crazy voltages troubleshooting 5E3

[mrtelemon]

hello all, new to this site and hoping someone can shed light on my troubleshooting dillemas.. V2 pin 7 getting 18VDC and pin 8 getting 55VDC...changed bad cap and 1 suspect cold solder joint and thought maybe we had it, but still same readings....any ideas ?? thank you in advance..telemon

[Jazz P Bass]

Do you have a schematic with the pins labeled?
Leo did not see fit to have them labeled.
Anyway, are you refering to the phase inverter half of the 12AX7?

[mrtelemon]

it's a Trinity kit out of Toronto and yes there is a diagram along with a schematic, but I'm not any good reading schematics.. I do know I shouldn't have any voltage on pin 7 and I have close to 20 and where i should have on pin 8 70.5 volts DC i've got 55.. that comes from an orange drop .1uf cap.. i'm lost at this point..

[g1]

Yes there should be voltage on pin 7, what says it should be zero? If the voltage is not shown on the schematic it doesn't mean it is zero. Without knowing what your power supply voltages are it is impossible to say whether the 55V on pin8 is correct or if it should be closer to 70V.
What is the complaint or fault you are trying to fix? Has the amp ever worked properly or is it a new build?
Here is a reissue schematic with some voltages shown: http://support.fender.com/schematics..._schematic.pdf
Once again, if your main voltage coming off the rectifier tube is different, all the voltages will be off a bit.

[mrtelemon]

it is a new build and the plans show the ideal voltages and there should be 0 at V2 pin7 ....Being a newby doesn't help either, but I took my time and double and triple and checked again before laying the solder to anything..i've got back around everything and resoldered hoping I didn't have another cold solder joint as I did find one..I tested 130.0 VAC line, then V1pin 1 143 and it says normal is 120vdc and V2 pin1 I got 181VDC and normal is suppose to be 167VDC..does that tell you anything ?? Thank you..

[cgates56]

These are the voltages on one of my 5e3 builds on V2

Pin 1: 141
Pin 2: 0
Pin 3: 0
Pin 4: Heater
Pin 5: Heater
Pin 6: 175
Pin 7: 15
Pin 8: 40
Pin 9: Heater

And it sounds great

[Jazz P Bass]

What's up with pin 3?
Zero volts?
That can't be correct.

[cgates56]

sorry had the meter on high range reading 1.1 volts

[mrtelemon]

This is the voltage chart that Trinity says we're suppose to have on their kits

V2

pin 1- 120
2-0
3-2
6-123
7-0
8-70.5 V1 pin 8 is suppose to read 2VDC which I'm getting, but V2 pin 7 is suppose to be 0 and like I said i'm getting 20 and pin 8 is suppose to be 70.5 and I'm getting 55....and although it sounds decent....but with 7 being too high and 8 being low I'm thinking one correlates to the utter... !!?? oh the joy of it..

[g1]

That is an error. Pin 7 of v2 is not 0 volts. Contact them. Everyone else that has listed voltages for 5E3 builds shows a voltage at the grid of the phase inverter half of V2.
Try swapping your 12ax7's around, you might get a higher voltage at v2 pin 8 with a different tube.

[mrtelemon]

I'm not sure what you meant by this, "shows a voltage at the grid of the phase inverter half of V2." So what do they show their V2 pin 7 voltages ??? and pin 8? my schematic shows V1 pin 7-0 ....pin 8-2.0......V2 pin 7-0....pin 8 70.5 ...I've swapped out the 12AX7 in V2 for another and it made no diiference...We had a bad reading on the filter cap, replace it, and again made no difference.... i'm about ready to pull my hair out.... But I will send a message to Stephen the owner and ask him about this voltage at pin 7 though....thank you for the heads up on that..

[Enzo]

If the grid of a 12AX7 is at zero volts and the cathode at +70v, that means the tube is biased to 70 volts!!! That would pretty much cut off the tube.

[mrtelemon]

would it make any difference then if the proper voltages that Trinity says I should have for the V1 side is again pin 7 with 0 and pin 8 with 2VDC ??? What are the preamp tubes normally biased to ?? thank you..

[cgates56]

would it make any difference then if the proper voltages that Trinity says I should have for the V1 side is again pin 7 with 0 and pin 8 with 2VDC ??? What are the preamp tubes normally biased to ?? thank you..

what I see is your tube voltages are normal the amp is running as it should, the voltages on your chart are a miss print

[mrtelemon]

Well, I'll get ahold of the company tomorrow for answers and let you know...thank you all..