hiya!
I have bought a new 6128 that I want to repair, this one on boot prints some random characters and most of the keys on the right side are not responsive.
I've read that this could mean that either the AY or a demux (what IC is that on the original 6128?) could be problematic, does that sound like the case?
TIA for any tips/help!
:)
@keropi (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1781)
Plug in the Joystick,
tell us what is on the screen for " Up, Down, Left,right. Fire Button.
Thanks Ray
Quote from: keropi on 21:23, 31 October 16
hiya!
I have bought a new 6128 that I want to repair, this one on boot prints some random characters and most of the keys on the right side are not responsive.
I've read that this could mean that either the AY or a demux (what IC is that on the original 6128?) could be problematic, does that sound like the case?
TIA for any tips/help!
:)
Hi Keropi,
the "demux" is actually just a 74LS145. However, I'd recommend just giving the membrane a good clean first to see if the problem is just gunk and dirt.
Bryce.
sorry for the late reply, I am away on a trip and I can't access the cpc until Friday... I do have though a *very quick* video of the problem:
https://www.youtube.com/watch?v=P2yNaB7twU8
you can see the auto-garbage on boot and the garbage that some keys produce :laugh:
The friend that keeps the cpc for me did a small test, removed the keyboard completely and the CPC does not register garbage keys ... he will try later with his own good working keyboard and report back, tbh I hope it's not a membrane problem - I very much prefer to change some ICs rather than hunting for membranes :laugh:
Sounds like the membrane though.
Don't panic, the thing to try is to gently separate the two sides of the membrane and gently blow away dust or any other thing that shouldn't be in there.
If that doesn't work, you can worry a bit, but not too much ;)
As robcfg says you can usually rescue a membrane :) There is even this varnish that has lots of silver particles and can be used to repair broken tracks. If you separate the two halves (they are sort of lightly glued) you can put them back together and then add a bit of sellotape on the outside to seal the membrane and prevent the dirt to enter again. I am saying sellotape because it is transparent, very thin and can be easily removed without damaging anything. Be careful when cleaning, though, do not use solvents, not even isopropanol.
Sticky gunk. A decent clean should solve the issue.
Bryce.
I see... I will clean it then.
thanks for all the help guys! :)
allright, I got the machine and plugged a joystick , it displays these characters when I press something on it:
(http://i.imgur.com/Mv2CD9Ll.jpg) (http://imgur.com/Mv2CD9L)
LEFT is working like backspace, it deletes on character at a time
no idea if this is normal behavior or not ::)
Is the keyboard attached on CPC?
yes it is
I am in the opening stage now, should I try with no keyboard attached?
Yes, check if the characters appear without keyboard.
I get the corresponding arrows now, up arrow for up , down arrow for down and so on... button1 is X.
so it's just the membrane, correct?
It seems to be.
Do you have a spare to try out?
Give a good clean to the membrane and try gentle to separate the two layers without cutting it.
Just slide your palms in circles, maybe the layers are stacked. Then plug the membrane without the keyboard.As for the keyboard, clean it well and use a brush underneath.
Quote from: VincentGR on 09:41, 04 November 16
It seems to be.
Do you have a spare to try out?
Give a good clean to the membrane and try gentle to separate the two layers without cutting it.
Just slide your palms in circles, maybe the layers are stacked. Then plug the membrane without the keyboard.As for the keyboard, clean it well and use a brush underneath.
I did just like this the last week, one 6128 with ramdon keys on screen.
I separate the two layers (be careful) and cleaned the contacts of the two layers with a cotton bud and alcohol isopropilyc.
the contacts seemed clean before, but the cotton was getting dirty and i finally use 10 - 15 cotton buds!!
Now the keyboard works like a charm, only 1 keyboard contact broke a little with the cotton, but the key still works!, this is why i recommed be very careful!
I'm on cleaning detail then! Will report back later :)
the whole machine needs a GOOD cleaning, too much dust
All fixed, cleaned the membrane and it seems it did the trick , thanks for all the help guys!
Now all that remains is to fix the drive, I can see the disk is not spinning so I guess I'll have to wait for a new belt and take it from there
thanks again! ;D
Congratulations. A cheap repair. If the drive isn't turning at all, then you've probably got quite a bit of gunk removal and cleaning ahead of you. I'd start doing that while you're waiting for the drive to arrive. Make sure you remove every bit of rubber from the two wheels, especially the small one as even the slightest bit of gunk will cause the belt to fall off the wheel within seconds.
