Author Topic: Galaga fried all to hell...EDIT: FIXED!!! (Read 12796 times)

Mauzy · « **on:** October 24, 2008, 06:41:30 pm »

I have a Galaga board that has worked well over the last year or so, but it suddenly has started freezing at the RAM OK, NVR OK (once in a while itll throw a random ROM error at me, reset and that goes away) screen. According to the nets, that could be a problem with 4J. Thats cool. I have four extra Z80s. Pop one in, works fine. Let it set for a while, reset it and it freezes at the same spot. Strange. I replace the Z80, works fine again. Took out the board today to get to the video harness, took out the boards, unplugged the harness and did what I needed to do. Put the boards back in, freeze. Crappy socket solder? reflowed all of the pins, fires right up. Now Im suspicious so I reset it a couple times, works fine. Put the boards back in the rack, freeze. Damn! Thats 2 down. Replace it, and it works fine. Tested the other seemingly fried, doesn't work. Put in the last known good one, works.

I can't find any broken traces unless it's something minute enough to require a magnifying glass.

What Im trying to ask is what is causing these Z80s to fry (if they are actually frying...)? They aren't getting hot.

EDIT: I just rechecked voltages and found that the 5 volt is at about 5.5 V. This isn't too high, is it? I have a switcher in the cab.

~~check new posts for newest of problems!~~

Check the newest posts for the fix!

SirPeale · « **Reply #1 on:** October 25, 2008, 12:04:01 am »

Yes, that's pretty high! Where are you checking the voltage at? On the PCB or on the harness or the PS?

Dial it down to ~5.1V on chip.

Mauzy · « **Reply #2 on:** October 25, 2008, 12:32:47 am »

That was at the harness. From which chip should I be testing?

Level42 · « **Reply #3 on:** October 25, 2008, 02:22:25 am »

On the processor itself between pin 11 (+5V) and 29 (Gnd).

Mauzy · « **Reply #4 on:** October 25, 2008, 10:56:25 am »

I got a steady read of 5.27V. Im going to order a new socket (took the old one out thinking I had a replacement

) and I have to find a place that sells Z80-Cs. I'm officially out. All I have left are Z-80 As and a couple Z80.

EDIT:Bob Roberts seems to have something called a Z80-CTC. Is this the same thing as a C? I have a pending order with him at the moment and Ill modify it if necessary.

EDIT 2:I was looking through the MikesArcade repair logs and found a case where there was a standard Z80 in the socket at 4M, so he replaced it with the proper Z80-A. I have been running this board with an enhancement pack and a Z80-C in this socket with no trouble till now. Are these interchangeable, or did I just get lucky? Now Im rather suspicious as to whether or not Z80s I have on this board are correct.

I have Z80-Cs at all (4M, 4H, 4E) CPU sockets.

EDIT 3: WOW I need to get my vision checked. The Z80s dont say "Z80C" on them, they zay 780C. That would be a Z80A, and it even says that on the MikesArcade Site.

How many is the record for most edits in 20 minutes?

Needless to say I want to fix this and soon.

EDIT 4: So do y'all think that having 5.5 volt on the chip is what has been causing my problems?

Level42 · « **Reply #5 on:** October 25, 2008, 06:16:42 pm »

5,5 is very risky. 5,27V is already on the high side.

Mauzy · « **Reply #6 on:** October 25, 2008, 07:19:26 pm »

Alright. I got it down to 5.11 V. I also ordered 3 Z80-As and a couple new sockets.

channelmaniac · « **Reply #7 on:** October 26, 2008, 04:42:41 pm »

5.1 to 5.15 on the CPU is good. 5.25 is the limit and any higher you risk damage to the chips.

As for the Z80 chips... you can use the Z80B or the D780B chips. NEC marks theirs strange.

In any case, you need 4MHz or faster rated Z80 chips. Z80C will run fine.

Now for the stuck at RAM OK. I've run into several boards with that problem. Bad CPU sockets, bad CPUs, bad ROMs, or bad ROM sockets will all cause that problem. So will bad 74LS368 chips that interface the 2nd CPU to the video board. It's a generic problem with many causes.

Your best bet on repairing ANY Galaga board is to replace all the CPU and ROM sockets on the CPU board first. They used some VERY ---smurfy--- sockets.

RJ

Mauzy · « **Reply #8 on:** October 26, 2008, 04:55:21 pm »

You mean Z80A? http://mikesarcade.com/cgi-bin/store.pl?sku=Z80ACPU
I misread a Z80A for a Z80C instead of 780C. NEC did go a little strange on the markings...

I just ordered 3 Z80s and 2 sockets (dunno why only two... oh well...)

I'll puttin new Z80s, then start checking further down the line. Thanks!

