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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 12th Nov 2019, 2:48 am   #1
Zelandeth
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Default Sun Microcomputer II Motortester 1215

I'm not *entirely* sure where this post should be...but I think the computer component is what really would have set this apart from most test gear you would have expected to see in a garage back in the day. This was a pretty impressively advanced bit of kit in its time.

Mods, if you think this would be better in another section please feel free to use your judgement...or if it's too much car diagnostic kit and not enough vintage electronics that's fair enough.

I don't get too much time to tinker with vintage tech too much these days, which is why you haven't seen much of me in the last couple of years. This struck me as an impressive enough piece of equipment that most people will never have seen inside of...so I'll be looking to keep you guys appraised of the electronic and electromechanical side of the restoration in more detail than I might on the automotive forums I'm on. If you're interested of course.

The computer in this is a whole little card cage under the right hand monitor (the left one is a pretty basic analogue scope, so not really too interesting)...and I'm really looking forward to getting into it and seeing what it's based on. Place your bets?

So...this morning I got to pick up an extremely shabby rental van from Sixt (won't be doing that again, Enterprise have earned my loyalty over the last ten years...will stick with them in future). What then followed was six and a half hours of horrible traffic and Google Maps deciding that I wanted to go on a rallycross tour despite my preferences clearly being set of "please keep me on motorways whenever possible please..." This is far less than ideal when you have a fragile, top heavy load on board which is really poorly secured because the van doesn't have any proper tie down points. That was a really annoying discovery!

Anyway...what was I renting a van for?

Getting home what must be a few hundred pounds of diagnostic kit from I think the early 80s. That was a few hundred pounds in weight...I don't even want to think about what this must have cost.


Only *nearly* killed me and my husband getting it through the door. Hiring a van with a tail lift was definitely a good call. The console itself is *just about* a two man lift so long as you don't need to go very far.

It looks to be in exceptionally good shape for industrial gear of its age...if rather filthy.

This didn't surprise me too much based on what I'd seen in the eBay listing...the prior owners looked to be the type of place which really look after their gear.

A quick wipe down has helped turn it back the right colour, though the whole case would benefit from a cut back with some appropriate polish in due course.

The flipdot indicators in the buttons are a lovely touch and the sort of detail you just don't see these days.

Anyone able to get a date out of the serial number?

I do have all of the leads, probes, timing strobe etc. Just removed them for transit as the boom is unwieldy enough without it swatting me in the face with cables every five seconds. Manuals and a load of data sheets as well.

This thing very much meshes my automotive and vintage technology restoration hobbies...so I'm really looking forward to getting stuck into it. Apparently it has been working recently, though I'm expecting it to need a bit of TLC. Shedload of vacuum tubing will want changing anyway at the very least. It's been better stored than my old Crypton Motorscope 335 so hopefully I'll have less issues with scratchy switch contacts...hard to say at this age though.

Everything else aside though, isn't it just a gorgeous bit of industrial design? Know the modern version will have massively wider functionality and be a quarter of the weight... won't have half the style though!

If there's anything anybody would like to see or questions about it let me know.
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Old 12th Nov 2019, 11:08 am   #2
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Default Re: Sun Microcomputer II Motortester 1215

It would be nice to see what all the functions are and how the circuits achieve it.
It is old enough that it will be relatively easy to understand if the circuit diagrams are clear.
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Old 12th Nov 2019, 1:56 pm   #3
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Default Re: Sun Microcomputer II Motortester 1215

I used to repair these, along with Crypton machines "back in the day", only thing to watch out for is the horde of Tantulum bead caps on the suppy rails. Probably based on the 6800 CPU
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Old 12th Nov 2019, 4:56 pm   #4
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Default Re: Sun Microcomputer II Motortester 1215

When you mentioned Sun, I immediately thought of something with a SPARC processor and imagined that you'd maybe acquired a 'development system' for vehicle electronics!

Alas, this Sun is a company nothing to do with Sun Microsystems.
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Old 12th Nov 2019, 7:18 pm   #5
Zelandeth
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Default Re: Sun Microcomputer II Motortester 1215

Oh joy...let's hope I get lucky on the tantalum lottery this time round...have played that game before.

