martin manning wrote:Pin 2 should read zero volts. Definitely a problem there. Look for a solder bridge or strand of wire shorting those two pins.
It was a small solder bridge. I cleaned up the joint on pin 2 and pin 1 is showing same voltage as pin 6 now.
I plugged in all the tubes and did one more check. I have a warm glow on everything but 2 two 12ax7s. They're dark. Proper voltages on 1 & 6, heater voltages are good.
I'm getting discouraged boys. I gotta call it a night.
Thanks again for all the help, I'll take another go at it tomorrow evening.
Reeltarded wrote:Close up picture of what is going on in that part of the amp would be good about now! It's simple. You are really close.
I know but my camera sucks in macro. I haven't figured out how to get sharp images without using the flash which blows out the exposure. I'll try it on a tripod without the flash tomorrow.
The filament glow can be hard to see on some tubes. If you have filament voltage at all of the sockets it may be that there isn't any problem. Put all of the tubes in and get voltage measurements at all of the tube pins so we can see where you are now. Any noise from the speakers? Lots of progress over the last two days...
Okay, here we go...obviously some issues to work out on V1 and V2. Looks like my PT is lagging as well.
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
It does look like something is wrong with pins 3 and 8 on V3, so there is value here. Its probably a good idea to track that down before upping the voltage. Look for a short to B+, or possibly a wiring error. They should be around 40V when you are at full line voltage, maybe 30-ish with the limiter.
martin manning wrote:It does look like something is wrong with pins 3 and 8 on V3, so there is value here. Its probably a good idea to track that down before upping the voltage. Look for a short to B+, or possibly a wiring error. They should be around 40V when you are at full line voltage, maybe 30-ish with the limiter.
Updated my numbers in previous post. I didn't see this post until I checked without the limiter...work can wait.
Definitely a problem on 3 and 8 V3. I'm unsure of 7 and 8 on V2 as well. Will investigate.
All other voltages came up nicely. I can actually smell the tubes burning in now. The PT voltages are back up to spec as well.
martin manning wrote:Where you have no voltage listed above does that mean that you read zero volts at that pin? If so V2 looks ok to me, but V1 and V3 do not.
martin manning wrote:Where you have no voltage listed above does that mean that you read zero volts at that pin? If so V2 looks ok to me, but V1 and V3 do not.
I've looked but can't find a list of the voltages I should be seeing and where. I know they'll vary depending on tubes and trans but is there a list that you know of that shows ballpark pin voltages for this circuit?
