Assembling the WB

[Phil Hunter]

--- Bruce P. wrote:
[snip]

I started w/ a different tack that may be of interest
to some, basically focusing on the power supplies,
building and testing as I went.

R19 & D9 seemed like a good place to start, I left
the component leads (to J11 & J12) uncut as convenient
connections for "alligator clips". I temporarily
used R5 (1K) in series w/ J11 to limit current to a
safe level and hooked up a 24Volt power supply,
confirming about 18V across D9. Three 9V batteries
could be used in series, if you don't have a 18+ Volt
power supply. At this point I lowered the "battery"
voltage to 13.8V and after C5, C8, U5 & C6 were
stuffed, checked for 8V across C6. R12 & R13 make a
voltage divider, 4V between the middle and Gnd (J12).

I chose to use sockets for the IC's so I could pop the
chip and bend a lead or two out and reinsert the chip
for debugging if I need to, w/o risking PCB damage due
to desoldering heat. I second Bruce's recommendation
of machined collet sockets. Just to be kinda on the
safer side, I only soldered the power pins (4 & 11) on
U4, and pins 1, 2 & 3, leaving the others unsoldered
for now, then checked for 4V from pin 1 to Gnd.

BTW, glad to see Steve C. didn't get the LM324's, they
have some "quirks" that may cause problems, I suggest
no one use them.

R37 & C11 came next, 4V from J7 to Gnd (J12). D8, R14
and R36 next, solder U4 pins 12, 13, & 14, measure
1.23V on pin 14. Put in R11 and now measure 0.45V on
pin 14. R23 & D11, 2.50V to Gnd (J12). CAUTION: the
following voltages will likely change later as more
parts are stuffed. R10, R20, U4 pins 8, 9, & 10, 2.50V
on pin 8. R21, R15, U4 pins 5, 6, & 7, 2.50V on J8.
We now have confidence U4 is working correctly.

That's as far as I got Wednesday, wrote this today,
may be a mistake or typo here, be careful, have fun.

regards,
phil
(digest)


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