Re: Tek 2215

 

On Sun, 24 Jan 2016 23:02:56 -0600 (CST), you wrote:

On Sun, 24 Jan 2016, David @DWH [TekScopes] wrote:
On Sun, 24 Jan 2016 22:11:50 -0600 (CST), you wrote:
On Sun, 24 Jan 2016, David @DWH [TekScopes] wrote:
On Sun, 24 Jan 2016 18:56:02 -0600 (CST), you wrote:
On Sun, 24 Jan 2016, jasontucker70@... [TekScopes] wrote:

I used new manufacture carbon comp resistors for the 1M ohm
resistors, however after the discussion on the list, I picked up some
high voltage rated film parts that I plan to replace those with the
next time I have the scopes opened up.
The Vishay VR25 and VR35 series high voltage film resistors are very
similar if not identical to the high voltage film resistors which
Tektronix used to replace the carbon composition resistors originally
used in the 22xx series focus chain. They are readily available and
inexpensive.
That's what I'm planning to install. I picked up 100 Vishay
VR37000001004FR500 for $13.60.
Lol. How many 22xx oscilloscopes are you rebuilding?
So far I've done 3 but I might rebuild one or two more 22xx scopes if I
manage to find them cheaply enough. At 6ea for the 3x 2213 scopes I have
that's already 18 out of the 100, and as useful as these resistors seem to
be, I plan to keep some stock of them in my parts cabinets. For whatever
reason the 1% parts were cheaper than the 5% too.
I only have the later 2230 and 2232 models and Tektronix used film
resistors for the focus resistor chain in them.

I would have expected there to be a clean cutoff date for when they
changed resistors in the focus resistor chain but that apparently is
not the case. The 2235, released in 1984, used carbon composition
resistors but the 2236 which was released at the same time used film
resistors and the 2213A and 2215A which were released later, both in
1986, used carbon composition resistors.

There was another resistor change Tektronix made and I think it was
for reliability. The 2213 and 2215 use two 1/2 watt 1% metal film
resistors in series for the collector loads at the output of the
vertical amplifier. These resistors run hot making them unreliable
and were the first 2213/2215 repair that I made and I know of two
other instances where they had to be replaced. The later models used
3 resistors in series for each collector load to distribute the heat
better.

The collector load resistors are not difficult to replace so I would
change them also.

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