Trace Elliot commando problems

[Twincam]

Bought a very cheap te combo a 100 at the guys house seemed ok. But now when I switch it on it has a little noise a little static and when I turn it off it doesn't half go pop! Not sure if it's the amp or speaker doing it!.
Also when I turn it off it takes ages and I mean ages to turn off like its holding power.
I've taken the head out. And can see no issues caps all look fine and it seems visually in good nik.

So what could this pop and holding power issue be? I've educated myself on old valve amps but don't really know that much about newer amps.

[Chienmortbb]

Many Amps in those days had the turn on/off thump. It is caused by one of the voltage rails rising or falling faster than the other. Contrary to what many people say it does not damage the speaker.

The noise probanly comes from the controls. They need to be cleaned with a good switch cleaner, preferably deoxit. It is the most expensive but it is the only one that works long term.

The other alternative is to replace the control pots themselves. If you can use conductive plastic ones as the last much longer.

Of course these are general statements and may not apply to your amp. If anyone has precise knowledge of the Commando, please chip in,

[rmorris]

[quote name='Chienmortbb' timestamp='1450437178' post='2932759']
Many Amps in those days had the turn on/off thump. It is caused by one of the voltage rails rising or falling faster than the other. Contrary to what many people say it does not damage the speaker.

The noise probanly comes from the controls. They need to be cleaned with a good switch cleaner, preferably deoxit. It is the most expensive but it is the only one that works long term.

The other alternative is to replace the control pots themselves. If you can use conductive plastic ones as the last much longer.

[/quote]

+1 The Caig DeOxit stuff is the stuff to use. Look through the product range as they have some specific products for pots etc. Of course you have to be able to get to the pots first !
yeah - if replacing CP pots are preferable though not cheap.

On the popping - how old is the amp ? Have another look round the caps for any sign of heat - scorching etc - or for misshaped resistors. Might be worth changing electrolytic caps in any case as they are generally the components that deteriorate most quicly with heat / time.

[icastle]

I don't know that amp specifically, but a lot of amps from that era had a capacitor soldered to the back of the mains switch.

If yours has this then change it.
It's a simple thing to do and the caps are cheap enough to make it a worthwhile punt.

[Twincam]

[quote name='icastle' timestamp='1450460808' post='2933139']
I don't know that amp specifically, but a lot of amps from that era had a capacitor soldered to the back of the mains switch.

If yours has this then change it.
It's a simple thing to do and the caps are cheap enough to make it a worthwhile punt.
[/quote]

It Does have two green packet things soldered onto the switch I assume these are some sort of caps? No value on them. So really unsure about them if they had a value I would replace them.

On the switching off thud this isn't a thud it's a loud bang/pop so I turn it down before I switch off issue solved.

I checked the caps and resistors and zero signs of any damage at all.

Amp sounds great really liking it, shame about the noise. it's useable for now though and not as bad as some old valve amps I've had.

[icastle]

[quote name='Twincam' timestamp='1450470485' post='2933231']


It Does have two green packet things soldered onto the switch I assume these are some sort of caps? No value on them. So really unsure about them if they had a value I would replace them.

On the switching off thud this isn't a thud it's a loud bang/pop so I turn it down before I switch off issue solved.

I checked the caps and resistors and zero signs of any damage at all.

Amp sounds great really liking it, shame about the noise. it's useable for now though and not as bad as some old valve amps I've had.
[/quote]


Aha!

Those green packet things are capacitors.

You can't verify their effectiveness by just looking at them though.
They act as a, somewhat crude, thud supressor.

On the side of them there will be some numbers and a letter... something like 104K.

Tell me what's written there and I'll tell you what value you're looking for.

[project_c]

can't offer much technical insight, but I have a Commando which pops in the same way, but if I turn the volume off it stops doing it, and it's never caused any damage.

[yustech]

I done some repairs on a few of Commando 15 in the past.Each having blown the power transistors plus a couple of resistors etc(can't remember the exact BOM).Within a couple years they end up coming back with the same problem.Was it because I didn't change enough components than I should or the circuit design was flawed.I begin to suspect the latter but I don't know.I just repair them or at least tried to.Hehe..