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Post by jukeboxmarty on Jul 2, 2023 17:34:34 GMT
I'm assuming you used a DC setting.
If those results hold up, you either have a bad 5U4, a bad power transformer, or the transformer is not getting power.
Sometimes the plug between the Amp and Selection Receiver doesn't make, which could cause this problem.
First I'd check to see if you have 120VAC across P101. If that checks out I'd check the pins of the 5U4 socket. You should get 5VAC between pins 2 and 8, and several hundred volts AC between pins 4 and 6. Careful with the high voltage.
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Post by jukeboxmarty on Jul 2, 2023 17:40:13 GMT
Our posts crossed! You seemed to have worked out a likely cause.
You should check across the two terminals (on P101) closest to the bottom of the selection receiver. You should get 120VAC.
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Post by prime on Jul 2, 2023 17:51:03 GMT
I got +vac 121 at those two posts. I feel i can not use chassis for ground, can i use ground at cap C120A for testing the voltages? at R126 127 and 129
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Post by jukeboxmarty on Jul 2, 2023 17:58:55 GMT
Yes the ground is appropriate at those points (C120A and resistors).
Do you check for the 120VAC at the selection receiver or at the Amplifier side?
You need to make sure the Amplifier side is getting the voltage.
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Post by prime on Jul 2, 2023 18:16:53 GMT
I checked the voltage on the amp side same posts got +120, i tried to use a ground lug and when tested at the resistor my fluke goes for a second to OL then drops down to + 4 vlts or less each resistor, but on a side note each time the power dropped the record ejected, when i used the ground from the cap, I got OL then it dropped to +4vlts or less but did not eject record. seems like the power is not getting to the caps or could it be a ground issue ?
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Post by jukeboxmarty on Jul 2, 2023 18:21:14 GMT
Check these voltages mentioned a few posts ago, pull the 5U4 before checking... "check the pins of the 5U4 socket. You should get 5VAC between pins 2 and 8, and several hundred volts AC between pins 4 and 6. Careful with the high voltage." |
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Post by prime on Jul 2, 2023 18:44:50 GMT
With the box playing a record, the 5U4 tube removed i get +5.6 vlts between 2 and 8 I get +75.4 vlts between 4 an6 pin
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Post by jukeboxmarty on Jul 2, 2023 18:59:47 GMT
AC scale? there is no + or -
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Post by prime on Jul 2, 2023 19:03:09 GMT
AC scale? there is no + or - Yes AC scale, tried two multimeters one analog, one fluke digital |
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Post by jukeboxmarty on Jul 2, 2023 19:05:46 GMT
That result is not good.
Check between pin 4 and ground, then pin 6 and ground.
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Post by prime on Jul 2, 2023 19:23:39 GMT
That result is not good. Check between pin 4 and ground, then pin 6 and ground. 4 and ground AC 36.6, 6 and ground AC 36.6 using chassis as ground two separate locations |
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Post by jukeboxmarty on Jul 2, 2023 19:37:04 GMT
That's not right. It should be hundreds of volts.
Unfortunately it would seem to indicate a bad transformer... providing the test results are correct.
I have a feeling something is elusive and is being overlooked.
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Post by prime on Jul 2, 2023 19:46:09 GMT
Im using the chassis for ground, is it somewhere else i should try. Just to confirm jukebox playing record, 5u4 tube removed, multimeter set on AC , auto range, red probe on number 4 pin , black probe on chassis. same for pin 6. Any other way to test transformer? thanks pete On another note. when i turn on the box and the sound that i have comes up, it starts out louder and fades off, not as loud as normal but definitely louder,
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Post by jukeboxmarty on Jul 2, 2023 19:54:26 GMT
Which the power off and the tube removed you could measure the resistance between pins 2 and 8, then pin 4 to ground and pin 6 to ground.
To tell you the truth I'm not sure off the top of my head what the ohms reading should be... I'd have to check.
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Post by jukeboxmarty on Jul 2, 2023 19:55:43 GMT
Are you sure there isn't some sort of range multiplier you're missing on your meter?
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