I can understand lager chillers or lighting triacs causing clicks and bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same time
and no other pub mains problem showing itself.

The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the
initial failure. Not doing so now its in front of me, not fully checked out
yet. Mains fuse always ok , just the HT one repeatedly failing after 4
seconds or so. At the same time as this HT one failed the mains fuse failed
on another Marshall connected to the same supply - that one just required a
change of mains fuse and is still ok.

Could a fault causing failure of HT fuse on one amp cause the failure of
mains fuse on another amp , with no pub wiring problem at all, even problem
local to the power ring/spur to the stage.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N Cook" wrote in message
...
I can understand lager chillers or lighting triacs causing clicks and bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same time
and no other pub mains problem showing itself.

The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the
initial failure. Not doing so now its in front of me, not fully checked
out
yet. Mains fuse always ok , just the HT one repeatedly failing after 4
seconds or so. At the same time as this HT one failed the mains fuse
failed
on another Marshall connected to the same supply - that one just required
a
change of mains fuse and is still ok.

Could a fault causing failure of HT fuse on one amp cause the failure of
mains fuse on another amp , with no pub wiring problem at all, even
problem
local to the power ring/spur to the stage.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




Absolutely certain that the supply is not losing the neutral outside
anywhere - particularly if an overhead supply to a country pub ? A friend of
mine had a similar problem at a remote monitoring station for water
treatment that he had to look after, and the mains kept randomly shooting up
to 440v. That would certainly cause the secondary voltage of the mains
tranny in the amp, to go up hugely, which would likely blow the HT fuse and
/ or the mains fuse. Might account for why a similar problem is happening to
two unrelated items of equipment, simultaneously ? Have they had any
problems with light bulbs failing, particularly any of those new-fangled eco
things ? Otherwise, I can't think of anything that takes out the HT fuse on
one amp, doing the same to the mains fuse on another.

Arfa

Arfa Daily wrote in message
...

"N Cook" wrote in message
...
I can understand lager chillers or lighting triacs causing clicks and
bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same
time
and no other pub mains problem showing itself.

The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the
initial failure. Not doing so now its in front of me, not fully checked
out
yet. Mains fuse always ok , just the HT one repeatedly failing after 4
seconds or so. At the same time as this HT one failed the mains fuse
failed
on another Marshall connected to the same supply - that one just
required
a
change of mains fuse and is still ok.

Could a fault causing failure of HT fuse on one amp cause the failure of
mains fuse on another amp , with no pub wiring problem at all, even
problem
local to the power ring/spur to the stage.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




Absolutely certain that the supply is not losing the neutral outside
anywhere - particularly if an overhead supply to a country pub ? A friend
of
mine had a similar problem at a remote monitoring station for water
treatment that he had to look after, and the mains kept randomly shooting
up
to 440v. That would certainly cause the secondary voltage of the mains
tranny in the amp, to go up hugely, which would likely blow the HT fuse
and
/ or the mains fuse. Might account for why a similar problem is happening
to
two unrelated items of equipment, simultaneously ? Have they had any
problems with light bulbs failing, particularly any of those new-fangled
eco
things ? Otherwise, I can't think of anything that takes out the HT fuse
on
one amp, doing the same to the mains fuse on another.

Arfa




City pub in Pompey
Owner didn't notice anything else wrong in the room at the gig and
confronting the landlord he said he'd had no problems.

I asked the owner if he used a nasty plastic extension lead and he did not
really reply but even a problem there could not put a surge on to the kit.

Checked the valves and transformers , caps etc and everything seems hunky
dory , no wavering of HT of about 440V on dummy load. I looks as though it
will have to be replacement 500V, twin 50uF electrolytics although no
suspicious heating or bulges /weeping, unless an indisputable reason can be
found. Fuses blew to black interior, ie not soft blown.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:
Arfa Daily wrote in message
...
"N Cook" wrote in message
...
I can understand lager chillers or lighting triacs causing clicks and
bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same
time
and no other pub mains problem showing itself.

The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the
initial failure. Not doing so now its in front of me, not fully checked
out
yet. Mains fuse always ok , just the HT one repeatedly failing after 4
seconds or so. At the same time as this HT one failed the mains fuse
failed
on another Marshall connected to the same supply - that one just
required
a
change of mains fuse and is still ok.

Could a fault causing failure of HT fuse on one amp cause the failure of
mains fuse on another amp , with no pub wiring problem at all, even
problem
local to the power ring/spur to the stage.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Absolutely certain that the supply is not losing the neutral outside
anywhere - particularly if an overhead supply to a country pub ? A friend
of
mine had a similar problem at a remote monitoring station for water
treatment that he had to look after, and the mains kept randomly shooting
up
to 440v. That would certainly cause the secondary voltage of the mains
tranny in the amp, to go up hugely, which would likely blow the HT fuse
and
/ or the mains fuse. Might account for why a similar problem is happening
to
two unrelated items of equipment, simultaneously ? Have they had any
problems with light bulbs failing, particularly any of those new-fangled
eco
things ? Otherwise, I can't think of anything that takes out the HT fuse
on
one amp, doing the same to the mains fuse on another.

