Foreplay III voltage question

[bainjs]

My voltages post did not go through. They are running (in my mind) very high.  Also initially both LEDs were working.  Now only channel A is lit.   I will send them again.  Terminals 4 and 5 have a heavier gauge wire attached and the label seems correct.

[bainjs]

The voltages are:

Power transformer terminal
4 - 39.3
5 - 39.4
6 - 230
7 - 230
9 - 232
10 - 232

H1 - 36.6
H2 - 43

1 - 233
2 - 232
4 - 230
5 - 0
6 - 232
7 - 465
9 - 0
10 - 410
11 - 0
12 - 208
13 - 0
15 - 120
16 thru 20 - 0
21 - 285
22 - 50
24 - 0
25 - 412
26 thru 30 - 0
31 - 95
32 - 208
33 thru 40 - 0

[Grainger49]

Joel,

The first readings on the transformer leads should be AC volts.  If your meter was set on DC volts you might have gotten odd readings  On terminals 1-33 the voltages most are either a little low or less than 10% high.

T12, T15, T21, T22, T25, T31 and T32 are all truly high.  I'll take a deeper look at the manual and see where those are attached and get back today.

[bainjs]

OK, and thanks for your consultation last night.  I'll re-check the transformer readings and re-post.

Joel

[Grainger49]

Joel,

Don't worry about the transformer readings, I highly suspect you were on DC.  The meaningful readings are after the rectifiers and on the tubes.  See below (you have an email).

More... The tubes may not be coming on.  Can you post the voltages at A1, A3 & A8, B1, B3 & B8?  The plate and cathode voltages tell a lot.  The plate voltage for the second stage (cathode follower) can be seen on T12 and T32 (both 58V high saying the tube is not turning on).  But the first stage (voltage amp) plate voltage is derived through a resistor jumping from one tube pin to the other on both 12AU7s.  

Let's see if the first stage is turning on.  I bet one is and the other isn't (the LED is the indicator here).

[bainjs]

Grainger:

I went back and checked the transformer voltages just to be sure.  The voltages are:

T4 - 3.63 VAC
T5 - erratic reading
T6 - 175.6 VAC
T7 - erratic
T9 - 175.9
T10 - erratic

The voltages you requested

A1 - 114.5
A3 - 1.6
A8 - 119.6
B1 - 280.6
B3 - .001
B8 - 0

Thanks

[Grainger49]

Joel,

It looks like the tube in the A socket, right channel, is turned on.  The one on the B socket is in trouble. 

Have you swapped the two 12AU7 tubes to see if it follows the tube?

The 1.3V to ground sounds good for one of these LEDs, IIRC.  The 280V at B1 versus 114V at A1 says the B tube is off.  Right now just swap tubes. 

If the problem doesn't swap channels rewet the solder on B1, B8, B6, T32, T31 and T39.

[bainjs]

I swapped the tubes and it did not make any difference in the voltages.  I will resolder the terminals now and let you know.

Thanks

Joel

[bainjs]

I re-soldered the terminals, however, it did not make any difference.

Thanks

[Grainger49]

Joel and I are getting together to troubleshoot this.

Joel is 1/2 hour away and we are going to have lunch, work on the FP III then, I'm guessing, listen to the FP III.

[Grainger49]

We beat it!  Joel is listening to his new FP III now.

[Paul Joppa]

What was the problem (besides the gas regulator tube - I suppose a solder joint...)?

[Grainger49]

Admission here, we don't know.  We did a lot of things, rewetting a number of solder joints and then it worked. 

The OD3 was fine as was the right channel.