How to disassemble Tek 2236 ? ... for A1 mainboard HV section


cc_electronic
 

Hello.
I have an old Tektronix 2236 with a focus problems.
Here, at link below, as you can see, the focus potentiometer is fully counterclockwise and the trace is blur:

http://picasaweb.google.com/116568688030447199475/DropBox?authkey=Gv1sRgCPzsm4302ZXSEw#5510425901585135602

Can you give me any aid?
And how to disassemble the circuit parts to have access in focus-circuit (R892, C893, Q885, etc.) in A1 main board ???

Thanks everyone!


 

get the service manual - the maintenance section gives you all you should need to know to dis-assemble it.


Regards,
David Partridge

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of cc_electronic
Sent: 28 August 2010 13:20
To: TekScopes@...
Subject: [TekScopes] How to disassemble Tek 2236 ? ... for A1 mainboard HV section

Hello.
I have an old Tektronix 2236 with a focus problems.
Here, at link below, as you can see, the focus potentiometer is fully counterclockwise and the trace is blur:

http://picasaweb.google.com/116568688030447199475/DropBox?authkey=Gv1sRgCPzsm4302ZXSEw#5510425901585135602

Can you give me any aid?
And how to disassemble the circuit parts to have access in focus-circuit (R892, C893, Q885, etc.) in A1 main board ???

Thanks everyone!



------------------------------------

Yahoo! Groups Links


cc_electronic
 

Thank you very much! ...Section 6 of the Service Manual :-)
Thanks to David and Tom (by e-mail)

I disassembled the CTM and power-supply shield circuit and now I have access to the focus circuit.

Do you have any suggestions for me to fix the problem? ...or some experience... or some particular topics on this board or related link to webpage/blog ?...

I noticed that when the instrument is power-on there are also "whistler" capacitors in these circuit parts (how can I identify whistling capacitors to replace?)

--- In TekScopes@..., "cc_electronic" <ciro.carbone@...> wrote:

Hello.
I have an old Tektronix 2236 with a focus problems.
Here, at link below, as you can see, the focus potentiometer is fully counterclockwise and the trace is blur:

http://picasaweb.google.com/116568688030447199475/DropBox?authkey=Gv1sRgCPzsm4302ZXSEw#5510425901585135602

Can you give me any aid?
And how to disassemble the circuit parts to have access in focus-circuit (R892, C893, Q885, etc.) in A1 main board ???

Thanks everyone!


Kevin Wood G7BCS
 

Do you have any suggestions for me to fix the problem? ...or some
experience... or some particular topics on this board or related link to
webpage/blog ?...
Mine exhibited a similar problem once and the culprit was a group of 4
series connected 510k resistors in the dropper chain that fed the focus
control. These run a little hot and one had failed.

Kevin


cc_electronic
 

Thank you Kevin. I check the series of 4 510Kohm resistors.
I will inform you

--- In TekScopes@..., "Kevin Wood" <mailinglists@...> wrote:


Do you have any suggestions for me to fix the problem? ...or some
experience... or some particular topics on this board or related link to
webpage/blog ?...
Mine exhibited a similar problem once and the culprit was a group of 4
series connected 510k resistors in the dropper chain that fed the focus
control. These run a little hot and one had failed.

Kevin


cc_electronic
 

You're right!
R889 was open... replaced it and the focus is now good.

before (R889 open) --> http://picasaweb.google.com/116568688030447199475/DropBox?authkey=Gv1sRgCPzsm4302ZXSEw#5510425901585135602

after (R889 replaced)--> http://picasaweb.google.com/116568688030447199475/DropBox?authkey=Gv1sRgCPzsm4302ZXSEw#5511299525766373474

Remained only one capacitor that whistles loudly. I tried with my ear to understand where it comes from and I think C906

Thanks again to all!

--- In TekScopes@..., "Kevin Wood" <mailinglists@...> wrote:


Do you have any suggestions for me to fix the problem? ...or some
experience... or some particular topics on this board or related link to
webpage/blog ?...
Mine exhibited a similar problem once and the culprit was a group of 4
series connected 510k resistors in the dropper chain that fed the focus
control. These run a little hot and one had failed.

Kevin


sbirdasn <sbirdasn@...>
 

--- In TekScopes@..., "cc_electronic" <ciro.carbone@...> wrote:


You're right!
R889 was open... replaced it and the focus is now good.
Nicely done!

The 2236/A is my favorite 2200 series scope!
I love the CTM on that scope. Best thing is that unlike many other CTM optioned scopes, the CTM goes easily to full rated bandwidth. If you can trigger it, you can count it.

Oh, and the 5000 count DMM side is great too. Love being able to trace down artwork shorts with 1/100 ohm resolution metering.

And that was in the day when >3.5 digit DMM's were both expensive and hard to find in the wild unless you worked in a very good engineering lab.

Your efforts will yield great returns on the test bench.

Sbirdasn.


Frank P
 

When a capacitor whistles loudly, what is that an indicator of? And, how is it resolved?

Thanks.



Remained only one capacitor that whistles loudly. I tried with my ear to understand where it comes from and I think C906

Frank P.


J. L. Trantham
 

Pickle?
 
 

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Frank P
Sent: Tuesday, August 31, 2010 10:25 PM
To: TekScopes@...
Subject: [TekScopes] Re: How to disassemble Tek 2236 ? ... for A1 mainboard HV section

 

When a capacitor whistles loudly, what is that an indicator of? And, how is it resolved?

Thanks.

>
> Remained only one capacitor that whistles loudly. I tried with my ear to understand where it comes from and I think C906
>

Frank P.


Glenn Little
 

Sounds like the capacitor is venting.
Replace the capacitor.

73 Glenn
WB4UIV

At 11:24 PM 8/31/2010, you wrote:
When a capacitor whistles loudly, what is that an indicator of? And, how is it resolved?

Thanks.



Remained only one capacitor that whistles loudly. I tried with my
ear to understand where it comes from and I think C906

Frank P.



------------------------------------

Yahoo! Groups Links



chipbee40
 

Whistle noise on these is almost always from T906 or T944.
I've never tried resoaking them in transformer varnish but it may work if you don't have access to replacements.
JC

--- In TekScopes@..., "cc_electronic" <ciro.carbone@...> wrote:


You're right!
R889 was open... replaced it and the focus is now good.

before (R889 open) --> http://picasaweb.google.com/116568688030447199475/DropBox?authkey=Gv1sRgCPzsm4302ZXSEw#5510425901585135602

after (R889 replaced)--> http://picasaweb.google.com/116568688030447199475/DropBox?authkey=Gv1sRgCPzsm4302ZXSEw#5511299525766373474

Remained only one capacitor that whistles loudly. I tried with my ear to understand where it comes from and I think C906

Thanks again to all!



--- In TekScopes@..., "Kevin Wood" <mailinglists@> wrote:


Do you have any suggestions for me to fix the problem? ...or some
experience... or some particular topics on this board or related link to
webpage/blog ?...
Mine exhibited a similar problem once and the culprit was a group of 4
series connected 510k resistors in the dropper chain that fed the focus
control. These run a little hot and one had failed.

Kevin