JerryFJA wrote:No loop on the Butcher. The most common problem with those is the ribbon cable connecting the power tube board to the main board burns up. Look for burn spots on the cable connectors. Do the power tubes heat up? If the cable is bad they usually don't. Check all the fuses on the power supply board too.
Jerry
the ribbon cables go from the input/control board to the preamp board. i checked them and they all appear fine and pass signal.
the connections from preamp to poweramp board is just heavy gauge wire, which passes signal fine as well.
Power tubes all heat up and the fuses are fine. thats why i'm thinking it is something earlier on/not power section related.
going to try testing the voltages on the preamp pins tomorrow when i get off work.
thanks for the advice. and the "SC" stands for Santa Cruz. too long of a trek for an angry family member.
while probing around and listening to ticks and pops i found several instances.
a few pins on the PI gave light pops and noises when touched. but the most response i got was from pin 6 on the first preamp tube (V5 on the schematic). it gave off a fairly loud scratch/pop sound.
Hmm.. hey man I don't think your input is wired correctly or something. You are getting some kind of signal on the plates..
What about on the board? Did you notice any place on the signal path where something changed? The signal near the input should be louder when probed because there is amplification of that signal downline.
What about the grids? pins 2 and 7. I am worn out so I can't think of anything else right now.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
BenSC wrote:while probing around and listening to ticks and pops i found several instances.
a few pins on the PI gave light pops and noises when touched. but the most response i got was from pin 6 on the first preamp tube (V5 on the schematic). it gave off a fairly loud scratch/pop sound.
does this sound like it could be the culprit?
Getting the voltages as described above is to confirm that power is being delivered to the tubes and that they are at a reasonable idle operating point. If that all checks out then the problem is likely a break in the signal path, or the signal is being grounded out somewhere.
The pop from pin 6 says that the signal path is working from that point on. I'm beginning to think that there is a break in the cable that connects the input jacks to the main board (if I'm understanding the layout correctly sight-unseen). Plug a guitar cable into the high input (leaving the other end hanging) and see if you get a pop from any of the other pins on V5. The cable will open the grounding contacts on the input.
Reeltarded wrote:
What about on the board? Did you notice any place on the signal path where something changed? The signal near the input should be louder when probed because there is amplification of that signal downline.
What about the grids? pins 2 and 7. .
Places on the signal path where something take place where something directly related to the previously mentioned pins are probed.
on V6 and V7 (according to the schematic) pin 2 produces noise, a light tap on V7 (PI tube) and a larger scratchy pop on V6. Both pin 7s produce a faint noise when probed. V6 and V7 differ from V5 (the first tube in the signal path) in which pins 2 and 7 produce no sound.
martin manning wrote:
Getting the voltages as described above is to confirm that power is being delivered to the tubes and that they are at a reasonable idle operating point. If that all checks out then the problem is likely a break in the signal path, or the signal is being grounded out somewhere.
The pop from pin 6 says that the signal path is working from that point on. I'm beginning to think that there is a break in the cable that connects the input jacks to the main board (if I'm understanding the layout correctly sight-unseen). Plug a guitar cable into the high input (leaving the other end hanging) and see if you get a pop from any of the other pins on V5. The cable will open the grounding contacts on the input.
Plugging a guitar cable in didn't seem to make a difference.
i tried to get the voltages, but i don't have an alligator clip to properly ground one of my probes on my multimeter to one of the grounding points on the board. would grounding it to the chassis be sufficient?
If you still don't get any pop from the other pins with the guitar cable plugged into the high input (that cascades the two triodes in V5), then that reinforces the idea that the problem is in or just before the second gain stage. Chassis ground should be fine for getting the voltages.
i'm not sure what to make of the voltage readings i got (and there is a distinct possibility that i fucked up, never having done it before).
But the DC voltages in V5 were extremely low, and the the DC voltages in V7 were so high they were unreadable by my multimeter. and V6 gace a mixture of low and too high.
martin manning wrote:Measure the DC voltage at the positive end of C2 and C7 and see what you get.
they both read 340 VDC.
Ok now we are getting somewhere. This says that V5 is not drawing any current, otherwise there would be a voltage drop from C7 to C2, going across R14.
Measure the voltage at both ends of plate resistors R13 and R10.
Check the voltage at the positive ends of C8 and C13, and both ends of R29. That will tell you if the other preamp tubes are drawing current and how much. It would be best to remeasure the voltages at the positive end of C2 and C7 at the same time, since your line (wall) voltage may be different.
Are the preamp tube filaments glowing? Check AC voltage across pins 4/5 (they are joined) and pin 9 on V5, V6, and V7.
You are getting some inconsistent results. 475 VDC is reasonably close to the schematic value for B+, but some of the other readings seem strange. Are you sure your meter is working? Changed the battery lately? What VAC do you get if you measure the incoming line voltage directly across the hot and neutral?
