Hi all,
I noticed my 7A13 amplitude was way down on a 70 MHz sine the other day, so figured I'd run through the calibration. I skipped the input resistance section that requires the precision DC divider, and I'm using a PG 506 fast rise for the HF compensation; it's slower than the 250 ps Type 109 the manual calls for, but easier than messing with the Type 284.
Through a 20 dB attenuator and 50 ohm thru termination, the 7A13 is showing about 1 div overshoot on a 5 division step from the PG 506, and I cannot adjust that out. It's so huge that I can't even see the effect of C113/C150/C250 on the corner. A bandwidth check with SG 503 says it's ~40-45 MHz.
I've tried swapping the 1-2 relays that I haven't drilled and cleaned in this 7A13 with a NOS relay, with no change. It affects + input and - input alike (unused input set to GND), which has me pretty confused, as I thought the signal paths would be independent. Anyone encountered this before or have ideas on what to look at?
Just as a sanity check, I tried a spare 7A13 that I'd never even plugged in, and it does not have the overshoot problem, and rise time is respectable (did not measure bandwidth because the SG 503 crapped out and started flashing 000).
thanks,
Adam
