[ARC5] Scope Question

Tue Mar 20 17:55:28 EDT 2018

I believe the front-end attentuator of the 22XX series is a resistor film
hybrid.  You would need a donor.  Otherwise, the rest of the circuits are
not hard to work on as Tom said.

The 24XX are terrific scopes....but.....they have several large hybrid
assemblies that are prone to internal delamination.  Those complex modules
are unobtanium so you would again need a donor.  The problem is very common
so donors are in demand. Sometimes the delam problems can be mitigated by
baking the module in a very hot oven (best done when the wife is
out-of-town).  Sometimes the delam is temp dependent and you can sweep the
problem under the rug by adding some cooling to the module(s). I have a
24XX that only delams on summer days after being on for hours.  I just
mounted a low profile heat sink under the case such that it contacts the
module.  It sheds enough heat to keep the scope reliable.

Dennis AE6C

On Tue, Mar 20, 2018 at 2:16 PM, Tom Lee <tomlee at ee.stanford.edu> wrote:

> Most of my scopes arrived with no trace. I own over 100 (possibly as many
> as 200); don't ask why. Of those, only two have had anything seriously
> wrong with the HV supply -- one Tek 465, and one Telequipment
> something-or-other. The 465 had a bad multiplier, which I was able to
> replace with a modded multiplier from an old color TV. Not pretty, but
> completely functional.
>
> I love older analog scopes precisely because their general lack of
> unobtainium parts gives me a fighting chance at repairing them. With modern
> scopes, if anything other than the power supply is the problem, they're
> often basket cases.
>
> I have also fixed many 22xx scopes (the switching supply seems to have
> many failure modes). I am not sure why someone would consider those
> particularly hard to repair. Except for the front end, everything is pretty
> accessible.
>
> --Cheers
> Tom
>
>
> --
> Prof. Thomas H. Lee
> Allen Bldg., CIS-205
> 420 Via Palou Mall
> Stanford University
> Stanford, CA 94305-4070
> http://www-smirc.stanford.edu
> 650-725-3383 (public fax; no confidential information, please)
>
>
> On 3/20/2018 2:12 PM, K5MYJ wrote:
>
>> When I buy old scopes  won't buy one that does not show a trace.
>> Replacing the HV(CRT) power supply can be difficult and expensive.
>>
>> I've been warned that the Tek 22XX and 24XX scopes can be difficult to
>> repair.
>>
>> I also find early HP digital test equipment can be a CRAP SHOOT! And I do
>> understand why, The earlier analog stuff is usually not a big problem.
>>
>> Bob Macklin
>> K5MYJ
>> Seattle, Wa.
>> "Real Radios Glow In The Dark"
>> ----- Original Message ----- From: "Kenneth G. Gordon" <
>> kgordon2006 at frontier.com>
>> To: "Michael Hanz" <aaf-radio-1 at aafradio.org>
>> Cc: <Arc5 at mailman.qth.net>
>> Sent: Tuesday, March 20, 2018 9:59 AM
>> Subject: Re: [ARC5] Scope Question
>>
>>
>> On 20 Mar 2018 at 12:16, Michael Hanz wrote:
>>
>> I've seen that procedural step sometimes used on the later solid state
>>> scopes to reduce the chances that you will start a measurement with the
>>> sensitivity switch set at, for example, .01v/CM, when you are about to
>>> measure say 800v p-p. Transistors don't like that. It's a last "do you
>>> really want to do this?" check before you make the measurement.
>>>
>>
>> Yes. That makes complete sense, but then why didn't the manual follow
>> that with advice to
>> 1) set the vertical sensistivity to "such and such", then
>> 2) set the input to AC or DC to take the measurement.
>>
>> The
>>> older tube input scopes are pretty immune to such errors.
>>>
>>
>> Yes.
>>
>> Or, it may be a manual error, as you suggest.:-)
>>>
>>
>> Yes. Well, I am also working on a couple of Tek scopes, a 2465B and a
>> 2467B (which had
>> been left out in the rain for at least a year before I got it), and I am
>> finding periodic small
>> errors in the documentation.
>>
>> BTW, the 2467B works just fine after I let it dry out for a month or two.
>> The 2465B doesn't
>> "work" at all, but it appears that the trace-blanking is locked on
>> permanently.
>>
>> Ken W7EKB
>>
>> ---
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