many possibilities.

The fact that it's 'gone' several times suggests some other underlying
problem
though as others have mentioned.

Does it run hot when idling for example ? When it originally popped was it
running hot ? Excessive heat is death for output devices.

Graham

Just a couple of 'simples'. Are you fitting a fuse that is the correct
*type* as well as rating ? Most gear of this kind will require " T " rated
types, otherwise unexplained intermittent failure at switch on is the
symptom you will get. Also, how is the fuse blowing ? Vapourised and
blackened, blob in the middle of melted wire ends, or wire just broken ?
This will give you a big clue as to what is causing the failure. What is the
purpose of the fuse. Is it the line power fuse ? Are there other fuses
either on the secondary windings of the tranny, or downstream of the bridge
? Also, Have you considered calling the manufacturers ? Often, they can be a
lot more helpful than you might imagine. If you are not an electronics
repair shop, just wing it, and tell them that you are. Sound confident and
just say " This is Bloggs Disco and HiFi Repairs in Vancouver. I'm looking
for some technical assistance with an XYZ 400. Can I speak with someone in
your service department please ? " Worth a try, and at least you will get a
proper opinion. It might be something as simple as the bias needing setting,
as someone else in the thread suggested.

Arfa


When it went the first time. The fuses where black, really black.
I replaced the fuse with the exact same fuse that came out of it. But
i have no idea if that first fuse was even the proper one.
The guy i bought it from might not have replaced it with the proper
type of fuse.
On the back of the unit it says the fuse type is 250v T 7A
The fuse that was in it was a 250v don't know if it was a "T" or not
6.3A

When the fuse blows now. It's not blackened it just looks like the
metal thread is snapped.

I'm guessing it's the line fuse. There's only 1 there and it's
connected to the power switch and AC cord. In series i guess.

I emailed American Audio, explained what was going on. They just send
me the schematics of the unit. I think that all i asked for.

I figured posting here is a good idea. Get some fresh perspective and
some things i would never have thought of.
I noticed when i got the amp back from the repair shop. He marked on
the heat sink the letters C A A C over top of each pair of i'm
guessing that these are the outputs?

When i got the amp back after the first repair. The first set of "A"
where different color than the rest and different than what was in
there before it went in.
When i got it back the second time those different color ones were
gone and the ones that are in there look like the rest.

I see there are markings on them 2 are C2837 then there are 2 A1186
then 2 more A1186 and then 2 more C2837 screwed onto the heat sink.

It's actually very educational researching and trying to diagnose the
problem. And i'm not affraid to get in there and get my hands dirty
and doing the repairs myself.

T = Time Delayed.
you need a slow blow.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

Power Amp Repair
 

Haaky wrote:

Eeyore wrote:
Haaky wrote:

I would probably start by troubleshooting the things external to the
amp given the description you gave.
Things like frayed speaker wires, damaged speaker coils, overdriven
inputs, etc all could be causing the repeat failures of the amp.

Checked and replace the speaker wires. Had the wedge monitors and
speaker wires hooked up to another amp with no problems.

Damaged speaker coils? Didn't check them. How would i check them?

You'll tend to know if they're damaged !

Overdriven inputs?. Was thinking about that. The only inputs going to
the amp are from the mixing board.

Was it running loud ? Decent pro gear is protected against overheating etc but
consumer ( and 'prosumer' ) products usually aren't.

From the appearance of it and the price I'd guess it's an 'also-ran' Chinese amp
and I wouldn't expect it to be that durable.

OK, American Audio is a DJ brand. DJ brands are normally total crap.

A Behringer EP1500 would be a far better choice btw.

Graham

That's the funny part. It wasn't running loud at all when it went.

That points more to a possible design fault like ultrasonic oscillation.


Had
it turned almost off while one of the guitar players was tuning up.
This amp is suppose to have overheating and surge protection circuits
build into it. I'm just wondering if it could be that.
Behringer EP1500 is pretty good eh?. I'll have to look into it. I was
looking at the Crown brands i think the 402 or the 602

It's definitely gonna be replaced with a new unit hopefully very soon.
This little amp has given it's all for me. I'm not about to chuck it:)
It's actually a pretty good sounding amp. Problem is once something
goes on it, you can be that that's just the start. It's usually
followed by other thing going too.

