Author Topic: Bought my first oscilloscope  (Read 5804 times)

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Offline david77

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Bought my first oscilloscope
« on: May 18, 2013, 09:48:38 pm »
Yes, I finally put my hands in my wallet and bought my first oscilloscope last week.
It's nothing special, just a 2 channel 40MHz scope but it really is the first scope I paid for myself. My Hitachi scope was a gift from a well meaning family friend, an EE himself, who recognised my interest in electronics and my Philips scope was rescued from the trash and fixed with some help from some guys on here.


Here it is fresh out of the box:


Yeah, all right.  ;D It is an old banger, I'll admit it. It cost me all of 35,00 euros, straight from ebay. I like ebay.
It is a Siemens Oscillar M07107 analogue storage oscilloscope. I did not know Siemens ever made scopes until I stumbled across this beauty, but apparently they had a small line up of scopes in the 50ies, 60ies and 70ies.
I'm a bit of a sucker for everything with the word Siemens on it, so I wanted it. Luckily nobody else wanted it as much as I and I won the bidding.

There's even the service manual available. The internet is a good thing, isn't it?
http://www.rainers-elektronikpage.de/SM-SIEMENS/SIEMENS-M07107.pdf
Only German, sorry.

The seller advertised it as defective, he claimed the screen showed a green flash after turning it on but nothing else happened.
So, at least there was a chance of the tube & HV section still working.
Postman Pat hauled the thing to my front door today, the box looked like it had been shoved and kicked around in the depot for a week. I had horrible images in my head what I would find inside...
The seller did a reasonably good job at packaging it, though. Lots of bubble wrap and paper and - oddly - an old T-Shirt protected the scope.

Something was loose inside, though. There were parts rattlig around inside the case. Not good.
At this point it was time for Dave's motto so off we went to the man cave lab to crack her open.

The rattly bits turned out to be small screws, I think from the hinges of the missing carry handle.

There is quite some dust accumulated inside the unit as you can see in the following pics, most of it around the 8kV HV section, obviously. The back of the unit is also dented, no idea if that is Pat's fault or if that happened earlier.

The scope is made up of three modular sections. The display unit contains the PSU, the tube and all the storage circuitry.
The deflection unit is bolted to the display unit using four thumb screws. It contains the timebase and trigger circuits and controls. The third unit is the 2 channel amplifier that slots into the deflection unit. There was also a 4 channel amp available, will have to look out for that.











It was becoming obvious that this scope will require some major work to become usable again. A first quick visual inspection showed no obvious signs of damaged components, so I decided to power it up to see what's what.
And would you believe it? The damn thing still basically works! After a bit of fiddling with the controls and minor adjustments to focus, astigmatism and trace rotation I got this on the display:



Now I will have to start cleaning it up and fixing what's broken.
The trace could be a bit sharper and I think I can see a bit of ripple in the trace, dead caps probably.

I will update this thread as I go along and I'm sure I'll have some questions for you guys.
If anyone has got some good advice for me don't hesitate I'm all ears. There are after all several guys on here who have rescued old beauties like this.

« Last Edit: May 18, 2013, 09:53:50 pm by david77 »
 

Offline hammil

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Re: Bought my first oscilloscope
« Reply #1 on: May 18, 2013, 09:53:36 pm »
That's a beautiful piece of kit.. Fantastic score there :D I wish I had such luck

I'll have to do a little 'teardown' of an old valve scope my granddad gave me. Love old analogue circuitry
 

Offline elgonzo

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Re: Bought my first oscilloscope
« Reply #2 on: May 18, 2013, 09:53:46 pm »
Ohh... that lovely old Siemens logo...

(EDIT: Siemens & Halske, to be precise)
« Last Edit: May 18, 2013, 09:59:26 pm by elgonzo »
 

Offline Hydrawerk

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Re: Bought my first oscilloscope
« Reply #3 on: May 18, 2013, 10:04:20 pm »
Well, this scope is probably 40 years old.  :) Does the waveform storage function work?
Amazing machines. https://www.youtube.com/user/denha (It is not me...)
 

Offline david77

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Re: Bought my first oscilloscope
« Reply #4 on: May 18, 2013, 10:14:01 pm »
You're right it is probably exactly 40 years old, the newest date stamps on the electrolytics are from February 1973.
The storage function seems to work as far as I can make out. Never used a storage scope before.
 

Offline don.r

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Re: Bought my first oscilloscope
« Reply #5 on: May 18, 2013, 10:20:22 pm »
What a beautiful scope. Lovely design unlike the toy-plastic faceplates of today. I love the curved switches. Easily serviceable too with all that through-hole 70's goodness.  :-+
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Offline Rick Law

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Re: Bought my first oscilloscope
« Reply #6 on: May 19, 2013, 03:16:13 am »
Well, this scope is probably 40 years old.  :) Does the waveform storage function work?

For that era, most likely the storage part of the scope is an add on option made by another company called "Polaroid".  The capture is near instant, and re-rendering takes about 2-5 minutes, but storage capacity is unlimited.

I used that kind of "storage scopes" for a few years.
 

