ZX Spectrum Toast Rack Repair - The RAM Killer

[@jaycee1980]

I've actually had this on a grey +2 that had faulty memory. I replaced one bad chip, tested quickly.. and it was ok.. but 10 minutes later it did the same thing.I ended up swapping out 5 of the chips - but it took an hour of soak testing between each one !!!

[@TRONMAGNUM2099]

Great job on the repair. Love the channel. I use a cheap Weller too. Melts the solder perfectly fine enough for me.

[@HappyLittleDiodes]

Thanks!

[@markretro3612]

had that a few times with +2's failing slowly after many hours. that have been previously been unused for some time. def put the sockets with the notch towards pin 1 or it would drive me crazy :)

[@cjmillsnun]

The burnt stuff is the flux from cheap solder. Had the same issue with some solder I got from ebay. Don't know what they put in it, but it always left some burn residue and destroyed the tip on my iron. With sockets, always notch in line with the chip orientation. That way you know which way to put the chip in.

[@RudysRetroIntel]

Interesting video and great repairs. As for the Weller iron, they do sell expensive ones. However, my Weller low-end model has been working for 40 years and is still amazing. Thanks for sharing

[@aldo8589]

the failed start is due to weak capacitance in the 5v line, and or 12 v line,replace the big cap inside the power supply. also replace the cap which filter the 5v line in the motherboard, start with this, then if the problem continue, replace all electrolytic caps in the motherboard

[@GianmarioScotti]

I always place the notch of the socket in the same direction as the notch on the IC, for mental hygiene. It helps me place the replacement IC in the correct orientation with a reduced chance of error.

[@HappyLittleDiodes]

Good it's not just me!

[@borayurt66]

@@HappyLittleDiodes Nope, definitely not just you. I couldn't care less about the lettering on them, they can face any which way, but I can't stand to have the notch facing the wrong way. Even if accidentally solder one upside down, it will come off right away. Having it installed the wrong way is just asking for trouble.

[@HappyLittleDiodes]

But what is the wrong way?

[@borayurt66]

@@HappyLittleDiodes Wrong way is the reverse of the correct IC orientation. The notch of the socket should face the same way with the correct IC orientation.

[@HappyLittleDiodes]

Aha so I'm doing it right that's good

[@tomdalby6552]

Amazing that all the RAM chips failed one by one, I've seen this with a couple but never all of them. Guess they were just near end of life and prolonged use finished them off as the new ones are fine. Taking about the membranes I've had a few of the new ones fail on me especially in the original 48k case. You have to be very careful with the bend when shutting the case or it can crease and sever the connection.

[@davebriggs610]

I think the chips must have already been on there way out. I can't think of anything that could cause a cascade ram failure like that, other than age/heat related issues. A run of over 1000 is proof positive that the RAM is now stable, you would still be getting fails if something was killing the ram. As for the Weller, Iv'e got the same one. I love it, it's perfect for what we do mate. On, the IC Notch, I always match the silk screen. Correct orientation is very important :)

[@borayurt66]

Have you checked the output of the old 7805? maybe it was a tad over voltage, which stressed the RAM ICs to their deaths? Also maybe the decoupling caps were leaky (electrically) and they caused an undervoltage on the 5V rail? I didn't like that 4.88V. Even though it is within TTL spec, it shouldn't happen unless there was an unwanted current drain somewhere...

[@HappyLittleDiodes]

It's discarded now but I did scope it and didn't notice anything

[@marky26uk]

I would recommend soldering the 3 wires directly to the 5v regulator, plugs and pins stupid idea for the regulator is a stupid idea in my opinion, with vibration the ground pin can become resistive resulting in the regulator giving more volts out, thus not good.

[@tonicparty1541]

I had a similar issue with a 2+ i think i ended up using it for parts...

[@Zanaz728]

What happened? I tried to watch this video when it first came out earlier then it suddenly disappear...

[@HappyLittleDiodes]

I saw a mistake in the editing so I re uploaded :)

[@Zanaz728]

@@HappyLittleDiodes thanks for explaining..

[@GrahamWikström]

Hi i really like your videos. But now you seemed to have added background music. I really find this annoying. I watch it to look at content and hear you. Not listen to music. I’m sure others find it annoying. Much better without music please.

[@HappyLittleDiodes]

Hi! You'll find that most of the videos have some background music, but I will reduce it in the mix a bit more from now, thanks :)