Nice repair video, well done. But to get things running, the Unisite needs to boot on a master floppy or a MSM module and with all the boards and adapters plugged. Until that, the self-test led will remain on indefinitely... (Also, about the previous video, don't touch the golden pin of the adapter: you could get a "fail" during the self-test just due to that... Use a little isopropyl alcohol to clean it, in case).

You could also point a thermal camera at the board while trying to power it up. That works like a charm for me every time I need to find a component that's shorting a power rail to ground. It's much faster than dicking around with a multimeter. You can record video with the thermal camera, and check it later, so you can do it quickly, to make sure you don't damage anything else on the board, trying to drive current through it.

Data I/O - engineered and built like battleships. My model 29B's (I have 3) just keep working with minimal maintenance over the last 20 years. I bought them used on eBay auctions (the shipping was more than the purchase price for one or two of them). It blows my mind that I am using equipment that I used BITD when I was a young engineer in the early 80's. I repair old arcade PCBs from the 80's and use them to program really old bipolar proms and early eproms.

That was a neat way to find the fault. After I see it it's kinda obvious but until then I would not think to do this. It's amazing what you can learn from just watching people who know what they are doing for a wee while. These are the kind of videos I like watching. Always things to learn! Thanks.

Easiest way to debug shorted rails is to stick an amp or two in from an external PSU and use a thermal camera. If it's so dead-shorted that it doesn't heat up, then using a mV meter to home in on it is usually easier than doing resistance measurements as you don't have the contact resistance issue.

As a noob hobbyist I have no problem following along, you have a great way of explaining things, and you give us a great view of what you're looking at. I really appreciate it, thanks Dave ;)

In the late '80's we used one of those as a large multi-gang programmer/tester. We were in a tightly controlled industry (nuclear power plant instrumentation), and so we developers made "Golden ROMs" that were cloned en masse for production. I believe the unit handled one master EPROM and 32 slave chips. The master had to be checksummed before and after each use. The slave chips were each validated multiple times after programming, over the full rated operational voltage and timing range for the chip.

Awesome Dave! you finally got your hands on an interesting repair, can't wait for the next one

Hey Dave. The video is older but: Will there be part 2? I would really be interested in whether you can repair the device. Greetings from Germany

Great job, Dave! I've already learned a lot from you and yet there is still more to learn. And I always enjoy gorgeous old electronic coming back to live as well.

So glad you're sharing the repair with us! I was hoping you would after the original video!

I so love tear-down and repair vids like this! This is a bit outside my skillset I would say, more just find bad e caps with my ESR or completely nuked components, but I certainly hope to be someday. I look forward to part two!

remove the kernel test jumper look for output.

Tantalum friends are very common to go happy like that :-D i'd replace ALL of them without even powerin up :D

Yes, I like that kind of repair videos much more than a auto routing soft test. Thumbs up on this one :)

I'm glad I watched this, once again very informative! :) I'm sharing this one around!

Super interesting troubleshooting! These old machines intrigued me.

From what I can see in the documentation (and I may be off the mark - I admit), the self test light stays lit until it sees a disk. I'm guessing the test routines are actually part of the OS bootstrap.

I have learned something new again from you. Thank you Dave.

Given you are getting messages from the tty port, I assume the 68k is resetting and fetching code from those EPROMs. ....but the lack of further output means it is wedged or in an endless loop with no messages to say what is wrong. Maybe use a logic analyzer to see the access to the EPROMs? May get a clue to see if it is stuck or see what sequence is occurring?

Really interesting mate, I can learn so much from you! Thanks

Nice vid. I like to see these trace & fix vids. :) But your other vids are great too! Thanks!!

Love these videos. IMHO you're just like the The Serviceman in the old Electronics Australia magazine. That was always the first article I read in each issue.

I didn't see the first "Tear Down" video on this one, but would LOVE to see a completed repair on it! I wonder if the problem could be a corrupted "self test file", sort of like having a "IF THIS, THEN statement that isn't completed anymore, and it is still waiting on what "then" is. I enjoy your programs!

around 10:00 that reminds me of the grid of transistors. Moving around the grid gives different resistances. I didn't see boards like that in the past. neat.

I used one of these a few years ago (also had the smaller 3900), from memory it looks for a terminal at boot/power-on as part of self test (already suggested previous comments I think?) we used a VT340 terminal to operate ours and later moved to using terminal emulation in Windows Hyperterminal as it had the option to emulate the VT340.

Where is part 2?

New technique for finding shorts is to use your power supply and supply small limited current to the 5v shorted rail and use a FLIR to find the component warming up.

