664 refurbishment

[reno]

Hi,


I was lucky to find a 664 for a not-too-crazy price last week (I negotiated €230 with a GT-65 + MP2F modulator, because the blue keys were really yellowed).


I tested the machine only briefly so far (turned on, tried all keys, made it beep, ran "cat" on a disk).
All keys seem to be working which is good news, but they are very yellowed.
The disc drive belt will need replacing (I had "disc missing"), I will order one later.


I've now opened it to give it a good clean and I have a few questions :


1. Main board cleaning.
I used canned air to remove most of the dust, then a dry paint brush, then sprayed some WD-40 Contact Cleaner (not the same thing as plain WD-40 I think) over the main board, as I had seen this recommended.
However, the WD-40 left many white traces on the board when drying !
So I tried to clear this out with 90° alcohol (I didn't have IPA in the local shop) using a tooth brush, and finally used some demineralised water.
Any comments on this process, things I should have avoided ?
Unfortunately a small ball of solder seems to have been ripped off the bottom of the board by the toothbrush. I can't see which via it came from, but I guess I will soon know if I broke something 
Any good hardware test program I can use to do a full check ? Something like the Arnold4 CPR, but that I could load on the 664 using an M4 ?

2. Cleaning keycaps

I've completely disassembled the keyboard and removed the keycaps.
My plan is to put them in the dishwasher (together with other keycaps from a 464), in the cutlery basket, 45° quick cycle. Sounds like a good idea ?

When it comes to de-yellowing the blue keys :
My plan is to use hydrogen peroxide + Oxi (containing TAED) + corn flour as a thickener then put that a few hours in the sun.
It's a common recipe in various forums, for example : https://www.classic-computers.org.nz/blog/2008-12-30-de-yellowing-old-cases.htm

I'm just worried that the blue won't be uniform (the top is currently yellowed but the sides are fine), if I apply the mixture to the whole key. Any experience with that ?

Thanks !

[llopis]

If the board has still some traces of gunk, I would recommend removing the socketed chips and washing it down with water and soap. Drying it with a hair blower and letting it sit for 24 hours to be REALLY sure all the water is gone.


As for the retrobrighting of the 664 keys, as a recent fortunate owner myself, I'm planning on doing some experimenting starting with this: https://www.amstrad-noob.com/2020/07/24/retro-brighting-attempts-on-a-cpc-664/

[betpet]

As someone who has recently acquired a 464 and a 6128, I'm in the process of doing the same. I've been using this to clean my boards:


https://www.amazon.co.uk/Rubbing-Alcohol-Cleaning-Isopropanol-All-Purpose/dp/B07DWCGQ1H/


and I've also been using a soft toothbrush and cotton buds.  It seems to be quite successful but it's a slow process. I suggest taking your time and not brushing too hard. My boards seem to have a coating of a substance that I can only liken to a can of coke spilled over it. It comes off but it just means doing several cleans rather than trying to do it all in one go.


Regarding the keys, there are several videos online about retrobriting but I've not done it myself so can't give you any advice. What I've seen amounts to:


Coat evenly
Cover in cling film but ensure that the parts you want to retrobrite don't have wrinkles (keep the end parts of the cling film on the underside)
Make sure the sunlight (I assume you are going to put them outside for a few hours) is consistent and no shadows are likely to cover things
It's not an exact science


Good luck!  I'd love to see some pics of your progress.  Maybe put some pics up of the motherboard (both sides) and, you never know, maybe someone will spot where the blob of solder came from!