[Test-Equipment] RCA tube manual (WO-33A schemo) error

[third Eric]

de N4TGC Eric

While reading TM 11-671, "cathode-ray tubes and their associated
circuits", I got interested in what type of circuit the two tube-type
o'scopes I have used.  One is the Heath IO-17, for which I have the
manual, so that was easy; on the others, the RCA WO-33A and B, I had no
info (it's available on the BAMA website, but I don't want the massive
.djv converter necessary to access it), so I looked in my '66 and '70
RCA tube manuals, which have representative o'scope schemos in the back.

Turns out, these schemos ARE the WO-33A!  Here's where it gets odd: in
studying the 12AT7 push-pull horizontal amplifier in the '66 edition, I
discovered a serious error in the schematic - which is repeated in the
'70 edition, even tho it's been re-drawn to a different size!

Look at the resistor array around the H POS potentiometer: as drawn, the
pot is shorted out, as is the 2.7 meg resistor to it's left; and the two
820k resistors would be in parallel.  To correct this, the trace from
pin 9 of the CRT should jumper OVER the two 820k res., not connect to
them!

I hope whoever might have built this circuit followed RCA's advice and
bought the kit - and that this error wasn't in the kit schemo!  Ya'll
check your RCA tube manuals, and WO-33A and B schemos - I'm curious as
to how far this error propagated!

BTW, neither of the WO-33's I have work well: both have muddy traces and
poor frequency response.  I'm hoping this is just bad coupling/filter
caps, and not a fault of deteriorated PC board.  I did find that the
response on the B was improved slightly by someone who altered the input
circuit (I forget exactly what they did, but it involved removing or
substituting the input capacitor in some manner.)	e