That is what pc hard drives must do, the hard drives internal cpu must detect power loss and reset the head to its default position with the last bit of charge to avoid data loss and damage to the hard disk.

haha - I was expecting it to be an AVX cap, but it's close enough. I could be wrong, but I think STC was "Standard Telephone & Cables", which used to own the old Nortel site in Paignton before it turned into Nortel itself. The AVX Tantalum division was literally building alongside the Nortel building. I worked at both places, so this vid is a bit of a weird coincidence. The Tantalum stuff could be a tad scary in the factory, as they had a sintering oven which used to work on the verge of catching fire and exploding every ten minutes. They said that if it ever did go up, it would probably take the rest of the building with it, so there were daily fire alarm tests and drills. There was also the slight risk of a Tantalum dust explosion, but they didn't really have many processes where there was a lot of dust floating around, luckily. I worked on the machine that used to pick up large metal pallets of Tant caps, then dip them all into various process tanks. Lots of potassium permanganate etc. (nicknamed "Mango"). The pallets would then go through 24-hour bake, so there were two large conveyor ovens which extended through the dividing wall. The machine took up two rooms which were about 30ft long. It was like a giant "soft toy crane". The software wasn't particularly clever though, so if the pallets ever got out of sequence, you'd have to hit the E-stop, figure out where each pallet was in the two rooms, use the manual controls to lift them onto a trolley (or physically lift them), then put them in the right places again. It could have done with a few more sensors as well, as it didn't know when things like a riser platform was in the up or down position, so it often used to drop the pallets from a height of about 8 feet onto the floor. lol The pallets themselves were about 3ft by 2ft, with welded frame which weighed maybe 8Kg each, so they used to make quite a lot of noise, and wake everyone up in the canteen next door. A relatively interesting job for the first few weeks, but I don't think I'd want to do the four 12-hour shifts again (four days on, four days off).

NICE ! I love you video, mate, can't wait to go back to OZ

A short on the board! Nice!

I liked the way you diagnosed that shorted cap. Great job Dave.

Amazing, very didactic too. Kudos

"$30,000.00 in 1986 had the same buying power as $67,664.41 in 2018"

OK! I found you! It is the next video, duh!. (I just watched #1060 and I am two years late. Better late than never! If this is the first video you are seeing on this, watch #1060 first. What a gorgeous device.

Self test failure due to modules not being plugged in ?

Hi Dave, a couple ideas that may have already been mentioned: connect the serial handshaking lines appropriately, connect one of the programming adapters that goes on top of the unit, and try putting any floppy in the drive since somebody mentioned it may never leave self test without one. HTH.

Dave This upgrade is for a later video after unit is fix, is to replace the disk drive with a floppy/diskette emulator.

hi i a new sub ty u for makeing a grate vid it cool see old stuff fix up and u see how long a way computer have come ty u chris

Yep I've been there, Quick tip, stick the cap in a blob of bluetack, = 3rd hand You had a result, happy days

With this insight I'mma go check all my 'dead' equipment for tantalum caps.

You are so entertaining. Thank you. You should have more comments but I guess there aren't enough nerds in the world.

Maybe try re-seating all the socketed IC's?

Have you ever gotten this fully working? Maybe a revisit, update video?? Love your work...it has taught me a lot so far

Pin 2 on RS-232 is called TX full stop. TX is an output at the DTE, an input at the DCE. The signal name on pin 2 is never different, it is always called TX. This can be confusing because of MCU and UART pin labeling, which always has TX as chip output and RX as a chip input. The signal name on such a chip only matches the RS-232 signal names when implementing a DTE. The chip signal names and RS-232 names will be swapped, e.g with a net names across the RS-232 level shifter, when the chip is in a device implementing a DCE.

My favourite way to track down a short was to apply a couple amps from a current limited supply and find the hot thing Saved a 3,000$ laptop from a shorted ceramic cap near the docking connector

It needs a boot disk to complete self test Dave. Check the data io yahoo group for a replacement hard disk module. Boots much faster and you can have the last released device library and software. I have had a few of these.

Can't wait for part 2.

Waveform card is obviously a precision adjustable power supply, that can run/test the chip at exact voltages, such as max/nom/min from datasheet. All the pin drivers may be powered from it too. And to avoid switching noise, it's probably all linear regulation, dumping all the excess voltage into the heatsink. Next test: Plug in a module to see if that's the unwanted condition leading to the RTOS shutting down and telling you "Shutdown complete, it is ok to POWER DOWN now".

It's good education videos these repair ones... Thanks :-)

You just make a shit ton of money, GOOD JOB! OLD AND GOLD! GOING W3ST

Dave, in case you missed it, in the other video someone mentioned that they still buy these back and refurbish them as there is some demand for them.

