Tektronix 2235 preregulator
I have a 2235 oscilloscope which appears dead (no lights, no trace). Fuse is not blowing. I have no voltage on the 43v preregulator line.
Is there any common problems with this model?
Kevin Wood G7BCS
HiI had a similar problem with my 2236 a while back. The switching
transistor (from memory, a MOSFET on a heatsink just behind the cooling
fan) had died. The fan had also seized up so I suspect it probably
overheated. Replaced the MOSFET and substituted the fan for a computer fan
of the same size and it's been fine since.
tom jobe <tomjobe@...>
Hi Graeme,toggle quoted messageShow quoted text
The Tekscopes message archive has lots of information about your 2235
question, including what common component to substitute for what, when you
Many of the 22xx's have the same basic power supply (PS), such as 2213A,
2215A, 2224, 2230, 2232, 2236 etc.
There is also a fine 22xx power supply repair document available from our
friend Hakan at:
His method of injecting the 43 volts from an external source works very well
in a case like yours. It is a big help in figuring out what is wrong in a
From my own experiences, the least likely thing to fail is the PWM chip
U930, but your testing will often make you think it is the problem when it
actually isn't. Obviously U930 can be bad, however unlikely that might be.
There is no "unobtanium" in the 22xx PS, and there are common substitutes
for the PS's components that are not proprietary such as the transformers.
Even the transformers are available used if you look around.
----- Original Message -----
From: "zl1gbb" <zl1gbb@...>
Sent: Monday, February 08, 2010 12:40 PM
Subject: [TekScopes] Tektronix 2235 preregulator
Hiis not blowing. I have no voltage on the 43v preregulator line.