Connecting my 6128 to a CTM640

[P5ychoFox]

I've recently bought a CPC6128 and fitted a new drive belt. I was hoping to test it worked by hooking it up to my CTM640 monitor (which I use for my 464).

I know the 12v for the disk drive wouldn't match up with the monitor but I used a 5v PSU (with tip as +) to pwer the 6128 itself and connected it with the 6 pin DIN from the monitor just to see an output from the computer.

I hoped to see the 6128's loading screen just to confirm the unit was functional but all I get is a rolling black & white picture (with no detail visible).

Should this set up have worked, or have I missed something?

Any help greatly appreciated.

[Blurredman]

The 12v is purely for running the disc drive and I can confirm that you can plug the 5v and DIN connection and it should work like that. But without access to the disc drive. Did you use an external 5v PSU or the one in the monitor?

Was the rolling screen anything like my problem in this topic?:

http://www.cpcwiki.eu/forum/index.php?topic=2388.45

[P5ychoFox]

Thanks for the reply.

The rolling image is different, here'a a vid I just did:


Amstrad CPC 6128 Problem

The high pitched buzzing is worryingly similar to that described in that other thread but I only put 5v into the machine.

[Blurredman]

Does the power light and computer turn off itself?


You're just like me. You've bought a broken Amstrad, but because of my incompetence, I blew up another two.


Out of interest, why did you first decide to use a different 5v connector then that the monitor provides?


I don't know if I would touch it until more experienced users of both Amstrad and Electronics post on this topic. 

[P5ychoFox]

No the power light stays on.

Ha ha, for some reason I thought the power wire from the monitor was 12v!

I've now tried it with the 5v from the monitor and get the same rolling image.

Does anyone know if it's a fault that can be fixed?

[robcfg]

Maybe you have a broken solder in the DIN monitor connector in the motherboard.

[P5ychoFox]

That's a possibility. I'll have to flip the board over and take a look.

[Bryce]

Things you can try:

1) Adjust the v-hold  on the monitor to see if you get a steady picture?

2) Check that the contacts in the CPCs DIN socket are clean.

3) Re-seat the ICs inside the CPC.

Unfortunately, it's worrying, that the picture was B&W, this would suggest that none of the RG or B outputs were sending anything. Not a good sign.

Bryce.

[arnoldemu]

That's a possibility. I'll have to flip the board over and take a look.

looks like the sync from the monitor connector is broken.

I would turn the board upside down, check and resolder the connectors to the monitor din connector.
another thing is to see if you can clean them somehow, both on the monitor and the plug itself (perhaps use some fine sandpaper).

the picture *looks* like blurredman's cpc6128 if the sync was fixed.


so on e-bay: are people selling lots of 6128 keyboards that have been broken by people putting the wrong voltages in to test them?

[MacDeath]

What external 5V power supply are you using ?

Are you sure about polarity ? (- and +)
Are you sure you use a powersupply powerfull enough (Amperage... must be like 3A from what I heard...)

Have you tried to run the CPC6128 with only 5v power supply (no 12v nor monitor plugged) to perform the beeper test ?

You can see (hear) if the machine is "actually" working by pressing del key continuously, so you hear a beep on the speaker (turn on the volume potentiometer of course).
If the beeper is heard, this mean most stuff work.
Also you may try this with an external speaker connected to audio-out jack plug too... just to be sure.

Do you have a scart adapter ? perhaps you should craft one too.


Also get a close look at the motherboard, clean it and verify the state of the various solderings and pins, check up for "exploded" capacitors too...


The power switch (on/off) is prone to be broken... as the lack of proper reset button and its design make it ... prone to break or have short circuits.

Most plugs and buttons as the volume potentiometer, power on/off, monitor plug are prone to break because of the mecanical force you apply to them when used... most especially when you're an 8 year old boy during the 80's... impatient to play or trying to get a cracked game working... or frustrated by some game difficulty.

My brother was a lot into this...
he started to play a game, loose a life and would franticaly reset the computer because he couldn't accept he wax just a lame player.
Not sure the button appreciated this.

Also parents were prone to confiscate the computer when the kids played to much... (me ? ok i must confess) so they often unpluged all this in a hurry and with anger... not good for the machine too.


Anyway.
A good cleanup and test of most connectics is clearly needed.
If already done, some chips can simply be broken too.

Also : wtfisthat ?

[Bryce]

That looks like the two screws that go in the side of the disk drive.

Bryce.

[P5ychoFox]

That looks like the two screws that go in the side of the disk drive.

Bryce.

Well spotted 

[P5ychoFox]

Many thanks for everyone's help. I'll do some re-soldering, further testing and check the caps.

[P5ychoFox]

Something that I've just realised from looking at images on CPC Wiki is that my 6128 has no metal shielding over the circuit board. Could this be causing the problem or would it only make a slight difference in the quality of the output signal to the monitor?

[Bryce]

It would make absolutely no difference, the metal shield is only there to adhere to a very stupid (German) regulation which is over the top for a CPC. UK CPCs never had the shield. I usually remove them and throw them away.

Bryce.

[MaV]

It would make absolutely no difference, the metal shield is only there to adhere to a very stupid (German) regulation which is over the top for a CPC. UK CPCs never had the shield. I usually remove them and throw them away.

Beware of the radiation!


I've wondered about the shielding myself. One of my 6128s does not have this shield, working without it is much easier.

Is this shield also over the top for an Amiga 500? I noticed that one of my two Amiga has one and the other doesn't. When does this shield make sense?

[Bryce]

Technically, it rarely makes sense. Before everything got standardised in Europe, every country had their own EMC/EMV regulations, some so strict that even the CPC needed to have a shield in order to get the device certified. At the time, the UK and Ireland used the BS standard (BS = British Standard NOT Bullshit as some people might suggest ), Germany had their DIN and France had their NFC. The shield is a very expensive part (manufacturing AND assembly costs), so it was left off if not required in the destination country. These days all European countries use the CE standard, although in some circumstances, they still insist on stricter local rules. If a CPC was being certified today in Europe it wouldn't require a shield.

Bryce.

[P5ychoFox]

Ah that's why some pics show it and others don't, thanks Bryce.  I've picked up a working replacement 6128 now...which has now died Time to give up.

[Blurredman]

Ah that's why some pics show it and others don't, thanks Bryce. I've picked up a working replacement 6128 now 

Well done.

In my quest to get a working 6128 I bought two non working ones, then when I eventually found a working one, there was another working one being sold by the same chap