Initial signs are good. Only had five minutes but after checking I had sane readings on the Megger I powered it up (it's been run up to demo to a prospective buyer recently). When doing that check showed the most recent PAT certificate on the mains lead dating from 2005. So it's not been out of use for that long compared to some stuff I've revived.

We do appear to have a video fault in that the computer display keeps dropping out, but it doesn't seem to be affecting the actual data on screen, so likely the video signal itself is intermittent...innthe grand scheme of things though I'll take that as a starting point.

Judging from how pin sharp the CRTs both are this hasn't done a massive number of hours...the photo actually makes it look far softer than it is in person.

Hopefully will get an hour or so to look at it after dinner tonight.
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Old 12th Nov 2019, 9:16 pm   #6
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Default Re: Sun Microcomputer II Motortester 1215

That looks in amazing condition!

I used to use one right at the start of my apprenticeship!
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Old 13th Nov 2019, 2:36 am   #7
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Default Re: Sun Microcomputer II Motortester 1215

Sadly didn't get much time this evening, but did find time to tackle the dead light above the displays.

Simple enough job. The diffuser is released by removing the piece of brightwork below it, just held on by three machine screws.

The moment this was removed it became apparent quite why this thing is so heavy. The photo attached shows the cross section of the brightwork! Must weigh a couple of kilos...would normally expect a flimsy bit of pressed tin.

Given the connection with the US in this thing it wasn't a huge surprise to find an F30W T12 tube in there despite them being quite a rare sight over here. I did wonder if it it might be original, but a quick look at the date code shows it to be from 1995 so it looks to have been changed at some point.

Didn't have any T12s in white (got a couple of nice Atlas Double Life green ones though), but do have a half dozen of NOS Cryselco white T8s which should work just fine in this application.

Everything back together and it very much looks the business I think. Nice to see the colours are as vibrant as the day it was made.

Hopefully I'll actually be able to get properly stuck into it tomorrow. At least once I've the back cover off I should be able to pin down the production date properly as I'm still not entirely certain beyond guessing "early to mid 80s" at the moment.
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Old 13th Nov 2019, 7:01 am   #8
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Default Re: Sun Microcomputer II Motortester 1215

The cabinets of these things have to be designed to take a direct nuclear hit, so the section of that top extrusion isn't surprising.

The styling has to involve a lot of showmanship to impress the punter, hence the large and brightly lit name across the top. Sticking 'Microcomputer' in the name is very 1980s and a 6800 or 6809 CPU would fit right in wit that era.

Datecodes on the chipset should help.

It's definitely too early for digital trace storage for the oscilloscope section, so that's going to be pretty straight-forward. The timebase and trigger may be the most interesting bit here.

I expect the microprocessor side will handle voltage and pressure measurements as well as a delayed strobe timing light, but I'm guessing it does a lot of guiding the user through the tests. Designed to look terrifyingly technical to the punter ( and thereby justify bigger bills) while actually de-skilling the job a bit.

I used to use an old Crypton at dad's garage. Interpreting waveforms was key to getting value out of the thing. The mixture meter that could go out on the road was excellent as was the delay strobe and rev counter so you could check advance curves.

Sun and Crypton were in fierce competition in the day. Their products did the same basic things, it was really operator familiarity that locked you into being a Sun shop or a Crypton shop. Their sales guys had a difficult time with clued-up customers who could see past he window dressing and see that each subsequent generation still did the same things.

CRT EHT systems and the signal input attenuator seemed to be the areas most likely to need attention as far as the scope side went.

Gonna get an 'Octopus' tester to go with it?

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Old 14th Nov 2019, 4:04 pm   #9
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Default Re: Sun Microcomputer II Motortester 1215

Yes, I usually found dust layered upon dust inside, they use a BU208 in the flyback/EHT generation, useful machines even today if you can get at the coil connections on a vehicle.the connecting leads, strobe and probe leads used to get a lot of hammer, best check them as well, press "C" to cancel the warmup and boot straight into >operating mode<
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Old 20th Nov 2019, 12:48 am   #10
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Default Re: Sun Microcomputer II Motortester 1215

Finally got a spare half hour this evening and got the back cover off.

