Amplifier problem - getting hot

[siocnarf]

Hi everyone.
This is my first message here and I hope you will understand it (english is not my mother tongue)

I am a happy owner of two 4-channels RAM Audio S4044 amplifiers (class H)
But one of them has a problem : even when nothing is plugged on it (no source, no speakers), it is getting quite hot.
The heat is generated only on the left side (see the red "circle" on the picture attached), but not enough to activate the protection mechanism.
(but this is probably because I am using it at low levels as it serves in a dedicated home theater room).

Apart from that, all 4 channels are working perfectly. But I am affraid that if I continue to use it without doing anything, the problem could get worst.

I have explained that problem to the manufacturer support, they told me it could probably be a problem with an SMD component.
Getting it repaired probably doesn't worth it regarding the cost and the value of the amp (it is a 2nd hand amp)
So I would like to troubleshoot it by myself... if possible. The only problem is that my electronic lessons are very... distant !
That amplifier is still manufactured so it is possible to get spare parts.

Maybe someone could help me to find which component could be responsible of the heat ?

I have a multimeter but that's all...
I also have the full electronic diagrams. Don't know if that could help.
(but of course I am not able to understand them)


Many thanks in advance for your help !

 

[Mooly]

Welcome to diyAudio

We would certainly need to see circuit diagrams in order to advise you...

Given that the amp is working, and given that you say it is Class H (which means the supply rails powering the amp vary) it is a possibility that the heat is being caused by a problem with the supply voltage being stuck at a high level.

Don't be under any illusions about fixing this as it is almost certainly not a quick fix and it would need detailed measurement and testing to diagnose where the issue lies. At the very least you would need to be able to identify parts on the PCB and then be confident to make voltage measurements without shorting anything out.

At this stage it could be anything

 

[Douglas Blake]

Hi everyone.
The heat is generated only on the left side (see the red "circle" on the picture attached), but not enough to activate the protection mechanism.
(but this is probably because I am using it at low levels as it serves in a dedicated home theater room).

You really do need the schematic...

In the mean time, you can remove the cover from the left channel (in the picture) and very gently probe with a gloved finger (for electrical insulation) to see what's getting hot. Once you tie it down to a geographic location on the board, it will be much easier to see the problem on the schematic.

 

[Mark Tillotson]

Being a pro amp it seems to have comprehensive protection circuitry, so its likely to protect itself and your speakers if it does get worse. Could be as simple as bias drift in one of the channels.

 

[Rick PA Stadel]

Indeed, welcome to diyAudio!

I, too, am willing to try to help -- if by "full electronic diagrams" you mean "schematics" -- though I promise that I'm not the sharpest tool in this toolbox!

And don't worry about your English -- its great. Plus, lots of the folks on here are working in 'not their mother tongue', and they write better than many of us with no second language!

That looks like quite an amp. If the schematics accurately include all those 'Txxx's marked on the board topside on the left, and other Test Points similarly provided in the power sections, success might not be completely out of reach. Keep in mind, though, Class H is among the most complex.

Regards,
Rick

 

[aparatusonitus]

RAM AUDIO S-1500 S-2000 S-3000 S-4000 S-6000 S-3004 S-4004 S-4044 S-6004 S-6044 SM Service Manual download, schematics, eeprom, repair info for electronics experts

 

[siocnarf]

Indeed @aparatusonitus, it is that document that I have... thanks for the link!

 

[nigelwright7557]

With no schematic and it not tripping and high cost of repair maybe its best to just use it until it dies ? If it has no fan the maybe leave lid off (if no kids or pets around.)

 

[indianajo]

In addition to class H, this is a switcher supply amp. I see a tiny toroid in the upper right, and a forest of big capacitors, probably 400 v rated.
These are VERY DANGEROUS to work on. Buy a class AB amp of 100 to 300 W and develop your skills on something safer. The category in ebay is "amp for parts or repair" under consumer electronics or musical instruments. Buy something produced before 2000, when switcher supplies & surface mount parts became popular. Or fix or build a mixer, preamp or riaa board, which has pretty safe 15 v supplies.

 

[Mooly]

So...

That is quite a complex amp. Douglas Blake earlier in the thread mentioned:

In the mean time, you can remove the cover from the left channel (in the picture) and very gently probe with a gloved finger (for electrical insulation) to see what's getting hot. Once you tie it down to a geographic location on the board, it will be much easier to see the problem on the schematic.

and given the complexity I think that is is the first thing to do. We have to know which channel is faulty to even begin to advise on further tests and checks.