I checked the 8640B that is not zeroing for S/N. Here is what I found:
1339A01128
The A2 board is 08640 60032
The working unit is 1943A12442 but that could be off as I was reading it backwards through a mirror!
The two manuals have are Jan 74 and May 91. The Jan 74 manual is not complete
Hope that helps someone track down what might be wrong..
Thanks,
Bill A
Artekmedia wrote:
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Bill
The 8640B was in production for nearly 20 years in the 70's and 80's and went through many changes over the years. For starters what are the serial numbers for your two units. Knowing that you have a better chance of getting the right manual. Knowing the actual part number of any given board in question is also helpful ( 08640-60xxx) as many units in circulation are recipients of "organ donor" boards from earlier and later units and the top level serial number is not always indicative of what is actually inside these days . Armed with the above information we can recommend the manual you should be looking for to best cover your unit
Dave
manuals@...
On 10/9/2018 1:34 PM, Willie wrote:
I just acquired a second 8640B and it works well except for one minor issue. The level meter does not zero at minimum level setting (CCW). The meter is different from my previous one in that it is auto ranging. I thought that was the cause but when I toggle the output off, the meter stays a little over 1 on the 10 scale. FM and AM zero OK.
In going through the manual, I found the drive offset pot (20K) on the A2 board. My manual and that board do not agree. My manual shows two IC's and 5 transistors. The board has 4 IC's and two transistors. Also I could not find TP4 as shown on the schematic SS13. I tried adjusting the pot for a zero on the meter but ran out of adjustment. Anyone have experience with this?
My HP435A agrees with full scale on the 8640B. 5V and -20V and +20V are there. I have not gone through all the manual changes. Maybe there is something there.
Thanks for any help.
Bill A
