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" <rich...@hughes.net> To: <time-nuts@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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.