Tube Amps / Music Electronics
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|12/28/2003 6:02 PM|
||Re: I killed my Traynor - debug help?|
A couple of comments on your last report.
With the tubes out I would have expected the -ve voltages in the bias circuit to be more -ve than shown on the schematic since the power supply is unloaded.
On a similar note, the unloaded B+ around 455V doesn't sound far off. These amps were designed to run a B+ of around 400V with 117VAC and you earlier reported you were at 124VAC, which is about normal these days.
You mentioned the arcing only occurred with your probe on the chassis - what happened with the probe removed? We need to find out for sure if the arcing is inside the tubes or on the socket.
Do you have another set of power tubes to try or access to a tube tester? In an earlier post you mentioned they were glowing red. Depending on how long they were glowing red they may be toast.
Hang in there!
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|12/28/2003 6:20 PM|
The arcing happened only when I flipped the standby to 'operate' mode. If there was no probe attached, it didn't do anything out of the ordinary. But if I turn the amp to standby, and attach the probe, the arcing would occur right when I turn standby off. There were also loud static-ey noises through the speaker.
I have new set of JJ's to put in, but the only thing keeping me back right now is I don't want them to burn or arc. If you recommend just putting them in and crossing my fingers, I'll do it.
Thanks for everything.
|12/28/2003 6:29 PM|
What is this probe you're using and where exactly are you connecting it?
|12/28/2003 6:43 PM|
It's just a standard multimeter that I was using to take voltage measurements. I clip the negative probe to the chassis, and use the postive probe to measure.
|12/29/2003 2:03 AM|
Is it AC powered, and is it rated for these voltages?
|12/29/2003 5:09 AM|
It's powered by a battery cell, but is rated for 500VAC/DC. It is:
I was using it with the tubes in yesterday, only just earlier today was when the sparking problem started.
PS: From the radio shack site:
An economical tester with big features! Measures up to 500 volts DC in four ranges, 500 volts AC in two ranges, DC current to 20mA in three ranges, resistance in five ranges. You also get diode-check to test conductors for opens and shorts. Overload and low-battery indicators. Auto power-off helps save battery. Indoor use only.
|12/29/2003 6:59 PM|
Just about 10 minutes ago I got it working. I lifted the board up trying to look for solder globs or shorts. Didn't find anything real problematic, but I plugged her in, and I heard what sounded like that tremolo noise that the tremolo makes....
...then one of the power tubes flashes blue. I turn it to standby, wait a minute, and turn the standby off. Bright blue coming from the right power tube. I swap them around, and the flash comes from the left tube. I pop in the JJ's, and everything is working.
Well, they're lit really bright, and put off a ton of heat, and I can smell them from about 5 feet away. I need to measure the bias, and probably rebias them. Since it is a fixed bias amp, would it be a candidate for removing the bias resistor, and putting in a bias pot? I'm not even sure which resistor it would be, probably R36 (1M).
But all else is good. The new speaker, Eminence GB12, is a lot louder at low volumes. I have not had a chance to crank it yet. I still have the old caps in; I'll wait until after I get to really use the amp for a few days before attempting this.
Thank you everyone for all your help. It was of utmost importance.
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