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Arcade King
10th May 2009, 08:59 AM
First thing I do is put new CPU and roms sockets in before even attempting to fix these PCB's

PCB just watch dogging
Found a tip here to isolate the MPU from the VSM sections of the PCB
http://www.ionpool.net/arcade/asteroidtech/asteroidsrepair.html
So I socketed and lifted pin one on the 74ls42 @ L6 to disable DMAGO

Problems with MPU

Bad 4116 ram @ D2

Program not running dead even with watch dog disabled.

74ls244 @ B2 pin 7 (a11) was stuck low.

Program still not running.
Bad 74ls32 pin 11. Output was stuck high no signal getting through to the chip select (pin 8) on the rams at D and E2

At this point The program is running and I can coin and play the game blind.

Putting it in test mode I get 3 beeps(2 high then 1 low) on the scope( connected to the audio test point) which indicates bad 4116 ram @ M4. Ran the test again and got 5 beeps this time (4 high 1 low), Ram N4 bad. Testing again no beeps so alls good with the MPU section of the board.

Now the MPU is fixed I can concentrate on the VSM.
Board just watchdog's
There was a dead 7497 @ K8, had to wait for parts so I could replace it.
The problem was a bad 74ls08 @ K6. Pin 8 was stuck High. This connects to pin 14 of a 74ls191 @ K5. This is part of the vector program counter circuit.
PCB now fires up and I can see the game running on my CRO in XY mode.

Problem: game has graphic issues. The asteroids sort of look broken in half. Putting it in test mode most of the diagonal test pattern is missing and whats there is messed up.
Fix: Traced it back to 2 bad 74ls191 counters @ C6 and D6.
Everything looks pretty much perfect now on the scope so time to put it in the cab.
Look good on in the cab except the top scores are slightly out of alignment and have a wobble to them.
Fix: seen this before, it really pays just to replace the 2 4016 and TL081's in the video output section. Chips are readily available and costs less then $2 to replace all 4 components.
Ok all above fixed time to fire up a game.
I previously replaced the 74ls139's @ E4 and L3. I forgot why but these have to do with rom select etc.

Sound
All the sounds are there except the ship sound is completely missing and the saucer sound is really messed up. Sounds like a fire engine or something and the small saucer sound just halts after a second.
Fix: missing ship sound was a bad LM324 @ P11 and the saucer sound was a bad 4016 cmos chip @ N10. I replaced the 4016 @ R11(ship sound) also to be on the safe side.
I should also note there were 3 big caps broken off the board which I had to pinch off another PCB.
Caps were @ C69(Ship Sound), C68(ship sound) and C64(Thump). Looking in the manual caps are a .1 uf 100v Radial Lead Mylar capacitor.

Board is now 100% :)

I attached a few images but not the best :laugh:

arcadus
10th May 2009, 09:17 AM
Another excellent log!, great to see an old vector board up and running and proves CROs can be useful in digital technology. :023:

dezbaz
10th May 2009, 10:03 AM
Amazing, very well done!

Roxbury
10th May 2009, 02:15 PM
Nice work!

Arcade King
10th May 2009, 03:21 PM
Another excellent log!, great to see an old vector board up and running and proves CROs can be useful in digital technology. :023:

Thanks for the comments guys.

I find myself using the CRO more than a logic probe lately. A really great tool.

stuba
10th May 2009, 07:28 PM
wow and thanks!
this level of IC diagnostic blows me away. hope i can learn to do it one day :)

Womble
10th May 2009, 09:32 PM
Thanks for the comments guys.

I find myself using the CRO more than a logic probe lately. A really great tool.

Nice job there!!

Same here, I seem to only use the logic probe when going over an entire board quickly looking for floating pins. I like to see what's on the lines too much these days, my last few fixes would have been virtually impossible without my cro, I love the thing!!

Arcade King
11th May 2009, 05:10 PM
wow and thanks!
this level of IC diagnostic blows me away. hope i can learn to do it one day :)

Mate all we need to do now is put it in your cab...any excuse for me to come over and drink all your beer :D


Nice job there!!

Same here, I seem to only use the logic probe when going over an entire board quickly looking for floating pins. I like to see what's on the lines too much these days, my last few fixes would have been virtually impossible without my cro, I love the thing!!

I hear ya mate. No F chips on any of this old Atari and Gollieb stuff good old fashioned fault finding. Time consuming but rewarding at the end.

Arcade King
25th May 2011, 08:10 PM
Captains Log 25/05/11

Bought a heap of boards last year from bumper. What really caught my eye was some Atari vector games in particular Asteroids and Asteroids Deluxe.
I wanted a spare AD for my machine and gave the Asteroids to Stuba

Anyhoo been fixing a few boards this week so I FINALLY got around to doing this one.

Before you start on any old Atari game of this era ALWAYS replace the sockets for the CPU and Roms. I've learnt the hard way if you want these boards to be reliable you've got to do it.
Its a good idea to put the 2114 rams @ L1 and M1 and the 82s129 tri state prom @ C8. As a rule of thumb I also socket the 74ls42 @ L5. This is so we can pull pin 1 out of circuit to disable the DMAGO which is handy isolating MPU and VSM (Vector State Machine) problems.

Ok 1st issue.
No clock
Fix. Crystal was broken off board and Bad 74ls14 @ B5. Common problems with these boards is they mount the crystal vertically and more times than not get damaged during storage or inserting the game board.

