Grandstand (Epoch) Astro Wars Repair

[mndn]

Hello everyone,

I have 2 Astro Wars here, one by EPOCH and one by GRANDSTAND. They are exactly the same I think (except for the top cover part).
The EPOCH ist very dirty and full of corrosion everywhere -in general not a very good condition -but it works!!!

The Grandstand looks much better inside and outside, but it doesn't turn on at all! It drives me crazy. Does anyone know how to repair this?
Occasionally I will have it powered on if I just try to press the on/off switch very fast and play around with it a little . In this case, if I am very very lucky, the screen just lights up for a VERY short moment and turns off again immediately.
Sometimes I only hear a 'tok tok tok..' sound (repeatedly) when it is 'on' , but nothing else (no screen, no real beeping sound). I think the sound is not coming from the speaker, but it's the sound of the display trying to turn on -not sure.

Does anyone have an idea? Will replacing caps work in such a case (is this the solution to everything TT-related, next to cleaning contacts) ?

Thanks, mndn

[blanka]

No, dead caps is not the first problem with table tops. Never had a issue with them. Things to consider:
- Check all contacts and switches, especially adapter-detection in the plugs and power switch corrosion are big trouble makers..
- Check for blown transistor in the power supply section, usually the D882 has blown.
- Check for damaged PCB tracks

Usually with any of the 3 above 99% of problems is fixed on VFD table tops.
_________________
Making the book on handheld games: www.2kboffun.com

[mndn]

Many thanks for your advice, I will take a closer look at the unit... "power supply section" -where is it? I will post some photos soon, I'm back from vacation in a week from now.

I replaced a cap on my Ludotronic Astro Vader which fixed it , but it was pure luck I guess.

Blanka, is your book coming out any time in the future? I will be one of the first to buy this for sure! Well, take your time.

Best, mndn

[mndn]

Thanks all. I tried fixing it again, but I still can't get this thing to work.
The AC Adapter plug was in no good order, it's fixed now. But still the screen rarely lights up (only a short blinking).

Blanka, What do you mean, "the D882 has blown"? I can see the part, but it looks fine. Can I actually see it or measure it -if it has blown?
Any tipps appreciated!

[blanka]

I always check the voltages. If they are right, the game must work, but if one is incorrect, you know where to look for bad components. First question: what CPU does it have? A 552 or 553?

Pin 21 is ground
Pin 42 is Vic

You should measure -10V between both pins.
Between the outer pin of the resistor arrays and P21 of the chip you should read between -25 and -35V.
_________________
Making the book on handheld games: www.2kboffun.com

[mndn]

Hi,
unfortunatey I don't know where exactly to check this. I am not sure if I have an A 552 or A 553. I guess it will say on the CPU, but I have to take the foam rubber off for this to see?
Or does it say anywhere else on the board (can't find this on either unit).

Also for the pins, what do you mean, where ist 21 and 42? I guess the top left pin is PIN 1 and the bottom left is PIN 21 and the top right is PIN 42 -when I have a top view of the board (game screen facing to me). Is this counting correct?
I do measure totally other values on the working Galaxy 2 (measuring between 21 and 42). It's frustrating

[mndn]

Here, for a better understanding, are some pictures of the unit and the board:









I can hear now that it "powers on", but it's only a very dim electric fuzzing sound, and the screen doesn't do anything.

[blanka]

It does not matter, 552 and 553 have same pin-outs.
Sorry, I made a mistake: you have to check voltage between pin 41 and pin 21.
You see the number 42 in your photo's. That's pin 42, 41 is just below. Pin 21 is diagonally across.
What do you measure?
_________________
Making the book on handheld games: www.2kboffun.com

[mndn]

OK, still not sure about the pins.
But I finally examined this again.

I assume PIN 41 is the one below 42 (in my photos), good.
I also assume that PIN 21 is the one on the lower left corner (like in my photos) or what do you mean "Pin 21 is diagonally across" ?

Anyway if I measure these 2 pins as described above It get:
-13,04 (if anything), then slowly goin up while I'm measuring (-13,03 , -13,02 , -13,01 and so on).
In most cases I do not read anything (-0,0), but then again I never know if the unit has power or not. Seems to go on and off..

I tried the same on the working unit as a comparison, here I read -9,8

Does it help? Did I measure the right spots?