Bryce.
Don't forget about the write protection pin!
When you open the disk drive, be sure that the circuit board is facing upwards, as there's a loose pin used to detect whether the disk is write protected or not and it's very easy to lose it. That will left you with a read only drive.
Not that it's not easy to replace, but better not to lose it in the first place.
The pin is only in one version of the drive, the other versions didn't have one. However, if your drive has a pin, the chances are you're going to loose it :D
I wrote a guide here on the types with and without pins and where it goes: http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/help-i-changed-the-drive-belt-and-now-my-disk-drive-is-suddenly-read-only/
Bryce.
Thanks again for the tips, I'll be more carefull now 8)
ATM the whole setup is in pieces, both 6128 shell and CTM644 ones went to take a bath - they were really dirty but luckily in very good condition.
I am debating wether I recap the CTM644 chassis or not.
I recently recapped a CM14 (I have a completely discharged CTM644 still waiting) and, certainly, when I checked the ESR of the old caps it had gone bonkers in quite a few cases. Actually, I recapped because I had some image issues. Problem with the CRTs is, as always, the danger when working with them. Does you screen have any problem?
The only problem I detected was the brightness pot that when you adjust it you get lots of parasites - that's easily solved with some electronics cleaner AFAIK (had the same issue with 1084 monitor pots, cleaning did the trick)
I was more worried about the onboard 6128 PSU tbh. I'll just replace all the electrolytics with chemicon/panasonics and call it a day. Unsure about the motherboard caps now , maybe I replace them as well ;D
it is done ;D
(http://i.imgur.com/pyvVDmYl.jpg) (http://imgur.com/pyvVDmY)
edit:
OK, it did not catch fire - that's always a concern :laugh: :laugh: :P :laugh:
(http://i.imgur.com/IsUsSa6l.jpg) (http://imgur.com/IsUsSa6)
That's a pretty decent picture you're getting. It's probably a bit late to mention it now, but I usually replace the thermal paste on all the heatsinks if I have gone to the bother of removing the entire PCB. The paste dries over time and those chips / transistors will be running hotter than they should.
Bryce.
^ heh!
I actually did that Bryce ,the thermal paste is brand new - I used arctic silver ceramique ;D
Proper job!
Bryce.
One day, I will know why the blue/yellow color combination was chosen instead of something more bearable :D I remember that, long, long ago, when I decided to customize the BASIC a little bit, the first thing I did was to change the default color scheme.
^ so what color scheme you chose?
I wish there was a project to install more stuff in the ROM, like a game or something... just like parados ... imagine having something like BB4CPC in rom , cool 8)
I tried different things and, at the end, I think that I chose black background with green font. I tested black background with white font, but the contrast was just too strong for my eyes and I went for something more conventional :) .
ah the classic green scheme... tested and relaxing on the eyes - though you do miss the iconic yellow/blue screen :)
That yellow/blue was so iconic... I used to only have a green monitor with my 464 and then 6128 back in the day. When I got a SCART cable and saw the big picture on our family TV... wow. The colours, man!
Same here with the CTM.
It wasn't yellow, it was PURE GOLD!
They should have changed it right before shipping the 464 :D The color combination is iconic now thanks to the nostalgia and the color imprint burned in our infant retinas. However, back in those days, they could have seen how plainly radioactive it was :laugh:
Oh I don't know, it always felt rather comfortable to me, at least until you changed to mode 2.
Nop, remember wearing sunglasses while hex-ing in Discology.
Ah for me Discology is GREEN. But I do remember it being VERY easy to change the colors.
Quote from: VincentGR on 15:53, 26 January 17
Nop, remember wearing sunglasses while hex-ing in Discology.
If you stay for too long in front of the screen you get tanned too :laugh: I still love the original Amstrad monitors, though, with all their imperfections. That is why I keep using them.
True, I have a CPC attached to a 1084. This is awesome but not the real thing.
Yes... I should buy and repair one 1084. Actually, I am tempted from time to time because it is so much better (and I would like to have an Amiga with the original screen some day). Then, I think about it and it is what you say, it does not feel the same...
That's what I thought, too, and to some extent it applies. However the 1084 is really great, it's of course old school anyhow, plus some of them also have a green mode. Can't beat that! :)