开云体育

Has anyone encountered a sweep discrepancy with the alternate mode on a 547? I have calibrated the caps and resistors in both time-bases to match each other. When using the A sweep by itself the trace is perfect. When using the B trace by itself it is again, perfect. When you use alternate mode the A sweep contracts as per the photo. The top waveform is the A. It is a 10kHz square wave. The effect is most noticeable at 50uS and higher which lead me to suspect stray capacitance in the horizontal switch or something, however if I electrically isolate the alternate traces by pulling the multi-vibrator transistors out, A sweep is again spot on even though the horizontal switch is set to Alternate mode. Very frustrating fault and annoying to use like this. This is the very last issue with my 547 as I have replaced nearly everything and it works brilliantly apart from this small niggling issue. Has anyone had this problem? Thanks!
Deon



/g/TekScopes/photo/274749/3423741?p=Created%2C%2C%2C20%2C2%2C0%2C0

On Mon, May 2, 2022 at 03:17 AM, TV7 wrote:

...
When using the A sweep by itself the trace is perfect. When using the B trace
by itself it is again, perfect. When you use alternate mode the A sweep
contracts as per the photo. The top waveform is the A.

If you have another scope and can look at collectors of Q465 and Q475, do you see 0V to 27.5V pulses with opposite phases? Perhaps one of the components (e.g. R474) drifted around that area and in switching state pulses are not reaching to their target voltage.

Ozan

Thanks for the reply Ozan, I checked the values of the components in the multi and they are all in spec, also the square wave is there and opposite phase between sections as it should be thanks.