Arfa




City pub in Pompey
Owner didn't notice anything else wrong in the room at the gig and
confronting the landlord he said he'd had no problems.

I asked the owner if he used a nasty plastic extension lead and he did not
really reply but even a problem there could not put a surge on to the kit.

Checked the valves and transformers , caps etc and everything seems hunky
dory , no wavering of HT of about 440V on dummy load. I looks as though it
will have to be replacement 500V, twin 50uF electrolytics although no
suspicious heating or bulges /weeping, unless an indisputable reason can be
found. Fuses blew to black interior, ie not soft blown.


Does these amps have valve rectifiers? GZ34 usually. The cheap Sovtec
ones have a habit of flashing over internally and that sees the mains
fuse off big time.

If the fault is repeatable, you might be able to sort of prove it by
temporarily fitting the amps with diode rectifiers for a couple of gigs.

2x 1n4007 in an old valve base (you can parallel up three a side if you
are worried) I always have one on my bench for testing, I see a lot of
duff valves these days.

Ron(UK)

"Ron(UK)" wrote in message
news

Does these amps have valve rectifiers? GZ34 usually. The cheap Sovtec ones
have a habit of flashing over internally and that sees the mains fuse off
big time.

If the fault is repeatable, you might be able to sort of prove it by
temporarily fitting the amps with diode rectifiers for a couple of gigs.

2x 1n4007 in an old valve base (you can parallel up three a side if you
are worried) I always have one on my bench for testing, I see a lot of
duff valves these days.

Ron(UK)


SS diodes in a tube rectifier receptable require a dropper resistor in
series as the tube rectifier drops ~50V whereas the diodes drop ~0.7V.
Otherwise your plate voltages will be too high.

Dave

Ron(UK) wrote in message
news
N Cook wrote:
Arfa Daily wrote in message
...
"N Cook" wrote in message
...
I can understand lager chillers or lighting triacs causing clicks and
bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same
time
and no other pub mains problem showing itself.

The 1987X from 2006 in front of me kept blowing 500mA HT fuses after
the
initial failure. Not doing so now its in front of me, not fully
checked
out
yet. Mains fuse always ok , just the HT one repeatedly failing after 4
seconds or so. At the same time as this HT one failed the mains fuse
failed
on another Marshall connected to the same supply - that one just
required
a
change of mains fuse and is still ok.

Could a fault causing failure of HT fuse on one amp cause the failure
of
mains fuse on another amp , with no pub wiring problem at all, even
problem
local to the power ring/spur to the stage.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Absolutely certain that the supply is not losing the neutral outside
anywhere - particularly if an overhead supply to a country pub ? A
friend
of
mine had a similar problem at a remote monitoring station for water
treatment that he had to look after, and the mains kept randomly
shooting
up
to 440v. That would certainly cause the secondary voltage of the mains
tranny in the amp, to go up hugely, which would likely blow the HT fuse
and
/ or the mains fuse. Might account for why a similar problem is
happening
to
two unrelated items of equipment, simultaneously ? Have they had any
problems with light bulbs failing, particularly any of those
new-fangled
eco
things ? Otherwise, I can't think of anything that takes out the HT
fuse
on
one amp, doing the same to the mains fuse on another.

Arfa




City pub in Pompey
Owner didn't notice anything else wrong in the room at the gig and
confronting the landlord he said he'd had no problems.

I asked the owner if he used a nasty plastic extension lead and he did
not
really reply but even a problem there could not put a surge on to the
kit.

Checked the valves and transformers , caps etc and everything seems
hunky
dory , no wavering of HT of about 440V on dummy load. I looks as though
it
will have to be replacement 500V, twin 50uF electrolytics although no
suspicious heating or bulges /weeping, unless an indisputable reason can
be
found. Fuses blew to black interior, ie not soft blown.


Does these amps have valve rectifiers? GZ34 usually. The cheap Sovtec
ones have a habit of flashing over internally and that sees the mains
fuse off big time.

If the fault is repeatable, you might be able to sort of prove it by
temporarily fitting the amps with diode rectifiers for a couple of gigs.

2x 1n4007 in an old valve base (you can parallel up three a side if you
are worried) I always have one on my bench for testing, I see a lot of
duff valves these days.

Ron(UK)







SS diodes in this one.

