Author Topic: Astro Blaster Z-80 Arcade Machine Help (Read 8249 times)

bluemanop · « **on:** February 10, 2005, 03:27:55 am »

Does anyone have much experience with repairing a full size Astro Blaster arcade machine? The machine currently posts to a completely blue screen and the speaker is making a low roar. The speaker in the unit was being worked on when the machine went dead.

I have clean power, I believe, a good monitor but I believe the main CPU board maybe dead. I believe this to be the case due to the red light CPU halt light on the CPU card being lit. The manual states that it could be a failure with the u26-u29 chips, C10615 ,which I believe to be memory chips or maybe even the Z-80a processor 8400W2N. Could there be any other problems that could have fried these chips like a bad sound card or would replacing any and all of these parts fix the problem?

Any help diagnosing / troubleshooting / fixing would be appreciated.

D_Zoot · « **Reply #1 on:** February 10, 2005, 12:44:18 pm »

I assume the board does not boot at all, no activity on the screen, no test mode available or working etc...

If you are sure that your voltages are spot on......

1) Carefully inspect the board for cracked solder joints, damaged traces or missing/damaged components.

2) Reseat any header connectors, edge connectors, ribbon cables or pin connectors (I'm not familiar with this specific board, so I don't know what it has)

2) Remove any socketed chips and reinstall.

If everything above checks ok, then it goes like this:

There are alot of things that can prevent a game board from booting. Bad cpu, failed rom, failed memory, loss of clock, failed reset line.... Further troubleshooting requires an O-Scope or at least a logic probe. It might be a good idea to have somebody familiar with board repair to have a look at it.

I wouldn't suggest just replacing any chips without some idea of what was going wrong with the board. It's easy to run yourself around in circles just trying to throw chips at it.

Regards,
D

bluemanop · « **Reply #2 on:** February 10, 2005, 09:35:36 pm »

Thanks for responding D-Zoot,

You are correct, the board should post to a memory test. It does not do anything but display a blank, blue screen. No game post at all.

I believe the power supply is still good but I have not hooked a multi-meter to the power supply as of yet. I will observe the manual for the proper power output to the power supply and see what I find.

I reseated all the cables & edge connectors but that did not yield any results. I suspect the main board because of the red error light on the CPU board. I thought to remove the chips and reseat them but I did not have a small screw driver on me or IC puller. I will do this the next time I am in front of the machine.

I was on the same page as you, a bad CPU (z80a) processor or memory chip. Not sure about a failed ROM or know what loss of clock is or failed reset line. I was thinking that the unit would have posted with something it had a good proc or mem chips. Manual stated something to the affect that it would note bad ROM chips after the initial memory post. I will definitely keep it in mind.

I was afraid someone would say logic probe or oscilloscope, all of which I don't have. I have considered visiting this guy's shop where I know he has these tools but he is somewhat of a miser and generally not open to visitors.

Would you have any good links to replacement arcade parts (spare processors and/or memory chips, etc.)? This is what I have read of the CPU board.
-----
CPU
Zilog Z-80A
8400W2N A
8030 PS
-----
Memory (No name just a logo that looks like an "S")
8047
C10615

I'm an old video game arcade nut and this is my first dabble into repair. Although I am not a complete rook in electronics it has been over 15 years since I have really done anything in this area aside from building PCs. I hope this experience with revive an old passion. I look forward to hearing some more input.

Thanks again.

D_Zoot · « **Reply #3 on:** February 11, 2005, 12:41:19 pm »

Quote

Not sure about a failed ROM or know what loss of clock is or failed reset line.

Okie then,

D_Zoot · « **Reply #4 on:** February 11, 2005, 08:35:28 pm »

Here's two case studies that you might find interesting.

bluemanop · « **Reply #5 on:** February 11, 2005, 11:47:13 pm »

I understand. This Astro Blaster machine sounds like a case that might be CPU related based on your notes. I found some information from the owner of the machine that may have led to the CPU dying. This is what happened:

The machine had a crackling speaker in the cab and the owner decided he was going to replace the speaker. He removed the marquee and snipped the speaker wires while the game unit was on. The screen went to a solid blue screen and that is where the machine has sat for 5 years.

I attached the speaker back up knowing that this would not fix the problem but I did want to see if the machine made any game sounds on boot. It does not make any sound but a low hum. As for the video, there is no pattern, no blips, no nothing, just a blue screen. I have tried to hit the reset and that doesn't seem to even show signs of life. I suspect the CPU is the cause but much like you said, not having a logic probe or scope to even test for a signal is like looking for a needle in a hay stack.

