The Amp Garage

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...

Spent the morning putting a PT from Mojotone in. Now the B+ is 458vdc in standby. Put it to Operate and saw a MAJOR arc in V8 and inside the amp at the same time. V8 heater opened and evidently shorted to B+. Cut the power immediately. Both 100 ohm heater to ground resistors smoked. Replaced 100 ohm...

Hi Glenn Apologies if this is me being stupid. Given that the #102 is providing 428V with a 340-0-340 @400mA PT isn't it reasonable you'd get the lower B+ reading of 414V from the 320-0-320 @450mA PT in the SSS with the same wall voltage? Could it be the higher 440V reading you noted was taken unde...

I had the same problem in one amp, when inside the box.. chassis and power transformer were extremelly hot.. while outside on the table, chassis and PT temp was just moderate, nothing to worry about... Then i discover that there is no sufficient air circulation in the cabinet, and tubes were heatin...

102 amp is still on, Operate, idle-no input. Transformer is very warm, I can only keep my fingers on it for 2-3 seconds. Similar in temperature to SSS transformer. This is after nearly 4 hours operation.

I just checked voltages on my 102 w/built in Dumbleator that has basically same PT and 6L6 power tubes.

B+ in operate is 428vdc
Power tubes biased to 42mA
Wall voltage 119vac
Secondary voltages in operate 333-67-0-333vac

Hasn't been on long enough for PT to reach stable temperature.

I only have one fuse, 3 amp slow on input power.

In Operate

118vac wall voltage
320-0-322 vac secondary. 320vac leg is also feeding bias circuit.

B+ 414vdc

Bias -360vdc at 5mA

PT's biased to 27mA with -49 volts.

Does anyone know if Heyboer will rewind one of their transformers for a fee? I’m thinking it would probably be cheaper to buy a new one. Interested to know if you find out. I agree it would likely be more. More work because they must remove the old windings and disassemble core prior to winding. I ...