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Post subject: Hot Rod Troubleshooting - Any help appreciated
Posted: Thu Nov 13, 2014 2:18 am
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Hi.

Picked up a used HRD today. Knew it needed attention but hoped it was just bad / worn valves.

Tried to set the bias but it wouldn't give a sensible reading: just '1'. Did notice the bias wheel was nearly all the way up though.

As you look at the amp from the back the left power tube has a faulty / intermittent connection but can be 'wiggled' such that it lights up. But as soon as you take it off standby, the right tube glows VERY bright orange. Enough that you want to knock the power off asap.

If it matters, the only date I can find is 2002. It's a chrome panel one. The amp does 'work' so to speak but sounds bad.

Thanks folks.


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Post subject: Re: Hot Rod Troubleshooting - Any help appreciated
Posted: Thu Nov 13, 2014 3:38 am
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Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
Where do you read " 1 " ? One (1 ) what ? DC volts

At TP 38 ?

Do you use schematic ?

Your bias is a way toooo hot or 6L6s tubes are short .

Remove 6L6s , plug your meter to pin 5 , you know how to read pins number on the socket and to use voltmeter ?


Power amp ON
Your meter should read between -35 to -50 volts DC or close if you turn bais pot.
If no reading , you have something wrong in bias circuit .

if yes , leave the bias pot at maximum negative DC volts. This is a cold bias and tubes should be glow normal ,not red orange .

If not , tubes look short or something broken on circuit feeding 6L6.

Good luck


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Post subject: Re: Hot Rod Troubleshooting - Any help appreciated
Posted: Thu Nov 13, 2014 1:59 pm
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Hi.

Thank you for that detailed reply. Confess I'm feeling out of my depth here and might just have to hand this over to a technician. I only managed the bias test because I'd watched a YouTube video on the subject. Even then I had the wife on stand-by (a nurse) in case I blew myself up. :-(

I did think I might just put new valves in and see how it goes but am now reluctant in case there's a fault and they get damaged as a result.

Thank you again. Much appreciated.

Molly.


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Post subject: Re: Hot Rod Troubleshooting - Any help appreciated
Posted: Thu Nov 13, 2014 2:08 pm
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
You are welcome

Molly :D


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Post subject: Re: Hot Rod Troubleshooting - Any help appreciated
Posted: Mon Nov 17, 2014 1:57 pm
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Could be bad solder joints on the tube sockets. An easy fix. If it's an 02, I'd look at a cap job too.

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