Pictures of my TRS-80 and System-80 score

[matsondawson]

http://imgur.com/a/2FCFA

3 x System 80's (1 fine, 1 disasssembled with lots of custom wiring on it, 1 diassembled some custom wiring, missing a tape drive)
2 x System 80 monitors.
1 x mint TRS-80 model 1 + tape drive + disk drive
1 x spare drive
1 x C128
1 x giant 30kg metal beast with 3 x drives
Some weird sound card thing in a wooden box (AY-3-8910)

Any ideas what the extras are on the System-80's or the beast?
Is the sound card thing a standard thing?

[TRS80]

Nice collection there. Looks like they belonged to a serious experimenter with plenty of custom mods. I don't recognize any of the "extra" boards.

Is the "big metal box" a complete Model 1 in a different case? It certainly looks like a Model 1 keyboard.

[matsondawson]

Here's a photo of the inside.
They keyboard does look TRS-80 of some description.
Maybe it was used in manufacturing somehow?
It has a wierd 4 prong power plug on the back that I don't have a cable for.

[TRS80]

That definitely looks like a Model 1 and Expansion interface packaged together as part of a control system. The board visible in the picture is the EI (hard to tell if it is the Radio Shack one or a third party). The Model 1 CPU board will probably be under the keyboard.

Power for the Model 1 and EI is normally 4 pins of a 5 pin DIN connector connected to the back of the CPU board and side of the EI board. Unfortunately it isn't +5v/+12v like more modern machines so don't just grab a standard power supply and try it out. It is approx +19VDC/14VAC and was normally delivered with an external transformer. It is possible to make a modern replacement (details at http://www.trs-80.com/wordpress/zaps-pa ... er-supply/). I have one for my Model 1/EI and they work well but not cheap to build (around NZ$80). Possibly a power supply from a System/80 would work (need to check the voltages).

Pity you aren't in Auckland or I could give you a hand getting them going (be sad to see them sit in a storage box). If you want to take a set of closeup photos and email/post them somewhere I can give you some pointers though.

JAQ

[matsondawson]

I'm wondering if it could have been networked?

I had a look under the keyboard, looks just like a model 1.
Couple more pics:
Back of machine showing extra strange plugs.


Inside showing some big caps (there about 5 huge caps in there).

[TRS80]

Cool. The best next step is to try and draw out a wiring diagram from the connectors on the back to the various internal boards particularly the funny 4 pin connector. Don't worry about the 34 pin connectors... pretty sure one is connected to the EI parallel port, one appears to be not connected from the last photo. The DIN connectors are most likely video (directly connected to the Model 1 board) and possibly the two cassette ports (likely connected to the EI).

If there are large capacitors in the back is there also a transformer? Because the floppy drives require +12v/+5v maybe there is a transformer and with the capacitors across the regulated outputs. The challenge with large capacitors that age is they often short internally and/or the internal chemistry changes and they will no longer hold a charge.

If you want to go down the track of getting this to work it will be a good idea to test the capacitors before attempting to power it up. I had a similar problem with the power supplies in the PDP11 and wrote a blog post about it and how to build a tester for the capacitors. http://www.quicktrip.co.nz/jaqblog/home/54-pdp1104powersupply3

[matsondawson]

A few transformers in there, that explains my hernia!
Luckily there's a manual in there that has circuit diagrams etc...
And when I took the back off a sticker fell out saying it was manufactured by David Reid Electronics. Sounds like a custom jobby.

[matsondawson]

I've identified the System-80's as a:
Video Genie System EG 3003
D.S. System 80 MkIII - Business Computer
D.S. System 80 blue label - third generation

[TRS80]

Those transformers (not the mention the metal case) will certainly put your back out.

If you can't find the power connector in the box of bits I would replace it with a standard power lead from a PC.

Before you you attempt to power it up I would still test the capacitors.

If you look at the markings on the capacitors you will find a voltage rating. It may be different for each of the capacitors.

To reform/test the capacitors you need to slowly charge them up via a resistor to fairly close to this rated voltage. To get the required voltage I have always used several 12v batteries in series. My batteries came from the UPS at work. For the PDP 11 I used three in series.

When reforming/testing a capacitor you need to disconnect it from the circuit. If you monitor the voltage across the capacitor when it it connected to the batteries you will see it slowly increasing until it finally matches the battery voltage. Depending on the resistor value it can take quite a long time (30-60 minutes) to get to the battery voltage. If you find the voltage across the capacitor doesn't rise it indicates that the capacitor is faulty and requires replacement.

Once all the capacitors are confirmed OK the next step is to power up the supplies and check the output voltages. Do this with the TRS 80/EI and drives disconnected.

[tezza]

Nice gear.

I've always wanted one of those Mk II business models.

[Gibsaw]

Nice gear.

I've always wanted one of those Mk II business models.

Isn't one of the ones on trademe right now a MK II?

[tezza]

Nice gear.

I've always wanted one of those Mk II business models.

Isn't one of the ones on trademe right now a MK II?

Indeed there is. I'm not interested though. It's not in good enough (and original) condition and doesn't have the numeric keypad.

[matsondawson]

Well the case is mint on the Mk2, and I suspect all it's missing is that keypad.
So if another Mk2 came up that was munted but had the keypad, it'd be worth it.

[tezza]

Yes, I suppose that is a point. However, at the moment my motivation for an incomplete machine in parts and not working plus another parts machine I don't want is not more than what's currently being bid. Also I imagine shipping would be a bit.

This might change as I think about it, but I really have enough System 80 spare parts gear now.

Out of interest are all the screws for the MKII case present? (I guess even if not, there should be enough between the two machines to get one set, yes)?

By the way if the RF modulator is missing from the MKII, that's the way it's suppose to be.