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Hope you all had a great holiday weekend, could you please help me get started to troubleshoot an issue with my ph3?
Started a while ago, listen to music for a bit, then terrible distortion. Sounds like when you turn your amp off in the moddle of a song, music distorts as power supply is used up. Only difference here is volume doesnt decrease. Situation corrects itself in a few minutes. It seems like heavy bass passages gets this started, but maybe that's coincidence.
Yesterday it was a bit different. After it occurring more frequently I changed tubes (uses 3 6922 tubes). Went from 6DJ8 to 6922, it just made it worse. Then it hit me, 6922 consumes a bit more current. This could be a power supply issue.
Last night the mute circuit kicked in mid distortion. I've only seen that happen once or twice before during "brown outs" in mid summer (when power company reduced line voltage across the board).
Sice this is a swinging problem I'm not sure where to start. Have you ever heard of a transfomer with swinging issues (swinging = fails, gets better, fails).
In your opinion what power supply component can behave like this?
I've got the schematic and it does list voltage at different points in the circuit.
Have you ever heard of anything like this?
If this is wrong forum excuse me, just let me know. Thanks, John
Follow Ups:
I appreciate your suggestions I'm taking it step by step, it's slow and I didn't want to seem like I'm ignoring you.
As I looked up audio research I tel number I couldn't help but notce the warning: they say they will not work on
modified units. Of course I've upgraded mine extensively, hell as the story goes that's how they got into developing the ph3se. They saw so many customers upgrading the ph3, and it made a big improvement. Ironic isn't it?
Oh well I'm sure I'll figure it out. Thanks again
What's happening is,the unit is going into partial mute and distorting most likely because of a DC change in voltage,or even a DC offset may be appearing at the outputs of the PH3...Fred gave you the best suggestion and the best way to troubleshoot it.Monitor the B+ out and it should be like 210vdc or something like that.You can also tap on the main board and the relays to see if you get it go act up before hand..
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
the PH3 is a hybrid using a JFET front end.
Edits: 07/06/16
Yes, check the power supply voltages, attach a meter and watch it when the problem occurs. Intermittent problems are usually temerature or vibration. Cold spray is good for finding temperature problems, any non conductive tool is good for finding vibration/bad connections which can be tube, socket, cracked components, bad solder joints etc.
cold or fractured solder joints or components is using wooden or plastic chop sticks. I know it sounds funny but works great and I don't have to get anywhere near the high Voltages with my hands. It's helped me a few times find bad connections, solder joints or cracked resistors.
Ditto!
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Contact Audio Research for help.
I suggest you very 'carefully' measure power supply voltages. Usually, you make the ground with a gator clip and then touch the red probe to what you are measuring using ONE hand keeping the other hand at your side. Just be careful not to cause more problems by touching two points at once with the probe. Figure out which points you are going to probe ahead of time. If you don't get the voltages you expect, then power supply problems are usually simple to figure out. Transformers rarely go as fuses and resistors and semiconductors burn out much more quickly.
Contact Audio Research.
Just trying to narrow the search down. I would guess a power supply transformer is all or none, but let me ask, is that true?
Same for rectifier and schotsky diodes right?
Thanks,
John
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