Carver PT-1250

[vintageAudio 3]

Have 3 Carver PT-1250 amps, 2 went out, fans are no longer operational and suspect they stopped functioning prior to the units. Wasn't aware or thinking of the fans failing since they were on low and not really audible, they most likely stopped and the unit over heated. Has anyone experienced a similar issue and what was the point of failure besides the fan (i.e., output op-amps/transistors)?🥲

[Yamacarver 797]

Hi and welcome to the Carver site.

I think most of these have thermal protection, have you downloaded the service manual?

[BobTFM35 2,767]

Hello and welcome to the Carver site.

 

If you do a search for information on the PT1250 you will find out that it is a rebadged PM-2.0t. So download that manual.

 

In it you will find more information than just the schematics that are in the 1250 service manual. 

 

In the owners manual for the 1250, it does as @Yamacarver indicated have individual CH1 and CH2 thermal protection along with three other protections. How all this interacts is a question for someone familiar with electronics and maybe this unit.

 

I must ask this next question so excuse me if you performed this..... Did you check the fuses, in and out of the holders?

 

If it did indeed overheat I might be concerned about the thermal compound between the mica insulators, transistors, and the heat sinks just due to its overall age.

 

This is the extent of my experience/advice so Good luck in getting your units working again.

[AndrewJohn 10,446]

Welcome to the site.  Glad you found us.

 

Start a thread with your diagnosis steps.  It's probably not a one-thing-fix, but a journey as you go through the steps.  That way people can pipe in with more guidance.

[timmyjim 449]

I'll skip the part where "if you don't have something nice to say, don't say anything".

These amps are VERY difficult to work on, both electrically and mechanically. 

The power supply is unlike any other Carver amp. I mostly enjoy debug and repair, not this one.

If you look at the PM2.0t manual, there is a description of bringing up the power supply with a variac  external variable supply. I'm not going to go back and look at it as I might start to convulse, but there is something. (I went back, see previous correction)

Ay any rate, you will find yourself removing many tiny screws to get at the necessary test points. 

You will end up with thermal paste all over the place.

The Darlington transistors in the PS section are difficult to source, as is the PWM IC.

If the power supply proves to be OK, then you probably have a chance at repair (I guess I did have a positive).

Good Luck.

Edited December 7, 2023 by timmyjim

[Rob 5,974]

Welcome to the Carversite. 

[Cring08 244]

Welcome!

[Dennis47 971]

WELCOME @vintageAudio and good luck with the PT-1250 amp projects.