Pioneer SX 1250
 

I think I'd look for power supply problems, especially bad solder
connections and bad small capacitors in the regulated power supply area. The
bias can be adjusted later, assuming it doesn't get really hot. I don't
really think it's related to the shutting down problem.


Mark Z.



"Ross Mac" wrote in message
...
Hi Folks,

I have a Pioneer SX 1250 Reciever that is giving me problems. It shuts
down
after about 30 minutes and the right heatsink seems warmer than the left.
I
have the service manual and have run a few tests but thought I might ask
around before I spend the next couple of days fighting this
one......thanks
for any help....Ross

Pioneer SX 1250
 

Try the obvious first. What condition is the heat sink compound in? If it's
dried out... replace the grease. Also... make sure the transistors are tight
to the heat sink. Maybe... swap L for R speakers and see if the problem goes
to the other side. Good luck...

Ross Mac wrote:

Hi Folks,

I have a Pioneer SX 1250 Reciever that is giving me problems. It shuts down
after about 30 minutes and the right heatsink seems warmer than the left. I
have the service manual and have run a few tests but thought I might ask
around before I spend the next couple of days fighting this one......thanks
for any help....Ross

Pioneer SX 1250
 

Subject: Pioneer SX 1250
From: "Ross Mac"
Date: 9/15/03 8:12 PM Eastern Daylight Time
Message-id:

Hi Folks,

I have a Pioneer SX 1250 Reciever that is giving me problems. It shuts down
after about 30 minutes and the right heatsink seems warmer than the left. I
have the service manual and have run a few tests but thought I might ask
around before I spend the next couple of days fighting this one......thanks
for any help....Ross


If it plays normally otherwise, I'd bet it's a bias problem. The carbon
trimmers they use to set bias are pure garbage, and they'll drift just looking
at them. There might be two adjustments per channel on this model. Flush them
out with a quality cleaner, and see if they set up normally. If so, replace
the pure garbage pots with mere crappy ones (one grade up ;) and re adjust the
bias.


John Del
Wolcott, CT

"Nothing is so opportune for tyrants as a people tired of its liberty."
Alan Keyes

(remove S for email reply)

Pioneer SX 1250
 

I did check the supply and it is a good clean 65Volts. All the connections
also look great. Especially for a 25 year old amp. I will look some more
today...thanks...Ross

"Mark D. Zacharias" wrote in message
ink.net...
I don't know - Pioneers are NOTORIOUS for regulated power supply problems.
The timing of his failure also suggests this to me.

Mark Z.



"John Del" wrote in message
...
Subject: Pioneer SX 1250
From: "Ross Mac"
Date: 9/15/03 8:12 PM Eastern Daylight Time
Message-id:


Hi Folks,

I have a Pioneer SX 1250 Reciever that is giving me problems. It shuts
down
after about 30 minutes and the right heatsink seems warmer than the
left.
I
have the service manual and have run a few tests but thought I might
ask
around before I spend the next couple of days fighting this
one......thanks
for any help....Ross


If it plays normally otherwise, I'd bet it's a bias problem. The carbon
trimmers they use to set bias are pure garbage, and they'll drift just
looking
at them. There might be two adjustments per channel on this model.
Flush
them
out with a quality cleaner, and see if they set up normally. If so,
replace
the pure garbage pots with mere crappy ones (one grade up ;) and re
adjust
the
bias.


John Del
Wolcott, CT

"Nothing is so opportune for tyrants as a people tired of its liberty."
Alan Keyes

(remove S for email reply)

Pioneer SX 1250
 

I will go ahead and calibrate the stabilizer and power amp circuits today.
If the pots are bad I will catch it then. Thanks for all your help....Ross


"John Del" wrote in message
...
Subject: Pioneer SX 1250
From: "Ross Mac"
Date: 9/15/03 8:12 PM Eastern Daylight Time
Message-id:


Hi Folks,

I have a Pioneer SX 1250 Reciever that is giving me problems. It shuts
down
after about 30 minutes and the right heatsink seems warmer than the left.
I
have the service manual and have run a few tests but thought I might ask
around before I spend the next couple of days fighting this
one......thanks
for any help....Ross


If it plays normally otherwise, I'd bet it's a bias problem. The carbon
trimmers they use to set bias are pure garbage, and they'll drift just
looking
at them. There might be two adjustments per channel on this model. Flush
them
out with a quality cleaner, and see if they set up normally. If so,
replace
the pure garbage pots with mere crappy ones (one grade up ;) and re adjust
the
bias.


John Del
Wolcott, CT

"Nothing is so opportune for tyrants as a people tired of its liberty."
Alan Keyes

(remove S for email reply)

Pioneer SX 1250
 

There's lots more than just the 65 volts. Probably + and - 65, 45, 13, etc.

Mark Z.


"Ross Mac" wrote in message
...
I did check the supply and it is a good clean 65Volts. All the connections
also look great. Especially for a 25 year old amp. I will look some more
today...thanks...Ross

"Mark D. Zacharias" wrote in message
ink.net...
I don't know - Pioneers are NOTORIOUS for regulated power supply
problems.
The timing of his failure also suggests this to me.

Mark Z.



"John Del" wrote in message
...
Subject: Pioneer SX 1250
From: "Ross Mac"
Date: 9/15/03 8:12 PM Eastern Daylight Time
Message-id:


Hi Folks,

I have a Pioneer SX 1250 Reciever that is giving me problems. It
shuts
down
after about 30 minutes and the right heatsink seems warmer than the
left.
I
have the service manual and have run a few tests but thought I might
ask
around before I spend the next couple of days fighting this
one......thanks
for any help....Ross


If it plays normally otherwise, I'd bet it's a bias problem. The
carbon
trimmers they use to set bias are pure garbage, and they'll drift just
looking
at them. There might be two adjustments per channel on this model.
Flush
them
out with a quality cleaner, and see if they set up normally. If so,
replace
the pure garbage pots with mere crappy ones (one grade up ;) and re
adjust
the
bias.


John Del
Wolcott, CT

"Nothing is so opportune for tyrants as a people tired of its
liberty."
Alan Keyes

(remove S for email reply)

Pioneer SX 1250
 

Looks like John had the correct answer...I found the bias trim pots to be
worthless garbage and almost unadjustable. I will replace today...I did
calibrate them the best I could and the amp worked great all night....just
ask the neighbors!!...hehehe....Thanks to all for your help!
.....Ross
"John Del" wrote in message
...
Subject: Pioneer SX 1250
From: "Ross Mac"
Date: 9/15/03 8:12 PM Eastern Daylight Time
Message-id:


Hi Folks,

I have a Pioneer SX 1250 Reciever that is giving me problems. It shuts
down
after about 30 minutes and the right heatsink seems warmer than the left.
I
have the service manual and have run a few tests but thought I might ask
around before I spend the next couple of days fighting this
one......thanks
for any help....Ross


If it plays normally otherwise, I'd bet it's a bias problem. The carbon
trimmers they use to set bias are pure garbage, and they'll drift just
looking
at them. There might be two adjustments per channel on this model. Flush
them
out with a quality cleaner, and see if they set up normally. If so,
replace
the pure garbage pots with mere crappy ones (one grade up ;) and re adjust
the
bias.


John Del
Wolcott, CT

"Nothing is so opportune for tyrants as a people tired of its liberty."
Alan Keyes

(remove S for email reply)