tektronix 2215

[smithy22]

Hi all I am new to the forum ,thank you for letting me join , my problem is that I forgot to turn off my 2215 scope when I  went to use it after about  a week it had no display , both beams had moved to the top of the display , the vert position control only moved the traces off the display,  the beam finder showed both beams .
I have had alook but cannot see any obvious burnt resistors or swollen caps .
Any thoughts please.
Steve.

[commongrounder]

This brought back a memory from a long time ago when the same thing happened to my 2215. It turned out to be a bad RCA transistor array IC. I found it with good old fashioned circuit tracing using the incredibly detailed service manual that came with it. Those were the days…

[bdunham7]

You're going to need the service manual w/ schematic, some test equipment like a DMM and perhaps another scope and a bit of patience and determination.  These are fixable, but they don't fix themselves.  If commongrounder had the exact same issue and can remember exactly which component it was that failed, that might be a 'silver bullet' sort of answer.  Silver bullets are good when you get them, but you usually don't.

Service manual is here if you don't have it:

https://w140.com/tekwiki/images/9/9a/070-3826-00.pdf

The first thing to do is carefully check all of your power supply voltages for voltage and ripple.  Given how it failed, it wouldn't be surprising to see bad capacitors in the PSU.

If that's all good, I'd guess that your problem is somewhere in the schematic on p. 159 of the .PDF that I linked, which I've shown here.  It is possible that the transistor array that commongrounder referred to is U197.

[smithy22]

Thanks for the reply ,much appreciated.

[jdragoset]

I had one do that, one of the four vertical output 340 ohm collector resistors (R 378,379,388,389) was open circuit, no burn or discoloration.
I was advised by someone on the forum to change all four and they are critical to frequency response.

[commongrounder]

I’ll pull out the manual for the scope and check what I found. This would have happened in the mid-1980s, so I’m a bit fuzzy on the specifics!

[David Hess]

I had one do that, one of the four vertical output 340 ohm collector resistors (R 378,379,388,389) was open circuit, no burn or discoloration.

I repaired a 2213 with exactly the same problem, but all of the output load resistors showed signs of operating hot.

The 2235 series which follows the 2213/2215 used 3 resistors in series for each output instead of 2.

[bdunham7]

The 2235 series which follows the 2213/2215 used 3 resistors in series for each output instead of 2.

As do the 2213A and other 100MHz models AFAIK.  But there are 3 150R resistors instead of 2 340R, so they actually run even hotter presuming the same voltage differential across the plates.  I have a 2213A main board here where those 6 resistors have been replaced and the board is burned to a crisp.

[commongrounder]

I’ll pull out the manual for the scope and check what I found. This would have happened in the mid-1980s, so I’m a bit fuzzy on the specifics!

Okay. Dug out the service manual. It was indeed U197, a CA3046 transistor array. Caused the traces to pin off screen. Loved that scope. It was my first big new equipment purchase for my fledgling electronics business back in the early 1980s. Got one as soon as they became available. I still have it, but it’s been in storage since I got into digital scopes. Gives me a warm feeling when I think of how many repairs I completed with that unit.

[David Hess]

The 2235 series which follows the 2213/2215 used 3 resistors in series for each output instead of 2.

As do the 2213A and other 100MHz models AFAIK.  But there are 3 150R resistors instead of 2 340R, so they actually run even hotter presuming the same voltage differential across the plates.  I have a 2213A main board here where those 6 resistors have been replaced and the board is burned to a crisp.

The 2235 was released before the 2213A/2215A, and the later are 60 MHz economy versions of the 100 MHz 2235.  Despite the model numbers, the 2213A/2215A are part of the 2235 series, and the 2213/2215 stand alone as a separate series of oscilloscopes with a different circuit and mechanical design.