Shruthi - Power test (step 5) Fail

When testing the power supply i am getting a reading of between +6.61 and +6.64 and between -6.36 and -6.42 using a PSU rated at 9v (this is a multi adaptor psu supple with different ratings, connectors and a polarity change) when tested with the PSU set to 7.5v i get a reading of +4.64 and -4.45. One mistake i made was to fit the DIP8 socket the wrong way. also i am unsure about the optional 10uF tantalum cap (C1) whether it is the correct cap, in testing i removed this as its stated that its optional and i got the same results. I am a noobee so any help would be much appreciated. Cheers, kieran.

So your readings look symmetric which is a good thing.
Replace the Battery in your Meter, its presumably empty. As most Multimeters depend on the Battery as reference your readings will get higher the lower the Battery Voltage is.

Thanks for the speedy response! i replaced them before i posted. now butchering a psu with a different polarity.

+7.46 and -7.15 with a modified korg electribe PSU

@fcd72 - great info re: multimeter

@serum114 - You may want to check the voltage of the power supply itself with the meter. The tantalum, I believe, is the fattest and most round cap. I think you did it right.

Thanks greenrange. Im not the best with a multimeter tbh but using it set at 20v i get +5.56 and if i test it as i have previously read by going off the diode (D1) i get a reading of 12.58.

20v direct current is that right for all these tests?

Is your 10 pF cap in the correct place?

Yep. its situated
just behind the dip8 socket.

What are the voltages on each pin of the regulators?

Furthest reg away from dc connector p1 being closest to the edge of the board . P1 = 11.85 P2 = 0 P3 = 6.77 Reg closest to the dc connector P1 = 0 P2 = -11.50 P3 = 6.53. Thanks for joining in Pichenettes

Hi. Still stuck. Can anybody throw any light on this? Also it seems strange that I get different readings when I change the rating of my PSU. Surely the regulators should insure that I only get +/- 5v what ever the rating is on my PSU (7.5v or 9v is what i’ve been using).

Have you checked the Regulators are not swapped???

ffs. right that could be the problem got them the wrong way around… Could i have damaged anything? I"ll de solder in a moment and test. Cheers.

Ouch. MAybe you have killed them…
The good thing is your LT1054 is working ;_)

EDIT: the orientation of the Regulators is OK, just checked the Pics, so check if the 7*8*05 is on the position close to the hole for the Screw (IC9)

Ok. i’ve repositioned them and im getting +5v but only receiving -0.83. May have botched the removal of the 7805 reg by forcing it a little…

What are the voltages on each leg of the 7905?

7905 - P1=0 P2=-11.50 P3=-5
7805 - P1=+11.82 P2=0 P3=+4.95

P1 being closest to the edge of the board

At which point do you have only -0.83? If the 3rd leg of the 7905 is at -5V, things should be OK, unless there’s a bad connection between the 7905 3rd leg and the board.