Amp is in pristine condition and owner never goes above 3 .
5 off 500mA (T) fuses blew black before but no problem while here.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N Cook" wrote in message
...
Ron(UK) wrote in message
news
N Cook wrote:
Arfa Daily wrote in message
...
"N Cook" wrote in message
...
I can understand lager chillers or lighting triacs causing clicks and
bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same
time
and no other pub mains problem showing itself.

The 1987X from 2006 in front of me kept blowing 500mA HT fuses after
the
initial failure. Not doing so now its in front of me, not fully
checked
out
yet. Mains fuse always ok , just the HT one repeatedly failing after
4
seconds or so. At the same time as this HT one failed the mains fuse
failed
on another Marshall connected to the same supply - that one just
required
a
change of mains fuse and is still ok.

Could a fault causing failure of HT fuse on one amp cause the failure
of
mains fuse on another amp , with no pub wiring problem at all, even
problem
local to the power ring/spur to the stage.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Absolutely certain that the supply is not losing the neutral outside
anywhere - particularly if an overhead supply to a country pub ? A
friend
of
mine had a similar problem at a remote monitoring station for water
treatment that he had to look after, and the mains kept randomly
shooting
up
to 440v. That would certainly cause the secondary voltage of the mains
tranny in the amp, to go up hugely, which would likely blow the HT
fuse
and
/ or the mains fuse. Might account for why a similar problem is
happening
to
two unrelated items of equipment, simultaneously ? Have they had any
problems with light bulbs failing, particularly any of those
new-fangled
eco
things ? Otherwise, I can't think of anything that takes out the HT
fuse
on
one amp, doing the same to the mains fuse on another.

Arfa




City pub in Pompey
Owner didn't notice anything else wrong in the room at the gig and
confronting the landlord he said he'd had no problems.

I asked the owner if he used a nasty plastic extension lead and he did
not
really reply but even a problem there could not put a surge on to the
kit.

Checked the valves and transformers , caps etc and everything seems
hunky
dory , no wavering of HT of about 440V on dummy load. I looks as though
it
will have to be replacement 500V, twin 50uF electrolytics although no
suspicious heating or bulges /weeping, unless an indisputable reason
can
be
found. Fuses blew to black interior, ie not soft blown.


Does these amps have valve rectifiers? GZ34 usually. The cheap Sovtec
ones have a habit of flashing over internally and that sees the mains
fuse off big time.

If the fault is repeatable, you might be able to sort of prove it by
temporarily fitting the amps with diode rectifiers for a couple of gigs.

2x 1n4007 in an old valve base (you can parallel up three a side if you
are worried) I always have one on my bench for testing, I see a lot of
duff valves these days.

Ron(UK)







SS diodes in this one.

Amp is in pristine condition and owner never goes above 3 .
5 off 500mA (T) fuses blew black before but no problem while here.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




Well according to this chap
http://www.russandrews.com/article-4...gfrequency.htm

the following is true:

The effect of incorrect mains voltages

The mains voltage has a surprising effect on the performance of a CD player.
The motor speed is voltage controlled not frequency controlled with a
crystal reference as most people would expect.

Even though the motor supply voltage is regulated, the mains voltage does
affect it, making it play slightly faster or slower.

The effect on the music is quite large, making it sound either fast and
exciting or slow and relaxed. I discovered this whilst experimenting to find
out why a 'Pandora' isolating transformer, that was claimed to improve CD
sound quality, did affect the sound. I discovered that the 'Pandora' was
simply increasing the mains voltage by 24 volts, hence increasing the play
speed and making the sound appear more 'exciting'




I would put the amp on a variac up to about 250v, to see if anything is
breaking down at a higher, yet still legal voltage than presently coming out
of your bench.

I would also be careful not to assume too much. The 2 faults may actually
be unrelated, or the amp you have may now have burnt something out that was
blowing the fuses. Your customer may also not be telling you what really
happened. Did he really use 5 slow blow fuses? Did the two amps really
blow at the same time? In a panic (gig) situation people tend to relate all
sorts of things that are just not true.

Strip the amp down and look for burnt components, arcing on PCB's etc. I've
found faults by sticking my nose in there and having a good sniff. With the
HT discharged of course! Perhaps a foreign body is floating around. These
days I tend to trust my own instincts, not the customers', who can waste
hours of your time if you let them.


Gareth.

"Gareth Magennis" wrote in message
om...
Well according to this chap
http://www.russandrews.com/article-4...gfrequency.htm

the following is true:

The effect of incorrect mains voltages

The mains voltage has a surprising effect on the performance of a CD
player. The motor speed is voltage controlled not frequency controlled
with a crystal reference as most people would expect.

Even though the motor supply voltage is regulated, the mains voltage does
affect it, making it play slightly faster or slower.