I would be willing to try to find a Z80 processor, although I am just unsure as to what Z80 to buy. Could you tell me if this is the same CPU as the part I have listed?

My part:
CPU
Zilog Z-80A
8400W2N A
8030 PS

Jameco Part:
Jameco.Com Link

The picture on the Jameco site seem to show a skinny version of my CPU, although I am thinking it is generic. You stated you have purchased stuff from them, is this generally a generic picture?

bluemanop · « **Reply #6 on:** February 12, 2005, 12:33:28 am »

I found this link that has a good picture of my CPU on the top of the page "Zilog Z80 8400W2N A" and also lists some others including that one sold by Jameco "Zilog Z80 Z0840004PSC"

http://www.cpu-collection.de/?tn=0&l0=cl&l1=Z80&l2=Zilog#8400W2NA

Do you think these two parts are interchangeable? Pins-outs, size, etc...?

D_Zoot · « **Reply #7 on:** February 12, 2005, 10:12:31 am »

A Z80a is a Z80a, the one from Jameco would be the right one.

Quote

but I have not hooked a multi-meter to the power supply as of yet

You probably want to do this before you order any parts. Make sure the +5v is at 5v and no lower. Sometimes you'll need to run it up to 5.1 or 5.2-ish.

Good luck!
D

bluemanop · « **Reply #8 on:** February 12, 2005, 11:24:45 am »

I plan on heading over to my buddies house this weekend and run the multi meter across the power supply. I also plan on re-seating the Z80 and the memory chips as well.

Thanks again for checking back on my progress. I'll let you know what I find.

bluemanop · « **Reply #9 on:** February 14, 2005, 07:50:28 pm »

Didn't get a chance to get out there this weekend. The person that owns the game was away but I schedule some time with the machine this Wed-Thur., I also purchased a Z80 chip from Jameco and a variable power supply from another source.

I have also been eye-balling a cheap O-scope on eBay but it has been a great number of years since I have used one. Nothing worse than chasing down a signal that I don't know if it should be there or not.

With a little luck I will have what I need to get this machine to post.

Here is a good question, do you know how many amps these boards greatly pull from the 5volt power supplies that power them?

D_Zoot · « **Reply #10 on:** February 14, 2005, 10:24:04 pm »

Quote from: bluemanop on February 14, 2005, 07:50:28 pm

Here is a good question, do you know how many amps these boards greatly pull from the 5volt power supplies that power them?

Nope, I don't know. I'm not personally familiar with that specific board.

Games of that vintage usually ran dandy with a 15 amp supply. Given that supplies were usually spec'd with some overhead, I'd say the total current draw on the +5 line should be well under 15 amps.

About the O-scope. If you are interested in getting your "feet wet" again with electronics and logic circuits, but are not sure about spending the dough on a scope, consider a logic probe. Logic probes can be had for $20 and will get you a long way in basic board troubleshooting. Most of the boards I work on I could have diagnosed with a logic probe alone.

Looking forward to hearing how you make out!

D

bluemanop · « **Reply #11 on:** February 15, 2005, 11:11:50 am »

Any recommendations on the logic probes? I have been looking at all my choices on eBay

for the last week or so.

bluemanop · « **Reply #12 on:** February 18, 2005, 12:22:29 am »

Well it looks like UPS managed to be a little slack. Even though I ordered the Z80 processor on Sunday, the part was shipped on Monday but it won't get here till this up coming Monday.

I did get a chance to get to the machine today and test the board with a re-seated IC chips. The machine powered up like it normally did to a blue screen. No change.

I did check the power supply and I did register about 5.1 to 5.2 volts from the power supply to the main board so I think there are no issues there. I am still thinking the Z-80 processor is dead but that is just a guess at best. We will see come Monday.

bluemanop · « **Reply #13 on:** February 22, 2005, 02:55:28 pm »

Well I am at a loss as to what to do next. I tried pulling out that Z80 processor and replacing it with another but it was a no go.

I tried pulling out boards like the sound card and powering up the unit and I still get nothing but a blue screen.

I am open for any suggestions at this point.

D_Zoot · « **Reply #14 on:** February 22, 2005, 10:48:32 pm »

Sounds like it's time for some serious board-level troubleshooting.. Scope or logic probe time....

If you wanted to send it to me, I could have a look at it.. I'm very backed up, (7 pins waiting for overhauls and 8 vids with problems). If you were in no rush whatsoever, I could have a look, but it could be weeks before I could get it on the bench. Otherwise, I think it might be good if you can find somebody local to you to help you troubleshoot it.