The Behringers are reliable and pretty much unbeatable value. They are based on the
QSC RMX models btw and are very similar.

Graham

Power Amp Repair
 

Haaky wrote:

Eeyore wrote:
Haaky wrote:
I'm wondering if it's something in the power supply?

Pretty unlikely.

It's seems like it's getting a surge of power when i turn it on. Not all the
time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.


So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.

I suspect I know what the problem is. I'll bet it does use a toroidal transformer
and the cheapskates haven't bothered fitting a surge-guard device.

This all points to poor/skimpy design I'm afraid.

Graham

Power Amp Repair
 

Haaky wrote:
I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Let me suggest that perhaps the idling current is set too high. Then
the output transistors start to warm up and after a while there is
thermal runaway and the fuse pops.

Check the idling current and adjust it if needed. Another possibility
is that the temperature sensor, usually a transistor or diode or
thermistor, is not properly attached to the heat sink and thus doesn't
react to warming output transistors.

Bob

Power Amp Repair
 

On Feb 4, 2:06 pm, Bob wrote:
Haaky wrote:
I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Let me suggest that perhaps the idling current is set too high. Then
the output transistors start to warm up and after a while there is
thermal runaway and the fuse pops.

Check the idling current and adjust it if needed. Another possibility
is that the temperature sensor, usually a transistor or diode or
thermistor, is not properly attached to the heat sink and thus doesn't
react to warming output transistors.

Bob

Would that be the cause of the fuse blowing at Power On though? That
seems to be the problem as of now. As soon as the unit recievies that
first initial
surge of power the fuse pops.
I'm keeping track of all the suggestions if i would have had this info
at the start i would have by-passed the repair shop and did this on my
own.
I'm a newbie at this but i want to learn as much as i can. I find it
really facinating. And if i can learn to fix stuff like this on my own
even better

Power Amp Repair
 

Did you say if you were using a slo-blo fuse or not?

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794

No i believe it a "T" timed fused i think that's what there called?

Power Amp Repair
 

"Haaky" wrote in message
ups.com...
On Feb 4, 2:06 pm, Bob wrote:
Haaky wrote:
I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Let me suggest that perhaps the idling current is set too high. Then
the output transistors start to warm up and after a while there is
thermal runaway and the fuse pops.

Check the idling current and adjust it if needed. Another possibility
is that the temperature sensor, usually a transistor or diode or
thermistor, is not properly attached to the heat sink and thus doesn't
react to warming output transistors.

Bob

Would that be the cause of the fuse blowing at Power On though? That
seems to be the problem as of now. As soon as the unit recievies that
first initial
surge of power the fuse pops.
I'm keeping track of all the suggestions if i would have had this info
at the start i would have by-passed the repair shop and did this on my
own.
I'm a newbie at this but i want to learn as much as i can. I find it
really facinating. And if i can learn to fix stuff like this on my own
even better



In one of the earlier posts, you stated "On the back of the unit it says the
fuse type is 250v T 7A. The fuse that was in it was a 250v don't know if it was
a "T" or not 6.3A."

If the original fuse was rated for 7A, and it's being replaced by a 6.3A fuse,
that could be your problem. I suggest that you try the correct fuse before
replacing any more components. If no more fuse blowing, then you might be good
to go. If the correct fuse blows, I would suggest that you replace all of the
output transistors at the same time. They are all available from MCM
Electronics.

http://www.mcminone.com/product.asp?...5Fi d=2SA1186
and
http://www.mcminone.com/product.asp?...5Fi d=2SC2837

If you can scan the schematic and post it on abse, we can probably come up with
some pretty good suggestions for you to go with. Does the schematic that you
have give the instructions for setting bias for the output stages?

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some days you're the dog, some days the hydrant.

Power Amp Repair
 

"Haaky" wrote in message
oups.com...
On Feb 4, 10:40 am, "Arfa Daily" wrote:
"Eeyore" wrote in message

...



Haaky wrote:

I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Did the repair shop fit the correct replacement part ? Did they
re-adjust
the
bias current ? There are simply so many possibilities.

