Dear Tim.....

[runamuck]

I have been plodding along doing a bit of work each spare evening and have gotten to the point of initial power-up and testing my 2- J99s. There has been nothing smoking so for that I am just proud as hell!!!!. There is one little problem though but before describing it let me copy and paste something I posted a while back:


"I am building 2 J99s. While soldering in some of the resistors, a tiny amount of solder found its way into the left pole of R12 before I had placed that resistor in there. I tried melting it back out with the iron and was unable to do so.

So I attempted to remove the solder with a very small drill bit, twirling the bit slowly by hand. It worked, but at the same time I inadvertantly removed some of the metal in the circuit board that the resitor lead should be soldered to.

I attempted to solder the R12 resistor in place but am worried that I may not have a good connection."


Ok, with that in mind, here's the issue. When testing both U1 and U2 with the probes at pins 4 and 5, I'm getting a reading of -27ishV instead of -14V. The other J99 is OK in this regard as are the tests on pins 3 and 4 on the board in question. Could this be related to the resistor problem or something else?

Two more questions.

To check voltages at U3 I dont know which pins are which number. Can you explain? Are they
1 8 ?
2 7
3 6
4 5

Also once I know which pins are which, I assume the positive probe goes to the pin but where does the negative probe go?

With much Love and Thanks,

Jim

[dkatz42]

I'm not Tim, and I don't play him on TV. However:

Your pinout on U3 is correct. The notched end marks the pin 1/8 end.

The most likely culprit on the -27 is that you haven't cranked down the regulator pot for the negative side.

The negative probe always goes to ground if not otherwise specified (pin 2 on the power connector is a handy one.)

[runamuck]

I tried turning down both regulators not knowing which the negative side was), but to no avail.

Any other ideas?


Thanks,


Jim

[tpryan]

R12 doesn't affect the power supply, so that's not the issue. Make sure D9 and D10 are installed the right way round. Make sure R32, R33, and R34 are the correct values. Make sure you don't have a solder bridge between pins 2 and 3 of U5. Let us know what you find.