The effect on the music is quite large, making it sound either fast and
exciting or slow and relaxed. I discovered this whilst experimenting to
find out why a 'Pandora' isolating transformer, that was claimed to
improve CD sound quality, did affect the sound. I discovered that the
'Pandora' was simply increasing the mains voltage by 24 volts, hence
increasing the play speed and making the sound appear more 'exciting'



Gareth.


I'm surprised that Russ Andrews would make such an incorrect statement;
true, the spindle motor is DC driven but it's controlled by A PLL reading
the RF frequency from the pick up, the motor speed is varied to maintain the
correct frequency and that will be locked to a master oscillator. The
oscillator frequency would have to vary with supply voltage for Russ's
statement to be true.
Martin
--
martindot herewhybrowat herentlworlddot herecom

"Martin Whybrow" wrote in message
...

"Gareth Magennis" wrote in message
om...
Well according to this chap
http://www.russandrews.com/article-4...gfrequency.htm

the following is true:

The effect of incorrect mains voltages

The mains voltage has a surprising effect on the performance of a CD
player. The motor speed is voltage controlled not frequency controlled
with a crystal reference as most people would expect.

Even though the motor supply voltage is regulated, the mains voltage does
affect it, making it play slightly faster or slower.

The effect on the music is quite large, making it sound either fast and
exciting or slow and relaxed. I discovered this whilst experimenting to
find out why a 'Pandora' isolating transformer, that was claimed to
improve CD sound quality, did affect the sound. I discovered that the
'Pandora' was simply increasing the mains voltage by 24 volts, hence
increasing the play speed and making the sound appear more 'exciting'



Gareth.


I'm surprised that Russ Andrews would make such an incorrect statement;
true, the spindle motor is DC driven but it's controlled by A PLL reading
the RF frequency from the pick up, the motor speed is varied to maintain
the correct frequency and that will be locked to a master oscillator. The
oscillator frequency would have to vary with supply voltage for Russ's
statement to be true.
Martin
--
martindot herewhybrowat herentlworlddot herecom




Well apart from any motor schenanigans, the data is simply clocked out at a
fixed 44.1KHz. I have no idea what this guy is thinking about. Most
bizarre.



Gareth.

Martin Whybrow wrote:
I'm surprised that Russ Andrews would make such an incorrect statement;
true, the spindle motor is DC driven but it's controlled by A PLL reading
the RF frequency from the pick up, the motor speed is varied to maintain the
correct frequency and that will be locked to a master oscillator. The
oscillator frequency would have to vary with supply voltage for Russ's
statement to be true.

I do know that if you use a modern DVD player as a CD player, line
voltage will have no effect at all on how it sounds. They all use
switching power supplies, most of them 100-240 volt autosensing.

No matter what you put into it, inside everything is run off of
5 and 12 volts DC.

What's silly about the faster running theory is that it's digital and
the frequency of the sound is based upon the sample rate clock, and
not the speed of the disk. Some CD players, usually portable ones
read ahead anyway and buffer the data, the ones that don't have
to keep the speed the data comes off the disk the same as the
sample rate and as you say have PLL locking circuitry to do it.

It's been a long time since I cared, but I think that audio CD's are
written (punched?) at different speeds to keep the data rate constant
as the disk becomes wider. They read from the center out, so the disk
spins slower at the center and faster at the edges. I think that's
called CAV (constant angular velocity), but I may be wrong.

The onlygimick I know of to improve audio CD quality that works is to
use a specific car polish on the disks, which makes them sound
"brighter". That's due to the way players use to handle read errors,
they just repeated the missing sample.

However that worked over 20 years ago, I seriously doubt that it
is needed now.

But buying a tranformer to up the power line voltage if it is normal
is IMHO just a gimick sold to the ignorant.

BTW, if you are in the EU, it really does not make sense because while
all players sold in the EU are designed for the 230 volt standard,
no one changed from 220 or 240 to 230, and so they really are designed
to work properly with a range of at least 220-240 and probably a lot more.

The last time I saw anything current production with a 220/240 volt
selector switch on it was around 1983. By 1985 all of the equipment I
saw was autoswitching between 220 and 240, and much of it between
120 to 240.

Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

"Martin Whybrow" wrote in message
...

"Gareth Magennis" wrote in message
om...
Well according to this chap
http://www.russandrews.com/article-4...gfrequency.htm

the following is true:

The effect of incorrect mains voltages

The mains voltage has a surprising effect on the performance of a CD
player. The motor speed is voltage controlled not frequency controlled
with a crystal reference as most people would expect.

Even though the motor supply voltage is regulated, the mains voltage does
affect it, making it play slightly faster or slower.

The effect on the music is quite large, making it sound either fast and
exciting or slow and relaxed. I discovered this whilst experimenting to
find out why a 'Pandora' isolating transformer, that was claimed to
improve CD sound quality, did affect the sound. I discovered that the
'Pandora' was simply increasing the mains voltage by 24 volts, hence
increasing the play speed and making the sound appear more 'exciting'



Gareth.


