Trace Elliot RAH600SMX powersection died?

[DiMarco]

Hi, my big bad dual poweramp TE doesn't make any sound anymore.
I replaced all the fuses in the back to make sure that's not it.

Input leds flash on gain, compressor and EQ have their inpact on the gain leds too so the preamp is alright.
The speaker outputs however are completely silent (not even a slight hiss) it is as if the powersection has switched off.
Both of the two poweramps have gone silent, I am thinking it might be the power transformer has died or something?

The moment it died was when I switched it off. There was a very loud high frequency tone going 'pew' and after that it never made any sound again.

 

Is there anything I can check myself before driving it to a tech?

 

Edited May 29, 2020 by DiMarco
typos

[Merton]

Sounds like one of the capacitors has given up the ghost possibly?

[DiMarco]

I am not sure, but also no expert. What I do know is there's two separate poweramps in there each handling a max. 4ohm load and both are dead. Logic dictates it is unlikely both the poweramps died at the same time and I figure they might not be getting any power anymore. They really are dead silent even at max volume.

Guess I will have an expert look at it along with the Hexa Valve that keeps blowing out its main fuse when using it - that one will most probably need a matched set of six 6550's. I am afraid it's gonna cost me, but these amps are worth it.

 

[Merton]

I wonder if the power supply has separate outputs to the pre and power amps because of voltage/current requirements of each. And it’s something that feeds the power amps that’s died? Certainly the noise suggests a capacitor I think

[DiMarco]

Thank you @Merton. I will convey this when having it checked. I think a proper checkup will be in place anyway with an amplifier this old.

 

[BassmanPaul]

11 hours ago, Merton said:

Sounds like one of the capacitors has given up the ghost possibly?

Unlikely to be either the big bad 'capacitors' or the power transformer. Your amp needs to be diagnosed properly, which won't happen across the internet, to discover what is wrong.

What tools do you have like a scope and Digital multimeter and what skills do you have working with electronics? Do you have the units schematic and if so can your read it?

 

 

Edited May 30, 2020 by BassmanPaul

[Bassybert]

I'd be very wary of poking around inside the power section of an amp unless you know exactly what you're doing. Some of those capacitors can hold 3-400v of DC current. Not something you want to be on the recieving end of!

[BassmanPaul]

In a tube amp you would be correct not so much for SS. Mind you you can get a good burn off them.

BTW it's voltage that caps hold. and some tube amps use upto 800V.

Edited May 30, 2020 by BassmanPaul

[BassmanPaul]

OP Just for laughs and giggles try linking the Send and Return of the Effects Loops with signal cables to see if your problem lies there.

Edited May 30, 2020 by BassmanPaul

[Lfalex v1.1]

One more to check- my SMX developed an issue brought about by the fact that they're modular (inside) by design.

The cable that fed the power stage the signal from the pre had worked it's way off- they're only a push fit

[agedhorse]

7 hours ago, BassmanPaul said:

Unlikely to be either the big bad 'capacitors' or the power transformer. Your amp needs to be diagnosed properly, which won't happen across the internet, to discover what is wrong.

What tools do you have like a scope and Digital multimeter and what skills do you have working with electronics? Do you have the units schematic and if so can your read it?

Thank you Paul for debunking the most commonly accused part that in fact is VERY rarely the problem.

There is a reason why diagnostics are done prior to replacing parts... it's so much more cost effective to identify the part(s) that need replacing before replacing random parts. 

 

 

[Merton]

Thanks to the real experts for pointing @DiMarco in the right direction; there’s a reason I didn’t get very far with electronics 20 years ago so I’ll keep my nose out of this sort of thing from now on

[BassBunny]

This could help.

 

[DiMarco]

Just noticed I posted this in the wrong category. I'm okay with moving the thread to the repairs section.

 

[BassmanPaul]

Hooray ! There's nothing like a good move now and again!!

[DiMarco]

So when the next wage is in I'm calling a nearby tech who also builds his own brand amp and is well known amongst musicians here. He owns a Hexa Valve himself so I guess he is okay to repair mine (it keeps blowing out its main fuse so I expect the 6550's having to be replaced and it sometimes goes silent slowly after a while) and he can also repair this RAH600SMX.

An update: When I route the fxloop1 send to another amp I have sound. In fxloop 2 the send does nothing even when I max out its volume dials on both the front and back of the amp. The Graphic EQ, pre-shapes and gain control are all in working order, but the potmeters will need cleaning as they all crackle while turning them. The dualband compressor does nothing on Effects loop 1 but maybe it is not supposed to.

Next up is testing the three D.I. outputs.

Edited June 1, 2020 by DiMarco

[DiMarco]

PRE-EQ D.I. works. POST EQ ones do not. Something on the stereo circuit board must have burned out. It did die when I had the Bi-amp crossover switched in at the time so this is the prime suspect.

 

 

Edited June 1, 2020 by DiMarco

[DiMarco]

Hi guys, had the amp fixed by a great tech, everything runs smoothly and the amp sounds SO good compared to my class D toys!
The only thing that tops it is my Hexa Valve - that one has even more heft.

Got some JJ ECC83S valves coming in, one will be going into the pre section of this RAH.

Yay!