[JMS] 90903 questions

[ronnie.hull]

Good morning y'all

I have had the good luck to come into a 90903 and a 90902 scope in the last 
few weeks. Both of them work. Sort of. The 90902 has a replacement front 
panel of shiney aluminum but otherwise is all there, with the exception of
the vertical and horizontal input posts on the FRONT. Actually, the 90902 is 
missing these too but I'm not worried about it.

The 90903, S/N 1983,  does not focus real well. This morning I checked all 
resistances and found all of them to be within 20%. I have NOT replaced any 
of the tubular or mica capacitors yet, though I will.

3 resistors shown on the schematic can't be found. R7, 1.8K Which should 
connect to one side of the intensity control, and R11 and R12, both shown to 
be 2.2 meg and hook to the wipers of the V. Centering and H. Centering 
controls. And, speaking of the controls, the V. Centering and H. Centering 
are shown on the schematic ( I have an original manual ) to be 3.3 meg each. 
BOTH controls measure only 90K. So, besides the controls being WAY off what 
is shown on the schematic, the wiper resistors are non existant. UNLESS, they 
are inside the socket on the 3KP1.

does anyone know IF those resistors are indeed inside the socket? Has anyone 
found the same abnormal values of the V. Centering and H. Centering Controls?

I would be glad to provide a copy of this original manual, scanned in PDF 
format, to anyone who wants it.

and btw...   the 90903 has a BLUE trace :)

thanks in advance

Ronnie