Re: Tektronix 7A26 problems
One of the difficulies with DC coupled amplifier chains is finding out whether any discrepancies are due to a preceding or following stage. Did you check voltages on pins 2 and 3 of U1550 on the input side? On the output side did you swap U1450 or U1550 with their partners in channel 2? Since everyone is supicious of resin dipped tantalums you could check the voltages around Q150A&B where there are C140 and C158 decoupling the +/- 15V rails. On my 7A26 Q150 appears to be soldered but as Craig says, if yours is socketed then check that poor contacts are not upsetting the DC operating point or gain.
You said at one point that the bandwidth switch moved the trace around, that is a little surprisng since they are after Ch1 and Ch2 are combined so a fault there should affect both channels. Q820 840, 860, 880 are usually socketed so easy to check.
Hope your persistence is rewarded,
Roger
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