I'm surprised that Russ Andrews would make such an incorrect statement;


Actually after a virtually insignificant bit of further reading I realised
what this Russ Andrews is all about.
http://www.russandrews.com/lookup/0/...Cable-3400.htm

I don't think any further comment is necessary, this kind of crap has been
done to death.



Gareth.

According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of 464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose nuts
holding the iron laminations on the filter choke, which I cannot see as a
problem. Otherwise inside and out it looks brand new, only some of the large
binding post (lead-free of course everywhere ) solder joints looked grey but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of 464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose nuts
holding the iron laminations on the filter choke, which I cannot see as a
problem. Otherwise inside and out it looks brand new, only some of the large
binding post (lead-free of course everywhere ) solder joints looked grey but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

Why?

Ron(UK)

"N Cook" wrote in message
...
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of
464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose nuts
holding the iron laminations on the filter choke, which I cannot see as a
problem. Otherwise inside and out it looks brand new, only some of the
large
binding post (lead-free of course everywhere ) solder joints looked grey
but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/





I'm not sure it is the job of a repair tech to "Mod" customers' equipment
unsolicited for whatever reason takes your fancy. Adding fuses may simply
be adding in unreliability.




Gareth.

Ron(UK) wrote in message
...
N Cook wrote:
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of
464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose
nuts
holding the iron laminations on the filter choke, which I cannot see as
a
problem. Otherwise inside and out it looks brand new, only some of the
large
binding post (lead-free of course everywhere ) solder joints looked grey
but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in
each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

Why?

Ron(UK)


On the assumption that the one of the 2x 22nF, 400V DC decouplers to the o/p
valves could have failed and self-healed, I replaced those.

And with all lead-free boards I now routinely put a 2Kg pull at each end,
via thin-nose pliers, of all 1 or more watt resistors, any resistors mounted
off board or any that look a bit discoloured. All passed - what should I
call this test ?

I'll add fuses if it bounces back, with still nothing suspect anywhere.
As for power surges , the owner was thinking of a protector - anyone any
suggestions ? can they protect from a surge to say only 255 volts ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N Cook" wrote in message
...
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of
464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose nuts
holding the iron laminations on the filter choke, which I cannot see as a
problem. Otherwise inside and out it looks brand new, only some of the
large
binding post (lead-free of course everywhere ) solder joints looked grey
but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


Oddly enough, I had an amp in a few weeks back (can't remember what it was
now - oh to be young again ...) which had a pair of rear panel fuseholders.
This amp used 4 x EL34 I seem to recall, and each fuseholder was located in
the anode feed of each valve pair. They were actually labelled "output valve
fuses". In all the years I have been mending these things, I can't ever
before remember seeing fuses in this position. Interestingly, I have an old
AC30 in at the moment which has shorted turns on one half of the output
transformer. This has completely thrutched the output valve on that half -
the anode was glowing orange and the inside of the glass is badly flowered.
Had the unit have had anode fuses, I guess the appropriate one would have
opened and saved the valve. But in general, I am not in favour of altering a
design, if only for that fact that it may compromise any electrical safety
approvals that the equipment has.

Arfa

Arfa Daily wrote in message
...

"N Cook" wrote in message
...
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of
464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose
nuts
holding the iron laminations on the filter choke, which I cannot see as
a
problem. Otherwise inside and out it looks brand new, only some of the
large
binding post (lead-free of course everywhere ) solder joints looked grey
but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in
each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


Oddly enough, I had an amp in a few weeks back (can't remember what it was
now - oh to be young again ...) which had a pair of rear panel
fuseholders.
This amp used 4 x EL34 I seem to recall, and each fuseholder was located
in
the anode feed of each valve pair. They were actually labelled "output
valve
fuses". In all the years I have been mending these things, I can't ever
before remember seeing fuses in this position. Interestingly, I have an
old
AC30 in at the moment which has shorted turns on one half of the output
transformer. This has completely thrutched the output valve on that half -
the anode was glowing orange and the inside of the glass is badly
flowered.
Had the unit have had anode fuses, I guess the appropriate one would have
opened and saved the valve. But in general, I am not in favour of altering
a
design, if only for that fact that it may compromise any electrical safety
approvals that the equipment has.

Arfa



No thermal fuses in those sort of transformers I suppose, asuming it started
with a few shorted turns and progressively worsened.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"Arfa Daily" wrote in message
...

