[Test-Equipment] HP-140T/8555A/8552B/8445A repair (II)

[Jose V. Gavila]

Hello!

I have good and not so good news about my HP-140T system repair. I have two 
good mainframes (another 140T and a 141A) but I wanted to get this 140T 
working as the other two host 8553B/8552B and 8554B/8552B pairs, so I 
looked at it yesterday to find that the usual LV supply voltages (-100V, 
+100V, +250V and -12.6V) were fine except for the last one, which was -22V 
on startup (without plug-ins) and then slowly drifted to close its nominal 
voltage. Circuit is not too complex but it took me some time to locate an 
open 432K resistor (without getting it out of the circuit I got a 
reasonable value). Once replaced, I was able to adjust all voltages to 
specifications and mainframe worked fine with plug-ins on it. Nice!!!

So, once I had the mainframe working, I got back to the 8555A. I have not 
yet got a suitable counter to deal with the LOs (as it seems to me that the 
YIG is not working) so all what I could check was DC voltages. All were on 
specs. My plan was to get an HP-5254C plug-in to be able to use my HP-5245M 
up to 3GHz, which would be enough to check LOs (if not at full range). 
There was a unit at eBay which ended today at 3:10AM Spanish time (!) but I 
have been brave enough to bid on it and have won the bidding war... BUT now 
I have found that the 5245M I have is not working :-(!. It is missing 
timebase and, probably, some other items. Well, I had forgotten about these 
'small details'...

So now I need some parts to get the 5245M working, to be able to use the 
5254C once I get it here. Is there any available for parts?. Could I use 
the lower-spec 5245L timebase, if I locate one?

Well, all in all I am happy as things are starting to work on this project. 
And, for sure, I will learn a lot in the process :-)!

Best regards,

JOSE
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  73 EB5AGV / EC5AAU - JOSE V. GAVILA
     La Canyada - Valencia (SPAIN) - Loc: IM99SM

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