Re: Tek 453 - Q913 Part Number


Howard Matthews
 

Repeating my private post (I guess, I'm still learning how the posts
work on Yahoo)...

The serial number given indicates the proper part number for Q913 is
the "selected" 2N3251, PN 151-0133-00. At SN 12680 this circuit was
redesigned and Q913 became PN 151-0220-00, a 2N4122 with no
indication that it was specially selected. My parts list is very
clear about this, my schematic is less clear, but shows a PNP.

If you have the right part in your scope, you can get a general idea
whether Q913 and it's surrounding parts work by measuring: Base=-
0.24V, Emitter=-0.18V, Collector = -3.8V. (Hmm, I'm guessing that's
a Germanium because of the .06V base-emitter voltage. That seems
low even for Germanium, but that is what the schematic says.)

But before you blame the Z-axis for lack of trace, check the
horizontal and vertical deflection pins on the CRT. They should all
be, or Horz/Vert centering should adjust to, about 47-48V. A
failure in either the horizontal or vertical amp boards can drive
the trace off the face, and appear as though there is no trace. I
know, I just fixed a "no trace" 453 with a bad transistor in the
vertical amp. It's a real smiley face experience to replace a
transistor in a $19 "parts scope" and suddenly get a decent trace!

Good luck,
-Howard

--- In TekScopes@yahoogroups.com, "Rolynn PRECHTL K7DFW"
<k7dfw@c...> wrote:



Q913 - Tek pn 151-0220-00 Silicon 2N4122 for Type 453
oscilloscope
===========================

Now I'm confused.

My manual, with SN 4395 written in, shows 913 as a 0133-00 which
is a
selected 2N3251 (a PNP) and the schematic shows it as a PNP.

That 2N4122 is a NPN.

K7DFW

..._._

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