"N Cook" wrote in message
...
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of
464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose nuts
holding the iron laminations on the filter choke, which I cannot see as a
problem. Otherwise inside and out it looks brand new, only some of the
large
binding post (lead-free of course everywhere ) solder joints looked grey
but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in
each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


Oddly enough, I had an amp in a few weeks back (can't remember what it was
now - oh to be young again ...) which had a pair of rear panel
fuseholders. This amp used 4 x EL34 I seem to recall, and each fuseholder
was located in the anode feed of each valve pair. They were actually
labelled "output valve fuses". In all the years I have been mending these
things, I can't ever before remember seeing fuses in this position.
Interestingly, I have an old AC30 in at the moment which has shorted turns
on one half of the output transformer. This has completely thrutched the
output valve on that half - the anode was glowing orange and the inside of
the glass is badly flowered. Had the unit have had anode fuses, I guess
the appropriate one would have opened and saved the valve. But in general,
I am not in favour of altering a design, if only for that fact that it may
compromise any electrical safety approvals that the equipment has.

Arfa


Marshall commonly do that on their more current models, but the fuses are on
the cathode.
Here's an example:
http://www.schematicheaven.com/marsh..._100w_2100.pdf


Gareth.

"Gareth Magennis" wrote in message
om...

"Arfa Daily" wrote in message
...

"N Cook" wrote in message
...
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of
464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose
nuts
holding the iron laminations on the filter choke, which I cannot see as
a
problem. Otherwise inside and out it looks brand new, only some of the
large
binding post (lead-free of course everywhere ) solder joints looked grey
but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in
each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


Oddly enough, I had an amp in a few weeks back (can't remember what it
was now - oh to be young again ...) which had a pair of rear panel
fuseholders. This amp used 4 x EL34 I seem to recall, and each fuseholder
was located in the anode feed of each valve pair. They were actually
labelled "output valve fuses". In all the years I have been mending these
things, I can't ever before remember seeing fuses in this position.
Interestingly, I have an old AC30 in at the moment which has shorted
turns on one half of the output transformer. This has completely
thrutched the output valve on that half - the anode was glowing orange
and the inside of the glass is badly flowered. Had the unit have had
anode fuses, I guess the appropriate one would have opened and saved the
valve. But in general, I am not in favour of altering a design, if only
for that fact that it may compromise any electrical safety approvals that
the equipment has.

Arfa


Marshall commonly do that on their more current models, but the fuses are
on the cathode.
Here's an example:
http://www.schematicheaven.com/marsh..._100w_2100.pdf


Gareth.



Oh Christ. What is happening to my head ???? You are quite right Gareth. It
*was* a Marshall, and I remember now, the fuses *were* in the cathodes. Was
there a LED across them too to indicate if they had failed ? Boy, my memory
is going. Must be mercury poisoning from my fillings, or lead poisoning from
the solder ;-)

Anyway, I guess the same still applies as cathode current very nearly equals
anode current ...

Arfa

N Cook wrote:

I can understand lager chillers or lighting triacs causing clicks and bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same time
and no other pub mains problem showing itself.

The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the
initial failure. Not doing so now its in front of me, not fully checked out
yet. Mains fuse always ok , just the HT one repeatedly failing after 4
seconds or so. At the same time as this HT one failed the mains fuse failed
on another Marshall connected to the same supply - that one just required a
change of mains fuse and is still ok.

Could a fault causing failure of HT fuse on one amp cause the failure of
mains fuse on another amp , with no pub wiring problem at all, even problem
local to the power ring/spur to the stage.

Brief surges ?

I had a JVC TV blow its internal mains fuse every 2 years or so even when not
active (but in standby). Eventually a plug-in surge suppressor stopped it.

Graham

Eeyore wrote in message
...


N Cook wrote:

I can understand lager chillers or lighting triacs causing clicks and
bangs
and noises off but blowing fuses on 2 Marshall valve amps at the same
time
and no other pub mains problem showing itself.

The 1987X from 2006 in front of me kept blowing 500mA HT fuses after the
initial failure. Not doing so now its in front of me, not fully checked
out
yet. Mains fuse always ok , just the HT one repeatedly failing after 4
seconds or so. At the same time as this HT one failed the mains fuse
failed
on another Marshall connected to the same supply - that one just
required a
change of mains fuse and is still ok.

Could a fault causing failure of HT fuse on one amp cause the failure of
mains fuse on another amp , with no pub wiring problem at all, even
problem
local to the power ring/spur to the stage.

Brief surges ?

I had a JVC TV blow its internal mains fuse every 2 years or so even when
not
active (but in standby). Eventually a plug-in surge suppressor stopped it.

Graham



Bet it occured at night.

Very few power stations/generator sets are needed to power the grid in the
middle of the night. At some point it becomes necessary to start up another
one and what happens to the grid at that time ?



--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:

Eeyore wrote in message

Brief surges ?

I had a JVC TV blow its internal mains fuse every 2 years or so even when
not active (but in standby). Eventually a plug-in surge suppressor stopped
it.

