Bricked a 1200XL. Need help identifying issue.

[ACML]

I had a very low time 100% working 1200XL motherboard that I installing 28 pin EPROMs so it could have the 1200XL OS Ver 11.  I've done this mod many times.  This time there is a difference, but I'll get to that in a minute.

 

I removed jumpers W7, W8 and W9 and installed jumpers in W11, W12 and W13.  Here's the difference, I forgot to remove W6.  I then installed my two 2764 EPROMS in U12 and U13.  Believe I got a black screen.  Swapped another set of EPROMS because sometimes the 1200XL just doesn't like a certain two and got same result.

 

I realized that W6 was still installed and promptly removed it.  Grinning and thinking, wow, had me worried for a second.  Now I get either a green or red solid screen.  Tried three more sets of EPROMs with same result.

 

I replaced SALLY, POKEY, PIA, ANTIC, GTIA individually testing every chip swap and no change, just solid green.

 

Then I replaced RAM, and every single socketed chip (only delay line is soldered in) one by one testing each chip swap.  At one point the screen is now always red. 

 

I looked over with magnification my solder work on the W jumpers and used a multimeter to ensure they weren't shorting on adjacent pins.  All checked good.

 

Like I said, I've done this 20-30 times and this is the second time I've bricked the machine just messing with the W jumpers (to go from 24 to 28 pin OS). I eventually gave up on the first board after many hours of troubleshooting. 

 

Could having W6 still installed with W11/12/13 cause damage somewhere else?

 

I have thoroughly enjoyed modifying and upgrading 1200XLs so they can go back out in the world to someone who will use them, but when these "mystery" gremlins pop up, it kind of takes a lot of the enjoyment out of it.  I don't have the patients I used to for such things.

 

 

 

Edited July 5 by ACML

[+scorpio_ny]

HI @ACML,

 

I had read a post with the same scenario that you are experiencing. It turned out to be bad single wipe sockets on the motherboard. After swapping out chips or flexing of the motherboard, they may cause issues.

 

Here is the thread that I was recalled:

https://forums.atariage.com/topic/266053-1200xl-boots-to-red-screen/

 

Hopefully this helps!

 

 

 

 

Edited July 5 by scorpio_ny

[ACML]

UPDATE:  Messed with this morning and re-installed W6-9 and removed W11-13 to get it back to 24 pin OS.  It boots!  Now, for some reason, it won't acknowledge a cartridge.  Apparently, some 1200XLs just won't tolerate an EPROM and will only run with a ROM. 

[_The Doctor__]

Perform all the fixes, Bob1200XL has a nice group of them. Once it's solid then perform your eprom update using a handful of differing eprom brands. Certainly you will have it sorted out. Only other choices if not good to go after that is to make sure power is clean, caps are good and support chips aren't suffering. I will only hope you've made sure all sockets are up to snuff and clean.

[ACML]

I checked all 24 pins between the two OS sockets and they all have pin to pin continuity except for pin 20, but that is expected as it is "chip select".  So it's back to working with original 24 pin Rev 10, but still no cartridge.  I will examine for any damaged traces.  Completely replaced all ICs, save delay line, so I think it's not a chip issue.

 

Edited July 5 by ACML

[+scorpio_ny]

Just now, ACML said:

I checked all 24 pins between the two OS sockets and they all have pin to pin continuity exempt for pin 20, but that is expected as it is "chip select".  So it's back to working with original 24 pin Rev 10, but still no cartridge.  Will examine for any damaged traces.  Completely replaced all IC, save delay line, so I think it's not a chip issue.

 

It may not even be the OS socket pins. It can be any socket. I remember working an 800XL mother replacing some RAM and the  machine would not boot up. Turned out the  socket for the CPU was on its way out. And I did not even work on the area. So it may have happened when the board flexed a little.

[ACML]

PROBLEM SOLVED!  Thanks in part to watching flashjazzcat's video troubleshooting a similar problem.  Broken traces, just different reason.  Lesson learned, be really careful with your solder tip around W11 and U12 socket!  Either when I was preparing W11 or de-soldering it to return back to stock, my solder tip broke two fragile traces on the PCB just to the left of W11 and close to U12 (see photo).

I managed to reconnect an existing trace on one of them and the second I jumped a 30 gauge wire to pin 13 of U12 on the back side of the PCB. I've done this so many times, I guess I'm getting complacent with the solder wand.  I will slow down and be more careful next time.

 

 

Edited July 5 by ACML

[flashjazzcat]

On 7/5/2024 at 4:30 PM, ACML said:

I will slow down and be more careful next time.

Glad you fixed and, and yes: please God, be careful. One generous DIYer gave me a dead 1200XL motherboard a year or two back, which he concluded he had somehow completely destroyed after resocketing U12 and U13. He had, but I was able to fix several destroyed vias and get the board up and running again, even though the owner believed he'd done a reasonable job of fitting the sockets. That misadventure had resulted in the board's owner (prior to my fixing the donated board) having to purchase another 1200XL to replace the destroyed one.