General issues while going over the board.
I found 2 broken traces both of which I'm positive were cause from the previous person who "Tried" to repair this board.

http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0143.jpg

http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0144.jpg

To repair I just jumped it on the back side of the pcb.

http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0145.jpg

At this point the board is powering up but is in a reset loop every second. I removed pin 1 of the 7442 @ L5 (DMAGO) to test the MPU section and all was go so next step is to poke around the state machine circuit.

Fix: Problem turned out to be a faulty 74ls161 @ D6 (Vector Timer) outputs at pins 11,12,13 and 14 were dead and pin 15 (STOP) was stuck high. STOP needs to be low so the state machine can advance so the next vector can be drawn.
Replaced the IC and the board fired right up.

Pic of the culprit IC's which have been replaced.
http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0142.jpg
I try to use Hitachi branded IC's where ever possible. They have proven to be one of the most robust manufacturers I've come across.

I put the board in my machine and she worked! amazing not a single graphics glitch. After starting a game however there was a single problem with the sound.

Symptom.
Thrust sound was more of a beep.
Fix: Easy to spot this one, both the .1uf (104k) Mylar caps had broken legs @ c118, c119. Found a scrap system 16 board with a pair :)
Before
http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0138.jpg
After
http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0146.jpg

Another problem was the 10k YGAIN pot was broken. (R152)

http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0148.jpg

This is the backyarder fix ;)
Found a 10k sound pot off a DKJ PCB.
http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0149.jpg
Always remember if it don't fit make it fit ;)

http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0150.jpg
End result
Its hard to take pics of moving stuff :b
Here's a short vid also.


http://www.youtube.com/watch?v=O_2PqFOTGqg

WOKA
25th May 2011, 08:16 PM
You need to have a stab at my spare Star Wars board sets.. ;)

dezbaz
25th May 2011, 08:18 PM
Nice work

Classic game

Woody
25th May 2011, 09:07 PM
Shit yeah. Well done mate.

I am always amazed at the knowledge you guys have when it comes to electronics. Awesome stuff.

I really want to learn this stuff, I bought a CRO, now to find my old textbooks :D

Arcade King
25th May 2011, 09:25 PM
If I can do it anyone can. :)

Womble
25th May 2011, 09:31 PM
If I can do it anyone can. :)

Same deal, I just decided to learn, so I did!

Rattanee
27th May 2011, 07:49 AM
Doesn't work any other way :) Every board you fix makes the next one a little easier... I still get some from time to time that get me stumped... that's when they go on the shelf... or when I'm in dire need of parts, they end up as parts.... happens :D

Homepin
27th May 2011, 08:43 AM
Brilliant work - well done!

GameDude
27th May 2011, 12:40 PM
Same deal, I just decided to learn, so I did!

+1

stuba
27th May 2011, 01:39 PM
nice work travs
:)

dokworm
2nd June 2011, 11:52 AM
Nice Job. I had to do some repairs on my Asteroids upright, next time I'll document them properly.

I really need to learn how to use a CRO, they are a bit of a mystery to me, but everyone who gets one ends up using it religiously!

Womble
2nd June 2011, 11:58 AM
Nice Job. I had to do some repairs on my Asteroids upright, next time I'll document them properly.

I really need to learn how to use a CRO, they are a bit of a mystery to me, but everyone who gets one ends up using it religiously!

As the saying goes, "there are none so blind as those without a CRO". :D

They make repairs and troubleshooting much easier, you will suddenly realise how little a logic probe actually tells you.

Arcade King
8th June 2011, 06:25 PM
Update

Problem....Left the ****ing cab on by accident over night and when I woke up could hear this infernal beeping noise..wtf is that. Well after blaming the Daughter thinking it was the alarm on her mobile phone I soon found out the Asteroids Deluxe cab was beeping down stairs :rolleyes, was quiet loud...hope the neighbours didn't mind.
Anyhoo the beeps do have a meaning and there was 2 High then 2 Low beeps.

Fix. From the manual the beeps correspond to the 4 rams located at M3 to R3.
Fat chance that all rams had failed and a quick probing revealed pin 10 (Write Enable) on each ram was dead. Quick check of the schematics lead me back to a 74LS32 (M)(Motorola) in which pin 8 was dead. Replacing the chip the board fired right up.
Just goes to show even though the PCB was reporting a bad ram its not always the case.

On another note I bought these 10k trim pots from David AVD and would highly recommend installing them on any Vector board that has X and Y gain pots
I got sick of every time I moved my cab or removed the pcb having to readjust the x/y gain. With these you set and forget.

http://www.aussiearcade.com/uploads/AK/asteroids/IMAG0172.jpg

HERE (http://www.advanced-tech.com/ic_logos/ic_logos.htm)'s a good link to help identify IC manufacturer logo's

dezbaz
8th June 2011, 07:35 PM
Quick check of the schematics lead me back to a 74LS32 (M)(Motorola) in which pin 8 was dead. Replacing the chip the board fired right up.
Just goes to show even though the PCB was reporting a bad ram its not always the case.


Nicely done, We can all learn a lot from that, my LL is doing just that right now

---------- Post added at 05:35 PM ---------- Previous post was at 05:35 PM ----------



HERE (http://www.advanced-tech.com/ic_logos/ic_logos.htm)'s a good link to help identify IC manufacturer logo's

Thank you, great link