8640b issues

Steve Do you have any numbers? What falls off - the frequency or the output levels in dbm? Do you have a repair manual? (You can download one at BAMA:

) I wish I was in your shoes, I have all the time in world to repair test equipment - aka lack of customers.

Tom

Steve, Is this unit the standard civilian or the military version (AN/USM 323- black face plate)? I will try to trouble shoot it for you long distance from here. Tom

Steve, Just another added thought - You might want to post you request for assistance in the news group:

sci.electronics.equipment

There might be more equipment repair techs visiting there then here.

Tom

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Also QEX (ARRL Publicati>Steve,

Steve, Just another added thought - You might want to post you request for assistance in the news group:

sci.electronics.equipment

There might be more equipment repair techs visiting there then here.

Tom

=20

=20

Also Yahoo group

Civilian version, I believe. Standard grey case, I can get the s/n and other specifics on monday.

Thanks, Steve

Steve-

The only common problem I've heard of, is cracked or broken nylon gears in the tuning mechanism. I've never had mine apart, so can't tell you what to look for.

I imagine that there could be additional circuits that must be tuned to track frequency. If a gear was broken, it would mess up the tracking and could explain low output at one end of the range.

The person who told me about this indicated that he had custom metal gears made for one(s) he repaired. They may not be commonly available.

Fred

There are sooo many stages and parts in these nice old generators, it could be most anything.

If it happens on EVERY range, then it's most likely in the big rocket-shaped oscillator. Too bad as that's acccording to HP a non-user-repairable unit.

IMHO the whole thing is a non-repairable unit! There are so many custom IC's in there it's a big crap-shoot. I was able to make ONE working unit out of three sick ones, but that's not terribly economical. The nylon gears, the digital readout, and the voltage regulator modules, the FAN, the lever knobs, the slide switches, all seem to be very weak points on these units. They're very ruggedly built otherwise, lots of gold-plating, heavy-duty castings. But too many weak points IMHO. You might consider parting it out! I'd sure bid on a working digital readout module!

Regards,

Oh I forgot a few shaky things: The power transformer, the power diodes, the Pc board they horridly mounted the power transformer ON, the many dipped-tantalum capacitors that tend to short out on the hidden motherboard and modulation boards, the board handles that crack off, the unobtainable power output IC's hidden under a ton of allen-head bolts, the modulation meters that stick or fail, the gold-plated slide switches that switch all the lc filters, under a ton of screws, the u-joints and flexible couplings that break, the often-charred output attenuator that is almost unrepairable. I could go on but I think you get the idea.

Thanks for the replies everyone. I had it apart a while ago, I remember checking out the gears, but don't remember the condition they are in. If memory serves, it does fall off on every range. We do have a working one that we use as the standard, so we'll probably keep this one as a part unit, I was just wondering if it was a quick-n-easy so we could have two (as is I have to run an 8 ft coax to a test bench whenever I do power meters). Again, thanks for the replies, I'll probably just leave it in the stock-pile of old stuff for future use, there's other things that need fixin that get priority.

Thanks, Steve

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

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