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Old 30th March 2013, 09:27 PM   #1
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Default Elgen Bass amp fault diagnosis

Hi folks,
I'm a new boy so be patient with me please.

I don't know if anyone out there can help with this but I thought it was worth a try.
I have a very rare Elgen bass valve amp that has just started to go bonkers. After switching on and leaving it on standby as usual, flicking the standby off results and a very loud low hum. It's not a high pitched squeal or earth hum, but a very noisy low frequency hum
I can hear my bass playing quietly in the background but the noise is horrendous!

The amp consists of 4 power amp valves and three pre amp valves

I realise it's a long shot that the problem can be correctly diagnosed like this but I'm just curious if it's possible to tell if it sounds like a valve problem or a blown cap

Thanks
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Old 30th March 2013, 09:31 PM   #2
kevinkr is offline kevinkr  United States
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Moved to Instruments and Amps. All musical instrument amp posts whether tube or solid state should be posted to the I&A forum. Please see the directives under each forum header. Thank you.
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Old 30th March 2013, 09:35 PM   #3
kevinkr is offline kevinkr  United States
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Sounds a lot like it might possibly be a power supply problem. (Possibly bad supply cap) In any event unless you can read schematics, understand basic troubleshooting technique, and know how to work safely with the voltages involved this is best left to a qualified service tech. (Note that if you are willing to make an investment in knowledge and the required test equipment we can probably help..)

Do not operate the amplifier in this condition - serious damage could result.
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Old 30th March 2013, 09:46 PM   #4
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Okydoke
Thanks Kevinkr, I am very interested in learning how to service this beasie myself. I do have basic schematic reading skills but I'm not clued up on how to protect myself from the large voltages involved. I think it would be prudent in the long run to be able to keep the thing trucking myself as I intend to use it a lot
Any help in where to start would be very gratefully recieved
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Old 30th March 2013, 10:00 PM   #5
kevinkr is offline kevinkr  United States
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Howdy,
First step is to carefully read this entire thread on high voltage safety: Safety Practices, General and Ultra-High Voltage

Next read this: On Line Tube Learning for newbies....

Then you'll need some basic tools including appropriate screw drivers, needlenose pliers, cutters, wire strippers, a decent solder iron and a digital multimeter or two..

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Old 30th March 2013, 10:03 PM   #6
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Excellent!
I shall do just that...
Just need a decent multimeter
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Old 30th March 2013, 10:18 PM   #7
JMFahey is offline JMFahey  Argentina
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Try to get the schematic.
There are many Tube sites with links to obscure amps.
Happy surfing.
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Old 1st April 2013, 06:13 PM   #8
Enzo is offline Enzo  United States
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And even for a layman, trying a different batch of tubes in it is a good first step.
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Old 3rd April 2013, 12:55 PM   #9
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Thanks for the suggestions

Just an update if anyone is interested. I had to move the amp to do a spot of cleaning and now it works
Do you think it could just be a dry solder or a loose connection?
Can a faulty cap jolt back into life for a short time from just being jiggled?
No wonder Tesla was bonkers
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Old 3rd April 2013, 01:04 PM   #10
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The amp was a custom job BTW so schematics won't exist. It was based on a Marshall amp though.
It was made for Nick Simper (former Deep Purple) who used two Marshall amps. One for top end and one for low end. The amp was built with two input channels.
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