The Amp Garage

JJ 6V6S could probably take the voltage. Need to disconnect two of the four speakers to increase the load to 8k.

The AB568 schematic shows 465V with a very lossy 5U4GB, so the voltage is a bit too high for 6V6, and it will be even higher with the reduced current draw.

As I've said before, it's best to refer to both a schematic and a layout when building. Unfortunately there isn't a schematic that exactly matches the layout, which makes it tough on the new players. Unless you are live on stage and need to switch into OD + PAB quickly, you might as well keep them s...

OT CT (red wire) is soldered to ground while the blue and brown primaries are tack soldered in to the output tube sockets. I ran the test again and still came out with results like those from the Mojotone OT: ~4 VAC on the secondary, ~44 VAC on the brown and blue primaries. Things were much clearer...

Hook-up seems ok, are you measuring the voltages from the plate leads to the secondary hot?

Yes, Cl = Clean, but the Clean Volume and OD Volume are the level controls at the outputs of the Clean and OD sections, respectively. On the layout, the clean volume is called the Master. I suppose that's because it is in the same location on the panel as the Master in the Master/Ratio system. OD En...

I'm not sure what to make of that. Are you sure you have it connected correctly?

I can think of reasons you might want to do it either way, but maybe it really doesn't matter. In my ODS all of the coax shields are grounded at the front of the chassis.

This NE555-based SMPS circuit has been around for quite some time. You can get a PCB from these folks and put one together, then breadboard your pedal circuit. It includes a 6V regulated supply for heaters, and it will operate on 12V for increased B+. https://frogpedals.com/index.php/product-categor...

Did you settle on a 'magic' hFE for the Q1 & Q2? I have built the Fuller model (other as well), it's nice to have the contour and bias knob in addition to the vol and fuzz. It's that rolled of vol on guitar that killer. For the Fuzz Face I built I followed recommendations from RG and Small Bear, hf...

I have played with that tester and mentioned (somewhere) previously that it can measure leakage current on Ge transistors. It's a handy little gadget in general. Never compared directly with RG's method, so it's nice to hear that they agree. edit: did you find that the leakage-corrected hfe using th...

Matt J wrote: ↑Mon Apr 29, 2024 1:55 am ...should I leave the PI cathode at 470r as on the original 2nd Gen circuits or switch to a 820r PI cathode seen later amps with a full presence control and 12AX7 PI tube?

I'd say for 12AT7 keep the 470R bias resistor.

Quick clarification: I went with the 3 position R/J switch for the PAB center. Is there any modification I need to make there or at the rear panel relay switches for this to work either with the footswitch or without? Dumble did not always wire the Manual PAB switch lugs on the back panel (see #102...

ynor wrote: ↑Sun Apr 28, 2024 3:38 pmI would appreciate if you could check if my voltage readings are as they should be (quality check :)

BTW, with 35 mV on the cathodes your bias is pretty cool at 0.035A X 432V = 15.1W, or just over 50% of max anode dissipation (30W). You could bring that up to 60%, around 42 mV.

ynor wrote: ↑Sun Apr 28, 2024 5:11 pmWonder if the filaments wiring are too close to the board on the left, and if that's what's causing the last remnants of hum?

I doubt it. They are twisted, and that side of the filter board is not sensitive. I suppose you could run the heater leads around the other side of the PT if you want to.