Smashup Volatges Off 1 Side [resolved]

[galyons]

Got back home and cranked up the Smash to finish  testing the AC hum on the PS.  Must have shorted something because the LED's  didn't light up as usual.  One board is fine, all four LED's lit.  The other board, the A side LED's light, but not the B side.

Here are the voltages:

IA   180-220V  = 205V, 205V

OA  150V ± 1%  = 202.4V, 149.4V

+reg  (A side) 2.5V = .426V, -1.51V

IB   150V ± 1%  = 202.4V, 149.4V

OB  45-75V  = 200.9V, 63.5V

Kreg (B side) 3-5V = 1.9V, 4.4V

Breg (B side) 150V ± 1%  =202V, 149.4V

+reg (B side) 150V ± 1%  =202.2V, 149.4V

B1 0V= 0V
B2 150V= 202V
B3 3-5V= 1.9V
B4 0V= 0V
B5 150V= 149.4V
B6 3-5V= 4.45V

So I blew one or more of  devices on the reg board.   Please let me know what I need to test to identify the culprit.

Cheers,
Geary

[Paul Birkeland]

Your regulator is not working and your 4P1L isn't drawing current.  This could just be a damaged ground wire going to the PC board that isn't letting either part function properly.

-PB

[galyons]

Your regulator is not working and your 4P1L isn't drawing current.  This could just be a damaged ground wire going to the PC board that isn't letting either part function properly.

-PB

Thanks PB!
I checked the ground wires to the boards. Both good.  Swapped in my spare 4P1L's. LED's are back!  Here are the voltages that are still off.


+reg  (A side) 2.5V = .644V, .765V

OB  45-75V  = 148.3V, 63.5V

Kreg (B side) 3-5V = 2.1V, 4.4V

B3 3-5V= 2.1V

Getting closer!

Cheers,
Geary

[Paul Birkeland]

You still don't have 4P1L conduction, can you check the voltage coming off the little filament regulator board?

[galyons]

PB,
I get:

1.98V from "Out" to board ground. 
1.51V from "Out' to chassis ground.


Thanks,
Geary

[Paul Birkeland]

1.98V from "Out" to board ground. 
1.51V from "Out' to chassis ground.

Yeah, that's a problem.  The 4P1L is setup for ~4V to heat the 4P1L.  You don't have 4V coming out of that board, so your 4P1L's can't conduct.

What kind of voltage is going into the board? (Measure from Ground to "I" on the PC board)

[galyons]

PB,
I get:

4.95V from In to board ground.

Thanks,
Geary

[Paul Birkeland]

PB,
I get:

4.95V from In to board ground.

Thanks,
Geary

Yeah, that's not enough.  The diode bridge will make more than that unless either a diodes is not well soldered/not working, or there's too much current being drawn.

You can lift the red wire at the 10,000uF cap, then retest the low voltage to see how much it pops up.

-PB

[galyons]

Low voltage goes up to 15.84V measured at terminals 26 & 27, with the red wire going to the reg board lifted.

Thanks,
Geary

[Paul Birkeland]

I just performed the same test.  On 127V AC line voltage, I get ~9V DC out of the raw supply.

Are you running the stock parts? 

I can't really figure out how you'd get 15.8V, unless maybe your meter is seeing a lot of ripple or something, but this is certainly where you need to look for your issue.

-PB

[galyons]

Hi Paul,
Yes, all stock parts in the filament PS.  Line @ 120.7VAC  Red wire still lifted, so regulator out of circuit,  13.8VDC with 9.4VAC along for the ride. So, yes, a ton of ripple!

Thanks for helping out on this!

Cheers,
Geary

[Paul Birkeland]

You can't get 13.8V from a 6.3V winding without changing from a bridge to a voltage doubler. 

I would suggest having a close look at all those 1N5818 diodes and the 10,000uF cap to see what's amiss.  Also try a second meter if you have access to one.

-PB

[galyons]

Already double checked the voltages with my other  meter, same.  I made no changes to the filament PS, so this befuddles me. I will double check the diodes and the cap.

Thanks,
Geary

[galyons]

You can't get 13.8V from a 6.3V winding without changing from a bridge to a voltage doubler. 

I would suggest having a close look at all those 1N5818 diodes and the 10,000uF cap to see what's amiss.  Also try a second meter if you have access to one.

-PB

Thanks Paul! Yet again you called it! The 10K uF cap had one leg loose.  I had to add fly leads to get the 10K uF cap away from the terminal strip to add the big film cap.  Must have nicked the wire stripping and moving things around broke the wire.  Re-soldered.  The 1N5818 diodes test fine. With the red lead to the filament regulator board re-soldered all voltages are back in spec with the exception of:

+reg  (A side) 2.5V = .92V, 1.1V


So, getting really close.

Cheers,
Geary

[Doc B.]

Now we just need a post where PB thanks me for suggesting to him it was ripple...