JSR03 - information

[Keljian]

Ok, in that to rule out latch-up, set the gain to 2 or around. Then you would get 13.5-14.0 volts. If you get those voltages you may have a problem with the opamp and the common mode limits. If so, try to solder in two diodes across the inputs.

Will you measure the opamp voltages with respect to ground.

so, you're saying change R8, R9 and R7 to set gain 2, while trying to keep R7 around 500 ohms, while trying to keep R8 and R9 in parallel = R7.

(which involves working out values for all of them and desoldering/resoldering (just making sure I hear you right)

measuring opamp voltages now..

[Keljian]

Pin 2 = 1.7 v
Pin 3 = 0.988v
pin 5 = 2.1v
Pin6 = 8.16v
pin7=  1.407v

the opamp with respect to ground

[peranders]

Pin 7 should have more or less the output voltage, check the schematic. Are you REALLY sure that you have 47 ohms or less? The AD797 takes 8-10 mA which mean that you will loose 300-500 mV.

If you want to test different gains, let R8 be and connect resistors in parallel with R8.

[Keljian]

Pin 7 should have more or less the output voltage, check the schematic. Are you REALLY sure that you have 47 ohms or less? The AD797 takes 8-10 mA which mean that you will loose 300-500 mV.

If you want to test different gains, let R8 be and connect resistors in parallel with R8.

R11 is 46.7 ohms exactly (just measured)

[Keljian]

I mixed up the pins, I'm tired.. sorry

pin 8= 2.1
pin 7 = 8.16
pin 6 = 1.407

[Keljian]

AD797 may not like too much differntial voltage. I don't recommend it as you may have noticed, still you can fix this by applying to diodes across the inputs.

Would you please measure:

Pin 2, 3, 4, 6, 7

Vout

Vin

Voltage across T4

2-6 = 6.45v

2-7 = .302v

3-5 = 1.1v

3-6 = 7.16

4-7 = 1.3v

Vin = 33.23v

Vout = 8.27

T4 = 2.57, and .574

will also mean I mixed up these, here are the fixed versions - sorry I had an exam today


2-7 = 6.45v

2-6 = .302v

3-8 = 1.1v

3-7 = 7.16

4-6 = 1.3v

[peranders]

Could you please repeat:

Pin 2

Pin 3

Pin 6

Pin 7

Output

At LM329, cathode

Have you notice how LM329 is, NOT like the LM431.
http://home5.swipnet.se/~w-50674/hifi_pics/hifi_100pr/jsr03r0_lm329.jpg

[Keljian]

Could you please repeat:

Pin 2

Pin 3

Pin 6

Pin 7

Output

At LM329, cathode

pin 2-3-6-7 relative to ground? or relative to each other?

working on it now

[Keljian]

Vout = 8.29

pin 2 = 1.7v to ground

pin 3= 0.988v to ground

pin 7 = 8.16v to ground

pin 6= 1.4v to ground

anode of LM329 = 0.239 to ground

cathode of LM329= 0 to ground

[peranders]

Check my picture. Notice also that you should not have R4-R6.

Of this you can see that if you want to replace parts you must also check very carefully in datasheets so you are sure that you know what you. I'll hope this was the problem, fingers crossed!

I will add LM329 as an option to LM431 so this has to be documented later on.

[Keljian]

Check my picture. Notice also that you should not have R4-R6.

.

so what should I do with r4 and R6?

remove them completely? replace with jumpers?

[Keljian]

Check my picture. Notice also that you should not have R4-R6.

.

so what should I do with r4 and R6?

remove them completely? replace with jumpers?

after just removing R4 and r6 there is no change

I'm guessing R5 has to be removed also?

[peranders]

Have you checked the picture above and turned the LM329?

R4-R6 removed.

[Keljian]

Have you checked the picture above and turned the LM329?

R4-R6 removed.

29.82 v after all that

on Vout

[Keljian]

26.4 under load (m3)

input is 33.3v

target is 28.5v (approx)

26 is a touch low..
but it'll suffice so long as it's low noise

LED goes off under load