[R-390] HP 8640B Question

[Jerry K]

I went through two 8640b's several years back and ended up with the same 
gear and output attenuator problems as everybody else before I threw up 
my hands and bought a clean used HP 8656B (from a defunct New York TV 
studio, no less), and it has been the best test equipment money I've 
ever spent. Even though it's relatively old technology, it's like 
stepping up from a Yugo to a Lexus for receiver work when compared to 
the 8640B. I especially like being able to quickly program sets of IF 
and RF alignment freqs and output levels for a bunch of different 
receiver bands, and recall any of them instantly with a couple of button 
punches during an alignment procedure. That is a HUGE time saver for 
bench work on R-390A's and such. I hate cranking signal generator knobs.

8656B's aren't what I would call expensive, but aren't being given away, 
either--maybe $400-$600 for a decent one with a money-back return 
privilege, admittedly not pocket change but worth every penny. The best 
part is what they DON'T have, which is nylon and plastic parts that are 
absolutely guaranteed to shrink, crumble, and self-destruct with age. I 
applaud efforts to resurrect piles of defunct 8640B's with new 
replacement metal gear trains, but for lots of reasons (speed/ease of 
use, programmable memory, and a much nicer display) I personally would 
never go back to an 8640B again even if somebody gave me one. There are 
too many better affordable options out there.

73, Jerry W5KP



Barry wrote:
>> Barry,
>>
>> There has been a LOT of discussion about these nylon/delrin (?) gear on 
>> the Test Equipment (qth) list.
>>
>> Apparently someone is "trying" to get a "good" one so that BETTER ones can 
>> be made.
>>
>> You may want to join and search the archives, or just search that lists 
>> archives.
>>
>> One site, <http://jvgavila.com/hp8640b.htm>, shows the split gear clearly.
>>
>> This causes the gear assembly to jump a tooth or two,, no doubt causing it 
>> to NOT be where it is supposed to be!
>>
>> Apparently, this is true of similar numbered instruments.
>>
>> Bob - N0DGN
>>     
>
> Hi Bob,
>
> It may very well have been on the Test Equipment list that I saw something 
> about the replacement gears.
>
> Yes, I did see the pics on Jose's site.
>
> There's one up for bid on eBay and I think its just in need of gear work.
>
> Thanks!
>
> Barry - N4BUQ 
>
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