repair of a ms2125

[Seanram]

I just grabbed this beautifull abused amp for a steal.
I'm going to replace the following parts:
-power supply fed's
-output stage
-ps caps

So far so good, but after taking a closer look i noticed a few thing:
-most of the fed's are a different type (not sure what is original)
-one of the yellow thermal sensors is destroyed.
-It looks like some kind of upgrade is done to the square wave mode of the ps. (not sure if its orginal does not look really professional).

I hope you guys could help me with the points above.
Does anyone know the exact types for all the fed (for ps and output stage)?
Does anyone know the typenumer for the yellow thermal sensor (or a good replaycement)?
Has anyone seen the modification?

Any help would be apreciated and in excange I will post pics of the repair .

[Seanram]

the amp inside looks ok (sorry for the crappy pics).

[Seanram]

yellow component

[Seanram]

the possible mod

[Seanram]

.

[Seanram]

Is there anyone who could help me (or at least with a couple of questions)
Any help is apreciated!!

[trickyricky]

I can, there's a power supply with 4 fets, 2 rectifiers and 6 Toshiba outputs....that's for one channel one side picture heat sink. So each side should be identical (mirror)..

I'll get you the exact parts numbers when i get home. Am on crutches so bare with me.

[Seanram]

Thank you trickyricky!! Your help is appreciated.

I noticed that all THE feds are bot equel (mirrord). Therefore my question, would love to revivescentie this beauty.

[Seanram]

I ment to say not equel

[trickyricky]

I believe I've seen that mod before on the 3rd pic, I'll have to check my MS amps. Doubt I've seen the thermal with the resistor added...might be there to bypass the cut off temperature (not good, unless it causes the amp to shut off at a lower temp than intended).

[Seanram]

THE mod looks legit i can imagine iT would be done to achieve steeper switching edges.
THE yellow temp. sensor on THE other hand looks like a quick fixup (iTS only done on 1 Side THE other one is normal)
As for THE ps. Feds these have Also Been replayced. Someone tried to fix iT without skills( soldering and leg bending is done poorly)
ITS commenly hard to find a replaicement sensor (i could messure THE karakteristics on THE working one)
I was hopeing someone here could point me to THE right direction for a replaicement.
Thanks again for your help!

[knightrider358]

What would be the point of the mod on the fet be for, what improvent would this do for the amp?

[trickyricky]

Where did you get the idea the square wave on the ps was modified? My MPS2500 has the same revision as yours (the semiconductor you have in a red square). So leave that alone, as for the thermistor why not compare it with the one on the opposite side?

[Seanram]

I Will compair iT to the working one.
I was hopeing someone would have Amy experience with replaicing them.
When THE comparison is done i Will update with a possible replaicement.

[trickyricky]

I Will compair iT to the working one.
I was hopeing someone would have Amy experience with replaicing them.
When THE comparison is done i Will update with a possible replaicement.

Replacing what?

The thermistors start at 150ohms and rise with heat, if that helps any..

[Seanram]

I need to replace THE thermistor (both THE legs are broken off at THE base of THE yellow coating).
Thank you for youre help

[trickyricky]

Since the resistance rises when the temp goes up then I would suspect it to be a PTC thermistor....




Check mouser and digikey... I would suggest a 90-95c as the temp cutoff any higher and you risk the chance of the amp over heating and not shutting off.


PM me if you can't find them...I have spare boards.