The fact that it's 'gone' several times suggests some other underlying
problem
though as others have mentioned.

Does it run hot when idling for example ? When it originally popped was
it
running hot ? Excessive heat is death for output devices.

Graham

Just a couple of 'simples'. Are you fitting a fuse that is the correct
*type* as well as rating ? Most gear of this kind will require " T "
rated
types, otherwise unexplained intermittent failure at switch on is the
symptom you will get. Also, how is the fuse blowing ? Vapourised and
blackened, blob in the middle of melted wire ends, or wire just broken ?
This will give you a big clue as to what is causing the failure. What is
the
purpose of the fuse. Is it the line power fuse ? Are there other fuses
either on the secondary windings of the tranny, or downstream of the
bridge
? Also, Have you considered calling the manufacturers ? Often, they can
be a
lot more helpful than you might imagine. If you are not an electronics
repair shop, just wing it, and tell them that you are. Sound confident
and
just say " This is Bloggs Disco and HiFi Repairs in Vancouver. I'm
looking
for some technical assistance with an XYZ 400. Can I speak with someone
in
your service department please ? " Worth a try, and at least you will get
a
proper opinion. It might be something as simple as the bias needing
setting,
as someone else in the thread suggested.

Arfa

When it went the first time. The fuses where black, really black.
I replaced the fuse with the exact same fuse that came out of it. But
i have no idea if that first fuse was even the proper one.
The guy i bought it from might not have replaced it with the proper
type of fuse.
On the back of the unit it says the fuse type is 250v T 7A
The fuse that was in it was a 250v don't know if it was a "T" or not
6.3A

When the fuse blows now. It's not blackened it just looks like the
metal thread is snapped.

I'm guessing it's the line fuse. There's only 1 there and it's
connected to the power switch and AC cord. In series i guess.

I emailed American Audio, explained what was going on. They just send
me the schematics of the unit. I think that all i asked for.

I figured posting here is a good idea. Get some fresh perspective and
some things i would never have thought of.
I noticed when i got the amp back from the repair shop. He marked on
the heat sink the letters C A A C over top of each pair of i'm
guessing that these are the outputs?

When i got the amp back after the first repair. The first set of "A"
where different color than the rest and different than what was in
there before it went in.
When i got it back the second time those different color ones were
gone and the ones that are in there look like the rest.

I see there are markings on them 2 are C2837 then there are 2 A1186
then 2 more A1186 and then 2 more C2837 screwed onto the heat sink.

It's actually very educational researching and trying to diagnose the
problem. And i'm not affraid to get in there and get my hands dirty
and doing the repairs myself.


OK. That's definitely a slow blo fuse that it needs, and if it is on the
back, then it is almost certainly the line power fuse. If there are no signs
of distress inside the fuse, just a broken wire with no signs of melting,
then this would normally indicate that it is breaking just because of metal
fatigue, which is exactly the symptom you get when a fast blo is wrongly
fitted in this position. A big tranny is almost a short at power up for a
few cycles, until the core gets magnetically 'charged'. If you have a
straight fuse in there, you can watch the wire sag until it almost touches
the glass at power up. A " T " rated fuse is designed either not to do that
( spring-loaded types ) or to withstand the effect ( spiral types ). So for
a start, I would make sure that the next fuse you fit, is definitely a " T
".

It is common practice in a repair shop to scribble " C " and " A " on the
heatsink over the transistors, just to make sure that when you have them all
out, the new ones go back in in the correct places. The transistors are
standard Japanese types and are actually 2SCxxx and 2SAxxx. They always
leave the " 2 " off the on-device print. The " A " is a PNP type, and the
" C " is NPN, so it's very important that they go back in right.

If the company were happy to send you service info just as a result of an
e-mail enquiry, then in my experience, they would probably talk to you on
the phone.

Arfa

Power Amp Repair
 

On Feb 4, 7:36 pm, "DaveM" wrote:
"Haaky" wrote in message

ups.com...



On Feb 4, 2:06 pm, Bob wrote:
Haaky wrote:
I need some advice guys.

