Print Page - Help with -5vdc for JSR-01

Title: Help with -5vdc for JSR-01
Post by: chilli6565 on July 19, 2011, 06:13:34 AM

I have already built the +5vdc version of the JSR-01 reg...but I am having trouble building a -5vdc version.
I have completed it but now get -7.6vdc on the output....I have done the following

input is -22vdc

H1 lamp is on

R10 = 47 ohms
C10 = 100 nF
C11 = Tin jumper

all above are done and ok

r4 wire bridge changed to r5 for neg version

6v8 zener in z2 position

t1 t2 and t3 are correct neg regs

tl431aid is in position ic8

any ideas??

pictures to follow

Title: Re: Help with -5vdc for JSR-01
Post by: chilli6565 on July 19, 2011, 06:39:39 AM

photos as promised

[attachment deleted by admin]

Title: Re: Help with -5vdc for JSR-01
Post by: peranders on July 19, 2011, 12:55:32 PM

DZ2 should be a LED. Use the same passive parts as for the +5v. When you have changed the DZ2, can you measure all voltages around the opamp? 2.5 V is a good start for pin 2 and 3 on the opamp. The voltages at the pins should be identical within a few millivolts.

Title: Re: Help with -5vdc for JSR-01
Post by: chilli6565 on July 20, 2011, 06:25:36 AM

Not sure I understand...in the +5v version I used the 6v8 zener in pos z2 and it works fine, but will change it here to a led and take measurements around op-amp :-D

Title: Re: Help with -5vdc for JSR-01
Post by: peranders on July 20, 2011, 10:09:15 AM

It seems that I may have forgot some details. This design didn't use a LED in this position. The zener should work in forward, meaning plus at the anode. Can you measure the voltages around the opamp?

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Projects => Power supplies => Topic started by: chilli6565 on July 19, 2011, 06:13:34 AM