Can I enlist a little help, crackle in valve amp

toms wait

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Toying with changing my amp! Again more times than forrest saw presidents!
Mastersound Duetrenta a possibility or Norma. Both with internal phono stage.
Totally different to each other.
Will most likely have changed my mind again by the morning!
 

slavedata

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"This is now a slight fizzing with the occasional pop.
Completely random and only on the left channel.
It is inside the amplifier, too low level and random to be interference from anything."

This is classic for Output stage valves starting to fail. I know because I've had a valve amplifier for 20 years. Next time you hear it have a good squint at the output valves. You will probably see a plate in the valve ( not the heater element) glowing red.
 
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toms wait

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I thought that. I have swapped channels for the output valves and it stayed in the left.
Also I swapped in a whole new set and it was the same intensity, randomness and in the left.
Also these valves are all relatively new supposedly bulletproof ex-military types.
 

toms wait

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Since putting this up and doing a little cleaning it has miraculously almost nearly but not quite stopped until it gets real hot. until you put music through it.
The power of the wam post!
Now my excuse for a new amplifier has evaporated, bugger I knew that were going to 'appen
 
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rabski

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There are still potentially different causes here. It's perfectly possible that it's a poor contact between a valve and its socket, so some further cleaning won't hurt. I'd personally avoid any of the liquid contact cleaners, as some seem to leave a residue and I'm far from convinced they do a perfect job. Good old-fashioned fine sandpaper on the valve pins, then plug and unplug a few times, carefully moving each valve around in the socket a little.

If the removing, cleaning and reinserting has changed the problem, it's still possible there is a poor solder joint on one valve socket, or a failing component soldered to it.
 

toms wait

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The amp has been on all day playing, and in the last 10 mins has started to fizz/crackle!
That really is intermittent!
 

toms wait

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Good news, no crackle, bad news no music.
Left channel completely packed in all of a sudden.
Some checking and looking for blown up things is in order!
 

Juancho

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If not an obvious blow up do all thye valves still light up? To stick to no risk testing you could test those pcb tracks with a multimeter. But now very easy for someone used to high voltage testing to check with multimeter and /or scope. Much better than an intermittent fault!
 

rabski

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But now very easy for someone used to high voltage testing to check with multimeter and /or scope. Much better than an intermittent fault!
Definitely.

A 'no sound at all' problem is almost always easy to sort out. An intermittent noise is everyone's worse nightmare.
 

myles

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Definitely.

A 'no sound at all' problem is almost always easy to sort out. An intermittent noise is everyone's worse nightmare.
Every intermittent fault I experienced in comms reared its ugly head after midnight - never in the day when we were flush with manpower.
 
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toms wait

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Do you want to fix this david?
Or should I go to Kevin's in trepidation of an empty bank account!
 

toms wait

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If not an obvious blow up do all thye valves still light up? To stick to no risk testing you could test those pcb tracks with a multimeter. But now very easy for someone used to high voltage testing to check with multimeter and /or scope. Much better than an intermittent fault!
The valves didn't change and there was no pop or bang.
Still might be time to retire the old dear!
 

toms wait

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Fixed! for the present.
The left signal valve had a broken connection, the pin that links across to an opposite pin.
Also the circuit board had a broken section at one of the resistors on the power supply board.
Playing now, bit early to tell if we still have the fizz!
 

DiggyGun

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Fixed! for the present.
The left signal valve had a broken connection, the pin that links across to an opposite pin.
Also the circuit board had a broken section at one of the resistors on the power supply board.
Playing now, bit early to tell if we still have the fizz!

Hopefully, that has also sorted out your earlier issues.

Keep us informed.

DG…
 
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toms wait

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No fizz playing happily now, but, going to retire it off to the loft!

Expecting a shiny new Triode Corporation 300b integrated on Wednesday.
20w/channel SET, never heard nor had such a thing.
 

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