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Hey guys, I'm almost done with my TC-15 build but I've got some incorrect voltages. For the rectifier voltage (without the rectifier installed) the spec sheet says pin 8 should be 298VAC, but I'm only getting around 5-10 volts and 0 volts when on standby. I've checked my wiring for this part and everything looks good. I just want to confirm that the 298VAC is without the tube installed.

Thanks,
Mac

P.S. I'm using Trinity Transformers and the latest turret board layout.

That's correct, you would be getting 290V AC.

Post some pics

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Thanks for the help, here's my voltages (Power ON, Standby OFF): on Pins 4 & 6: 323VAC, Pins 2 & 8 start around 7.7VAC, but then slowly drop down to about 2.8VAC

Pics (I can post more):

Wiring of the tube looks fine.

Check to see if your getting any voltages from the secondary of the transformer. Do you read 6.3V AC across the green heater wires?

If you don't then something is wrong with the primary wiring of the transformer.
Do you have a fuse in?
Does the indicator light come on?
Have you double checked the wiring of your IEC socket, fuse, indicator light and 117-0-117-0 wires on the transformer?

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Yes, I'm getting 6.7VAC across the green heater wires

Yes, I have a 2A slow blow fuse installed
Yes, the indicator light comes on
Yes, I've double checked the IEC wiring

Could it be a problem with the large capacitor in my 3rd pic?


(Thanks for taking the time to help!)

No that's not the issue

Just reread your post

With no tube installed you should read 5V AC on pin 8. With a tube installed you should read the B+ voltage which is 300V-400V DC.

As long as pins 8 and 2 have 5V AC across them and pins 4 and 6 have 600V AC across them I'd say install the tube and move on with the next step.

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Thanks for all the help. I ended up installing the rectifier (which gave me some pretty high voltages on the rectifier pins, but I got the right B+ voltage at the capacitor. Then I checked the voltages on the tube sockets, some of them were signtificantly higher than what they're supposed to be. After double checking my wiring, I ended up just saying to heck with it and plugging the tubes in. Everything worked great and it sounds amazing. Nothings blown up, burned up, or red-plated, so i think everything's good.

Good news. In the manual on start up procedure it says

Check the plate voltages on the tube sockets. Measure from pin to Chassis ground.
12AX7, AY7, AT7 etc plates are pins 1 and 6; EL84 plate is pin 7 and 6V6, 6L6, KT66, EL34 etc plate is pin 8. The plate voltages will be slightly higher than the voltages listed on the schematic because there is no load provided by the tubes. .

That explains the high voltages.

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Stephen
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