Hello Vid,

Do you have any advice specific to System 9 games? I just acquired a Space Shuttle, which seems to boot and run normally with no obvious errors. But I know it's not a matter of "if", but "when" things crop up.

I have already done the rectifier fuse mod. Previous-owner botched a battery holder install with marble-size blobs of solder, and I'll have to clean some corrosion in the ground area... not too worried there yet.

I guess my main question is, how to determine what the "safe substitute" components are. I want to change the lamp matrix resistors as mine are rather... mesquite. I've recapped and rehabbed electronics including tube hi-fi's before so I'm familiar with the 1-for-1 process. And I understand Ohm's law to a point as far as some subs go (after all, those hi-fi components required some non-like subs)... but I'm not an EE so changing "this value for that one..." or "trade that transistor for this specific MOSFET option A or B"... how do you know it's better and/or safe?

Do you have any System 9 specifics to watch out for, or will most of this System 7 stuff apply?

Thank you for your guides. I've read a few of them and the playfield one inspired me to go a bit further on mine than I ever intended....

Heh, turns out mine was replaced with the supply from a Comet - I think that's a Sys11. There's no connector as the wires go straight to into the PCB. It works, but looks odd as the GI harness connector has two leads, but the mate from the PS has 4. I'm not real pleased with how they hacked that either. But it's obviously worked for a lonnnnnng time, based on what I heard from the PO.

I definitely intend to rehab the power section. My game has 5 of the plasma displays, but only one is its original, and the driver board was replaced too - making the display section a 5-game Frankenstein! Hey, if it works it works. For now. I'd like to keep it that way.

I have a cart filled of basics you covered from GreatPlains. At a glance of my setup, is there anything else that sticks out to you, before I order?

Boards-879.jpg

It's literally only approximately a $5 or $6 mod that uses common parts available almost anywhere. And one of the easiest to do since everything is in easy reach.

I did mine immediately after acquiring the machine, and before I did anything else. At least now if my machine catches on fire, I'll have small comfort that it was NOT from something I could have easily prevented.

I know sometimes it's not always convenient to run across town or the hardware store or whatever, but at the very least this mod should be REQUIRED before you ever place a single order and/or spend money on any other part.

Now the labels, though? That's another matter. Labels are a PITA. I blame my wife and the mess in her cra(p)ft room, losing the labelmaker again...

OK, time for me to come by hat in hand and ask how stupid was I, and what should I prepare for...

Long story short, while waiting on pf clear to cure and other things, I did the MPU transistor and zero-ohm resistor mod for the lamp matrix, as detailed several pages back. Everything went really well: my solder connections on the mount pads beneath the board were as quick, clean, and good-looking as the factory.

Trouble is, when I looked at the *topside* of the board, it didn't seem like there were good clean solder mounds on all the pads under all the transistors. I probably didn't have enough flux in spots, or rushed myself trying not to have heat applied for too long, etc.

So I tried to rectify this. And I did, except... well there are a ton of transistors in close proximity there, on a Sys9 board. I had my iron dialed up to ~550 deg. I think I probably got too close for comfort on those transistors, especially that 3rd row, sandwiched between two others...!

I didn't really touch anything, at least not to where it scorched or melted stuff. But I've heard horror stories about how sensitive those components can be....

...it will be a while before I can test this in the machine. What's the worst that would happen if a few got cooked? Is there a way to check them outside the machine? Or should I bite the bullet and order a stash of spares?

Yeah, it's frustrating: everything I read says to use the lowest heat possible and that makes sense. But in practice it's never quite that simple and seems like there is a price of tradeoff: apply lower heat for a longer time until you get good flow, etc... OR use nuclear fusion so you get quicker results? Which is worse?

Good flux helps and I used what seemed like appropriate amounts... a quick touch of the iron and I had a nice shiny silvery puddle within a second or two, sealing the thru hole while looking as good as factory with no slop. Sometimes I had to touch up the top-side of the board, which was easy enough with radial components. That transistor bank just packed everything in too tight. I will probably get a finer tip after this.

It seems too, that the procedure for testing the MOSFETs I used to replace the transistors, is not the same as a generic transistor. Always new things to learn.

That's pretty much what I was shooting for, and happily most of them were more in the 2-3 second range once I got in the zone. The rest of your and Vid's advice makes sense. The "top surface touch-ups" were mostly incidental - between the MPU and power boards, I easily shattered my record for most soldering in one session so I was bound to have a couple or five of those.

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And so now the hopefully, tentatively good news: pulled the MPU board and tested the transistors. In the matrix I was concerned about, none of them tested failed or open, and all of them tested at the exact same values (give or take .005). So I take that to mean either 1) There's no problem after all and I'm just being my usual overly-cautiously-paranoid self... or 2) I am SO FRIGGING AWESOME that I fried ALL them in the EXACT SAME MANNER OF DEGREES....

*ahem* Honestly I'm not sure. Hopefully it's #1.

And get this: while at it, I tested all the other transistors, and found a few flaky ones I never even touched. Ha! I would not have thought thar be dragons. So, can anyone tell me, are TIP122's still the proper and available replacement, or is there an "upgrade" part I should substitute for those?

Thanks again for all the help...

Oh, speaking of rectifiers: my refurbed / restored Space Shuttle has been getting played to death with no issues - including a solid 7 hour stretch during a party I just hosted. I have no doubt that's due to Vid's advice, well taken.

So while cleaning the machine after all this fun, I noticed one of my rectifier fuses is looking a little worn: lightly singed, but intact and not misshapen. But the other fuse looks clean as the day I installed it. Both are 8A SB.

I take that as a warning symptom... what should I check? Or is it simply the associated rectifier going bad?

A possible "easy fix" for the voltage surge/drop might be the start/run capacitors on your HVAC motors. I'm not a pro tech but I researched this issue when doing some DIY repairs to motors that failed in my systems (outside AC condensor; then the inside duct blower). Each requires a large capacitor to handle the surge current when they start... and like all electrolytic caps, they have a lifespan and the ones on my system were approaching 20 years old. At any rate, after replacing them I noticed the household "brownouts" when they turned on were far less dramatic... more like a brief flicker. (By replacing out of sequence I can confirm this was due to the caps, not the motors).

Might be worth some reaearch. In my case the caps were not expensive, only about $10 and 10 minutes to replace.

Another thing to check might be old wall switches. We moved to a 50yo house with original hardware and one particular circuit had odd symptoms. On a hunch I inspected a switch and it had some connections that had worked loose. After tightening them up the circuit became much more stable. Old/flaky in-line outlets could probably cause the same issue. If you have lots of old original hardware installed, it might be worth checking out. Start by replacing any polarized-only outlets with properly grounded ones - that's a great excuse to get into each one and perform an inspection en route to a worthwhile upgrade.