What's wrong with my Hartke amp?

[Gunsfreddy2003]

This amp was working fine until last Friday night, signal cut out, it was really hot and then started making this noise. In the video the volume is turned down to 0 and it still makes the noise.

Any ideas anyone and someone who might be able to repair?[attachment=220896:IMG_1513.MOV]

Edited June 6, 2016 by Gunsfreddy2003

[MoonBassAlpha]

Could be one rail of the power supply gone. Have a look for any fuses internal, mounted on the PCB(S) and see if any have gone.
Usual warnings about poking around inside gear apply - Unplug from mains etc.

[Gunsfreddy2003]

Apologies - the video clip was not playing properly. Will have a look at some of the fuses tomorrow and see if I can see anything obvious.

[Phil Starr]

I couldn't play the clip but something which makes a noise and isn't affected by the volume control sounds like a power supply fault to me too. If the sound is a very loud buzzing I'd suspect the power supply capacitors. If it is you shouldn't mess around with them unless you know what they do. They can give you a nasty shock even with the amp unplugged/switched off.

[paul_5]

[quote name='Phil Starr' timestamp='1465428387' post='3068230']
They can give you a nasty shock even with the amp unplugged/switched off.
[/quote]

This - their job is to store charge until called upon to discharge it. All at once, right up your arm.

Not pleasant.

[Gunsfreddy2003]

Hmm - I don't like the sound of that.

Can anyone recommend a good repairer who might be able to take a look at it?

[Phil Starr]

where in the SW are you? Andy in Axe Music Axminster has a good repair man.

[Gunsfreddy2003]

I have opened up the amp and can't seem to see any fuses on the PCB - happy to be enlightened if anyone can see something that I am missing on the pic!

Where are the power supply capacitors that I need to wary of?



[quote name='MoonBassAlpha' timestamp='1465212811' post='3066109']
Could be one rail of the power supply gone. Have a look for any fuses internal, mounted on the PCB(S) and see if any have gone.
Usual warnings about poking around inside gear apply - Unplug from mains etc.
[/quote]

[Twincam]

[quote name='Gunsfreddy2003' timestamp='1465760767' post='3070822']
I have opened up the amp and can't seem to see any fuses on the PCB - happy to be enlightened if anyone can see something that I am missing on the pic!

Where are the power supply capacitors that I need to wary of?
[/quote]

The caps are the black can looking things and smaller blue ones. But keep away from the large ones.
Is it me or does the resistor between the heatsinks look a little burnt on the board??

Since you didn't know which were the capacitors then I advise you fasten it back up take it too a tech as you really can get hurt.

Edited June 13, 2016 by Twincam

[Gunsfreddy2003]

Yes, I think that is probably the best course of action - I was just hoping for a quick fix I could have done myself.

I'm not sure that the amp is worth spending the money on for any kind of repair to be honest.



[quote name='Twincam' timestamp='1465787584' post='3070949']
The caps are the black can looking things and smaller blue ones. But keep away from the large ones.
Is it me or does the resistor between the heatsinks look a little burnt on the board??

Since you didn't know which were the capacitors then I advise you fasten it back up take it too a tech as you really can get hurt.
[/quote]

[Mottlefeeder]

Amps where the components can be changed are often quite cheap to repair, and parts will be available for many years to come.
More modern class D amps use modules, and will be much more difficult to repair when the manufacturer stops making those modules.

In short, check the cost of repair before binning it.

David

[3below]

[quote name='Twincam' timestamp='1465787584' post='3070949']
The caps are the black can looking things and smaller blue ones. But keep away from the large ones.
Is it me or does the resistor between the heatsinks look a little burnt on the board??

Since you didn't know which were the capacitors then I advise you fasten it back up take it too a tech as you really can get hurt.
[/quote]

+1 and the 2nd resistor above the inductor (greeny-blue coil) on the right hand side above big smoothing capacitors also looks a little 'charred'. (might be shadow in photo though).

The big plus is that your Hartke is traditional discrete components on 'big' PCB. This means repairable at sensible costs. I doubt the components that need replacing cost more than £5, this money will be in labour costs, diagnosis and time.

Edited June 13, 2016 by 3below