Zenith 25CC25 horizontal sweep problem

[Chuck]

On Mon, 26 Jul 2010 08:19:04 -0700 (PDT), Jim Adney
<jadney@vwtype3.org> wrote:

On Jul 21, 11:22 pm, Jim Adney <jad...@vwtype3.org> wrote:

Finally, I checked the DC bias on the HOT. The Zenith manual says it
should be -80 V, so I was expecting it to be lower. It's actually -65
V. So there must be something else wrong in that circuit.

In comparing my Sams & Zenith manuals, I find that Zenith says the HOT
control grid bias should be -80 V but Sams says -48 V. I now have -65
V. I'm going to guess that Sams is right and I need something closer
to -50 V, which should turn things up a bit more and get me to the 26
kV that I should have for the HV. I also checked the tube data sheets
for the 20LF6 and 26LF6 and found that typical control grid bias
values are -10 and -20 V. So I can afford to boost that voltage quite
a bit higher (more positive) than the -65 V where it's at now.

The set is put back together now, but I'll pull it apart again once
our houseguests (arriving tomorrow) are gone. In the meantime, it
looks like I should try to buy one of those odd 63-5440s. AFAIK that's
the one remaining part in there that might be the problem, but I'll
check around the circuit, too, to make sure I haven't missed
something.

As an aside: Was it common for the Sams to be more accurate than the
Zenith manual? Or, to put it differently: Did the Zenith manuals have
a poor reputation?

thanks,
If I remember correctly, there were usually more mistakes in the Sams

manuals. Chuck