Bet it occured at night.

I don't recall any particular pattern to it. It may even have had a transorb
itself - and it was over sensitive. Putting another effectively in parallel took
the load off it.

Graham

"Arfa Daily" wrote in message
...

"Gareth Magennis" wrote in message
om...

"Arfa Daily" wrote in message
...

"N Cook" wrote in message
...
According to Regulation 27 of ESQC Regs 2002, UK mains should be
230V +10% - 6%, which gives a range of 216V to 253V.

I variaced up to 250V , switching on and off a few times, giving HT1 of
464
, nicely stable with amp under load.

A thorough inspection of all components only revealed slightly loose
nuts
holding the iron laminations on the filter choke, which I cannot see as
a
problem. Otherwise inside and out it looks brand new, only some of the
large
binding post (lead-free of course everywhere ) solder joints looked
grey but
otherwise sound.

Whats the teams opinion of adding 300mA axial (so quickblow) fuses in
each
of the two EL34 anode supplies as well as the 500mA (T) regular fuse ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


Oddly enough, I had an amp in a few weeks back (can't remember what it
was now - oh to be young again ...) which had a pair of rear panel
fuseholders. This amp used 4 x EL34 I seem to recall, and each
fuseholder was located in the anode feed of each valve pair. They were
actually labelled "output valve fuses". In all the years I have been
mending these things, I can't ever before remember seeing fuses in this
position. Interestingly, I have an old AC30 in at the moment which has
shorted turns on one half of the output transformer. This has completely
thrutched the output valve on that half - the anode was glowing orange
and the inside of the glass is badly flowered. Had the unit have had
anode fuses, I guess the appropriate one would have opened and saved the
valve. But in general, I am not in favour of altering a design, if only
for that fact that it may compromise any electrical safety approvals
that the equipment has.

Arfa


Marshall commonly do that on their more current models, but the fuses are
on the cathode.
Here's an example:
http://www.schematicheaven.com/marsh..._100w_2100.pdf


Gareth.



Oh Christ. What is happening to my head ???? You are quite right Gareth.
It *was* a Marshall, and I remember now, the fuses *were* in the cathodes.
Was there a LED across them too to indicate if they had failed ? Boy, my
memory is going. Must be mercury poisoning from my fillings, or lead
poisoning from the solder ;-)


Each push/pull pair have their cathodes connected together and are grounded
via a fuse. There is a LED and resistor across the fuse so if it blows the
LED lights.

It should be noted that if a faulty output valve blows a fuse, the valve is
toast and you would not normally change just that one faulty valve, or at
least I wouldn't. So these fuses are not really there to protect the
valves. Quite possibly why they are not universally used?





Anyway, I guess the same still applies as cathode current very nearly
equals anode current ...

Arfa


There is also the Screen Grid G2, used as a second anode to consider, which
is not normally directly connected to the Anode.

Here's another Marshall schematic showing switchable Triode/Pentode type
operation and a cathode fuse.


http://www.schematicheaven.com/marsh...x_45xx_50w.pdf

Gareth.

N Cook wrote:


Very few power stations/generator sets are needed to power the grid in the
middle of the night. At some point it becomes necessary to start up another
one and what happens to the grid at that time ?


Generating systems don't just get "slapped on line" at startup, at least
here in the USA. I don't believe you'd find that in any but third-world
countries.

The generator is brought up to speed/frquency and voltage (and
stabilized) to match that of the grid before it's brought on line. Only
then does the plant operator raise output in conjunction with the rest
of the grid providers. It's a constant job to maintain the grid at
nominal levels and requires constant voice and data transfers amongst
the providers.

I'm not going to say that surges don't happen when abrupt loads are
dumped on or dropped, but that's another subject too long to explain in
one post.

Marshall commonly do that on their more current models, but the fuses
are on the cathode.
Here's an example:
http://www.schematicheaven.com/marsh..._100w_2100.pdf


Gareth.



Oh Christ. What is happening to my head ???? You are quite right Gareth.
It *was* a Marshall, and I remember now, the fuses *were* in the
cathodes. Was there a LED across them too to indicate if they had failed
? Boy, my memory is going. Must be mercury poisoning from my fillings, or
lead poisoning from the solder ;-)


Each push/pull pair have their cathodes connected together and are
grounded via a fuse. There is a LED and resistor across the fuse so if it
blows the LED lights.

It should be noted that if a faulty output valve blows a fuse, the valve
is toast and you would not normally change just that one faulty valve, or
at least I wouldn't. So these fuses are not really there to protect the
valves. Quite possibly why they are not universally used?



