[time-nuts] My 5062C tale

[Tim Schulz]

Greetings, I thought I would update the list on the repair progress on 
my 5062C.  Some of you might recall that I had queried the list several 
months ago for troubleshooting help.  I would like to really thank Corby 
for the troubleshooting tips and Stan for the power supply page scans 
from the service manual.  It turns out that I had a dead ion pump high 
voltage power supply, but it took me a while to get the diagnosis.  I 
had thought it was the 18v power supply card.  This particular unit is a 
Navy 1695A/U badged model with the battery backup and all the optional 
features.  I got it off ebay about a year ago, and had been working 
pretty well for 8 months prior to the failure.  I had made an assumption 
that the 18V regulator card was bad because it looked seriously 
overheated, but the only way to know was to pull the bottom cover and 
probe the motherboard from below.  HP used these damn tinnerman nuts on 
the brackets to secure the sides of the cover and all of my screws were 
over torqued and the threads cut such that there was no way that the 
bottom was coming off without a fight.  In the mean time I won another 
5062C carcass of ebay missing its Cs tube but otherwise powering up and 
putting out signals.  I think that "I'll just swap 18V modules", but 
predictably that doesn't work and I have to drill out rivets holding the 
brackets and eventually figure out that the enabling signal from the ion 
pump power supply is not active.  The carcass has a ion pump power 
supply present, but it too is dead.  These are in little soldered shut, 
deep-drawn cans, so I carefully cut them open with a dremel moto tool 
and cut off wheels.  The innards look like a 17KHz switcher driving a 
pulse engineering transformer module and then a final (I assume) potted 
voltage multiplier.  I think the voltage multiplier is dead.  Anyway, I 
have a 2.5Kv 50ma power supply from an old IR scope tube and I wired 
that up though an old 100uA FS meter movement to the connector of the 
power supply module.  I also jumpered a resistor bridge onto the 18V PS 
enable signal line and reinstalled the module into the 5062C.  I had to 
put a variac on the input to the HV supply because it turned out to be 
too lightly loaded and the voltage was at 6Kv, arcing over to a near by 
cap.  There was an initial pretty high current reading, but it very 
quickly dropped to what looks like close to zero.  I powered the 
standard up and it and would give me a green light, and would stay green 
as long as I was in the shop, but the alarm light comes on and the green 
light goes out overnight.  All of the meter readings seemed to be normal 
for the 1st two days though the 2nd harmonic reading bounces between +25 
and +35 at about a 2hz rate.  Yesterday when I checked on it, the ion 
beam current had crept up past 50, so I turned it down to 30 and made a 
1st attempt to tweek the frequency adjustment.  Can't say that it made 
any difference, still got an alarm on the overnight run. I did find a 
smallish ionizer power supply that is flyback based and runs on 5v in 
the junk box that I was thinking about as a substitute.  The original 
standard says 2.6Kv on the PCB, and the newer model carcass says 3Kv - 
is the ion pump voltage critical?  Also, my Cs tube, PN 05062-60500, has 
an SN of 1516A0596.  I am assuming that its an old tube and that the 
only replacements will come from other machines... I looked at the FTS 
web site, didn't see any indication that they support it.  I was 
wondering what the remaining tube life might be and should I just keep 
the standard powered down most of the time with only the ion pump 
active.  Anyway, thanks again for the help!  tim