Hi.
I jealously keep a PM3212 Philips Oscilloscope buyed as used in the '80 years.
I've use very much this instrument during my hobbyist and study phases.
Several years ago the sync it's not looking at the Channel B.
It doesn't matter if this problem is for me and for you small or big, because I want to repair it.
At the begin I was imagining that having two channels this task could be simple respect what really is. I was convinced to apply the same "CAL" signal to both channels and compare it: yes, but using what?
Going to the point: what I can record?
The two channel are quite the same, with very small difference.
The Y input signals A as B, pass to several stages, to finally go to the deflection system on the CRT.
This is all OK, for both my channels A and B.
What don't go well is the Sync signal B that (as for A) is derived from the stage called "Impedance Converter", by the coaxial cable called "Channel B Pick Off".
It's a very silly thing: the Y signal from his input run to the CRT, without any fail, but the "Channel B Pick Off", derived from it it's not good if checked on the S16 Group, the Sync Source Selector.
So I was hoping that the problem was the coaxial cable, that connect the origin of the "Channel B Pick Off" to his destination board, but also this hypothesis fall through because the cables are not in short circuit and there are no interruptions.
I have also exchanged the coaxial A with B and the problem turns now on A. This is an important verification (now A coax is returned on A as B is returned on B).
I have measured many voltages inside the circuits with V611-V612, but all the measurements on the Channel B are very similar to the same on the Channel A.
I have just one oscilloscope, this. So it is not so easy to look "inside" the circuit.
I need some suggestion to exit from this "stall" phase.
Thank you.
I decide to write this, after reading the interesting discussion:
https://www.eevblog.com/forum/repair/philips-pm3212-oscilloscope-a-channel-problem/msg1096835/#msg1096835