I have an American Audio GX-300 Power Amp i use in my studio. Bought
it used off of EBay. Been working like a charm for almost a year. One
day while tunning up a guitar the amp shut off. Found it blew a fuse.
I replaced the fuse switched it back on and it blew again.

Finially had to take it in . I was told that an Output had gone. Cost
me 140 bucks Canadian to replare it.

I get it back a week later. Take it home, plug it in. And bang the
fuse blows again right away. I return the amp to the repair shop. 2
weeks later i get it back. They told me the Output the guy replaced
was fautly and get this he wanted more money to fix what was suppose
to be fixed properly in the first place.

Any i get the amp back, worked fine for a week. Then 1 day i turn it
on and it pops the fuse again. I replaced the fuse and it worked fine.
A week later turn it on again and it popped the fuse again.

I'm not taking it back the the these guys again. I'de rather try and
diagnose the problem myself and fix it.

Any ideas to where and what i should be looking for and were to start
looking for the problem?

I've been doing alot of research and am comfortable with electronics
to try and narrow down the fault and fix it.

Any help would be greatly appreciated. If you need any more ifo i can
provide it. I also have the schematics for the amp aswell. That was a
bonus courtasy of American Audio Inc.

Let me suggest that perhaps the idling current is set too high. Then
the output transistors start to warm up and after a while there is
thermal runaway and the fuse pops.

Check the idling current and adjust it if needed. Another possibility
is that the temperature sensor, usually a transistor or diode or
thermistor, is not properly attached to the heat sink and thus doesn't
react to warming output transistors.

Bob

Would that be the cause of the fuse blowing at Power On though? That
seems to be the problem as of now. As soon as the unit recievies that
first initial
surge of power the fuse pops.
I'm keeping track of all the suggestions if i would have had this info
at the start i would have by-passed the repair shop and did this on my
own.
I'm a newbie at this but i want to learn as much as i can. I find it
really facinating. And if i can learn to fix stuff like this on my own
even better

In one of the earlier posts, you stated "On the back of the unit it says the
fuse type is 250v T 7A. The fuse that was in it was a 250v don't know if it was
a "T" or not 6.3A."

If the original fuse was rated for 7A, and it's being replaced by a 6.3A fuse,
that could be your problem. I suggest that you try the correct fuse before
replacing any more components. If no more fuse blowing, then you might be good
to go. If the correct fuse blows, I would suggest that you replace all of the
output transistors at the same time. They are all available from MCM
Electronics.

http://www.mcminone.com/product.asp?...roducts&produc...
andhttp://www.mcminone.com/product.asp?catalog%5Fname=MCMProducts&produc...

If you can scan the schematic and post it on abse, we can probably come up with
some pretty good suggestions for you to go with. Does the schematic that you
have give the instructions for setting bias for the output stages?

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some days you're the dog, some days the hydrant.

I was affraid to put in a 7A fuse even though that what is on the back
of the unit. Ever since i've owned the amp it has had a 6.3 fuse it.
I might try a 7 if it keeps popping. Thanks for the link to the
websites. I might order me some just to have as spares

I'll post the schematics of the amp

Power Amp Repair
 

Jamie wrote:

Haaky wrote:
Eeyore wrote:
Haaky wrote:

I'm wondering if it's something in the power supply?

Pretty unlikely.


It's seems like it's getting a surge of power when i turn it on. Not all the
time just on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.

sounds like a bad bridge or caps.

No it sounds like magnetising current actually. Toroids are notorious for it
because of the low reluctance of the magnetic circuit.

Graham

Power Amp Repair
 

Jamie wrote:

T = Time Delayed.
you need a slow blow.

Actually he needs a T type to IEC specs.

Slow-Blow is unique to the USA and has different characteristics. In fact all US
fuses are different to IEC ones.

Graham

Power Amp Repair
 

Haaky wrote:


Did you say if you were using a slo-blo fuse or not?

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794

No i believe it a "T" timed fused i think that's what there called?

That is the correct type to use.

Graham

Power Amp Repair
 

DaveM wrote:

If the original fuse was rated for 7A, and it's being replaced by a 6.3A fuse,
that could be your problem

Pretty unlikely actually. 7A is not a preferred value so it'll be hard to come by. You
could always try 8A though to see if it makes a difference.