Any pointers to the mean to triangulate a dead component like you did? I'm watching the video for the second time and I have trouble seeing which pins you mesure and how you managed to close on the dead component. A document on the general theroy behind this (or even a book maybe) would be great. Thanks!

Don't you love it when a 30 cent part kills a $30,000 piece of gear. [prices approximate] :) Looking forward to part 2 where you might complete the repair.

Fantastic.

any switches or jumpers that could enable a diagnostics mode? what about that 'remove for kernel test thing'? You could do some very basic checks on the 68k like looking for activity on DTAK and BERR during start up which might indicate logic faults.

Thank You, Steve Leibson! (You have just been added to my dictionary). :-)

Have you tried sending it a command to see if it can respond?

That tantalum cap at 11:00 I spotted because of the colour, it stood out as the bad one to me even before you tested it, it is slightly darker which happens when they get hot from shorting.

That was a great troubleshooting tutorial Dave. Thanks for another repair video. Always great to see the master at work.

20:58 Can anybody tell me what was used to decode the serial data? Thanks. EDIT: Ah, OK, I guess it was the scope. I'm not used to the capabilities of an expensive scope.

What is the piece of equipment Dave used to interpret the serial line output?

There's a video of Jim Williams fixing a friend's Tek 465 and the culprit was also... a tantalum capacitor.

I am learning and was looking for a program to help test circuits do you have any you could recommend or have you used EveryCircuit?

Yay a repair video! I’d love this to program my arcade and pinball stuff

Where is repair Part 2?!?

Would 4 wire probes have helped?

Would you upload a tutorial on smell tests?

dave you should give that cap a proper send off and hook it up to the mains, that would also be an example to the other caps, so they'll behave

You might try to put in the proper floppies. I believe that the self test finishes up AFTER the floppies are read for the programming software.

Can you talk about why you wouldn't replace that power supply decoupling tantalum cap with a ceramic or an electrolytic?

Don't need to desolder the whole thing. Just cut one of the legs. In this case it worked out, but in some cases that will safe a lot of time finding the right cap.

Where is the rest of the repair?

I noticed the non-skippable ad, is it working? You made that look too easy brotha.

Are there any memory modules in there that are wiped by UV? It was mailed overseas, so it was xrayed? Just a WAG of course.

Newbie here, could someone explain the concept around when Dave measured for resistance and checking against ground and there being a reading and sometimes 0.0?

Perhaps it is looking for a boot disk for the test program.

Are modern tantalum caps any better than the old 80's ones, or are they likely to go the same way in another decade or two? Or maybe the modern tantalum caps are even worse than the old ones?

would it not work properly, until all of the components are plugged in? just curious

Any updates on this?

I noticed the module connector plugs don't have their round screws you took out. Plug in the modules as well, and see what happens.

Hmmm ... did plugging it into the PC enable DTR at the RS-232 port? Some cables just run 3 wires. It could be that self-test does not properly start if DTR is not high when the box is powered up. DSR will typically be asserted by a box (not necessarily the type of unit at hand) so a bridge between the two as well as CTS/RTS does all the necessary hardware "handshake" to let data flow. Did you chuck out your serial breakout box?

Check all the TO-220 devices too for shorts.

It's looking for the boot disk, 99% sure it has a disk sense line and does not leave self test until it sees one

Where's part 2 ??

There's a second tantalum cap at 11:00 to the left of the bad one of the same value / voltage. Sure that one didn't go as well? Never saw you test it for the 5v rail.

Maybe probe clocks/ICs for activity.

Didn't know about the 'triangulation' technique. I'll try that on my recently fried GPU!

Great video as always Dave!

Would this thing still be useful today if it were interfaced with a modern PC running modern software, or are there simply better and cheaper solutions today?

Hmm, this reminds me a lot to my repair of the first MK1 synth i got, it tried to power up, had also shorted tatalums and, after removing these, it got stuck in the selftest, as the main CPU crashed, everytime...And it got soundcards inside, about 12 total, each card has two Voice CPUs on it, as well as tantalums and DACs and analog stuff. I narrowed it down to a faulty voicecard, by just putting two (this is the absolute minimum the OS needs to have to boot up) in and done a powercycle. May be this it´s the same here with all these 4Ch pindriver cards....may you can test one by one and may you find a non working one...

Tantalums, and RIFAs. The bane of retro computer repair.

"haych" gets me every time

Any harm in hooking it up to a current limited supply to heat the component up? Then use a thermal camera to see it.

Great job Dave👍👍👍

5:17 Ohww... Thats such a mood

9:19 holy smokes that is a lot of stuff

Hook it up to a current limited 5v voltage source and pour some alcohol on it. It worked for Louis Rossmann it'll work for you :D

Check all the other tantalum caps on the waveform board for shorts.