Author Topic: Faulty 6128+  (Read 4932 times)

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Offline steve

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Faulty 6128+
« on: 01:48, 22 September 10 »
I received my latest machine today, a 6128+ and it is faulty, when I switch the machine on I get a continuous tone from the speakers, if I press f1 I get the copyright screen and a stream of characters being put on screen, 93222222222222222 to the end of line 255 characters, I then press enter, I get syntax error and if I press one of the keys qweasdzxc caps lock tab esc right cursor, I get the numbers, keys v23. and numberpad decimal point don't work, other keys produce their characters.
If I press f2 I can play burning rubber.
Any experience of where the fault lies? It may be the scanning circuitry or the keyboard itself, any ideas where I can get a new keyboard or a new membrane?
Thanks for any help on this.

Online robcfg

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Re: Faulty 6128+
« Reply #1 on: 02:08, 22 September 10 »
I would try to open it, take the membrane and see if it has a lot of dust. Is that is the case, gently remove the dust and try again.


In case you open it, take some pictures and post them here, maybe if it's another fault we can spot it in the pictures.

Offline TFM

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Re: Faulty 6128+
« Reply #2 on: 02:38, 22 September 10 »
Possible explanations:
 
1 EPROM on cartridge corrupt (try a second cart)
 
2 keyboard sluggish connected (open Plus, disassemble keyboard, clean everything carefully, assemble it)
 
3 some "wires" on the pcb disconnected (search them)
 
4 error in ASIC (say a prayer)
 
Good luck!
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Offline MacDeath

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Re: Faulty 6128+
« Reply #3 on: 03:23, 22 September 10 »
Yes, I second...

Just open it and remove all the dust you may find.

I had a faulty CPC... keys seemed to... not work or work automatically...
Well, I had something like 0.5 centimetre of compacted dust between the keys and the membrane...
worked quite better without... ;)


But yeah, sometimes the hardware may fault... chips may explode !
And beware, an exploding ASIC is considered a Nuclear weapon of mass disapointment... ;D


Also beware, if you open it, the warrant is void...
 

Offline TFM

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Re: Faulty 6128+
« Reply #4 on: 04:22, 22 September 10 »
Also beware, if you open it, the warrant is void...

Right... I forgot... but you can open it 2011, when the 20 year warranty is over.
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Offline steve

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Re: Faulty 6128+
« Reply #5 on: 08:58, 22 September 10 »
Thanks for the replies so far.

I will open up the machine but first I want to get some retrobrite to remove the yellowing of the plastic, I will take pictures but cannot say how long it will be before I actually start.

I did try a different basic cartridge but the problem was still there.

I have two 464+ machines and may simply swap a keyboard until this one is fixed.

I have just downloaded the service manual for the plus machines and it mentions the rp11 diagnostic cartridge, does anyone have one of these, has the rom been read and stored on line somewhere so maybe we could make our own diagnostic cartridges?

Warranty? who needs it, most of these machines are still working after all these years so I will risk it. ;D

Seriously, is there a problem with the asic in general?

Offline arnoldemu

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Re: Faulty 6128+
« Reply #6 on: 11:18, 22 September 10 »
Thanks for the replies so far.

I will open up the machine but first I want to get some retrobrite to remove the yellowing of the plastic, I will take pictures but cannot say how long it will be before I actually start.

I did try a different basic cartridge but the problem was still there.

I have two 464+ machines and may simply swap a keyboard until this one is fixed.
Swapping the keyboard is an easy thing to do, they are identical

I have just downloaded the service manual for the plus machines and it mentions the rp11 diagnostic cartridge, does anyone have one of these, has the rom been read and stored on line somewhere so maybe we could make our own diagnostic cartridges?
Yes I have the source and the rom image. And it can be found on www.winape.net (downloads) and in other archives.
It does some basic tests of the cpc+ functionality, nothing much in the way of serious tests.
So it can't identify exactly what is wrong


Seriously, is there a problem with the asic in general?
No.

But in the rare case that it does break, it is almost impossible to find and replace (being surface mount and not made anymore ;) )


Generally the CPCs seem to be quite reliable, unless somebody has purposely done something stupid to it.

Compare that to the Speccy 48k where the ram is the most common component to fail (and for which you have to replace if it does).

