Do these voltages look correct?

[Charvel_King]

Just measured all the voltages in my 2204 clone, JCM800 2204 i should mention, before i go ahead and wack in an FX loop.

I will say it is very lightly modded, changes made are:

V1a cathod resistor changed to 2K2
V1b cathod resistor is stock with 2K7/.68uf
V2a cathod resistor 820 ohm bypassed with .68uf cap
PI fizz cap increased to 100pf
Used a 32uf+32uf can cap for pre-amp filtering (although i have seen both 47+47 and 32+32, so i went with the lower)
Added depth knob control.

Other than that it is to Marshall spec.

Anyway most of the voltages look okay looking on the Marshall date sheet. My HT/B+ is a bit higher, i think, but then again i have 245VAC at the mains coming in so that might infulence it. Alsp, heater voltage is a tad low, typically is somewhere around 3.15 ish..

Anyway, the numbers:

V1

1) 105.3v
2) /
3) 4.49v
4) 2.9v
5) 2.9v
6) 117v
7) /
8) 5.23
9) 2.9

V2

1) 167.4v
2) /
3) 1.16v
4) 2.9v
5) 2.9v
6) 312v
7) 169.3
8) 174.6
9) 2.9

V3

1) 248v
2) /
3) 42.4v
4) 2.9v
5) 2.9v
6) 223v
7) /
8) 42.5
9) 2.9

V4

1) /
2) 2.9v
3) 487v
4) 486v
5) -48.3v
6) 488v
7) 2.9v
8) /

V5

1) /
2) 2.9v
3) 489v
4) 485v
5) -49.8v
6) 486v
7) 2.9v
8) /

What do you'll think?

 

[FourT6and2]

From the data sheet I have, your measurements are a bit off (but not by much). But I'm looking at a stock JCM800. Turn the thing on and see if it works?

In order from Pin 1 to pin 8/9:

V1:
217
Signal
2
3.15 AC
3.15 AC
260
Signal
3
3.15 AC

V2:
168
Signal
1.1
3.15 AC
3.15 AC
302
168
170
3.15 AC

V3:
218
28
42
3.15 AC
3.15
214
28
42
3.15

V4-V5
0
3.15
485
476
-45
480
3.15
0

 

[Charvel_King]

From the data sheet I have, your measurements are a bit off (but not by much). But I'm looking at a stock JCM800. Turn the thing on and see if it works?

In order from Pin 1 to pin 8/9:

V1:
217
Signal
2
3.15 AC
3.15 AC
260
Signal
3
3.15 AC

V2:
168
Signal
1.1
3.15 AC
3.15 AC
302
168
170
3.15 AC

V3:
218
28
42
3.15 AC
3.15
214
28
42
3.15

V4-V5
0
3.15
485
476
-45
480
3.15
0

Beleive me, it does work. It sounds great, just like a 2204 should sound. I was just taking measurments now so once i have put in the FX loop and can make sure they haven't driftef to much.

Yeah my V1a and V1b plate voltages are quite low, pins 1 & 6. Not sure why that is. Other than that its not too far out.