C84 Rev. 1.6 Parts List Doesn't Match PCB

[ryansteele]

On the parts list, it calls for...

Q6, Q13 - BC550
Q5, Q12 - BC560

However the board doesn't match up. The spaces are screened as Q3, Q4, Q7, Q8.

Can anyone tell me what goes where?

Thanks.

[ryansteele]

All the transistors are mislabeled......need updated list for all Q's.

Thanks.

[tpryan]

Rev 1.6 schematics and updated BOM are now available.

[goldcut]

hi Tim

a quick update here on the forum of the calibration procedure (R19, R63 and R67 on PCB v1.6) would be greatly appreciated as is it the only thing remaining to do before using it in my studio.

and to know wich pin is #1 on the u1, u2 and u3 would be great to know to.


thx
Mathieu

[tpryan]

a quick update here on the forum of the calibration procedure (R19, R63 and R67 on PCB v1.6) would be greatly appreciated

Make the offset adjustment with your meter connected to pins 2 and 3 of the output connector, or at L3 and L4, whichever is more convenient. Adjust your meter to read 200mV DC full scale. Set the gain to step 9 and adjust R19 for minimum offset. Be sure to allow the module to run for about 15 to 20 minutes before making the final tweaks.

[goldcut]

as for the minimum offset (R19), i guess the point is to put it to 0 volt offset.

but what do we do exactly with R63 and R67? those are used to correct the voltage sent, in relation with, i guess, U1 and U3.

thx Tim


Mathieu

[tpryan]

but what do we do exactly with R63 and R67?

Step 38. The pots are now numbered R63 and R67 instead of R68 and R72.

[goldcut]

thx Tim

then what is the sure way to know wich pin is #1 on U1 and U3



thx again

[tpryan]

then what is the sure way to know wich pin is #1 on U1 and U3

http://focus.ti.com/lit/ds/symlink/opa2604.pdf

[goldcut]

hi Tim

i've checkup my thing here and i think i made a mistake.
i've put the op amp on U1, U2 and U3 without checking the voltage (as explained on point 38) before. now i've check up with R63 and R67 at them minimum and i have +27V and -27V on both C84 i've built. The op amp are hot but i still can touche them without being burn.

then if i change the R63 and R67 i've got no variation on voltage on pin 4 and 8 on U1 and U3. do i have to remove U1, U2 and U3 to set the voltage and then reinstall them? (urghhhh)

this is happening on both C84 i've built.
what can i do?

thx!

ps.: i've received the 2 pieces, thx!

Mathieu

[tpryan]

now i've check up with R63 and R67 at them minimum and i have +27V and -27V on both C84 i've built

Are you absolutely sure you haven't swapped U4 and U5? Are D14 and D17 oriented correctly?

[goldcut]

yeah U4 and U5 where swapped on both unit.
on unit i was able to save the piece and now everything is normal and working.

on the other one, i had to go to electronic warehouse and buy 1 LM317T and 1 LM337T.

i put them on board, now i have +18 and -18V on U1 and U3, only thing is for the offset (R19) it start at -25V and was only able to put it back to -20V and then im at the max of the R19. hos is that possible?
im sure the piece i bought to replace are replica in spec.

thx Tim

[tpryan]

For the malfunctioning C84, can you post the voltages you measure at U3, pins 1 through 8?

[goldcut]

U3

Pin 1 : -12,98V
Pin 2 : -2,23V
Pin 3 : -2,32V
Pin 4 : -18V
Pin 5 : -2,42V
Pin 6 : -2,48V
Pin 7 : 12,78V
Pin 8 : 18V


Negative is on pin2 of J3 and positive is on the U3 pin 1 to 8


Thx

[goldcut]

so what do you think Tim?



thx