Repair and Re-build of SE Labs SM 112 Scope

[Skywave]

I have another scope so I'm not stuck but I'd love to get this one going again.
John.

That second 'scope will almost certainly be needed to mend your defunct SM112. You say there is no time-base. Presumably that is on all T/B speeds. If so, that implies a fault in one - or more - of the following: the T/B self-triggering cct., PSU (missing rail voltages), blanking cct. or a defunct horizontal O/P stage - which is where I'd look first - then the PSU etc.

Let us know if you get stuck; good luck with it.

Al.

[Yorkie]

At least they're original manuals to - not photcopies of dubious quality, but always best to use such sources as a last resort, only when exhaustive efforts have failed, as was so in John's case. Out of curiousity, I've just checked out 'Hameg 203-7 manual' and it came up with one in good condition at the very reasonable price of $7.00US (no idea about P&P though, as Alan points out). However, Hameg's policy, which is very helpful, is to make available for free download from its website, full manuals of current and obsolete scopes in German and English. Occasionally (as with the 203-7) the PCB overlays are only in the German version, but that's no problem - just download both manuals and take the layouts from the German one into the English one.

There's lots of stuff on Tektronix, Gould, Heathkit, AVO, Taylor etc sprinkled across the web FOC, but the site that John has highlighted looks like an excellent fallback if all else fails.

(Is it my imagination, or have things gone spookily quiet on the forum?)

[Tedzed1]

It has gone a bit quiet as of lately, but it has been bloody cold,

[Skywave]

Yes, I noticed that things had gone quiet . . . I was going to comment on it . . .
Some of us have outside 'facilities' only, and some of those are unheated - like mine! Obviously, that's a bit of a disincentive to get 'stuck in'! As for the lucky members, I can only assume that they're busily beavering away on some repair or restoration that we will all get to hear about - hopefully soon.

Al.

[Geaney]

John,
That looks like a site worth saving, although as you say the prices are a bit steep. On the other hand you do get a real Manual not a tatty unreadable copy.
One question: search as I might I can't find any Postage costs. What are they to the UK or Europe?
Alan

Put it this way Alan, the postage is like ordering one CD from Amazon US - the postage doubles the price. For the SE Labs manual the postage is about the same as the manual. After looking for months I figured I wasn't going to find one elsewhere so I bit the proverbial bullet, etc. Mind you they gave me a tracking number so maybe I'll have a look and see how long it will be before it gets here.
Cheers, John

[Geaney]

Service manual arrived yesterday. It is a genuine original and full of all the test and setup info I'll need as well as excellent circuit diagrams even including waveforms at major test points, etc. No excuses now - except the day job means it will probably be a fortnight before I find some spare time in the workshop.
Cheers, John

[Yorkie]

Didn't take long to arrive John.

Looks an excellent outfit to deal with, which only supplies original manuals - never photocopies. At least it shows that they aren't just keeping one copy of each and churning out scores, maybe hundreds, of photocopies, in effect, using a photocopier as a 'money printing press'. Best of luck sorting the scope out!

[Geaney]

Well the weather has warmed a bit (at least for now) so I've started to have a look at the SM112. A lot of previous work has been done on it and the quality of workmanship is pretty bad. There are three boards in the power section and all look to have been repaired. The fourth (HT) looks largely untouched.
I removed the modules for the channels and for the timebase and I had a very close look at the timebase main board. This was covered in flux and solder splashes so someone spent a lot of time on this and left it in a dodgy state. I found solder splashes lying across tracks so that's probably what happened - one day I popped it up on the bench and something shorted out.

So I've spent a while cleaning it all up so it looks half way decent. There are some very poor solder joints that will need attention before going further. Some large caps in the power supply also look bulged at the ends so I'll need to replace those as well. There are various heat-discoloured resistors as well so I'll replace those too.

I made a video clip but despite re-encoding it a few different ways I can't get it to upload to YouTube. I'll keep at it.

This one could indeed take a while but at least I've got started on it.

Cheers, John

[Yorkie]

You're the man for the job John!

Good luck every step of the way as you embark on your voyage of discovery unpicking the imcompetent work of those who have passed before.

At least they were running scared when it came to delving into the HT section.

[Geaney]

I finally got the video clip uploaded - though pretty low res so I'll try again with higher res version.

For the curious among you the clip is here -

http://www.youtube.com/watch?v=0O8A7dmoSow

Cheers, John