Invaders from Space repair

gtsamour · Posted: Mon Dec 09, 2019 9:32 pm Post subject: Invaders from Space repair

Hello,

recently a defective Invaders from space from Grandstand came to my possesion, I thought it would be an easy fix but no.
First thing i did was to check if power was reaching the main board and it did.
Replaced all the caps and all the transistors with new ones (original not equivalents) but still no joy.
I cleaned the board thouroughly because there was an area where battely fluids had leaked onto and checked for continuity, everything checked ok and no copper line was damaged.
The VFD lights up nice and bright but only showing the number 8 on top of the display and no sound comes out of the speaker.
Also measured the voltage reaching the CPU (between pins 21 and 41) and got 9.8V so I guess it is as it should be.
Also removed the cpu and soldered a base in case I manage to find a replacement. Later I learned these chips have rom inside them so thats pretty much a lost cause.
Measured all resistors and they seem OK. Also the diodes and zeners conduct only one way so they seem OK.
So it has to be either the oscillator (TDK FCR 400) or the CPU (D552C 054) which both are impossible to find.

Any thoughts that would help please?

If someone has a D552C 054 from a spare board and willing to part with it, I'm willing to buy to resurrect my dead invaders from space.

Rik · Posted: Fri Dec 13, 2019 2:15 am Post subject:

Damn, always a shame when you can't resurrect one...
The little transformer (the TDK thing) provides voltage to the VFD display. The fact that it is showing anything at all suggests the transformer is working... Which leaves the CPU... as you've noted, these are specific to each game, so you'd need to get one from another game...

Sounds like you've already done everything else I can think of...

gtsamour · Posted: Fri Dec 13, 2019 3:49 am Post subject:

Rik · Posted: Fri Dec 13, 2019 3:04 pm Post subject:

Oh yeah, sorry, wasn't paying attention to the labels... Just saw 'TDK' on the transformer and thought that was what you were talking about...

Tried to search for that too, not finding much... There are adjustable oscillators, could something like that work just to test it out?

I have a few broken games (not this one unfortunately), but I'll check the boards and see what parts they have... Might get lucky.

gtsamour · Posted: Sat Dec 14, 2019 12:09 am Post subject:

gtsamour · Posted: Sun Dec 15, 2019 11:21 pm Post subject:

I think I found an equivalent oscillator.... CSB400J (400Khz). Ordered it, fingers crossed.

https://www.ebay.co.uk/itm/LOTx2-KERAMIK-FILTER-CERAMIC-FILTER-400KHz-CSB-400J-MURATA-NEU/322900080460?hash=item4b2e58374c:g:KKsAAOSwaB5XneEY

EDIT:

No, unfortunately it wasn't the crystal either, it has to be the only thing thats left, the CPU.