Zenith 25CC25 horizontal sweep problem

Jim Adney · 2010-07-19T01:14:46+00:00

I'm trying to fix my '73 Zenith 25CC25. The problem is that thehorizontal sweep is not wide enough, so my picture is compressedhorizontally. I've lost about 10% of the width on each side. Otherthan that, it's fine. I have both the Zenith service manual and theSam's for this set.I've tried other hor osc tubes (6U10) and hor out tubes (20LF6) andnone of the ones I have (which should be good) worked any better (butsome were a bit worse. Not too surprising.)This is a hybrid set, with 3 Zenith Duramodules. I have spares foreach module, but swapping in the appropriate spare made no difference. I checked the B+ in the Horizontal stages, and it's fine, 274 V.The Vertical also seems fine, but I just tried to check the 2nd anodevoltage, and got garbage readings from my HV probe. I'll take thatprobe to work tomorrow and check it to see if I can nail down thatproblem. It says I only have ~6800 V, which seems impossible. It'ssupposed to be 26 kV, so if it was really that low I believe thevertical sould be WAY overscanned, which it's not.I've checked a few resistances that I can get to easily, and so farthey all seem good.What I haven't done so far is try to get a scope in there to look atthe signal at each stage, so at this point I don't know where theproblem starts.I'm hoping someone here will still be familiar with this old set andcan suggest some good places to look next.thanks,