AY 160 turntable issue

[prime]

Jul 2, 2023 19:55:43 GMT jukeboxmarty said:

Are you sure there isn't some sort of range multiplier you're missing on your meter?

Im using two meters but i will confirm all readings later. As far a ohm readings i get with juke off , 5u4 tube out between 2 and 8 pin .1 ohm   4 to ground 38.7 ohm   6 to ground   41.9 ohm 

[prime]

You are right sorry for the loss of time, the fluke only goes to AC 600 vlts on auto, I grabbed another multimeter i mostly use for caps. Set it on 1000 ac volts and got a fluctuating range from OL down to 780 vlts

[jukeboxmarty]

Without confirming, those resistance readings seem like they could be correct.

As far as the voltage values you measured for the B+, they would seem correct if there was a 10x multiplier. (For instance 754VAC vs 75.4VAC)

[prime]

Still at the resisters 126,127 and 129 i just get about ac 4 vlts. i tried measuring from both sides of resisters, https://pothe photos show the R126 r127 and r 129 that i tested for voltages. What would cause the voltages to be so low at r126 127 and 129   


postimg.cc/gallery/Ppt3Cjw

[jukeboxmarty]

I've got nothing else at this point.

The measurement you reported at the 5U4 pins is definitely off, either the reading is wrong or the transformer is bad.

Since the resistance seems correct, I'd guess the voltage reading is wrong.

Hard to go forward without knowing.

[prime]

What should the reading be at pin 4to6? also when we look at 2to8 we get 5vlts and i see pin 8 wire goes to R129, how do the resisters 126 and 127 get up to 325 vlts?

[jukeboxmarty]

The reading between pins 4 and 6 should be in the 700 volt AC range.

The reading between pins 5 and 8 should be around 5 volts AC.

When the 5U4 heats up and begins conducting, the AC voltage at pins 4 and 6 will be rectified through the tube, available as DC voltage present at pin 2 or 8.

[prime]

Then i am ok at the 5u4 ,i get about 745 at 4 and 6 and 5.6 at 2and 8. My issue seems to be at the filter caps, no high voltage. pete

[jukeboxmarty]

Sorry, I totally missed this post about the corrected voltages.

Jul 2, 2023 20:47:15 GMT prime said:

You are right sorry for the loss of time, the fluke only goes to AC 600 vlts on auto, I grabbed another multimeter i mostly use for caps. Set it on 1000 ac volts and got a fluctuating range from OL down to 780 vlts

[jukeboxmarty]

If you are not getting the correct DC voltages with the 5U4 inserted, either the 5U4 tube is bad, or there is a short somewhere downstream. Maybe even capacitor C120D.

[prime]

I hate to admit this but i reread entire thread and not sure how i missed it but you clearly stated the voltages at the R126 127 and 129 where DC, I was testing in AC, i will be slowing down and reading everything twice. My voltages at those three locations are 370-390 a little high for the 126 but it always seems higher when i test any of the boxes. I guess this confirms no issue with power supply . Must be bad connection, bad cap or bad resistor.

[jukeboxmarty]

LOL, back to the beginning!

Where do we go now?

[prime]

Correct me if im wrong, Im thinking i need to figure out what area of the amp can actually affect both channels at the same time ,then check each connection, cap and resistor in that area. Not sure how i will figure this out but as im sure you like i love when a puzzle like this is solved. Thankyou for being so patient with me pete

[jukeboxmarty]

Other than the power supplies, there isn't much else in common.

If you had an oscilloscope (and knew how to use it), you could get this figured out in 5 minutes!

[prime]

Sadly i do have an oscilloscope but havnt learned to use it yet pete when i tested the volume pot i got 25000 up to 1,500.000    I assume the fact that it changes it should work ,  just checking