Hmmm. I certainly wouldn't replace one output valve on its own, but I am not
convinced that a period of sufficiently excess current long enough to blow
the fuse, is going to result in the valve becoming 'toast', unless you are
suggesting that the valve is toast in the first place, and that was what
lead to the fuse blowing ? If so, I think it is pretty rare to find any
internal faults, apart from the occasional inter-electrode short, which
result in valves drawing excess current. Most times when I've seen the
condition, it has been due to external failures, such as a fault in the bias
supply, or a leaky grid coupling cap from a phase splitter anode. Or a wire
off the grid - see my post in Mr Cook's "Marshall" thread :-)

It's hard to see what other reason than protecting the valves, Marshall felt
that they had for putting fuses in.





Anyway, I guess the same still applies as cathode current very nearly
equals anode current ...

Arfa


There is also the Screen Grid G2, used as a second anode to consider,
which is not normally directly connected to the Anode.


Yes, that is why I said "very nearly equals", the additional g2 current
flowing in the cathode, being small at only a few mA, compared to the anode
current.



Here's another Marshall schematic showing switchable Triode/Pentode type
operation and a cathode fuse.


http://www.schematicheaven.com/marsh...x_45xx_50w.pdf

Gareth.


Interestingly, the cathode fuse is about what you would expect at 300 mA (or
possibly 500, it's not too clear) but the main HT fuse appears to be rated
at a staggering 3 amps ! Only the output valves are fed from the 'raw' HT
line, everything else preamp / phase splitter-wise, being fed via a 22k
resistor, R30, which is going to limit any downstream current to what ?
about 10 mA to keep an HT rail of a coupla hundred volts at all the ECC's ?
What on earth were they thinking of, when they put a fuse of that rating in
the HT line ? I know it says that it's an 'F' and that it is a picofuse, but
even so ...

Am I missing something here ?

Arfa

"Arfa Daily" wrote in message
...


Marshall commonly do that on their more current models, but the fuses
are on the cathode.
Here's an example:
http://www.schematicheaven.com/marsh..._100w_2100.pdf


Gareth.



Oh Christ. What is happening to my head ???? You are quite right Gareth.
It *was* a Marshall, and I remember now, the fuses *were* in the
cathodes. Was there a LED across them too to indicate if they had failed
? Boy, my memory is going. Must be mercury poisoning from my fillings,
or lead poisoning from the solder ;-)


Each push/pull pair have their cathodes connected together and are
grounded via a fuse. There is a LED and resistor across the fuse so if
it blows the LED lights.

It should be noted that if a faulty output valve blows a fuse, the valve
is toast and you would not normally change just that one faulty valve, or
at least I wouldn't. So these fuses are not really there to protect the
valves. Quite possibly why they are not universally used?



Hmmm. I certainly wouldn't replace one output valve on its own, but I am
not convinced that a period of sufficiently excess current long enough to
blow the fuse, is going to result in the valve becoming 'toast', unless
you are suggesting that the valve is toast in the first place, and that
was what lead to the fuse blowing ? If so, I think it is pretty rare to
find any internal faults, apart from the occasional inter-electrode short,
which result in valves drawing excess current. Most times when I've seen
the condition, it has been due to external failures, such as a fault in
the bias supply, or a leaky grid coupling cap from a phase splitter anode.
Or a wire off the grid - see my post in Mr Cook's "Marshall" thread :-)

It's hard to see what other reason than protecting the valves, Marshall
felt that they had for putting fuses in.





Anyway, I guess the same still applies as cathode current very nearly
equals anode current ...

Arfa


There is also the Screen Grid G2, used as a second anode to consider,
which is not normally directly connected to the Anode.


Yes, that is why I said "very nearly equals", the additional g2 current
flowing in the cathode, being small at only a few mA, compared to the
anode current.



Here's another Marshall schematic showing switchable Triode/Pentode type
operation and a cathode fuse.


http://www.schematicheaven.com/marsh...x_45xx_50w.pdf

Gareth.


Interestingly, the cathode fuse is about what you would expect at 300 mA
(or possibly 500, it's not too clear) but the main HT fuse appears to be
rated at a staggering 3 amps ! Only the output valves are fed from the
'raw' HT line, everything else preamp / phase splitter-wise, being fed via
a 22k resistor, R30, which is going to limit any downstream current to
what ? about 10 mA to keep an HT rail of a coupla hundred volts at all the
ECC's ? What on earth were they thinking of, when they put a fuse of that
rating in the HT line ? I know it says that it's an 'F' and that it is a
picofuse, but even so ...

Am I missing something here ?

Arfa


Kind of puzzled me too - only thing I can see is to protect against a
shorted reservoir cap after the 100 ohm resistor, or a faulty Triode/Pentode
switch. Maybe these can arc if you switch them at full power or something,
or maybe its to protect against running the amp without a speaker connected.
Dunno. I'm sure they had their reasons, unless that is a typo.






Gareth.