The Amp Garage

Here is a schematic (w/voltages) of one 1983 Marshall 2204 (owned by mhuss) These are typical voltages of a 1983-era 2204 amp --- This does not mean that EVERY 1983 2204 will match these voltages exactly --- this does not mean that EVERY Marshall 2204 ever made will match these voltages (my '79 Mar...

martin manning wrote: ↑Tue Mar 26, 2024 11:14 am

lgehrig4 wrote: ↑Mon Mar 25, 2024 6:43 pmLooking good now! The only questionable reading it V2 pin6 (336), which is approximately 80 higher than the chart. Should I be concerned about this?

That appears to be an error in the voltage table you linked. It should be ~350, same as the B+4 node voltage.

Thank you for clearing that up!

Looking good now! The only questionable reading it V2 pin6 (336), which is approximately 80 higher than the chart. Should I be concerned about this? V1 V2 V3 P1 285 189 251 P2 0 0 28 P3 2.96 1.1 46 P4 - - - P5 - - - P6 248 336 243 P7. 0 189 30 P8 2 190 46 P9 - - - Heaters are 3.3

sluckey wrote: ↑Mon Mar 25, 2024 3:10 pm Voltages will be high until you plug in the power tubes.

Thank you for letting me know! That makes me feel a little better

I started testing the build using a variac. Right now I have preamps installed, but not the power tubes. At 120V there is 362V AC going to the diodes and the reading after the 5th diode (connected to the 220K resistor) is -51V DC. So far does this seem ok? If so, lets jump to the preamps. I don't wa...

Hi! I'm about to order the orange drops for my build and none of these are still available at Mouser. I was wondering if you could take a look at the screenshot and let me know what the best replacement would be? Or perhaps none of these? Disregard the value, I'm just referring to the type. Orange D...

Thank you for all the replies so far!

On a less technical note, what are you Dumble users using for your builds in general? Aside from the few that require 2W+, are you using 1/2W or 1W all around?

Hey! This is more of a general question, but since I'm building a Dumble I wanted to post here. I'm looking at a layout of the smaller boards (Relay, Bias Supply, FET Preamp, etc) and a few resistors specify the wattage (.5W, 2W, 1W), but most do not list the wattage. Is there a default value that i...

Hi, I'll take a 100W set in black if you still have them. White is fine otherwise. PM sent!

Not sure if it was me or the cold solder joints causing the erroneous measurements.

V2
pin7: 29
pin8: 60

Thanks for checking! the cap wasn't touching and those wires with the shrink tube weren't the issue, but when I started smacking the lugs on that pot it started to work!! Looks like it's just cold solder joint!!! That shrink tube really pissed me off because I had cut the wires too short. I'll proba...

I just finished my 5E3 build this weekend. I tested for continuity and the AC voltages voltages are within range. I'm having an issue with the channels. The bright channel volume does not work and the tone pot doesn't have a noticeable effect. The normal volume, however, does work for both channels,...

Just wanted to update this thread. I ended up doing the Bainzy mod on this amp (adding 3rd preamp) and I absolutely love what it did, plus the bonus is that I can switch it off and have a stock plexi as well. Actually 2 bonuses. I had a cap on the bright volume push/pull and I never cared for how it...

I suppose you could do it. It would work as it does in the Chupa if you set your "Normal" gain to minimum . The "Pussy Trim" in the Chupacabra is a 1M pot to ground in place of the 470k Mixing resistor. What about those 68k resistors in the Plexi? Also connect to pin 7? 68k resistors are on the inp...

Roe wrote: ↑Tue Oct 27, 2020 9:44 am not a great idea. just adjust the unused volume of the jmp50 instead, since it affects the voltage divider used on both channels

I'm sorry, but could you provide a little more detail. I don't understand what you mean but I'm curious.