[time-nuts] Update on HP-5345A (long!)

Jose V. Gavila eb5agv at ctv.es
Wed Jul 26 07:31:18 UTC 2006


Good morning!

Following this comment I made some days ago:

>Well, yesterday I was lucky enough to buy an HP-5370A in unworking condition
>(just lights POWER led) for the princely sum of 57.50 Euro (and NO shipping as
>it is a local buy :-) ). From same seller I got an unworking (but complete!)
>5345A for 37 Euro. And also a paper 5370A service manual (14.59 Euro). And some
>other cheap HP things...

I have some news. As you know, I got the 5370A working as it had just a shorted
tantalum and an open fuse resistor.

So yesterday I went for the 5345A. I have a working unit and also a box of parts
I got from the shipment-damaged unit (the one pictured here
http://jvgavila.com/hp5345a.htm)

First than anything else, I opened the unit to find it was missing the fan, and
fan wires (which have on them 115Vac when powered!) were hanging around,
touching some cards!. I was lucky to open it BEFORE powering on, as I could have
ruined the unit. Hint: ALWAYS take a look inside units BEFORE powering on!

My 5345A stack of parts included the fan and all needed hardware to fix it on
place so I did it. Unit seemed complete except for the HPIB card empty space
(unit had not that option; if somebody has an spare, I would love to buy it).
One curious thing is that the ovenized oscillator is not HP but another brand. I
guess it is a cheaper unit. Date on it is 1986 whilst this 5345A seems to have
been made around 1982 so it appears to be as a later add-on. Anyway, I have also
an spare from the parts-unit so it could be replaced if needed.

Once I had visually checked the unit and replaced the missing fan, I powered the
unit. All I got was fan noise (these units do really generate a _bit_ of noise!)
and all '0' digits (not really; one position had a faulty segment; I swapped the
7-segment unit with the first one, which only uses the center segment). Of
course, counter function didn't work. Well, at least there was no smoke!

I had not opened bottom cover and I did it... to find a nice metal part loose on
the bottom cover. Hint #2: open ALSO bottom cover to check for weird things!

And then, checking from the bottom side, I found a suspicious thing: one
connector to the input assembly was semi-unplugged!. Somebody else had obviously
been there before and had tried to fix the unit (without success, I must add).
So I connected it and after some vacuum-cleaner work (there were some spider
rests around), I powered the unit again. This time I got a promising display,
showing the ARMED sign, '*' and all '0's. Good!. So I put a 10MHz signal on
INPUT A... and got a 99.xxxxxx mHz indication. So, obviously, there were some
other faults on the unit.

I took the Service Manual (also in paper form, which is VERY convenient to work
on large foldouts) and started the troubleshooting procedure. It is curious but
all my previous works on HP gear didn't need of any 'special' thing. But in the
5370A there was even an special card (I was quoted US$250 and US$1490 from two
sellers for the repair kit). And in the 5345A there is lots of logic analyzer
work... but, as I had a complete parted-out unit, I was confident I could fix it
the fast way (i.e. replacing modules) and then perhaps working on the faulty
assembly.

As I wanted to check if the spare cards I had were good, I began replacing them
from left to right and checking each time if there was any change in the counter
operation. I put it on the CHECK position, waiting for the 100 MHz display...
First six cards I had, except one, worked same way as original ones. The other
one just didn't work, so I replaced it with original unit, hoping it was not the
faulty card. And then, replacing next one (A9 MAIN GATE ASSEMBLY), I got the
counter working :-)!!!. I checked it also with an external signal and it went
right up to 500MHz with good sensitivity. NICE!!!

I swapped all the cards for the original units, except A9, and counter continued
to work. So I have a good set of spares (except one), just in case.

Once unit was working, I looked at the poor front panel. It seems unit had been
stored and transported without care and it was badly scratched. Fortunately, my
parts unit front panel was very nice looking. But as it was an older version, it
was not directly compatible, as power connector was completely different. Also,
it had sustained some frame damage. So I took out all the knobs and nuts in both
and got the aluminum plate swapped among units. Once the knobs were carefully
cleaned, 'new' front panel looked really good.

So this is the end of this long post (hope somebody arrives to this point ;-)!)

All in all, from the three large HP units I got last Friday (5370A, 5345A,
8660B), I have already fixed two :-). The other one (8660B) has some missing
parts and will sure take a lot more time (BTW, does somebody on the List have an
8660B parts-unit?)

Hard work begins now... I need to fit the units in my crowded workbench :-)!

Best regards,

JOSE

----------------------------------------------------------------------
 73 EB5AGV / EC5AAU - JOSE V. GAVILA
    La Canyada - Valencia (SPAIN) - Loc: IM99SM 
    
 Vintage Radio: http://jvgavila.com 
 Vintage Test Equipment: http://jvgavila.com/testeq.htm 

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