4230 problems

Any idea where I can get information on test points and voltages for the boards for this receiver? Service manual doesn't give me much. I tried AI but the same question often gets different results.
 
Soldering equipment looks OK. I set my iron to 350C. As for the SM and voltages, I haven't seen any schematics with voltages marked... yet.
 
According to the schematic, J809 comes off of the transformer secondary driving the dial lamps so it should be an AC voltage.
According to the board layout diagram in the SM:
  • J809 & J806 should measure ACV
  • J807 & J808 should be ACV? You should also be able to measure ACV across J807/J808 since it comes from the transformer secondary.
  • J814 = J801
  • J819 = not connected
  • J811 = J10 = J12 = GND (0v)
  • J803 = J813
  • J820 = not connected
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Yes, you will get full power off the DBT. If you're getting 35v, chances are everything is fine with the PSU. I would not run on normal mains power though if you have a bright DBT.
 
Currently the bulb is very dim because I have the bad amp board out. when I put that amp board in, the one that was rebuilt, I got a bright bulb but as we found out there were some bad parts that didn't look bad.1000002558.jpg
 
While you have the good P700 board installed, I might recommend that you measure the ECB voltages of each transistor. It will be assumed that these are the reference voltages to compare the bad board against to locate the problem. The circuit is symmetrical so you may not need to measure all voltages. Also, turn the Volume control to minimum.
Here is the list:

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No, the other board is not working correctly either, it just doesn't give me a a bright bulb.... I only get very distorted sound, and no volume. I'm sure there are hidden problems there too. That's why I was checking the power supply for a possible problem? Youtube is great for sending me down rabbit holes! Thanks for your help!
 
Checking across J717 and J711 for bias it starts around 150 millivolts and just rapidly climbs to above one volt. Checking between Jay 712 and
J718, I can adjust it to 15 millivolts with no problem.
It's set to zero volume the selector is on CD nothing is plugged in.
 
So, with this board that you are currently working on (assuming the left channel board), what is your +voltage rail coming into the board at J722? It should be around 48VDC.

Also, just to verify, ensure that your output leads are going to the correct pin locations on the board. Here is a good reference:
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Try removing the base at H001 and see if your bulb goes dim. If not, then try H003. You need to find where this excess current is coming from. If the DBT goes dim, then you've eliminated the output stage as the issue. Work your way back from that output to the C726 as that is the output path. With my experience on these P700 boards, the usual culprets are either the outputs, emitter resistors, or the driver transistors. I would check all of those out of circuit.

Also, the way this boards looks, you may have a solder bridge, a marginal cap, or a stressed component.

If the other board does not have significant solder and burn issues, then you may want to start with that one and get it up and running first, then work on the one in worse condition. If you have one working board, it's useful to help with fixing the other.
 
I removed the output resistors and check them they're all between 0.67 and .68 ohms. Any reason to believe they may have problems or too far out of spec?1000002576.jpg
 
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