As a last resort, you could exchange it with eldoradogames.com They would swap your's with a rebuilt one for $119. I've used them in the past and had good luck with the boards I've bought there. They aren't very good about email, so it's best to call them if you needed to get in touch with them.

D

bluemanop · « **Reply #15 on:** March 01, 2005, 09:26:50 pm »

I may have found some replacement boards. They are suspect but it is the best shot for the time being. I will get the package some time this week. I will let you know what happens.

Rocky · « **Reply #16 on:** March 02, 2005, 10:00:40 am »

Thanks for following up on this.

bluemanop · « **Reply #17 on:** March 06, 2005, 12:58:56 pm »

Well D_Zoot, you can't blame a man for trying. I got that replacement cage, with suspect boards (may work or may not). I placed the cage in the astro blaster machine and sure enough it seemed to do the same damn thing. Frustrated I sat there and began the troubleshooting process in my mind again. Thinking that it must be something else, either that or the same thing that is occurring in the original just happened to be the same thing that is going on with the replacement cage of boards; which is possible but may not be the case.

I broke out the schematics for the machine and sure enough I was looking around and I saw something that I didn

RayB · « **Reply #18 on:** March 06, 2005, 10:16:44 pm »

Look for burn marks...

D_Zoot · « **Reply #19 on:** March 06, 2005, 11:07:05 pm »

Alrighty.. I had a quick look at the supply board schem... Here's some notes that pop into mind:

When you look at the PS schem, break it down into three seperate parts.. If you draw a line across the page at about the middle, everything from this imaginary line and up is the 5 volts regulated circuit. You can pretty much see this circuit kinda stands alone from the rest of the diagram.

Let's look at the 5 volt first, as it's the most crucial to board operation. Let's measure at the PS board itself so it's easier to follow the schem. With your meter in DC Volts mode, place your BLACK meter lead on pins 4, 5 or 6 at the PS board (they are all the same, ground circuit). Place your RED meter lead on pin 8, 9 or 10. You should be reading 5.0v DC or so (sounds like you are from your post)

Now, leaving the black meter lead where it was, probe pin 7 with the red lead, your meter should read -5.0 v (give or take a little here is ok) Note the MINUS before the reading, this is the negative 5v circuit and should read as -5.0 on your meter.

Ok, moving along, let's look at the lower part of the schem. This lower part we can break down into two smaller parts, left and right. The left part is the 12 volt DC regulator circuit and the right part is the audio amp.

Starting at the left part, we'll check the 12v reg circuit. Again, with the red lead of your meter (leaving the black where it was from above) check pin 2, it should be 12v DC or so. This could be one or two volts higher or lower, which would probably be normal. Now check pin 1, it should read -12v DC (again, note the minus).

The rest of the circuit, on the RH side of the schem, is the audio amp. If there is a problem with the amp, it shouldn't really cause a problem with gameplay, just sound issues. Still, you should be getting close to 0v on the speaker wires with no sound occuring, so this does lead me to suspect your supply/amp board is damaged. Sounds like one of the amp transistors is shorted (the TIP120 would be the likely culprit). But again, this shouldn't be bringing the whole game down.

For now, let's focus on getting the board up and running and worry about the sound a little later on, I'd disconnect the speaker and also see the connection labeled "Audio In" on the PS/Amp board? Disconnect that too and focus on the largest problem for right now.

Post back with your voltage measurements as I described above and we will see where you need to go next.

As for your ROM question. The only way to test them (besides in a working board) is to read them with burner and compare checksums to good images. A burner is not something I'd recomend you get quite yet, it's not something you would use hardly at all (if more than once). But, I don't think your root issue is the ROMs. But at this point I am concerned about logic board damage from incorrect voltages. That's why I am curious what voltages you are getting on what pins of the PS board.

Regards,
D

bluemanop · « **Reply #20 on:** March 08, 2005, 12:16:49 am »

Not sure what pins you want me to check based on the schematic of the power supply. I brought it up and cut the schematic in half, looking at this view I can see the pins you are referring to on the right hand side. I'm just wonder where I can find that on the power supply board.

I will try to go by my friends house and take a good look at the power supply board and I think I might be able to take the power supply with me to test it from home as well. Even better I will take a really sharp picture of it and post what I see. In the mean time I included what I am looking at in this post, just to make sure we are on the same page.

