Telequipment D1011 oscilloscope repair

[Wozzaaah]

Messing around with my scope yesterday and noticed one of the switches felt a bit odd and didn’t seem to do much.
A quick google told me it’s a very common thing on these and some of their other models.
Stripped it down and sure enough, the trigger selection switch had fallen apart.

Two of the wipers had come off and got mangled up. The one on the left is how it’s supposed to look.



They’re held on by nothing more than little plastic stubs that get melted over.

I carefully straightened out the wipers, superglued them to the switch and used dressmaking pins as “rivets” to hold them more securely.

All ready to refit:


It all now seems to work as it should, the trigger level control that didn’t do anything now does something and the trace no longer dances about on the screen.

 

[500e]

Nice repair

 

[Carl Wilson]

Very interesting and very nice repair.

 

[Carl Wilson]

One day I will get around to sorting these.

 

[500e]

Long long time since I saw a Phillips top hat variable cap

 

[Seadog]

AKA a beehive trimmer

 

[500e]

yep same thing different name

 

[sardine]

My brother used to design oscilloscopes, if you've got any questions I'll pass them on to him.

 

[D1011scope]

Messing around with my scope yesterday and noticed one of the switches felt a bit odd and didn’t seem to do much.
A quick google told me it’s a very common thing on these and some of their other models.
Stripped it down and sure enough, the trigger selection switch had fallen apart.

Two of the wipers had come off and got mangled up. The one on the left is how it’s supposed to look.

View attachment 152963

They’re held on by nothing more than little plastic stubs that get melted over.

I carefully straightened out the wipers, superglued them to the switch and used dressmaking pins as “rivets” to hold them more securely.

All ready to refit:
View attachment 152964

It all now seems to work as it should, the trigger level control that didn’t do anything now does something and the trace no longer dances about on the screen.

Hi,

Thanks for this great and really helpful post.

I've got the same scope and am having a problem with the CH1 beam not showing. After reading this post, I suspected that the CH1 switch might be broken and the channel turned off, in which case the beam wouldn't show.

I decided to take it apart and found that the switch is indeed faulty and looks very similar to the one you showed on the photo.

I would like to repair it but am not entirely sure what it should look like. The one in the above post has a number 3 on it, so does mine. However, I could only find two small metal platelets but not three, as in the post above.

Does anyone know what the contacts on a fully functional CH1 switch should look like (2 or 3 contracts and at which positions)?

I'd be eternally grateful for some advice.

Thanks
Peter

 

[Wozzaaah]

Hi Peter, welcome to the forum, I'm glad this thread has been useful to you.
If you look at your switch lever you can see where the plastic pegs have sheared off. It looks like that switch may have only ever had two sets of wipers on it.
It's been a while since I did my repair but if you look where the wipers have rubbed the tracks it should be easy to see where they need to go and if you do have anything missing.

 

[Martin-Sy]

It looks like it's a double pole 4 position switch. First bit of the circuit from the manual below. It's S901a for one of the poles:

But I couldn't see how the OFF bit worked. Then I twigged that the switch has two poles and the other pole S901b, is shown on a different circuit sheet:

So if I've got the right manual, and relevant circuit diagrams, you should have two of the wiper things and four contacts (or do they rub onto exposed tracks on the PCB).
Your pictures didn't seem to show enough bits. Did anything fall out?

I got the manual here in case you don't have it:

http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Telequipment/D1010.pdf

Looks like that's in Poland!

 

[D1011scope]

Thank you both, Wozzaaah and Martin-Sy, for your detailed reply!

Please find attached a picture of the PCB as well.

I think I'll give it a go with the two sets of wipers and attach them where the pegs have come off.

 

[D1011scope]

Your pictures didn't seem to show enough bits. Did anything fall out?

Thanks. I did check if anything fell out but couldn't find anything. It's still possible that I missed it but it looks like there were only two wipers to begin with. Does that sound reasonable to you based on the picture of the PCB?

Thanks
Peter

 

[500e]

Have 3 of these iif you think you can make use off

 

[Martin-Sy]

Yes, that's perfect.
The little bits that fell off are the switch wipers.
They link the inner arc of PCB trace to the outer arc sections.
The wipers both move in unison.
I have annotated your picture with the function stated on the front panel for each of the four switch positions :

You should be able to follow the physical arrangement of the PCB traces to the schematic in my earlier post.

So all you have to do is to get the wipers stuck back to the plastic in the right places so they make these connections.

 

[D1011scope]

I have annotated your picture with the function stated on the front panel for each of the four switch positions :

This is pretty amazing! A huge thank you, Martin-Sy, for your detailed reply. I've learned a lot!

Following your advice, I attached the wipers so that they can switch between all four positions. Although I'm not proud of my glueing, it seems to do the trick. Channel 1 is now up and running again . I'm super happy that the scope is working again!

 

[D1011scope]

Have 3 of these iif you think you can make use off

Thanks a lot for the offer but it looks like the switch is working again .

 

[Wozzaaah]

Nice job, glad you got it sorted.