left channel suddenly out of balance [resolved]

[kill_surf_city]

Turn up that heat!

Okay, i re-flowed every joint and im still getting 178-180mV on KregA. Heat on my iron is up as high as it goes.

[Paul Birkeland]

Are both halves of the 12AU7 glowing?

[kill_surf_city]

Are both halves of the 12AU7 glowing?

sorry it took me a bit. but yes, both sides are glowing. I even swapped out the tube that came with the kid and put in an RCA.

[Paul Birkeland]

The next thing to do would be to set your meter to beep when you touch the probes, then start probing all the pairs of all the transistors and the 431 regulators on the board above the D socket to see if any of them are internally shorted.

[kill_surf_city]

The next thing to do would be to set your meter to beep when you touch the probes, then start probing all the pairs of all the transistors and the 431 regulators on the board above the D socket to see if any of them are internally shorted.

I'm not sure my meter has that option. Also, I probing around a min ago and caused another spark. this time at the resistor at reg on side B. Now none of the LEDs turn on and the voltage on side B is now siting around 170v while on side A it is still at 260v

[kill_surf_city]

The next thing to do would be to set your meter to beep when you touch the probes, then start probing all the pairs of all the transistors and the 431 regulators on the board above the D socket to see if any of them are internally shorted.

Both of the 100KΩ 3W are beeping on opposing ends. Also one end of each of the 0.1 μF 400V film capacitors, the 431 resistors on side B and A as well as the 2.49KΩ resistors

[kill_surf_city]

Also, I think I may have figured out where the issue was in the first place. The wire connected to D8 wasn't soldered so well, but while i was probing and trying to find an issue with a resistor I caused those sparks that I'm sure shorted out one or even all of the resistors that are now beeping. Let me know which one's I should buy replacements for.

[Paul Birkeland]

If a resistor shorts, typically it will burn itself up in the process.  If that hasn't happened, then the beep may be an instantaneous beep that goes away after a short time due to a capacitor charging.

[kill_surf_city]

If a resistor shorts, typically it will burn itself up in the process.  If that hasn't happened, then the beep may be an instantaneous beep that goes away after a short time due to a capacitor charging.

The beeps I get are continuous until I remove the probe. When you say “burn up” would this be something I can see on the resistor? Also should I hold the probe on the resistors that are beeping for a while to see if the beep stops?

[Paul Birkeland]

Yes, and we also would expect the resistor to fail to a state that's completely open.  Keep in mind that you need the probes across the part itself, not one probe on ground and the other probe poking around the circuit. 

[kill_surf_city]

Yes, and we also would expect the resistor to fail to a state that's completely open.  Keep in mind that you need the probes across the part itself, not one probe on ground and the other probe poking around the circuit.

Ohh okay. I was attaching my black ground clip to the ground near the power switch and then probing the lead of each resistor with the red probe. But you’re saying I need a probe on each of the of the resistors correct?

[Paul Birkeland]

You need to probe each pair of pins on all the solid state devices (transistors and regulator chips).

You do not need to probe the resistors.  A blown resistor avails itself with sounds, sights, and smells.

[kill_surf_city]

You need to probe each pair of pins on all the solid state devices (transistors and regulator chips).

You do not need to probe the resistors.  A blown resistor avails itself with sounds, sights, and smells.

Okay so you’re saying on the underside of the board I need to probe the points where I soldered them in? Sorry I’m just confused by what the “pins” are.

[Paul Birkeland]

Yes, the pins of the transistors and regulators are the leads that are poking through the bottom of the PC board.

[kill_surf_city]

Yes, the pins of the transistors and regulators are the leads that are poking through the bottom of the PC board.

Okay, so I disconnected the board and took it off, flipped it over and probed those regulators. The LM431 regulators give me a constant beep as long as I hold the probes on any two pins. Same goes for when I probe the PN2907A pins. The pins on the MJE5731A on side B also give me a constant beep and ones on side A give me the same but with different pins being probed. Does this mean all of the regulators and transistors are shorted and that I need new ones?