Troubleshooting Resistance Checks

[ksolis01]

I ran through the resistance checks and terminals 22 and 23 aren't giving the correct values. They should be *, fluctuating value, but instead when I probe each, the multimeter doesn't even respond to the probe. I tried re soldering all the immediate wire connected to the terminal and rechecked that those wires were in the right place. All the other resistance checks are good, just these two. Appreciate any help.

[Paul Birkeland]

No response is consistent with the note provided for the asterisk.   22 and 23 are your incoming line voltage, so not getting any resistance reading there is a good thing.

[ksolis01]

Ok. I only had time in the morning for the glow test. On the circuit board over the B socket on the A side of the board, both leds don’t turn on. I didn’t get time to voltage checks but where should I start troubleshooting because of those two leds.

[Paul Birkeland]

The voltage checks provide infinitely more information than "the LEDs don't glow".

[ksolis01]

The voltage checks provide infinitely more information than "the LEDs don't glow".

Got them.
Terminal     Voltage (DC)

Low Current C4S
IA        150V   (187.6)
OA 60-90V   (79)
KregA  3-6V   (1.947)
bRegA 150V    (188)
IB        150V   (148)
OB   60-90V   (55.2)
KregB   3-6V   (13.04 )
bRegB   150V   (148.1)

High Current C4S (D socket)
IA         190V   (192)
OA        150V   (148)
bA         0V   (0)
IB          0V   (0)
OB  90-110V   (82.5)
bB        150V   (148.1)

High Current C4S (B socket)
IA         190V   (188)
OA        150V   (186.9)
bA         0V   (0)
IB          0V   (0)
OB  90-110V   (0.025)
bB        150V   (0.044)

Headphone Jack
Tip          0V    (0.01)
Ring        0V    (0.04)

[Paul Birkeland]

Low Current C4S
IA        150V   (187.6)
KregA  3-6V   (1.947)
bRegA 150V    (188)
OB   60-90V   (55.2)
High Current C4S (B socket)
OA        150V   (186.9)
OB  90-110V   (0.025)
bB        150V   (0.044)

bB ties to OA with a red wire.  bB is 0.044V, OA is 186.9V.  They are not connected.

[ksolis01]

bB ties to OA with a red wire.  bB is 0.044V, OA is 186.9V.  They are not connected.

Ok, soldered that connection again. These are the only two value that change significantly and were the problems ones. They seem within range but the two leds I mentioned in my previous post still didn't turn on.

High Current C4S (B socket)
OB  90-110V   (95.9)
bB        150V   (186)

[Paul Birkeland]

Recheck all your voltages.  bB isn't going to be 186V without one of the Kreg voltages being off.  Also, bB should be extremely close to 150V. (within a volt or two)

[ksolis01]

Recheck all your voltages.  bB isn't going to be 186V without one of the Kreg voltages being off.  Also, bB should be extremely close to 150V. (within a volt or two)

KregA and  and KregB are significantly off, especially B.

Terminal     Voltage (DC)

Low Current C4S
IA        150V   (187.7)
OA 60-90V   (79.3)
KregA  3-6V   (1.936)
bRegA 150V    (187.7)
IB        150V   (148.1)
OB   60-90V   (54.6)
KregB   3-6V   (12.9)
bRegB   150V   (148)

High Current C4S (D socket)
IA         190V   (190.5)
OA        150V   (148)
bA         0V   (0)
IB          0V   (0)
OB  90-110V   (81.4)
bB        150V   (148.1)

High Current C4S (B socket)
IA         190V   (188.3)
OA        150V   (186.7)
bA         0V   (0)
IB          0V   (0)
OB  90-110V   (96.5)
bB        150V   (186.5)

Headphone Jack
Tip          0V    (0.01)
Ring        0V    (0.04)

[Paul Birkeland]

I would suggest flipping over the high current C4S board with the troubling voltages and reheating all of the solder joints on that board, as well as the socket under it. 

This builder had similar issues that ended up being resolved by reheating the solder joints, with particular emphasis on the center leg of each MJE5731A.

[ksolis01]

I would suggest flipping over the high current C4S board with the troubling voltages and reheating all of the solder joints on that board, as well as the socket under it. 

This builder had similar issues that ended up being resolved by reheating the solder joints, with particular emphasis on the center leg of each MJE5731A.

Ok, I reheated all the joints. However, when I connected it, something under both high current C4S boards started to smoke. Immediately disconnected it. On the B socket, the 237Ω 1/8 W resistor connecting B5 to B6 got burnt. On the D socket both 220Ω 1⁄4W connected to the ground lug intertwined got burnt.

[Paul Birkeland]

Can you show me pictures of that area on your amp.  Neither of those parts is under any thermal stress whatsoever, but a short on or around the socket could cause damage like this.

[ksolis01]

Hopefully this is enough photos. First 9 are the B socket. The rest are D socket

[Paul Birkeland]

I would wonder if the tube socket lug where the 237 ohm resistor connects got shorted to the black wire next to it.

Is this the wire provided with the kit?

[ksolis01]

I would wonder if the tube socket lug where the 237 ohm resistor connects got shorted to the black wire next to it.

Is this the wire provided with the kit?

Ye, the whole build is stock. Going to wait on getting the new resistors and then recheck all related wiring to try to find how the short happened.