[time-nuts] New request for HP 3458A info

[Greg Burnett]

Dick,

Measuring the A1 DC Board with another DC voltmeter, I'd expect near zero 
volts DC between circuit ground and the junction of A1R19 and A1C23. (This 
is the Low Voltage DC Input Line of the Input Signal Conditioning 
circuitry.) If seeing a large positive DC offset I'd suspect A1Q26. If 
seeing a large negative DC offset I'd suspect A1Q27. Both are J-FET N 
Channel transistors, Agilent p/n 1855-0793.

If you don't have a DC offset problem there, I'd suspect some other fault 
upstream on the A1 DC board. (The A1 DC board occupies the right half of the 
top side of the instrument.)

Cheers,
Greg



----- Original Message ----- 
From: "Dick Moore" <richiem at hughes.net>
To: <time-nuts at febo.com>
Sent: Friday, July 31, 2009 7:53 PM
Subject: [time-nuts] New request for HP 3458A info


I'm looking at an HP 3458A that boots up with a failure -- message is
OVLD. Running the self test the first time returned the following:

ERRSTR 209, "HARDWARE FAILURE -- INTERNAL OVERLOAD: 72"

I turned it off, waited a bit, turned it back on and got:

ERRSTR 202, "HARDWARE FAILURE -- SLAVE TEST: OVERLOAD"

A while later, powered up and got the original 209 error again. There
are no further errors behind these two, just them. The Assembly Level
Repair Manual has some error codes, but no details -- it appears to be
a fault in the DC measurement section. Anybody seen either of these
errors before, or have any idea what's wrong? Any and all help
appreciated. The power supplies appear to be working correctly.

Dick Moore

_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to 
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.