Graham

Power Amp Repair
 

Haaky wrote:
On Feb 4, 1:06 am, Eeyore
wrote:
Haaky wrote:
I'm wondering if it's something in the power supply?

Pretty unlikely.

It's seems like it's getting a surge of power when i turn it on.
Not all the time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

Graham

So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.

They may have missed a failing bias diode or another bias related part may
be failing. Doesn't sound like they have much experience with these types of
intermittent recurring failures.

Mark Z.

Power Amp Repair
 

On Feb 5, 7:54 am, "Mark D. Zacharias" wrote:
Haaky wrote:
On Feb 4, 1:06 am, Eeyore
wrote:
Haaky wrote:
I'm wondering if it's something in the power supply?

Pretty unlikely.

It's seems like it's getting a surge of power when i turn it on.
Not all the time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

Graham

So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.

They may have missed a failing bias diode or another bias related part may
be failing. Doesn't sound like they have much experience with these types of
intermittent recurring failures.

Mark Z.

My confidence in this repair shop went down the tubes. I thought they
would be good. They have a good rep, are always busy, very helpfull
Supposedly the repair guy has 30 years experience. But i wonder if
it's in electronic repair?:):):)

Power Amp Repair
 

Pretty unlikely actually. 7A is not a preferred value so it'll be hard to come by. You
could always try 8A though to see if it makes a difference.

Graham


Wouldn't i be running a bigger risk putting in an 8A fuse instead of a
7 or a 6.3?

I'de rather the fuse blow instead of a more expensive part.

Power Amp Repair
 

In article . com, "Haaky" wrote:
On Feb 5, 7:54 am, "Mark D. Zacharias" wrote:
Haaky wrote:
On Feb 4, 1:06 am, Eeyore
wrote:
Haaky wrote:
I'm wondering if it's something in the power supply?

Pretty unlikely.

It's seems like it's getting a surge of power when i turn it on.
Not all the time just
on occasion.

You mean it sometimes goes HUMMmmmmm...... at switch one ?

That's quite normal especially with toroidal transformers.

Graham

So far it's done it twice since i got it back. As soon as i hit the
power switch the fuse in the back popped. When i replaced the fuse and
switched it back on
it worked fine. Seems to be an intermitten thing, i hope. I don't mind
that so much if it only happens on occassion, i'm just affraid that
eventually something else will go wrong with it. And i know it will
happen when the warrenty they gave runs out.

They may have missed a failing bias diode or another bias related part may
be failing. Doesn't sound like they have much experience with these types of
intermittent recurring failures.

Mark Z.

My confidence in this repair shop went down the tubes. I thought they
would be good. They have a good rep, are always busy, very helpfull
Supposedly the repair guy has 30 years experience. But i wonder if
it's in electronic repair?:):):)

I have built things that have had seemingly intermitant problems. A
transformer will pull different currents depending on time
of the AC waveform. You can probably figure what percentage the waveform
will be max, and most of the time it will not blow. Then you hit it and it
blows. Also tends to give off loud noises. This might be part of the problem.
For the price of that unit, a good shop could not afford to play with throw
away equipment, or, your not going to like the bill a good shop will charge.

greg

Power Amp Repair
 

"Haaky" wrote in message
ps.com...


Pretty unlikely actually. 7A is not a preferred value so it'll be hard to
come by. You
could always try 8A though to see if it makes a difference.

Graham


Wouldn't i be running a bigger risk putting in an 8A fuse instead of a
7 or a 6.3?

I'de rather the fuse blow instead of a more expensive part.


If it's knocking out a 6.3 amp fuse, and the correct rating that it's
expecting to have in there is a 7 anyway, then trust me, it will have no
problem taking out an 8. I wouldn't necessarily say the same about a 10A,
but the extra couple of microseconds to blow an 8 is not going to damage
anything else. Have we actually established if you have the proper " T "
rated type in there yet, anyway ? If you haven't, then all of this
conjecture about what *might* be wrong is a useless waste of time, as there
may be nothing at all wrong other than an invalid fuse type for that
application ...

Arfa