No sound, no tubes lighting up - did resistance checks

[Paul Birkeland]

The 12AU7 looks like it's lighting up well.

For your connections to the power transformer, wrap the wires around the top of the terminal.  That will provide a lot of contact area between the wire and the terminal, and the solder will flow between them to provide a lasting connection. 

Sorry about the mixup on the soldering.  We went through enough tech support posts that started with "I think I have a bad power transformer" that we added power transformer testing in the revised Crack build manual! (I think we once had a bad power transformer in a Crack about 8 or 9 years ago, but my memory is a little hazy on that)

[drewhaynes]

Thank you so much for all the time you've spent helping me. Do I need to retest voltage anywhere prior to trying headphones?

[fullheadofnothing]

Do all the voltage checks.

[drewhaynes]

I have no manual. I can find a list of proper voltages on here, but are all they tested against the ground lug?

[Paul Birkeland]

You want to see about 60-90V on terminals 1 and 5.  You want to see 80-110V on terminals 7 and 9.  You want to see 0V on 6 and 10.  If all those are OK, the rest of the terminals will be in line.

[drewhaynes]

Again, I'm not sure if I'm supposed to test against the ground lug, but these are my readings from ground lug to the 6 terminals you referenced (all being transformer terminals):

1 = 122V
5 = 5.6V
7 = 173V (but seems to fluctuate a little from 172 to 174)
9 = 171V
6 = 170V
10 = 172V

These are all drastically outside the ranges you mentioned, so I am hoping I am just testing wrong (not the ground lug?).

[Paul Birkeland]

We generally recommended using terminal 12 for your ground probe.

I'd recheck those spots again, but from the strangeness I see, I would be looking for one of the black wires that lands on the headphone jack being loose and not all the way soldered.

[drewhaynes]

May be a silly question, but we are talking AC Voltage right?

[Paul Birkeland]

DC.

[drewhaynes]

DC Voltages from Terminal 12:
1 = 0.1V
2 = 0.0
4 = 0.0
5 = 0.0
6 = 77.1
7 = 78.9
9 = 77.4
10 = 78.7

I checked the two black wires at the headphone jack (one coming from the volume control and one coming from terminal 12) and that solder joint looks solid on the jack.

[Paul Birkeland]

Ugh, that's no good.  Be sure not to run the amp like this for long.

What DC voltages do you get at:

21
13
15

I'm concerned that you have voltage at terminals 6 and 10, this means your amp is extremely unsafe to use.  The 2.49K resistors on the headphone jack bleed this voltage down, though they won't do that if the 100uF caps are in backwards or of there are solder joint issues on the heapdhone jacks itself. 

You mentioned that the LED's lit up on the 9 pin socket, if this is still true, then you are having an issue with measuring, as 0V at terminals 1, 2, 4, and 5 would not allow for the LED's on the 9 pin socket to light up. 

[drewhaynes]

21 = 214V
13 = 170V
15 = 192V

The 2 LED's on the small tube socket are still glowing red.

As far as capacitors being installed backward - the amp worked wonderfully "once upon a time", so I'm assuming that's not a possibility? The silver band on both capacitors are facing "outward" - away from each other.

[Paul Birkeland]

21 = 214V
13 = 170V
15 = 192V

These voltages indicate that your amp is drawing the correct amount of current.  Terminal 2 connects to B2, B2 connects to B5, and B5 connects to 13.  Since these are all connected by wire, they will all have the same voltages.  What voltages do you get at each of those terminals in the list?

 I would suggest reflowing any solder joint in the amplifier where a black wire connects, then rechecking the voltages on terminals 1-10.

[drewhaynes]

These voltages indicate that your amp is drawing the correct amount of current.  Terminal 2 connects to B2, B2 connects to B5, and B5 connects to 13.  Since these are all connected by wire, they will all have the same voltages.  What voltages do you get at each of those terminals in the list?

 I would suggest reflowing any solder joint in the amplifier where a black wire connects, then rechecking the voltages on terminals 1-10.

Just got these readings:
2 = 0.0V
B2 = 172V
B5 = 169V
13 = 170V still

Does that point to anything? I don't mind trying to touch up the solder on all black wire points (although I'm not sure how I'll reach *some* of them). I'm helping someone move some furniture in about 40 mins, so resoldering all those will be later this afternoon.

EDIT: Also, I'm assuming when you say Terminal 2 is connected to B2 you mean it connects somehow through the internal workings of the transformer? My Terminal 2 is only connected by 1 black wire to the power cable receptacle.

[fullheadofnothing]

The terminals Paul is calling out are on terminal strips. Are you measuring the terminal strips or the power transformer?