Offline quantumvolt

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Re: Bought my first oscilloscope
« Reply #7 on: May 19, 2013, 05:26:42 am »
It seems not to be a generic 2-ch scope. Here is a similar instrument with a 4-ch amplifier.

http://www.ebay.co.uk/itm/4-Kanal-Speicher-Oszilloskop-SIEMENS-OSCILLAR-S-M07107-/330791915201?nma=true&si=jko0nnqAdLz2CodTuCjIitS9zvw%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

Seems you got yourself some new nerd friends also ;)

http://www.radiomuseum.org/r/siemens_oscillar_speicher_oszill.html

Anyway - being a European soon to be 60 yo it reminds me of many things - including champagne and female companionship on the lab bench  :wtf:
 

Offline EEVblog

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Re: Bought my first oscilloscope
« Reply #8 on: May 19, 2013, 06:03:35 am »
Never seen one of those before!
 

Offline david77

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Re: Bought my first oscilloscope
« Reply #9 on: May 19, 2013, 07:52:51 am »
It is an odd beast, isn't it?

It's 9.30 A.M. here now and I'm going to bed. I've spent the whole night in the workshop taking the display unit apart. I brushed all the loose dirt off the PCB's, did some metal work to remedy the bent back of the unit and recapped the whole thing, apart from two caps because I didn't have 470µf/100V in stock.
I readjusted the power supply to give the proper power rails as per manual. Then treated the pots and switches using Kontakt 60 contact cleaner, then WL to wash the dirt out and then relubricated them.
I put the thing back together, switched it on, got a trace and heard a loud pop sound. The trace disappeared. No smoke, no smell, no fire. Just dead.
I rechecked all the 'lytics - maybe I put one in back to front? No I did not, would've been too easy.

In desperation I turned to the manual for help and found out it's missing vital parts. Parts of the adjustment procedure and parts of the circuitry are missing. Bugger.

After lots of poking around I figured out the rectifier for the 6,4V flood gun heaters had died.
Replaced that and got a trace back on the screen - for about 3 seconds, then it faded away. Turning the intensity down for a while and then turning it up to full would bring the trace momentarily back. So I assumed something in the brightness control/HV section had failed.
But that is exactly one of the diagrams that's missing.
After careful examination, logical thinking and traceing wires in thightly packed looms I found the board responsible for brightness and focus adjustments. Loads of HV foil caps and HV resistors to check. I desoldered every single component until I found a shorted 68nf foil cap. Found a replacement for it. Now it works!

I hope I can find a better manual as I'd really like to readjust the display unit.

Here's one of the PSU boards coated with dust - mmmmmm yummie!



Aren't hand drawn PCB's nice? No diagonal traces, no flood fill...

« Last Edit: May 19, 2013, 07:54:31 am by david77 »
 

Offline david77

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Re: Bought my first oscilloscope
« Reply #10 on: May 20, 2013, 12:16:41 am »
I've finished the display unit today. The final steps were to readjust the PSU voltage rails tweaking the focus, brightness and geometry and cleaning the frontpanel and the knobs.

Here's what the panels looked like before a bath in hot soapy water.





The right tongue angle is important when tweaking trimmers.





I also had to replace some knobs, thankfully even 40 years after this scope was built there are still very similar knobs available and I have a good assortment of them to hand.



The V/div vernier knob for channel one was a bit of a challenge as the original was broken and needed to be replaced. Of course it is one of those stacked knobs that are notoriously hard to get. With some luck you can make them yourself.
The problem here was the potentiometer shaft the knob sits on is very thin, only 2,5mm. No standard knob will fit this.
The knobs used on this scope have a brass insert and a collet that clamps down on the shaft. The knobs I had available work the same way but with standard 4 or 6mm collets. So I had to transplant the collet of the broken knob into the new one.



Heat is your friend for this kind of job. I just stuck the iron into the old knob and pushed the brass insert out. Then did the same with the new knob. The diameter of the insert in the new knob is a bit bigger so I glued the brass part from the old knob into the knob with a bit of epoxy. Let it set and it's ready for assembly.



Doesn't look too bad. Here's the cleaned and repaired Y Amplifier



It's a pity the clear indicator discs around the time/div and V/div knobs are yellowed. I don't know if I can replace them with new ones as those are usually knob specific. I'll probably leave it like that.

While working on the deflection unit I noticed more parts of the manual are missing, which is a problem for me as I wanted to realign the scope properly. I will have to contact Siemens if they have a complete copy of the manual.






« Last Edit: May 20, 2013, 12:20:01 am by david77 »
 

Online xrunner

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Re: Bought my first oscilloscope
« Reply #11 on: May 20, 2013, 12:37:12 am »
Very interesting model. Love the green display. I'm still using a 20 year-old Hitachi analog here so I can tell you they still are very useful!  ;)
I am a Test Equipment Addict (TEA) - by virtue of this forum signature, I have now faced my addiction
 

Offline david77

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Re: Bought my first oscilloscope
« Reply #12 on: May 20, 2013, 12:42:47 am »
Yes, I know. This isn't my first scope - just the first I actually paid money for  8). I have a Hitachi, too.
 

Offline ddavidebor

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Bought my first oscilloscope
« Reply #13 on: May 20, 2013, 05:11:18 am »
You'll learn a lt of things repairing scopes that nobody want... I 've done the same...

Davide Bortolami,
Fermium LABS srl
 


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