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 kunalraiker

Valve amp loosing channel

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I seem to have an issue with the amp phasing out one channel intermittently and the getting it back.

Would it be th valves. If so whether it will be the driver or power tubes.

The stepped attenuator also has noise when changing volume.

Sometimes hen I completely cut sound, there seems to be a discharge of volume into a channel.

I have a de-oxidising spray, should I spray it on the attenuator?

Edited by jojo

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Would it be th[e] valves. If so whether it will be the driver or power tubes..

It seems to be your keyboard.  :)

 

We're rather short of details - how old is the equipment, how many hours, what equipment?  

 

Is it P2P or PCB based?    There's so many things that could cause it - dirty RCA/speaker connectors (common if cables are rarely unplugged); failing cables (common if cables are regularly unplugged) ; valves with dirty or loose pins;  dry joints in PCBs.   All before we get to actual component faults.

 

On your stepped attenuator, without any knowledge of the switch architecture, also can't help much.   Could be dirty contacts, could be any of the faults above.  

Edited by thoglette

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Could be a number of things, bad tube in phase splitter if present, bad valves, bias problem etc. Seems the problem disappears as soon as the amp gets hot enough.

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Opposite to what I had, mine was OK for about an hour then I'd lose one channel, when I swapped the splitter valves the fault moved with the valve, great news NOS Mullard 6922s fitted and sounded better than ever.

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May be its not the valves, as the stepped attenuator gets noisy as I click through the volume and one channel  -  the right one phases to a lower volume.

Gets stable about 15 mins into music listening.

 

The DIYers could probably chime in, as they might know the cause of this behavior.

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Just a guess on my part, but I might suspect a "dry" solder joint, possibly in the stepped attenuator.

Since there may well be dangerous voltages present within your amplifier even when turned off, I would respectfully suggest that you have it checked by a competent professional familiar with valve audio equipment.

Depending on your location, one of the forum sponsors such as Earle Weston or Goldenage Audio, may be able to assist.

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Just a guess on my part, but I might suspect a "dry" solder joint, possibly in the stepped attenuator.

Since there may well be dangerous voltages present within your amplifier even when turned off, I would respectfully suggest that you have it checked by a competent professional familiar with valve audio equipment.

Depending on your location, one of the forum sponsors such as Earle Weston or Goldenage Audio, may be able to assist.

Thanks, although the issue is not bothering me as much.

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If it's a switched attenuator, then the Deoxit mini-spray is the product for metal contacts.:

http://www.jaycar.com.au/productView.asp?ID=NS1434&w=deoxit&form=KEYWORD

 

Caig have different product for wiper pots & conductive track faders.

 

That should fix the switch noise (crackle, popping etc).

 

The 'fading' symptom however, i would not normally associate with a resistor attenuator.

Do you have replacement valves to swap-in, one by one, to check if it's a valve issue?

 

Cheers, Owen

Dark Lantern blog - http://darklanternforowen.wordpress.com/

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If it's a switched attenuator, then the Deoxit mini-spray is the product for metal contacts.:

http://www.jaycar.com.au/productView.asp?ID=NS1434&w=deoxit&form=KEYWORD

 

Caig have different product for wiper pots & conductive track faders.

 

That should fix the switch noise (crackle, popping etc).

 

The 'fading' symptom however, i would not normally associate with a resistor attenuator.

Do you have replacement valves to swap-in, one by one, to check if it's a valve issue?

 

Cheers, Owen

Dark Lantern blog - http://darklanternforowen.wordpress.com/

I might do that, swapping the tubes around and seeing if the problems moves to the left channel.

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