Another Asteroids Fixed from ebay

[Monstermug]

Bought a faulty asteroids on ebay a few days ago. He has quite a few for sale but this one looked the most nicest candidate for a revival. It arrived today flat packed wrapped in two layers of cardboard which wasn't expected but did the job I guess.

Even before plugging it in, I saw there were a number of things I needed to do to first.

There were blue sockets on it that were supersized. One was not flushed to the board and resting on resistors.

Some were not even the proper sockets but looked like it did the job.

Some weren't even making proper contact.

I decided that it was time to redo what the previous technician did and just remove all the sockets and replace with quality dual wipes as I didn't have any turned pins.

Next was to spot the missing components and populate them. Missing 6502A CPU and 74LS06 @ N9.

Saw that the Crystal was looser than a hooker on commercial street so I replaced that too.

All the Ram chips were socketed and the buffers were socketed too. I decided to pull all the socketed chips and test them. Found 3 bad chips. SN74LS245N @ E3, 139N @ L3/L4 was also bad so I replaced them with fresh ones.

This picture I took showed it put in the wrong way around, but I did eventually get it right. It was still faulty the correct way up

The Ram had all red dots on them which usually means suspected bad/faulty so I decided to test them. 3 out of the 6 were bad so I replaced them all. Was really glad that the ram were all socketed which was a relief. I didn't even get a chance to use Philmurs Asteroids Ram PCB thingie.

Last thing to do was to verify the 3 program roms and 1 vector rom. They all tested good and were still the original ones

Finally time to give the pcb a good clean!

and did a first power on test and got this!

Fixed it and didn't even use a probe

A thing to note though, 74LS06 at N9 seemed to control the sound effects as I had accidently put a LS00 in and got a loud hum and no sound. I couldn't find a LS06 so I substituted a LS04 and got sound but kind of high pitched.. Finally found a LS06 and got proper sound.

Any how, at least I got a spare board for the rainy day.

Monstermug2017-03-15 23:28:38

 

[Hurray Banana]

Great fixing mate

 

[aeroflott]

Good work!

 

[phillv85]

Good work! How reliable do you find those IC testers? I got one a while back but I'm not sure how much I trust it.

 

[Monstermug]

Good work! How reliable do you find those IC testers? I got one a while back but I'm not sure how much I trust it.

I don't trust it at all

When it says it's working I take it with a pinch of salt. When it says faulty it usually always is. I tend to use it as a guideline though rather than full on fact like my mm.

 

[phillv85]

cheers for the reply. I'll continue taking the results with a fist full of salt then.

 

[Mitchell Gant]

Good work! How reliable do you find those IC testers? I got one a while back but I'm not sure how much I trust it.

I don't trust it at all

When it says it's working I take it with a pinch of salt. When it says faulty it usually always is. I tend to use it as a guideline though rather than full on fact like my mm.

I've got one of these testers too, I trust it's results just as much as my mates ABI Boardmaster 8000 IC tester that cost just a bit more than this cheap one.

Which is a less than 100% trust

Having said that I can't remember where it said a bad IC was good, it's a good tool for the cost. Would be awesome if it did 2114 RAM.

Good work on the Asteroids fix BTW.

 

[darthsylly]

Great repair!

 

[Bensonrad]

nice one

 

[Monstermug]

The saga still continues!

I noticed a very slight problem whilst playing it today when soak testing it. When asteroids explode instead of the dots you see forming the explosion, you would get a vertical streak instead. This would only occasional happen and seem to occur less frequently as the game warms up. Deja Vu because at Bonehead's meet, I also noticed his asteroids would do this as well. It's ever so slight and the flash is really quick but it's still there. My other Asteroids PCB has this problem as well! It was only a small problem before so I dismissed it as fully working but in mame it doesn't do that at all, ever.

Apart from this the game runs perfect. Something to do with the dacs? Maybe. More likely however, it seems that the position counters may have been messed up, especially the "X" counters. So I decided to finally break out the schematics and start probing that section. Everything seem to look as they should be until I got to the 74LS191N's at F9 and J9. Some of the pins weren't pulsing properly when compared to the 191's in the "Y" section.

I forgot to note down which pins unfortunately

. I thought this must be the problem. First I removed F9 and tested it. Bad. Then H9. That was also bad.

At this point I went ahead and removed J9 and that tested good.

All seems fair as F9 and H9 both had the same date code: 22nd week of 1980's. Replaced all three F9,H9 and J9 with fresh 191's and the problem never came back!

100% fully fixed. Time to give the other pcb the same treatment.

Exactly same problem. F9, H9 both bad.

So if you have this problem, good chances are F9 and/or H9 are your culprits. I think if you get this happening across the Y axis, it would most probably be C9 and D9.

 

[Ronnie Dent]

Great write up and good of you to log it for others.

Do you think that ic tester is a good buy for a novice? I guess at the price it's not bad unless import duty is levied!

Ronnie

 

[Monstermug]

Great write up and good of you to log it for others.

Do you think that ic tester is a good buy for a novice? I guess at the price it's not bad unless import duty is levied!

Ronnie

Depends if you fix enough pcb's to make it worth your while. It's definitely useful. Fixing a car in the dark with a candle is better than no candle.

A little tip on using it though. I also find that the auto search function is very useful too. You pop it in and auto search. If it finds the IC it always passes the test. If it says not found, then it either doesn't support that IC or the IC is bad. There are a few chips that it is supposed to support for but always report it as faulty for some reason. So like I said in my previous post, take readings with a pinch of salt and you be fine

I need to make a list of all the one's that don't work for future references. Could be that my unit is faulty maybe.

 

[Ronnie Dent]

Thanks, at 22 quid I guess it's handy to have, but I have seen me cutting the legs of chips that are hard to remove to save track damage! nothing left to test after that