 

An increasing proportion of my work involves rectifying issues on valuable motherboards, either inflicted by their owners or by careless technicians enlisted to perform relatively mundane socketing work. The competency crisis currently being endured is certainly reaching into all aspects of daily life, such that the tech down at the local computer shop appears to be incapable of putting a socket under the CPU on a 130XE without rendering the machine unbootable.

Edited July 8 by flashjazzcat

[_The Doctor__]

3 hours ago, flashjazzcat said:

Glad you fixed and, and yes: please God, be careful. One generous DIYer gave me a dead 1200XL motherboard a year or two back, which he concluded he had somehow completely destroyed after resocketing U12 and U13. He had, but I was able to fix several destroyed vias and get the board up and running again, even though the owner believed he'd done a reasonable job of fitting the sockets. That misadventure had resulted in the board's owner (prior to my fixing the donated board) having to purchase another 1200XL to replace the destroyed one.

 

An increasing proportion of my work involves rectifying issues on valuable motherboards, either inflicted by their owners or by careless technicians enlisted to perform relatively mundane socketing work. The competency crisis currently being endured is certainly reaching into all aspects of daily life, such that the tech down at the local computer shop appears to be incapable of putting a socket under the CPU on a 130XE without rendering the machine unbootable.

This is the exact reason the advice to practice on cheap crap and scrap pcb's from other common junk can't be stressed enough. It just isn't a good idea to start a hobby that begins with destroying and mangling the objects and machines with no real understanding of melting points, solder types, and temperature effects on traces/components. Sadly this is all too common. Even long time members get around to doing some things they really should not until thoroughly acquainting themselves with the knowledge as well as skill needed to undertake working on machines from the time period.

 

Even if you did this work for a living at on point in life, it's still a good idea to brush up before tearing into these Atari projects. The quality of irons, solder, and flux vary greatly today. Using the correct iron and solder being crucial. Don't know the number of times someone picks up a modern soldering iron and modern solder and start into it. Sadly the iron is way too hot and the solder has way too high of a melting point. The old PCB's just de-laminate, stress, traces crack/fracture and pull, via, through hole connection et al  destroyed. Pressing harder is not an answer either, it just makes more damage etc etc.

Edited July 8 by _The Doctor__

[ACML]

My excuse is being impatient and rushing.  I use an old school 1980's 40 watt wand and low temp old school 60/40 solder. 

I might be guilty of too much time on target when melting solder to suck out of through holes.  I need to not let the wand dwell on one spot too long. This solder works really well!

Edited July 8 by ACML

[+bf2k+]

7 hours ago, flashjazzcat said:

The competency crisis currently being endured is certainly reaching into all aspects of daily life...

You said a mouthful there... nothing but the truth.

[flashjazzcat]

1 hour ago, ACML said:

I might be guilty of too much time on target when melting solder to suck out of through holes.  I need to not let the wand dwell on one spot too long. This solder works really well!

I have my Hakko FX-951 at 450 degrees centigrade 100 per cent of the time, much to the dismay of anyone dying to tell me I'm doing it wrong. However, I work very quickly with 60/40 solder and Amtech flux and do not damage boards. There's nothing more frustrating than watching people struggle with unsufficient heat (and/or insufficient flux) when soldering on YouTube videos. You can tell straight away what the problem is, although I resist the temptation to jump into the comment section. I just sit there and wince.

[+Stephen]

650F (350C) on my soldering station, 60/40 solder too.  People tell me that is too hot.  I've never marked a board - including white U1MB PCBs, where I removed the large headers.  Proper flux, proper technique.  I've also had gravity make a 40-pin socket drop out, when using a hand solder sucker and braid.

[_The Doctor__]

heat and time applied, major points. also tip size/type and how much stored heat in said tip mass.

[Beeblebrox]

I have my iron at 430C. I used to have it between 350C and 380C on an older iron. When that iron finally broke last month, (internal ceramic heating rod snapped), I found my cheapo replacement iron yeilded much better results - in particular with XE boards - running at 430C. 

 

My new Iron: https://www.amazon.co.uk/dp/B08YD1MD81?ref=ppx_yo2ov_dt_b_product_details&th=1

For all solder work (with the exception of removing things like RF modulators) I use this style/size tip:

 

 

The only annoying thing I find is the cables on these irons are a little short.

 

 

[flashjazzcat]

Looking at the reviews (and bearing in mind the fact that dissatisfied buyers are perhaps more likely to voice their opinion), the temperature display does not appear to be very accurate and the measured temperature is likely to be somewhat lower than what is indicated. This is often the case with cheap irons, of course, and given the price of a Pinecil iron these days (whose heating element is built into the tip, unlike the typical 'sleeved' tip which slides loosely over the heating element), it's difficult to justify generic Chinesium tools for anything but casual soldering.

[TGB1718]

On 7/8/2024 at 12:38 PM, flashjazzcat said:

The competency crisis currently being endured is certainly reaching into all aspects of daily life,

Sometimes, I'm glad when I started my career many, many moons ago I spent 6 years in a 3rd line aircraft electronics repair bay.

 

These days I think these people leave university with a degree in Media Studies and that gives them all the knowledge they need 🤪☠️

Edited July 13 by TGB1718