I am new to this forum and the reason I am here is… an old GEM WS1… a none working one i.e:
To me this is a project were I would like to revive this cool machine again.
So far I bought this workstation as not working.
What it does when turning on:
- The lcd lights up but no letters/numbers
- My FM radio (while listening to music) started to give static (noise) pushing the music away and hearing a faint sound through the radio as someone pressing the keys on the keyboard continously.
- Nothing works (no sound from the workstation) while pressing keys.
So I opened the workstation and looked at the boards for any clues.
- Battery (3,6V) for memory missing, must have leaked a bit but no real damage.
- No obvious problems visual
There are 4 boards.
- Power amplifier & supply board
- CPU, CMos etc board (flat cable attached to keys prob a board under keys as well but havent checked yet)
- Control board with “toggle” ball and switches for start/stop etc
- Button board with display
What I did so far is checking the Power amplifier & supply board:
- AC inlet and fuse (ok)
- Transformer AC 230V to 2x ~13V (transformer has center tap)
- Bridge rectifier (ok)
- replaced the big filter caps (6800uF 25v and 2200uF 25v)
- replaced 2 caps 470uF 16v
- measured the power switching regulator (L4960) Vin 46V and Vout 5V
- replaced 2 transistors (BC549C) that were measuring not correct.
But now I am running into territory I am not familier with…the amplifier side of it.
I do not know and also understand how much voltage should go to the other boards.
A schematic of the WS1 is not in my grasp and it looks bleak if I will find one.
All over the other boards I find 5V and about 2,6V leaving from the Power amplifier & supply board.
I think there is a short somewhere…but can’t figure out how to find it.
So…help wanted please!