Right Channel Issue, Continued...
- Thread starter Jameson
- Start date
Play a 60Hz tone into your SEX at full volume from your phone. Measure the AC voltage between ground and the center pin on each level of the pot with the pot all the way up, then half way up. Report those values here. The SEX does not need to be on for this set of measurements.
Alright. This is where we start to see the seams of what I know.
I took a series of measurements because I was unsure how to get at what you're looking for. It's possible my multimeter might not be up to snuff. Attached is a picture of the dial.
See the attached photo for a key of the multimeter settings.
Setting 1 (I believe this to be AC volts, but the lowest setting I have is 200V):
Setting 2 (I believe this isn't what you're looking for; this seems like DC amperage):
Setting 3 (This is DC voltage, again not what you asked for):
I took a series of measurements because I was unsure how to get at what you're looking for. It's possible my multimeter might not be up to snuff. Attached is a picture of the dial.
See the attached photo for a key of the multimeter settings.
Setting 1 (I believe this to be AC volts, but the lowest setting I have is 200V):
| Reading | Right | Left |
| 50% | 00.1 | 00.2 |
| 100% | 00.1 | 00.2 |
Setting 2 (I believe this isn't what you're looking for; this seems like DC amperage):
| Reading | Right | Left |
| 50% | 2.7 | 5.2 |
| 100% | 2.7 | 5.2 |
Setting 3 (This is DC voltage, again not what you asked for):
| Reading | Right | Left |
| 50% | Ranged from 0 to 0.4 | 1.5 |
| 100% | Ranged from 0 to 0.4 | 1.5 |
While your meter is totally accurate for checking DC voltages in our kits, that AC scale doesn't go down low enough. The ~$20 meter at Hazard Fraught is going to be really helpful for this debugging:
Meter
This meter with a set of $30 Fluke probes is the best meter you can get for $50.
While the probes aren't so wonderful, the actual meter is excellent. On the 2V AC setting, you should get a much clearer reading of those levels.
Meter
This meter with a set of $30 Fluke probes is the best meter you can get for $50.
While the probes aren't so wonderful, the actual meter is excellent. On the 2V AC setting, you should get a much clearer reading of those levels.
Which one did you get? I like to try to have a few recommendations when people ask.
This multimeter (AstroAI WH5000A) and these leads (AstroAI leads with alligator clips and others).
The middle pin of each level of the pot should give you a different AC voltage reading as you turn the pot.
-PB
-PB
One of these days I'll read slowly and thoroughly enough get your meaning the first time around. I was measuring at the RCA output level instead of the pot lugs. Here are the updated readings.
Right 50%: 36mV
Left 50%: 34.5mV
Right 100%: 403.4mV
Left 100%: 402.7mV
Right 50%: 36mV
Left 50%: 34.5mV
Right 100%: 403.4mV
Left 100%: 402.7mV
OK, that is good, you have a working pot.
The next test is to check for channel balance at G1 on each 12 pin socket. Again, you can do this without the amp on. This is the AC signal voltage at pin 10 on each 12 pin tube socket.
If those balance, power up the amp and turn the pot all the way up. With the tone playing check and compare AC voltages at:
Terminal 4 vs. 18
Terminal 3 vs. 17
It also came to my mind that a 1000uF/35V cap that wasn't well connected would give you some pretty terrible performance out of one channel.
-PB
The next test is to check for channel balance at G1 on each 12 pin socket. Again, you can do this without the amp on. This is the AC signal voltage at pin 10 on each 12 pin tube socket.
If those balance, power up the amp and turn the pot all the way up. With the tone playing check and compare AC voltages at:
Terminal 4 vs. 18
Terminal 3 vs. 17
It also came to my mind that a 1000uF/35V cap that wasn't well connected would give you some pretty terrible performance out of one channel.
-PB
Swap the tubes and repeat the AC tone voltage checks on those last 4 terminals I listed.
-PB
-PB
Now measure the AC across the binding posts.
Well. Something’s gone haywire now. The right side is making no noise, and the left side is making a god awful buzzing sound. Voltages were 3.4mv on the right and 402.4 on the left. I assume something is now definitely broken and I should repeat the voltage and resistance checks?
Yes, you may have a loose connection somewhere that you've disturbed enough to now be able to locate.
