I'm in the troubleshooting phase of building a GGG Fuzz Face, early 70's, and am baffled as to what the issue is. Here is the layout (https://generalguitargadgets.com/pdf/ggg_ff5_lo_b70.pdf), here is the schematic (https://generalguitargadgets.com/pdf/ggg_ff5_sc_b70.pdf). Clean works fine, but with the fuzz on, output is very quiet, with minimal fuzz. I've reflowed all of the solder, double checked all of the parts, and can't find the issue. I see that my transistor leg reads are wrong.
Q1
E: 0 (should be 0)
B: 4.8V (should be 0.6V)
C: 5.4V (should be 1.4V)
Q2
E: 0.7V (should be 0.8V)
B: 5.4V (should be 1.4V)
C: 6.0V (should be 4.5V)
The Q1 collector and Q2 base are directly connected, hence them both being wrong. R2 is in place and I can read that its resistance is correct, but I'm still seeing 5.4V at the lower leg of R2, way above the Q1C and Q2B numbers I should see. On the Q2 collector side, I show the R5 upper leg to Q2 collector is 6k of resistance, as it should be. Any help is appreciated!
I should note that I added all of the optional parts, with the exception of D3, which I removed to increase the volume.
I'm pretty sure you have a pin out issue.
What you have as the collector is probably the base.
The common pin outs (viewed from the bottom) are
\e b c / us
\c b e / eu
\e c b/ jp
Putting a jp pinout in a board intended for us or eu would show what you are seeing.
In short just check the pinout and the rest will follow.
There may be errors even in connections that you have made correctly dozens of times. And at some point you did it automatically, on autopilot, and soldered two connections the wrong way around. It happens. And sometimes you have to check each connection.
The C and E are in the wrong location on the schematic, which screwed me up. Rob Strand, you are a sanity saver! Thanks!
Quote from: Juan1 on September 23, 2024, 09:26:31 PMThe C and E are in the wrong location on the schematic, which screwed me up. Rob Strand, you are a sanity saver! Thanks!
I'm still not sure what is going on :icon_mrgreen:
The schematic looks good to me!!!
I was twisting things around in my head and I came to the conclusion that if you used PNP transistors instead of NPN transistors you could get voltages like you measured.
I'm going to ask a stupid question. What transistors are you actually using? What is actually marked on the body of the device themselves?
I'm with Rob here, you may have PNP devices and not NPN. PNP devices would show voltages similar to what you are reporting.
Came with the kit:
2N 5088 241
CEN 2N 3904
CEN 2N 3906
Found happiness with:
Q1: BC109C - Emitter tab facing the E on the wiring diagram.
Q2: 980 M9093 7302 - Emitter tab facing the C on the diagram. Don't remember where I got the transistor.
Quote from: Juan1 on September 25, 2024, 10:55:54 AMFound happiness with:
Q1: BC109C - Emitter tab facing the E on the wiring diagram.
That makes sense.
bottom view
\e b c / us 2N3904
\c b e / eu BC109C
\e c b/ jp
So in order for the BC109C to be placed as c to c, b to b, e to e it will look physically reversed in the PCB.
QuoteQ2: 980 M9093 7302 - Emitter tab facing the C on the diagram. Don't remember where I got the transistor.
I'm assuming you mean the layout diagram and not the schematic.
Really we need c to c, b to b, e to e regardless of the what the pinout is. But wiring E to C would mean you either have the E/B/C misidentified on the actual part, or, the part has e & c flipped. Transistors will work with e and c flipped but the hFE (DC gain) is much lower and the DC voltages might be affected (I would need to check by how much).