On Wed, Dec 19, 2018 at 05:24 AM, Colin Herbert wrote:
I have both Tektronix Service manuals for the 486. Volume 2 is P/N 070-3516-00
and the latest revision is December 1982. On schematic #8 it shows +13.0V at
the bases of Q958 and Q987A. Bear in mind that R971 connects to the +15V bus
at one end, but then goes to chassis via R970 (the B sweep start pot) and
R972. So, the voltage on the slider will vary according to the position of the
slider of R970. If my arithmetic is correct this variation will be 12-13V, so
your maximum 12V is low and your minimum 9V is also low. Maybe R970 has a
dirty track?
Colin.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of lop pol
via Groups.Io
Sent: 18 December 2018 02:14
To: [email protected]
Subject: [TekScopes] 468 still
Im still troubleshooting my 468. My schematic is blurry and I was wondering if
anyone could tell me the proper voltage at the base of Q958 and Q987A on the
A15 board. I have 15V on one side of R971 but he other side is wildly
fluctuating between 9V and 12V I don't think thats right. Thanks guys.
I replaced R970 with a used variable resistor which ohmed out correctly. I guess I should get a new one just to make sure. We are all on the same page, so at least that is good.
