Last night I completely disconnected, cleaned off solder and meticulously rewired all three 9 pin sockets. I made some progress in the voltages but still a few gremlins to deal with.
V1 Pin 1 & 6 is still low. And pins 3 & 8 on V3 have swung the other way. The voltages are now low at 7.8vdc. According to the schematic, they should be about 10x that. I checked it at the single end of the 470ohm that they connect to and the voltage is the same. Checked to the junction of the 470 and 2 1M and there's 0vdc.
Maybe this means something, maybe not. I metered the single ends of the 1M ans the left showed about 6vdc and the right showed 0vdc.
Thinking it might be the tube, I swapped 12ax7s but no change.
Here are the new numbers...I left out the heaters to simplify.
Line=121VAC
F1=468v
F2=465v
F3=430v
Bias after diode -64v
Bias at15K/second filter cap -57.5v
Top of 10K 2W 429vdc
Bottom of 10K, +of 8uf cap, junction of 100Ks 350vdc
Standby switch from pin 8 V6 476vdc
I metered the junction of the two 100K resistors that feed pin 1 and 6 on V1. I get 350vdc. I metered the 100K that connects to pin 6 and it's down from spec at 194vdc but much closer than pin 1. The 100K that feeds pin 1 is at 119vdc. What else could it be but the 100k resistor? It's R meters okay in the circuit but I'm going to pull it, check it and re-solder it. Must be a bad solder joint.
Guitarnut wrote:I metered the junction of the two 100K resistors that feed pin 1 and 6 on V1. I get 350vdc. I metered the 100K that connects to pin 6 and it's down from spec at 194vdc but much closer than pin 1. The 100K that feeds pin 1 is at 119vdc. What else could it be but the 100k resistor? It's R meters okay in the circuit but I'm going to pull it, check it and re-solder it. Must be a bad solder joint.
Peace,
Mark
something is not wired correctly, you are still about 150-160v too high at V3 and the cathode voltage is too low. .Have you tried a different tube at V1?
ToneMerc wrote:
something is not wired correctly, you are still about 150-160v too high at V3 and the cathode voltage is too low. .Have you tried a different tube at V1?
tm
I just tried a different 12ay7 but no change.
Here's how things meter leading up to pins 1 and 6 on the PI.
Peace,
Mark
I'm working on pics and will hve them up in a few.
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ToneMerc wrote:
something is not wired correctly, you are still about 150-160v too high at V3 and the cathode voltage is too low. .Have you tried a different tube at V1?
tm
I just tried a different 12ay7 but no change.
Here's how things meter leading up to pins 1 and 6 on the PI.
Peace,
Mark
I'm working on pics and will hve them up in a few.
you are sure that you have the correct value(470)resistor on the PI cathode?
