AY 160 turntable issue

[prime]

Hi checked wires from cart to carriage, perfect, checked from connections on carriage to three prong connector, perfect. I am trying to test the volume control, with this many connections not sure where to test as far as which pins, also would i expect near nothing to about 25000 when moving the volume button. Pete

postimg.cc/gallery/BSvR2WX

[prime]

Hi guys i thing the volume pot is ok, i get about 25000 at low and about 1.5 million at full. This may not be exactly to spec but should give volume. I have been trying to troubleshoot using the AY 160 service/trouble shoot manuals i got from Victory glass, i just noticed i have a SHFA-5 amp in there and the trouble shoot is for the SHFA-3 anyone have copies of the trouble shoot pages for low volume for a SHFA-5. This may help me find the issue. Strange its on both channels. I checked the switches and they ae opening and closing as they should. Pete

[jukeboxmarty]

Being that the sound is out on both channels, I would continue to look for issues common to both channels.

This includes the input from the cartridge (I know you've already checked this), the speaker wiring, and the power supply circuits in the amplifier.

You could check for proper DC voltages with your multi-meter (Warning! High Voltage!), and to some extent check for AC signal voltages at each stage.

Unfortunately, there are billions of things that could be wrong (that's an exaggeration, it's only millions!).

I looked at the amp trouble shooting guide, it's not very comprehensive.

The best trouble shooting tool would be an oscilloscope, provided one knows enough electronic theory to utilize it properly.

BTW, the 6973 tubes are rather sensitive to 'red plating'. During your testing make sure the plates in those 6973's are not turning cherry red.

-Marty

[prime]

Hi Marty, I found a wire disconnected from the volume pot, not sure if it just happened moving the amp around or if this is the culprit. Do you or anyone here know where this wire should attach? thanks pete

[jukeboxmarty]

Look for the red arrow.....

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[prime]

Thanks reconnected the wire but no change, must have come off when testing the volume pot. I think there are two output transformers so with the problem being in both channels it rules them out ?? 

[jukeboxmarty]

Yes, I'd rule out the output transformers.

The DC (B+) power supply is a common factor, as well as the negative bias -35VDC/-30VDC power supply.

[prime]

Jul 1, 2023 1:01:18 GMT jukeboxmarty said:

Yes, I'd rule out the output transformers.

The DC (B+) power supply is a common factor, as well as the negative bias -35VDC/-30VDC power supply.

Do you have a clear schematic showing those values so i can test for them..??   I reconfirmed its not the cart or wires connected to the cart all the way down to the three prong, tested all tubes, checked for loose wired and checked for cold solder. I find nothing, before removing caps and resistors to test values i just want to make sure im getting enough power. thanks for any help pete

[jukeboxmarty]

Here's the schematic for a Seeburg shfa5, I'll keep it up long enough for you to download it...

[deleted link]

[prime]

I know im being a pain but do i need the unit in play to test voltage, if so this will be difficult because if the units are in the box the wiring is not accessible, ?
Also can i just test at the 5U4 GB socket for both voltages, if so which pin should have which voltage?   Just realized i can maybe test 5U4 socket with tube out, then i can load record while testing,   or am i barking up the wrong tree.    pete 

[jukeboxmarty]

Take the rear back door panel off to have access to component side of the amplifier.

I'll be a little blunt... at this point, you'll need to refer to the schematic to figure out where to measure your voltages. They are clearly displayed on the schematic. (Hint! Look for R126, R127 and R129 for the B+ ***warning almost 400 volts***)(Hint number 2: Look for R131 and R132 for the -35VDC supply).

-Marty

[prime]

Jul 1, 2023 19:36:32 GMT jukeboxmarty said:

Take the rear back door panel off to have access to component side of the amplifier.

I'll be a little blunt... at this point, you'll need to refer to the schematic to figure out where to measure your voltages. They are clearly displayed on the schematic. (Hint! Look for R126, R127 and R129 for the B+ ***warning almost 400 volts***)(Hint number 2: Look for R131 and R132 for the -35VDC supply).

-Marty

Yes i saw the 275 at R 126   325 at R 127  and 370 at junction C120C and R 129 ,,I just thought the value should be tested at tube socket, quite obviously i was wrong, thanks for being blunt, kind of use to it after dealing with Ron, ill admit i got it alot. Just want to always make sure of anything i do.  thanks for your help  pete

[jukeboxmarty]

LOL, I hope I don't become as blunt as Ron was!

Time will tell!

[prime]

I gots a problem , testing at R 131 i get -40 at R132 i get-58 but testing for plus at R 129 at the +junction at the C120D cap i only get +4 vlts also about the same at R126 and R127 while record playing. Im using the chassis for ground i have done this in the past with success. What are your thoughts on this. Pete

[prime]

I want to make sure of the 120 coming into the amp on the terminals in the attached photo, which posts do i check across to confirm voltage, i tried using chassis and i just get +4vlts, thanks pete