Promethium

[Kroars]

Built a couple Promethium’s again, this time one of the two has a signal when bypassed but nothing when active. I initially thought I had a short to ground somewhere, but no continuity where there shouldn’t be. Started taking voltage readings and noticed some fairly big difference between the two at the 2N5457 (Q1) D-0v, S-0v, G-0v. Also at IC1 pins: 8-9.1v, 7-1.60, 6-1.60, 5-1.74

swapped all trannies and IC’s between the working Promethium and non working one, same result. So those all seem to be good. Every component tested prior to installation on both (built two at same time).

Solder joints are beautiful (even got a fancy flux pen I’ve been using. All legs snipped nicely and both boards thoroughly cleaned. Before I take it apart I’m wondering if someone could recommend testing a particular component that would feed either Q1 or IC1?

 

[Sturdag Lagernathy]

You could check continuity between pin 1 of Q1, and +V. You can also check resistance from pin 3 of Q1 to ground, should be 10k ohms.

 

[Kroars]

You could check continuity between pin 1 of Q1, and +V. You can also check resistance from pin 3 of Q1 to ground, should be 10k ohms.

Thank you! Will do once I get home tonight and will report back.

 

[benny_profane]

There are a lot of socketed components that could be possible sources of open circuits. My first step in this situation is to go through with an audio probe simply to rule that out.

 

[Kroars]

There are a lot of socketed components that could be possible sources of open circuits. My first step in this situation is to go through with an audio probe simply to rule that out.

I get that, although I’m testing the actual socket and getting 0v at Q1. That seems to be an issue.

 

[Kroars]

You could check continuity between pin 1 of Q1, and +V. You can also check resistance from pin 3 of Q1 to ground, should be 10k ohms.

No continuity between pin 1 (D) of Q1 and +V. Also DMM reads 5M (on manual) between pin 3 (G) and ground. I’m guessing that should be closer to 1M?

EDIT: Turns out I’m just an idiot (again)…. Check out the legs of the sockets…. Yup, only one is soldered on each set. I do that so I can ensure their nice and straight. The trick is to make sure you solder the rest once they are. Anyway, thank you as always! You folks have the patience of Saints

 

[fig]

Hey great news! I kinda looked over your shoulder at the resistors and stuff..thought I spotted something but it was just that, a spot.

...and Benny was spot on!

Chuck's law man. Learn it. Live it.