looks like a cool machine! Best of luck for the restoration.

What is the keyboard/synth behind it on the second picture?

Jonas-fr wrote:

The wire colors aren't matching those of a standard AT power supply though.

I recapped the power supply to no avail, I also changed the dead BIOS battery, but it still wouldn't boot. I'm stuck for now I have to admit, would you know what I could test now?

Nice, it looks interesting for sure! 😀
I've seen another 486 system named "Shuttle", "SpaceStation" or similar.

I assume the power supply is something proprietary (don't trust the colouring!).
Perhaps you can measure the voltages from the floppy power connector ?

Some PSU testers do also have a molex port, which you could access by an floppy-molex adapter.
Another idea is to replace the power-mosfet transistor (if there is any in the psu) or the transistors/diodes in the power-good circuit.

Also make sure the voltages regulators are fine, too (are they discoloured ?)
If you can, ask your local electronics shop for assistance (the type of shop that sells electonics parts).

The people there should be familiar with 780X-type regulators and Mosfets.
They can also order the necessary replacements parts for you.

Sorry, that's all I can recommend.
It's always difficult to help someone from the far.. 😅

Jo22 wrote:

Nice, it looks interesting for sure! :) I've seen another 486 system named "Shuttle", "SpaceStation" or similar. […]
Show full quote

Jonas-fr wrote:

The wire colors aren't matching those of a standard AT power supply though.

I recapped the power supply to no avail, I also changed the dead BIOS battery, but it still wouldn't boot. I'm stuck for now I have to admit, would you know what I could test now?

Nice, it looks interesting for sure! 😀
I've seen another 486 system named "Shuttle", "SpaceStation" or similar.

I assume the power supply is something proprietary (don't trust the colouring!).
Perhaps you can measure the voltages from the floppy power connector ?

Some PSU testers do also have a molex port, which you could access by an floppy-molex adapter.
Another idea is to replace the power-mosfet transistor (if there is any in the psu) or the transistors/diodes in the power-good circuit.

Also make sure the voltages regulators are fine, too (are they discoloured ?)
If you can, ask your local electronics shop for assistance (the type of shop that sells electonics parts).

The people there should be familiar with 780X-type regulators and Mosfets.
They can also order the necessary replacements parts for you.

Sorry, that's all I can recommend.
It's always difficult to help someone from the far.. 😅

You helped me well! I'll check again the power supply and its power-mosfet transistor transistor/diodes, I'm just no familiar with them for testing, I only know how to find a damaged capacitor ^^. Regarding the floppy drive it's a 26 pin version (the pinout seems non standard also but I can't find the service manual (TEAC FD-335H) for now) so no power connector to test!

MMaximus wrote:

looks like a cool machine! Best of luck for the restoration.
What is the keyboard/synth behind it on the second picture?

Cheers! The two synths are a small Casio PT-80 and a big ol' GEM Rodeo 37

Dude! Totally jealous! Did you get this from a guy on FB in some eastern country? One popped up on there not too long ago that I had made an offer on but he wanted too much for it for my taste. 🤣

Also nice keyboard, at first I thought the GEM was a MiniMoog with the top down. 🤣

King_Corduroy wrote:

Dude! Totally jealous! Did you get this from a guy on FB in some eastern country? One popped up on there not too long ago that I had made an offer on but he wanted too much for it for my taste. 🤣

Yes it was the one. Not the best transaction I had, since I paid a bit too much for a non working, corroded/marked externaly computer but, hey, now it is here and I have to rescue it!

Well there is so news, we're approching resolution 😀

I started looking again at the power supplies. Yes they are two of them. The first one is the primary one and it is external. It converts the 230V~ into three continuous voltages (-15V, +15V and +18V) and a ground. The second one in internal (under the keyboard next to the motherboard) and is the secondary: it takes the 3 voltages from the primary (again -15V, +15V and +18V) and outputs 4 voltages (4 wires: -5V, +5V (currently non working), +12V and -12V) plus a ground (on two wires) on a AT connector (non standard pinout).

Long story short, after I checked for the Nth time the primary, I took a short electrical shock (it's been 24hours I'm well I reassure you) and since then the voltages output by the primary are reversed (they are now +15V, -15V and -18V). Furthermore the transformer outputs 4 wires of two voltages normaly: 2 x 15V~ (thick blue wires on the pictures below) and 2 x 18V~ (thick yellow wires on the pictures below). I didn't mesured them before but now one of each set ouputs 0.5V~ instead of +15V~/+18V~ respectively (so I've got two +0,5V~, a +15V~ and a +18V~), I don't know if it could be the reason of the reversed voltages at the end.

Below are two pictures of the only PCB in the primary (provided that there isn't one under the wrappoins of the transformer). It consists of two big diodes and a PB152M bridge rectifier. The small resistor you see on the pictures is for the power led indicating when the primary power supply is ON.

Well that's as far as I am. If you got some info on how to test the big diodes and bridge rectifier I'm all ears! If you know why the transformer is outputing two +0.5V~ instead of +15V~/+18V~ I'm listening too 😀

Power supply fixed: for the reversed votlages it was only a matter of inversed leads on my DMM, I feel very dumb! Regarding the secondary I've changed a transistor (TIP42C) and now I've got a +5V! It was near the 5V wire so I said to me, why not change it, it doesn't cost much 😉

Now I'm in the process of trying it on the motherboard, I will keep you posted!

EDIT: It boots! The problem was the TIP42C transistor into the secondary power supply which was dead and thus no (vital) 5V was provided! I'm so happy it works

Some news?

His last post was in July and guess he found other interests

FlashCade wrote on 2019-10-13, 15:20:

Some news?

I've got a lot on my plate but I still got this little puppy on the backburner and I will get to it in the following weeks so I'll update this topic with more pics and info. In the meantime if you have question just ask away, I might have some answers : )