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Just did an easy fix on a 800XL PCB, POKEY related.


Level42
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Hey guys....

 

I've had a 800XL PCB (and case) having on the wall of my attic (which used to be my "computer room") as a decoration.

 

It was dead...the cartridge connector was completely ruined by my nephew (it was my sister's/former brother in law's machine) and I never bothered trying to fix it.

 

But now....

 

So I removed it from the wall.

 

I actually remembered I had stolen the POKEY from the board (can't remember if it was for an arcade PCB or for Stereo Pokey :D :D ) and to make it look populated still I had inserted a YM2149.....hey it's still an Atari sound-chip :D :D.

 

Anyway, took it of the wall, removed the ST sound chip, put in a POKEY and powered it up. It started up in memory test right away and sure enough there were red blocks.

 

It had the infamous mT RAMs (proudly made in the USA....hah! ) but I still was curious how many would be dead. Turned out it was only 1, swapping them for Sharp 2164's soon figured that out.

 

Decided to put in all the Sharp's I head (7) and one Mostek and now it ran fine. The color of the BASIC screen was green though but a small adjustment of the color pot corrected that.

 

Next I decided to remove the badly damaged cartridge port, I feared some pins would actually short so better to get rid of it now... had to cut the bugger into small pieces but managed to remove it with nice clean holes left waiting for a new connector.

So there was a 100% working motherboard again....I thought.

 

While fiddling around I noticed that sometimes the board would boot, sometimes not. (I got the blue screen and the cursor, but no rattling sound of BASIC starting up).

 

At one moment I noticed that when I bent the board a bit it would boot, but untouched it woud not anymore. I figured I might have made a short near the cartridge connector so I checked that with a microscope but all was fine for sure.

 

Next I started probing around with my oscilloscope probe....started with the big IC's on the right lower corners (where it would react to the bending of the PCB). When I arrived at POKEY and touched pin 2 the machine started the familiar rattling booting sound of BASIC ! I really only touched it gently so I was quite surprised....would the scope do something to....no that's impossible.

 

Well then it had to be a contact problem. I removed POKEY, bent the pins in on both sides by pushing them all at once to the edge of my table and re-inserted it.

 

Problem fixed :)

 

90% of electronics problems are contact problems....this was yet another :)

 

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90% of electronics problems are contact problems....this was yet another :)

 

 

The cheap single-wipe sockets Atari used on most chips certainly don't help either. A lot of times, removing a chip just once or twice is enough to bend the wipe or even potentially crimp it to the point it's useless. I learned this restoring my Ugly Duckling 1200XL.

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Well......let's be happy they USED sockets :)

 

To be honest, so far I haven't had any problems with them on A8's.

 

All Atari arcade PCB sockets are single-wipe too....it saved a lot of money and they never intended the machines to run for 30 years ;)

 

But yeah, machined pins are nicer but I see no reason to exchanged them just for this.... whenever I do have to replace a socket I use machined for sure....I have nothing else in stock ;)

Edited by Level42
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I just recently discovered I had a contact problem on the U1 memory socket of my 1200XL, I had a similar booting issue, sometimes it would work, sometimes I'd get a black or red screen. it first started when I bumped my 1200XL up on my desk (I have it slightly overhanging the edge for comfortable typing), but I didn't equate that to the start of my problem until I started swapping out drams at U1, and thought I had several bad spare drams, because they didn't work when inserted, then I finally found one that did. Everything booted up o.k., but soon after, I bumped my 1200XL again (getting clumsy in my old-age I guess) and the symptoms started all over, but after wiggling the U1 dram, all worked well again. But this wasn't a chip that I could just bend the pins, this was a contact issue with the socket, cold solder point. Fixed now, of course, I swapped out the socket completely, just in case but it surprised me because the 1200XL motherboard I bought new just a year ago.

Edited by Gunstar
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The shop owner let me test the boxed 800XL before I committed to buying it but had no way to test and actually allowed me to take it home. I promptly broke it. :(

 

Old pic:

d8a62b588caef22b2fc04071608d4dee.jpg

https://i.imgur.com/NSKtZ8Rl.jpg

 

I literally put Pitfall! II The Lost Caverns in, tested it, switched to my Atari 800's BASIC cart (which was defective and gave nothing), switched back to Pitfall! II The Lost Caverns, and found that nothing worked. I couldn't even load BASIC/Memo Pad without a cartridge. The connectors in both carts were fine with nothing out of order so I figured Activision's cheap and funny-fitting cartridges were likely to blame.

 

I ended up buying and fixing it. Best Electronics told me that the replacement part was something like $2.50 so I almost just ordered it without trying to see if I could fix the original. Instead I desoldered the original and ejected the bent pin. IIRC, I didn't even need to bend it back (just slide it back into the correct position). It looks and works like new again and has withstood many insertions of Pitfall II since!

 

Several keys were not working but we traced that to the shift registers/encoder chips and replaced those for pennies to restore the keyboard to 100%. Now it's just awesome. :)

 

Good luck with yours. I had a new desoldering station but I wouldn't even attempt it without that.

 

Well......let's be happy they USED sockets :)

 

To be honest, so far I haven't had any problems with them on A8's.

 

All Atari arcade PCB sockets are single-wipe too....it saved a lot of money and they never intended the machines to run for 30 years ;)

 

But yeah, machined pins are nicer but I see no reason to exchanged them just for this.... whenever I do have to replace a socket I use machined for sure....I have nothing else in stock ;)

I've seen plenty of people saying to only use machined pins in machined pin sockets. Most recently, Hi-Def NES was having issues with them but the sentiment is all over retro-computer places like lemon64.
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