No sound from 18 watt TMB

[lpresnall]

I'll get the rest of the readings tonite, but the AC voltage at the rec is:

Across 1 and 7 with tube 6.8VAC
Pin 3 10.1VAC

Across 1 and 7 no tube .08VAC

Pic of board:

[Firestorm]

This is a 6CA4 right? Something screwy with those readings.

[Phil_S]

Let us have a picture of the whole inside of the chassis, not just the board.
Show us a close up of the rectifier socket wiring. Then I suggest you divide the inside into 3 sections and show us close ups of them.

It is really hard to help someone when you don't have the amp. We depend on the pictures. The sooner you post them, the sooner you'll get responses.

I only see two filter caps, the big blue one and the grey one in the middle of the board. Where are the other two?

Did you run any wires on the underside of the board? If so, tell us where if you can. In particular, I don't see how you wired the + side of the big blue cap. I see a from the top side of the board, black wire>resistor>blue cap+>nothing!

We should see: wire from rectifier pin 3>cap>2.2K>cap>8.2K>cap>2.2K>cap. We want DC voltage readings (referenced to chassis ground) where you see the ">". If your string of components is different, tell us what you used.

You are fortunate to have caught Firestorm's interest here. He knows more than I do Since I won't be here for a couple of days, I'm going to make a graceful exit sometime this evening (EST).

[lpresnall]

DC Volts at V4 and V5 are:

V4 Pin 2 34.8, Pin 3 30.9
V5 Pin 2 31.3 Pin 3 31.2

[lpresnall]

I only see two filter caps, the big blue one and the grey one in the middle of the board. Where are the other two?

Did you run any wires on the underside of the board? If so, tell us where if you can. In particular, I don't see how you wired the + side of the big blue cap. I see a from the top side of the board, black wire>resistor>blue cap+>nothing!

We should see: wire from rectifier pin 3>cap>2.2K>cap>8.2K>cap>2.2K>cap. We want DC voltage readings (referenced to chassis ground) where you see the ">". If your string of components is different, tell us what you used.

Phil, here's the layout I used. There is underboard wiring from "big blue" and parts east.

[lpresnall]

Here also is a sketch of what I've actually done. I'm checking against the layout and schematic now:

[Firestorm]

It almost looks like you have rd/yl and gr/yl going to a positive terminal on the can cap. You didn't do that did you? A photo of that area of the power supply would help.

[mark enger]

Make sure ez81 is working, pin1 and 7 should be 300 vac, set meter to AC
or about 600 volt across both pins 1 and 7, can you confirm? if not fix your powertranys wiring mark

[lpresnall]

Red/Yellow and Green/Yellow are going to the star ground at the transformer bolt. The bare ground from the transformer bolt is going to the single lug on the can cap. Pic:

[lpresnall]

Just realized that pic is pretty poor. Here's a better try. iPad is lacking - if this one isn't clear I'll resort to actual camera:

[mark enger]

what about the ez81 is it getting AC voltage and turning it into DC? mark

[lpresnall]

I'll check Mark. Will post back here in a bit. By the way, you guys are awesome! I can't wait til I know what I'm doing...

[Phil_S]

if you want the best help, clear pictures are essential. I think you should use a real camera. New cell phones generally have good cameras, but they don't zoom as neatly as a regular digital camera.

I am urging you to stop doing this piecemeal. Take all the pictures, hi res pictures. Make sure they are clear and have good contrast. Take your time. Be thorough. We will be here, and so will your amp. We need to be able to see the tube socket wiring on the rectifier. Try an angle instead of directly overhead., maybe one from each side. Give us one comprehensive shot including everything. We need that for orientation or we have to guess what is where. Then 3 or 4 or more closeups showing 1/4 or 1/3 of what is inside the chassis. It's OK to tilt the camera if it captures something of note. Include whatever else others asked for.

Get us the DC voltage (B+) at the 4 filter cap nodes. Clip your ground probe to the chassis. There is a nice bit of naked wire running to your chassis ground point and that is a nice spot to clip onto if you can. Probe with the red to each + in the can cap, and the + side of the blue cap, and the larger grey cap. This should take you a minute or two. It's quick. You'll spend more time getting the photos done.

To check AC voltage from the transformer, use the two lugs on the terminal strip to get a reading. That is an unencumbered spot and tells us what we need to know, with tube and without. This is the only place you are checking AC voltage. The rest is DC, with the black probe to the chassis.

You followed the Ceriatone layout? Does that mean the resistor between the two terminals on the can cap is 1.5K? We need to know to calculate current draw.

The empty hole near the rectifier is meant for your chassis ground. Use of a transformer bolt is not advised. You can move this later. You have other work to do first.

Do what you need to. Post it all at once. Good luck. I see others are here to help.

[mark enger]

I've built a bunch ceriatone tmb

[lpresnall]

Good points, all, Phil! I'm getting ahead of myself here and your reminder that it'll all still be here later is welcome. I'll get the pix tonite if possible and post. Thanks again to everyone in the thread.