TRS 80 M100 Recap rescue and Molex mishap Part #1, 'Trio of strange problems'
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- Опубліковано 22 сер 2024
- Video sponsor: PCBWay: $5 for 2 layer PCBs with 24hr turnaround at www.pcbway.com/
In this video we take a look at the first of a pair of TRS-80 Model 100s that a friend sent me to repair. We fix up a few issues from his first attempt at a recap job, but hey we all start at the same place and you never learn anything new without trying and practicing.
Then we delve into a really interesting trio of strange problems. The first problem we look at was only evident because of my bench testing set up. We then move on to the graphical corruption of the LCD. Strangely we find that the source of the LCD issue is also the source of the serial port issue as well.
In part #2 we will take a look at the second TRS-80 Model 100 which has a mangled Option ROM socket and then we’ll try out a ‘SuperROM’ and ‘REX CPM’.
Timeline:
01:55 - Evaluation
06:55 - Thermal Relief
08:49 - Re-Re-Capping
15:43 - LCD Flicker Issue
16:38 - Test Harness
20:00 - Power Off Problem
31:39 - LCD Corruption Problem
41:08 - If an IC falls in the woods
42:19 - Wrap up
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Credits
PCB Thermal relief from Wikipedia: By User:Romanski - Own work, CC BY-SA 3.0, commons.wikime...
Chiptune Thing No. 3 "Victory" by Steven O’Brien / stevenobrien
Creative Commons - Attribution 3.0 Unported- CC BY 3.0
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Music provided by Music for Creators • Chiptune Thing No .3 V... - Наука та технологія
The amount of knowledge shared on this video is remarkable. Taking notes the entire time. You have mad skills and work ethic that is inspiring!
This was an interesting problem. I'm still amazed it worked as well as it did given that 3 of the data lines were messed up.
Excellent video. Your detailed explanation of your troubleshooting path is so very appreciated.
Nice vid Jeff great fault finding skills mate 🙂☺️
Thanks Kim!
thanks for this
You are welcome.
The way I deal with large heat sinks on a board is to use an iron that can flow lots of heat energy quickly. Specifically, I have a station that takes t15 tip/heater cartridges; and I use the biggest “hoof” tip they make (however, big chisel tips work also). IIRC, the station is 70w. I don’t think I’ve ever had a cold joint with it.
There are situations where putting a lot of heat into a joint quickly is handy, for example soldering battery tabs. It can also let someone without experience create a lot of damage quickly.
With PCBs with a large ground plane on the top layer it is very hard to get the top layer hot enough without leaving your iron on the joint too long. Some components can also be damaged by heating/cooling too quickly. It is these types of cases that a preheater really helps. They make PCB specific pre-heaters, the little heat gun is sort of a 'poor mans' substitute. :)
@@HeyBirt Yeah... I’ve got a surface-mount rework station with a pre-heater. My experience, with my specific setup, is that my iron is sufficient to deal with large planes & component tabs without the pre-heat. Of course, YMMV. 😉
The temperature of the tip on my station is controlled tightly enough that I can set it at just a bit above the solder’s melting point, get a good joint, and still take my time without worrying about damaging the board. From what I understand, this is principally due to the all-in-one bonded heater-sensor-and-tip design of the t15 cartridge; supposedly irons that don’t have this feature don’t work as well (this I gather from watching other UA-cam videos; I haven’t done a soldering station shootout myself).
🤔
I originally misunderstood your comment to be the old canard of "Turn the iron up and apply lots of heat quickly using only 1 second of dwell time." Which of course leads to disaster much of the time. I should have taken more time to read your comment carefully.
Not everyone has the luxury of nice rework tools like we do so I try to cover other rework methods that work with simpler tools. As you mention if someone is using an iron that is not temp controlled one can very quickly lift a pad, etc.
Generally my Pace rework station does not have an issue with applying enough heat. This is an issue with the ground plane being on the top side and it is difficult to get enough heat through the small through hole. The iron is not the limiting factor it is the heat transfer to the other side of the PCB. Even when soldering the part back in with a 90W iron the heat transfer limits the flow through to the top side of the PCB, but if the through hole plating is is good shape that is not a huge problem.
UA-cam are really pushing ads (x14!) in this video for me, stuff I'll never buy. In between all the ads there was some very enjoyable repair work.
Sorry! I forgot to go back and adjust the ads. I will do that now.
Not your fault Sir. But it does detract from your efforts.
They won't let you adjust the ads until after it is complexly uploaded and fully processed. Probably so folks will forget, like i did. I agree the number of ads they insert is absurd.
Where did you get the awesome test harness?
One of the people on the M100 mailing list made it. I'll have more information on it in the next video.