It's surprisingly clean inside to be honest and is free from obviously bodgery.

Found a sticker confirming that the production date is Aug 1984 which is pretty much bang in the middle of the period I'd guessed.

The issue with the display dropping out seems to be influenced by wiggling the "CRT" card in the cage, so hopefully just a dirty contact or dry joint in that area. Will let you know how it goes when I get time to strip it down a bit further (have to remove the faceplate to get the cards out fully sadly).

Watch this space.
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Old 20th Nov 2019, 9:54 pm   #11
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Default Re: Sun Microcomputer II Motortester 1215

Now we're getting somewhere.

Removing two nuts allowed the whole front bezel to be removed, allowing unimpeded access to the card cage.

This allowed me to make the first surprise discovery - the CPU. I was expecting something 8-bit, probably a close relative to processors we were used to seeing in the 80s. What I was not expecting was a 16-bit chip. A National Semiconductor INS8900D. Clocking in at 2MHz it's hardly going to set the world alight, but even so a 16-bit CPU must have been quite a bold claim to stick in the marketing literature , especially keeping in mind that this machine has its roots in 1979.

Pulling the "CRT" board didn't reveal anything obviously amiss or obvious tarnish on the contacts. There were however several socketed ICs, so these were all removed and reseated. Surprised to see that among the ICs in sockets is a 555 timer...wonder if they've had issues with reliability there.

Pleasingly powering it back up after this resulted in a rock steady display, the issue with the display dropping out apparently having been resolved.

Granted, the self test has raised other things in need of attention, but that's not wholly unexpected. If I'd been abandoned in a shed since 2005 I'd probably be claiming that service is required!

Despite this, it does happily go into testing mode, and correctly displays data.

Issues we've got to deal with:

HC, CO, amps, volts and ohms testers all fail the self test. It's also claiming that the line voltage is low. Oh, and the temperature probe thinks it's sitting at 160C.

I did carefully clean the mirrors of the gas analyser as it was full of gunk in the hope that might spring back to life that simply, but no such luck.

First port of call will be to do the remove/reseat routine on socketed chips throughout the machine I think, and especially on the IO/Mux boards...then have another look and see where we are.

While I had the front panel off I took the opportunity to clean both it and the CRTs as they were filthy.

The display looks really quite special I think with the way it just "floats" in the huge expanse of smoked glass (well...polycarbonate or acrylic).
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Old 20th Nov 2019, 9:58 pm   #12
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Default Re: Sun Microcomputer II Motortester 1215

The only other work I've done today was to replace all of the vacuum lines (which had taken on the consistency of dried pasta). This post also has the rest of the photos from today.

Still surprised by how sharp the computer display CRT is.

The second image here shows the deep IR source in the gas analyser, this is simply a carbon rod that it heated to the point where it is just about visible as a dull red glow to the eye.
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Old 20th Nov 2019, 10:02 pm   #13
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Default Re: Sun Microcomputer II Motortester 1215

Last couple of photos to show the "live data" display, the mirror and IR detectors in the gas analyser section.
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Old 21st Nov 2019, 12:42 pm   #14
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Default Re: Sun Microcomputer II Motortester 1215

Lots of blue tant beads to have a go at, they drag line voltages right down without smoking up or discoloring. Calibrating the gas bench without a cylinder of "cal gas" may prove problematic, I presume it's a 2 gas bench.
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Old 21st Nov 2019, 1:43 pm   #15
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Default Re: Sun Microcomputer II Motortester 1215

That's a good shout to be honest...I should really check all the boards and do a count of how many there are and get some replacements ordered.

