No sound after upgrade install [solved]

[mcwhart]

Very sorry about that.  Meter was on auto setting.

Here we go again:

Volume Pot all the way up with power off and 60 Hz tone:

top lugs, from A side to B side:  .5 mV, 1.377 V, 1.377 V

bottom lugs, A side to B side:    .5 mV, 1.039 V, 1.039 V

Volume pot all the way up, Power on, 60Hz tone:

A1: 17.36 V              B1: 23.1 V

9:   17.38 V              19: 23.1 V

Thanks for your help and patience

[Grainger49]

Ok, the signal is getting through to these points.  A lot of signal!

[mcwhart]

Is a lot of signal good or bad at this point?

[Grainger49]

Let me make sure I am following you.  The first measurements should be from the three lugs on each side of the pot to ground or the chassis.  The second measurements are to pins 1 of each tube (grid of the second stage).

If you are measuring this, you are getting amplification from the volume pot (about 1V) to the grid of the second stage of the tube (17V AC/23V AC).  That is what is supposed to happen. 

You should also get more AC voltage on pin 2 of each tube.

[mcwhart]

Yes, this is correct.  By lugs on the pot I am assuming you mean the upper and lower row of three tabs, or lugs(?) on the volume pot.  Those are where I took the first six AC voltage measurements, followed by A1 and B1, then 9 and 19.

Thanks

[Grainger49]

Yes, we are moving in the right direction.  I'm guessing it will be something silly like I did 2 weeks ago.  So far you are doing all right.

[mcwhart]

Great.  Thanks!

[mcwhart]

Any suggestions as to where to go next with this?  Thank you

[Grainger49]

The output section of the tube is pin 2.  You should have DC and AC amplified voltage there.  You should be able to turn it on, re-verify the AC voltage on tube pin 1 then you should read more on pin 2 of each channel. 

If the DC there messes with the reading measure instead to terminals 20 and 40.  That is after the Parafeed cap and the input to the output transformers.  There should be a transformer wire on terminals 20 and 40 as well as the Parafeed cap.

If you get amplified voltage on these terminals the signal is dead somewhere in the transformer wiring to the speaker outputs. 

Or, maybe, the headphone jack has failed and permanently opened the circuit to the speaker outputs.

[Paul Birkeland]

Your C4S upgrade is working perfectly, we can now move completely away from that as a source of not having sound.

Grainger is correct, pin 2 on each tube socket is the next place to measure voltage. 

Then terminals 15 and 25.

Then where each red wire connects on the binding posts.

[mcwhart]

Here are the AC voltage readings I get for points you indicated:

A1: 16.5v

A2: 218v

B1: 23.2v

B2: 239v

Terminal 20: blinks back and forth between about 240v and about 405v

Not sure where terminal 40 is?

Terminal 15:  222v

Terminal 25:  246v

Binding Post red wire on A side:  8.15v

Binding Post red wire on B side:  9.03v

Thank you

[Paul Birkeland]

Binding Post red wire on A side:  8.15v

Binding Post red wire on B side:  9.03v

You have sound coming out of your SEX amp...

[mcwhart]

Ah, yes I do.  Thanks for your help.

 Still a low level hum that was not there before attempted upgrade install, and the right channel is definitely louder than the left.  Tried switching tubes and connection wires, no change.  Any ideas about what might be causing that?  The amp was much quieter and balanced before the upgrade than it is now.

Thanks

[mcwhart]

Any advice as to where I should be looking to resolve low-level hum issue and stronger signal from right channel?

Thank you

[Paul Birkeland]

Still a low level hum that was not there before attempted upgrade install, and the right channel is definitely louder than the left.  Tried switching tubes and connection wires, no change.  Any ideas about what might be causing that?  The amp was much quieter and balanced before the upgrade than it is now.

Your tests revealed that the voltage coming into the SEX is out of balance. 

Low level hum could be from a loose wire or a capacitor that only has one lead well soldered.

If you have this hum in both channels, look at the 220uF/250V caps first.  I generally will poke at them with the amp off and be sure that when they move, they move with the terminal strips, not independently from them.

-PB