EDIT: Oh. missed the "or faster" line.

channelmaniac · « **Reply #9 on:** October 30, 2008, 02:11:22 am »

It's a good thing to order sockets. The CPU sockets that were put on the Galaga boards at the factory are complete garbage

Mauzy · « **Reply #10 on:** October 30, 2008, 09:51:37 am »

Yeah. Too bad my order got screwed up so It didn't ship till yesterday. MikesArcade is a great place to get stuff so Ill let this one slide. No big deal really.

channelmaniac · « **Reply #11 on:** October 31, 2008, 10:33:57 am »

Sometimes real life happens. For example, my business is a hobby based business and the day job can sometimes get in the way - large looming deadlines or travel.

On the other side... the travel comes in handy as when I go to San Jose there are several places I like to go scrounge around for obscure parts.

Mauzy · « **Reply #12 on:** October 31, 2008, 05:37:15 pm »

I got the parts in today, changed the socket and put in a new Z80 and it works with one problem. Bullets don't fire. It makes the shooting noise, but no bullet moves across the screen and none of the aliens blow up...

Mauzy · « **Reply #13 on:** November 14, 2008, 08:03:32 pm »

Ok. I fixed the problem above (the Enhancement pack rules...). Went to turn it on tonight and wouldn't you know, NVR OK, RAM OK. CRAP IN A HAT! This time its different though: usually, the star field would freeze at this stage. Now it still moves, but it "freezes" at the OK stage...

Level42 · « **Reply #14 on:** November 15, 2008, 03:59:59 am »

AFAIK the starfield is generated without any involvement of the CPU (maybe it turns it on or off though, not sure).

Mauzy · « **Reply #15 on:** November 15, 2008, 09:45:59 am »

True. I guess that means my "starfield generator" is good then.

Mauzy · « **Reply #16 on:** November 16, 2008, 02:53:59 pm »

The star field doesn't move when a Z80 isn't present in the socket this time. I measured, and I only have 1.5 volt at the socket but I have 5.1 at the harness.

. My guess is that this may be my problem.

channelmaniac · « **Reply #17 on:** November 17, 2008, 09:06:37 am »

OOPS.

Sounds like you pulled a pad or a platethru when removing the old socket. Better check all the traces going to that socket against the schematic.

Mauzy · « **Reply #18 on:** November 17, 2008, 10:34:35 pm »

Got the voltage right this evening. Re-flowed the 5 volt pin and the voltage came back to normal, but that Z80 was still bad. swapped out that processor with a new one and it works for now...

SavannahLion · « **Reply #19 on:** November 18, 2008, 03:02:19 pm »

Quote from: channelmaniac on October 30, 2008, 02:11:22 am

It's a good thing to order sockets. The CPU sockets that were put on the Galaga boards at the factory are complete garbage

Can you elaborate on the sockets?

channelmaniac · « **Reply #20 on:** November 19, 2008, 10:29:33 am »

They make poor connections with the pins. Not sure if it's corrosion or if they just get weak and aren't as springy to hold against the chip legs... but they sure are a common problem on those boards.

Replace the sockets and the problems go away. Well... As long as you don't booger up the traces while replacing them.

SavannahLion · « **Reply #21 on:** November 19, 2008, 01:08:19 pm »

Wouldn't the new sockets also exhibit the same problems after a fashion or is this a specific problem to a brand/type?

Level42 · « **Reply #22 on:** November 19, 2008, 06:49:36 pm »

Not if you use the more expensive types with round (wound) holes. These cannot loose tension and usually have better metals.

Mauzy · « **Reply #23 on:** November 19, 2008, 07:52:39 pm »

Well, I already replaced the socket and checked the traces. Everything, to my knowledge, is solid. I dont even want to fire it up because I don't want to see it freeze...

SirPeale · « **Reply #24 on:** November 20, 2008, 01:45:03 pm »

One thing I want to stress is that you do *NOT* want to combine metal types. Don't combine gold with tin, for example. It'll work - initially - but over time they will oxidize heavily because there is a reaction between the gold and the tin.

Level42, do they make a socket like that with tin wrapping? Most chips I've seen have tin legs, not gold.

ChadTower · « **Reply #25 on:** November 21, 2008, 09:04:32 am »

I prefer SIP sockets anyway... easier to see underneath them and they are the same circular contact type. And they do come in tin.

If you want one piece, however, they do come that way in tin.

SirPeale · « **Reply #26 on:** November 21, 2008, 11:03:04 am »

Find me those on Mouser.com, would you?

What is the difference between solder tail and solder pin?

ChadTower · « **Reply #27 on:** November 21, 2008, 11:10:45 am »

That I don't know. I usually toss them in with pinball parts orders. I know GPE has them - Pinball Life might as well.

channelmaniac · « **Reply #28 on:** November 21, 2008, 02:32:42 pm »

I use good quality double wipe sockets and don't have problems... Personally, I avoid those machine pin sockets because of a couple of issues...

1. Pins on the chip have to be absolutely straight or they bend when you go to insert them.
2. If you ever have to desolder the socket you have a much higher chance of pulling the trace off the top of the board. (big shoulder that sits right on top of the trace is difficult to cleanly desolder, even with the Pace station I have)

Level42 · « **Reply #29 on:** November 23, 2008, 04:20:17 pm »

Quote from: channelmaniac on November 21, 2008, 02:32:42 pm

I use good quality double wipe sockets and don't have problems... Personally, I avoid those machine pin sockets because of a couple of issues...