Showing how long it is since I was last doing this sort of work, I'm struggling to remember what the usual practice for replacing these is. Just like for like I'm assuming as there's nothing fundamentally wrong with tantalum caps...they're just operating a fair way outside their anticipated lifespan at this point in time. Is that correct or is there a modern better suited capacitor technology out there?
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Old 21st Nov 2019, 2:11 pm   #16
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Default Re: Sun Microcomputer II Motortester 1215

Quote:
Originally Posted by Zelandeth View Post
I'm assuming as there's nothing fundamentally wrong with tantalum caps...they're just operating a fair way outside their anticipated lifespan at this point in time. Is that correct or is there a modern better suited capacitor technology out there?
Tantalum bead capacitors have been dismally unreliable forever, and they still are. They have a large capacitance in a small case size, and excellent equivalent series resistance, so they were popular for decoupling applications. However, they're very sensitive to pulses of even minor overvoltage or heavy current, so they have an annoying tendency to go short-circuit when connected across power supplies. Which is how most of them are used. Having been bitten by failures too many times, I've long since given up designing them in to new circuits unless absolutely necessary.

Fortunately, aluminium electrolytics have come on in leaps and bounds since the 1970s, and a good quality modern electrolytic (I specify Panasonic FC series out of habit, but plenty of others are available) will almost always substitute for an old Tantalum bead.

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Old 21st Nov 2019, 4:20 pm   #17
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Fortunately, aluminium electrolytics have come on in leaps and bounds since the 1970s, and a good quality modern electrolytic (I specify Panasonic FC series out of habit, but plenty of others are available) will almost always substitute for an old Tantalum bead.
Excellent. That's exactly the sort of recommendation I was hoping for. Space isn't too tight in this case so smallish electrolytic caps should do just fine.
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Old 21st Nov 2019, 11:42 pm   #18
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Default Re: Sun Microcomputer II Motortester 1215

It could be the gas bench is working but full of dust or a communication error with the main board. Amps clamps were always "victims" of abuse by garage tech's "snapping" their jaws together, the sensor in them is a hall effect <blob> stuck on an aluminium plate, careful dismantling work and examination of the cord may reveal a simple fault. I used to replace the tant beads on sight with aluminium electrolytics, there's plenty of space on the boards. Good luck.
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Old 22nd Nov 2019, 1:41 am   #19
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Default Re: Sun Microcomputer II Motortester 1215

I have a sneaking feeling given that we've got a reference voltage either missing or way out of whack given the symptoms we've got...

Voltage readings are all over the shop (they do respond to input, but not correctly and not consistently).
Vacuum reading never settles to zero, and wanders.
Temperature probe is reading nonsense, apparently offset + about 150C.
No valid calibration reported from the gas analyser.
Current clamp reading nonsense.
Ohmmeter giving no reading, no voltage present on the test leads.

The screenshot below was taken with the voltage probes shorted together and everything else just sitting next to the machine.

Just strikes me that all of these could well be impacted by a fault of this type...so I think the sequence of events needs to be to get the voltmeter sorted first I think. Wouldn't surprise me at all if once that was up and running it a lot of other instruments followed suit.

Given the tiny signals that the photodiodes in the gas analyser (assuming that's what the detectors are, rather than pyroelectric sensors...have to confess slight ignorance on that bit) are I think expecting that to play ball when we've got potential power supply or reference voltage issues is vastly optimistic. It was filthy throughout on receipt, but has been (very carefully!) cleaned now. One thing which does seem odd is that the detector is pushed right over to one side of its mounting slot...though there's no witness marks to suggest that this has happened recently, so it may well have been set up like that originally. I'm not about to go messing with the alignment unless I'm given an actual reason to. Oh...and I'll need an imperial set of Allen keys for that anyway as those as with every fastener on the machine are imperial because it's American.

I'll pull all the boards again tomorrow if I get a spare half hour and do a head-count to find out how many Tantalum caps I've got to replace...Figure I may as well just do the lot as one job as it won't really take long and at least then I know it's done and something I can tick off the potential gremlin list.
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Old 22nd Nov 2019, 3:52 pm   #20
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Default Re: Sun Microcomputer II Motortester 1215

I think I swapped out about 30 in a Crypton 353 mototester, the thing was full of them, the regulator transistors on the +18v -18v rails got really warm, 33mf @25v, I tested them afterwards and found 3 that were 0.1 ohm resistors, best be rid of the lot.
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