D_Zoot · « **Reply #21 on:** March 08, 2005, 05:52:24 pm »

The pin numbers I referenced would be for the connector to the main game board. I'm not sure how the board is connected, so I can't be any more specific. Those pin numbers came right out of the schematic. Looking at the schem and the supply, you should be able to correlate those terminal numbers.

While testing the supply on a bench at home would be easier, it would be best to test it connected to the game so that the supply is under a load and your measurements are accurate for actual conditions.

D

bluemanop · « **Reply #22 on:** March 08, 2005, 09:27:31 pm »

I believe I can borrow the spare cage assembly and the power supply. I will let post some pictures as soon as I get over there this week.

bluemanop · « **Reply #23 on:** March 14, 2005, 09:30:12 am »

Well I got over to my friends house and pulled the power supply and took the cage with all the boards in it. I will get to testing the voltages from the pin outs this week.

Here is a good question, if the old monitor in the astro blaster is a typical RGB monitor found in arcade machines. Could an equally old Amiga or Mac RGB monitor be a good sub if I were to find the pin out configurations of the monitor? Basically what I am trying to do is make a good test rig from my house that would give me a video screen at least.

I'm going to go research this on the net for a bit. Anyone got any ideas for this or has utilized an old RGB monitor for this purpose?

bluemanop · « **Reply #24 on:** March 22, 2005, 10:22:14 pm »

Ok, I'm back. Work hasn't completely taken over my life.

Here are my results:
PIN

bluemanop · « **Reply #25 on:** March 28, 2005, 03:57:26 pm »

Anyone got any ideas out there?

crsdawg · « **Reply #26 on:** March 29, 2005, 11:58:50 am »

what are the output voltages of the psu? if they are typical you could swap it out for a switcher. it would be a good idea even it the power supply isn't your problem.

bluemanop · « **Reply #27 on:** March 30, 2005, 12:10:32 am »

I have a new power supply from WEI-YA Model P031 but I am thinking that I am going to be out of luck on the -12 volts side. This does +5, -5, and +12. Do you think I can just flip the wires on the +12 volts?

I am rookie when it comes to arcade machines, so bare with me. Do you think I should run this through the isolation transformer that is currently powering that old power supply? or can I just cut a computer power cord and run wall current to this new power supply on the AC/N and AC/L inputs?

crsdawg · « **Reply #28 on:** March 30, 2005, 12:55:26 am »

well, i'm no guru on the subject but i'll try to help best i can. make sure to get more than

Rocky · « **Reply #29 on:** March 30, 2005, 10:56:25 am »

I'll confirm that you don't want to use the Isolation transformer for your new power supply.

bluemanop · « **Reply #30 on:** March 31, 2005, 07:55:01 am »

I'm thinking of going out and buying a digital volt meter. This analog one is ok but I'm thinking I would do myself good if I get one that is newer. I will do this and re post my readings.

bluemanop · « **Reply #31 on:** April 08, 2005, 12:47:47 am »

Well I researched a little bit in regards to a new multi meter. I purchased a new digital meter that will measure, capacitance, resistance, diodes, transistors and of course AC/DC voltages. I suspect it will be here by Monday via UPS.

This should allow me to work a little closer with the schematics for the power supply board and test a little more accurately. I will let you know what I find in the next week of testing.

RayB · « **Reply #32 on:** April 08, 2005, 12:58:39 pm »

You sure this game is worth all this? ;-)

bluemanop · « **Reply #33 on:** April 09, 2005, 01:06:39 pm »

Yes. I believe that solving the problems with this machine will make repair on most other machine seem simpler. This is a non-jamma machine with some pretty proprietary parts which will force me to tool my bean more towards fixing the failed electronics. I would love to preserve a little bit of history, no matter how crappy the machine

, they get more rare every day.

Well I got my new multi meter in today. I am going to start metering parts across the power supply (with it unplugged), with the schematic & parts list and see what I may find.

Rocky · « **Reply #34 on:** April 09, 2005, 02:17:49 pm »

It is definitely worth it.

bluemanop · « **Reply #35 on:** April 12, 2005, 08:12:44 pm »

I have gone through most of the resistors on the power supply board. It seems that there are some discrepancies in some of the resistors. I.E. 4.7k resistor is metering out at 2k or 1k.

I am currently looking around for cheap prices on the net like Jameco.com but I plan on checking out a couple local electronics places as well.

Just in case anyone that doesn't have an astro blaster machine out there but is following this thread for general repair information. Here is a good link for reading color bands on resistors if you don't have a parts list and/or schematic and want to meter some resistors.

http://www.csgnetwork.com/resistcolcalc.html


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