The Amp Garage

martin manning wrote: ↑Sun Jun 02, 2024 11:51 am I always connect a load when the output tubes are installed. If an oscillation starts, the amp will create its own signal.

Truth. Unfortunately I have a pretty new matched quad of 6L6's with at least one bad tube from this very thing.

Does anyone have an experienced opinion on Jupiter and/or JJ radial electrolytics?

Were the capacitors themselves bad? Or was it just that Fender used the lower temperature 85Degree ones? Admittedly higher ratings are better, but Sprague Atoms are 85°C rated. 85°C = 185°F Actually, Sprague Atoms are commonly only 65°C rated!! Which is complete garbage . . IMG_8138.jpeg Learn some...

When I built my 124 I gave up on finding the proper value axial so went with Nichicon radials from Digikey. I like them but can't give you a comparison to others due to my limited experience.

I used the 2k Dan already suggested from Mouser.

Hello Franco,
Can you describe the amp you wish to set the trimmer on? What kind of power tubes does it have? How many? Do they have 1 ohm resistors installed on the cathode?

What test equipment do you have available?

Been doing some work with this amp today. A while back I robbed the PT from it to replace the one in my SSS. I just received and installed the replacement from Amp Parts Direct. A Heyboer for a Fender 100Watt, but with 320-0-320 vs the 340-0-340 Heyboer from Mojotone that I removed. New voltages: 10...

martin manning wrote: ↑Sun May 26, 2024 4:33 pm

GAStan wrote: ↑Sat May 25, 2024 2:35 amThe bleeder is definitely a good idea.

I made a small tweak to the eyelet board .pdf on this. Increased the current limiter to 47R, and decreased the bleeder to 150k. Should have it drained in a minute or so.

Thanks for the heads up, I'll check it out.

Hope that solves it! The speaker output should be in phase with the PI input. Yours will be the first with the new resistors added to the bipolar supply. I’ll be interested to hear how that works in hardware. It did fix the problem, thanks. The bleeder is definitely a good idea. The +170 volt caps ...

Found a problem. Hopefully the problem. Circled 270k should be 270r. Voltages on V6 are much higher than on Viperdoc's schematic. Will work on this more tomorrow.

I've been working on an oscillation. It's only in the power section, from the PI to speakers. Goes away if feedback from speaker is disconnected. First three of the below are Channel 1: 8 ohm dummy load; Channel 2: PI (V6) Pin 6. 400 hz signal. 8 ohm dummy load. Refer to Viperdoc's schematic . Pic 1...

Completed installation of bipolar power supply. Amp is now working again with better B+ and other voltages. Question: with the decreased voltage the bipolar supply provides V7 does this limit the clean headroom? Volume? Is there a noticeable tonal difference between the original and bipolar supplie...

Completed installation of bipolar power supply. Amp is now working again with better B+ and other voltages. When plugging in 8 ohm dummy load had a déjà vu moment. I used Puretone jacks on the unswitched outputs because they have better contacts than Switchcraft. However they are a little harder to ...

Sockets are how i see new.. and Belton, so means high quality.. Never failed any in my life. So there is only 0.1% of chance that sockets are a problem.. Probably output tubes.. Yes brand new Belton sockets. I found nothing wrong, no signs of tracking and no residual carbon from the resistors that ...

This is bad tube problem.. pls measure resistance directly on the tube pins, between 2-3. Using a Fluke 87 DMM, one tube has no continuity on any pin to any other pin (open heater). The other three only have continuity from pins 2 to 7 (heaters), no other pins have continuity to any other pins. I'm...

Once you have an arc occur there may be carbon tracking on the tube sockets which must be completely removed to prevent more arcing. If the socket material has been burned, replacing the socket may be necessary. So what caused the initial arcing? I think it was most likely an oscillation in the pow...