1. Pins on the chip have to be absolutely straight or they bend when you go to insert them.
2. If you ever have to desolder the socket you have a much higher chance of pulling the trace off the top of the board. (big shoulder that sits right on top of the trace is difficult to cleanly desolder, even with the Pace station I have)

1: NEVER had that problem, even with used chips. Getting all the legs straight is always a good idea BEFORE inserting them into any kind of socket. You can already feel the machined pins have a better grip on the pins when you insert the chip.
2:

Whenever would I want to desolder a good quality socket ?

Why do you think the machines one's are so much more expensive ? It's because they're better.

channelmaniac · « **Reply #30 on:** November 26, 2008, 02:08:10 pm »

Quote from: Level42 on November 23, 2008, 04:20:17 pm

1: NEVER had that problem, even with used chips. Getting all the legs straight is always a good idea BEFORE inserting them into any kind of socket. You can already feel the machined pins have a better grip on the pins when you insert the chip.
2: Whenever would I want to desolder a good quality socket ?

Why do you think the machines one's are so much more expensive ? It's because they're better.

1. Try to remove a fragile custom chip from a Galaga/Bosconian/Pole Position or any other Namco game from that era. You'll rip the pins right off the chip. They will be stuck in the socket and you will be stuck trying to repair it. Also if you don't have the pins 100% straight they'll bend like mad.
2. See #1. When the pin breaks off you are stuck with desoldering a "good quality socket"

They are more expensive because it requires more metal and more time to make. More expensive does not always mean the right part for the job. A $15 toilet seat from Home Depot is just as good as a $300 toilet seat that the military buys.

RJ

Level42 · « **Reply #31 on:** November 27, 2008, 04:52:10 pm »

Not that I want to continue this pointless yes-no game, but I've never seen an original board with machined sockets. And I have got quite a few. The manufacturors had no interested in a game running for 20+ years at all, so why would they use the more expensive one's ?

Again: the cheap one's loose their spring tension over time. Machined one's don't. They corrode as well.

Mauzy · « **Reply #32 on:** December 16, 2008, 08:43:25 pm »

Well, this bastard is flat out dead now. Looks like it'll be sent off for repair after the holidays. I know it needs sockets, but who knows what else. For a hundred bucks I'll let a pro do it.

ChadTower · « **Reply #33 on:** December 17, 2008, 11:15:12 am »

Just out of curiousity, what kills a new cpu? Overvoltage on the supply line? Voltage coming in on the wrong pins?

2600 · « **Reply #34 on:** December 17, 2008, 11:34:21 am »

Well first we have to assume they are dead instead of the board is just not working correctly and a different CPU just happens to fix the problem for a little while.

What kills a CPU:

Heat
Cold
Moisture
Static
DC Voltage High
AC Voltage High
DC being applied backwards
To much current

Too little current and too little voltage may prevent a CPU from working and isn't good for a CPU, but I don't think it would kill it. Probably more things, but that's all I can think of right now.

Mauzy · « **Reply #35 on:** December 17, 2008, 03:55:49 pm »

I can confirm all of the CPUs I've pulled and switched are infact dead. Switching them with a new CPU fixed the problem for a short time and the old ones will not run any other boards.

The 5.1 volts going to the CPU is still constant, the basment is a constant 60 degrees, I don't see how the AC would affect it (doesn't that get taken care of in the SMPS?), the air is dry (nothing molds or has water damage at least), and I have no idea about static.

This is the only boardset out of many that I have problems with. All boards get the same power in the same environment.

2600 · « **Reply #36 on:** December 17, 2008, 04:30:34 pm »

The power supply is suppose to regulate the 5V, but with those 30+ year old caps I wouldn't just check it off because it's suppose to be doing it's job.

If it's killing the CPU's then I'd check to see how much ripple is getting through and check for a short. The short may only come when it gets a warmer. The sockets are known crap and some of the resistor networks are crappy as well.

When you say this is the only board and they get the same power, do you mean you have other Galaga board sets and swap them into the same cabinet?

Mauzy · « **Reply #37 on:** December 17, 2008, 06:13:01 pm »

Not other Galaga, but I've used the same cabinet with the exact same wiring and PS (using adapters of course) to run this, a Gallag board, a Ms Pac Man, and a Ninja Clowns JAMMA PCB.

I never thought of doing a cap job, but what else might have been taken out due to bad power? I don't know anything about the resistor matrices or how to test them. How do I test for ripple, and what do you mean by ripple?

Keep in mind only 4J has been a problem. I've never had to replace.

ChadTower · « **Reply #38 on:** December 18, 2008, 08:47:32 am »

Ripple is AC current that has made its way into the DC lines. That is usually as a result of dead filter caps and/or a faulty bridge rectifier. You would test the resistor matrix by testing each resistor individually.

Mauzy · « **Reply #39 on:** December 18, 2008, 10:08:35 am »

Oh that sounds bad. I'll check that out within the next week (crazy holidays coming...)


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