J
Jim Adney
Guest
I'm trying to fix my '73 Zenith 25CC25. The problem is that the
horizontal sweep is not wide enough, so my picture is compressed
horizontally. I've lost about 10% of the width on each side. Other
than that, it's fine. I have both the Zenith service manual and the
Sam's for this set.
I've tried other hor osc tubes (6U10) and hor out tubes (20LF6) and
none of the ones I have (which should be good) worked any better (but
some were a bit worse. Not too surprising.)
This is a hybrid set, with 3 Zenith Duramodules. I have spares for
each 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 anode
voltage, and got garbage readings from my HV probe. I'll take that
probe to work tomorrow and check it to see if I can nail down that
problem. It says I only have ~6800 V, which seems impossible. It's
supposed to be 26 kV, so if it was really that low I believe the
vertical sould be WAY overscanned, which it's not.
I've checked a few resistances that I can get to easily, and so far
they all seem good.
What I haven't done so far is try to get a scope in there to look at
the signal at each stage, so at this point I don't know where the
problem starts.
I'm hoping someone here will still be familiar with this old set and
can suggest some good places to look next.
thanks,
horizontal sweep is not wide enough, so my picture is compressed
horizontally. I've lost about 10% of the width on each side. Other
than that, it's fine. I have both the Zenith service manual and the
Sam's for this set.
I've tried other hor osc tubes (6U10) and hor out tubes (20LF6) and
none of the ones I have (which should be good) worked any better (but
some were a bit worse. Not too surprising.)
This is a hybrid set, with 3 Zenith Duramodules. I have spares for
each 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 anode
voltage, and got garbage readings from my HV probe. I'll take that
probe to work tomorrow and check it to see if I can nail down that
problem. It says I only have ~6800 V, which seems impossible. It's
supposed to be 26 kV, so if it was really that low I believe the
vertical sould be WAY overscanned, which it's not.
I've checked a few resistances that I can get to easily, and so far
they all seem good.
What I haven't done so far is try to get a scope in there to look at
the signal at each stage, so at this point I don't know where the
problem starts.
I'm hoping someone here will still be familiar with this old set and
can suggest some good places to look next.
thanks,