Tube Amp Archive

Thanks for all the input guys. I had big plans to go through the amp over the weekend, but naturally life got in the way - hopefully will get into it this week. I plan to dissect the PT, but I don't plan on reusing it. RG - first thing I thought of when I rushed the amp outside was your Premier Guit...

Anyone have any ideas of why this might have happened? I'm having a hard time coming up with a plausible scenario. Saw similar in a 60's Fender Bassman head where there was a short in the pilot fixture. Burnt insulation off CT as well as one of the 6.3V leads. I fixed that amp @ 25 years ago, and i...

pdf64 wrote:Maybe there's a power tube short, sending B+ via the heater CT?
Has the B+ been fused?

No - it's a straight clone. Only fuse is a 3 amp on the mains.

That's a good idea - thanks! I'm figuring the PT is gone, but that may show something.

Hi guys. Had a weird situation last night at band rehearsal. We just picked up a keyboard player and he didn't have his amp, so I plugged him into my 5E7 clone. About two hours in, the amp started smoking - smoking enough that I pulled the plug from the wall socket and rushed it outside before it ca...

Good enough for me. I don't see why the electrolyte wouldn't dry out like a normal polarized cap anyway.

Thanks

Hi guys, A friend brought a 73 Fender Rhodes over for repair. I traced the problem back to failure of the voltage converter. The old germanium transistor is dead, so I plan to replace that with a new unit that Vintage Vibe sells for this particular model, and replace all the 40 year old electrolytic...

What's the diff? Bandmaster 5e7 and Super 5f4? The only diff I can spot is the local feedback resistor around the second preamp tube: 10M on Bandmaster, 4M7 on Super. The 5E5 (1x15), 5E7 (3x10), and 5F4 (2x10) circuits are all pretty much the same amps with different speaker configurations and slig...

I've experienced this problem. Basically wanting something between a 6V6 and a 6L6 based amp. The 6L6 doesn't break up at all at band volumes, but the 6V6 breaks up too early. (Especially when you have a drummer trying to outdo John Bonham). Perhaps a 6L6 run at lower voltages. There's no reason yo...

Fixed! :D I ended up disconnecting the OT primaries to test the diodes. They were fine. While I was in there, I tested the OT for shorts and it came up fine. Poked, prodded, cursed, and scratched my head for a while until I was satisfied nothing was hooked up incorrectly, and then went back through ...

The mini-watt has been out of the circuit - the symptoms I'm describing are without the mini-watt. I took it out as soon as I cooked that resistor. But I'll check out the diodes and ditch the bleeder - thanks! BTW - the mini-watt is great for what it is; a small VVR-type circuit to reduce B+ for vol...

I don't know about the rest of you but while I like the safety factor of the light bulb limiter...it has mislead me too many times to trust at full power up. Good for certain things, sure. I still use it for first time startups and questionable older electronics. But when the rubber hits the road I...

Try a new set of output tubes... Swapped in a known good set of output tubes and still have the same symptoms. Ugh...this may be heading toward OT ugliness... :cry: Another thing to consider, the Mini-Watt installation puts a 25µf/500 volt & .047µf/600v filter cap pair in parallel to ground on the ...

Pull all tubes, does the light bulb glow bright (large current draw)? Negative - no glow Now put in the recto tube, does the light bulb glow bright (large current draw)? Negative - no glow. B+ peaks and holds steady at 477vdc. Continue with power tubes and preamp. My guess is you have an issue some...

Hi Chris!

That's the procedure I used at first start up and there were no issues. I didn't go back to that though, after the screw up, so I'll go back and check again.