For cpc+ it mostly seems to be down to cleaning it (dusting it), bad contacts in keyboard possibly, and bad contacts in the cartridge.
But generally they are almost like military grade built ;)
« Last Edit: 11:21, 22 September 10 by arnoldemu »
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Offline MacDeath

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Re: Faulty 6128+
« Reply #7 on: 04:38, 23 September 10 »
Quote
Warranty? who needs it, most of these machines are still working after all these years so I will risk it.
Haow come on !!!
Can't you see a joke even when a french did it ? ;D

Quote
Seriously, is there a problem with the asic in general?
In general ? not really... it's an old fashioned chip, cheap but enduring...

Yet sometimes, you know, it's always the un-changeable bits that get faulty...

But ASIC is rarely faulty as in "do not work"...
most of time because "it bugs a bit yet works..."

DMA channels are notoriously bugged per example... :(

Or perhaps as in : "WTF you only add this to a CPC in 1990 ? "

"Alan Sugar you're such a dovche !!! this is your fault !"


Well yeah, more DMA, or more sprites, scrolls, xblitters, whatever...
But hey, it'"s still better than a good old CPC "old" ! perhaps only 2 years late actually...

And actually better than many spectrum or MSX (1&2..2+ and turboR may be superior...).)

May even compare with C64...
 
« Last Edit: 04:51, 23 September 10 by MacDeath »

Offline steve

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Re: Faulty 6128+
« Reply #8 on: 07:05, 23 September 10 »
Haow come on !!!
Can't you see a joke even when a french did it ? ;D

Yes, I got the joke and it made me laugh, :laugh:
My reply was also a joke because the warranty expired years ago,  I would not be risking it by opening the case.

Offline arnoldemu

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Re: Faulty 6128+
« Reply #9 on: 11:39, 23 September 10 »
Yes, I got the joke and it made me laugh, :laugh:
My reply was also a joke because the warranty expired years ago,  I would not be risking it by opening the case.
There is a sensor inside the computer. When you open it, a telephone call is made to Alan Sugar.
He then *KNOWS* you've opened it and you are guilty.
If you make modifications, he'll be around to make sure you undo them.
So tread carefully.




(The above is a joke in case Alan Sugar or any of his heavies or his legal team are reading ;) )
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Offline Executioner

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Re: Faulty 6128+
« Reply #10 on: 04:29, 24 September 10 »
It could also be a fault with the AY since that's separate to the ASIC, but it's used as the IO chip for the keyboard. I had the AY go on my standard 6128, still played music though, just the IO ports were dead.

Offline Bryce

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Re: Faulty 6128+
« Reply #11 on: 11:19, 24 September 10 »
An AY failing by itself is really unusual and extremely rare. Were you "experimenting" with the CPC at the time? And are you sure it wasn't something connected to the I/O port of the AY (the resistor bank or a dodgy solder joint) that caused the issue?

Bryce.

Offline arnoldemu

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Re: Faulty 6128+
« Reply #12 on: 11:34, 24 September 10 »
An AY failing by itself is really unusual and extremely rare. Were you "experimenting" with the CPC at the time? And are you sure it wasn't something connected to the I/O port of the AY (the resistor bank or a dodgy solder joint) that caused the issue?

Bryce.
Amstrad Action did mention of people breaking their AY by plugging in a joystick.
Maybe this is similar?
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Offline Bryce

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Re: Faulty 6128+
« Reply #13 on: 12:11, 24 September 10 »
Even that would be extremely difficult. The AY is an N-Channel TTL part, not CMOS, so it should be immune to even large static discharges. The I/O pins can take 0-5V, which is all the port could deliver too. So even wrong connections within the joystick wouldn't be an issue. Unless those people had some sort of Autofire Joysticks that had an internal 9V Battery, I really can't think of any way to damage the chip. Unless of course there was a bad batch produced?

Bryce.

Offline Devilmarkus

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Re: Faulty 6128+
« Reply #14 on: 12:13, 24 September 10 »
Amstrad Action did mention of people breaking their AY by plugging in a joystick.
Maybe this is similar?

I remember I had a faulty 464 in the 90s. It's keyboard worked only when no joystick was connected.
Any ideas, why?
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Offline Bryce

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Re: Faulty 6128+
« Reply #15 on: 12:27, 24 September 10 »
You're joystick probably wasn't 100% CPC compatible and was permanently pulling one of the inputs low, which would knock out an entire section of the keyboard matrix or cause unwanted charaters to appear. This would happen if the two "common" pins were connected inside the joystick for example. I remember "editing" a joystick for someone with that problem.

Bryce.
« Last Edit: 12:28, 24 September 10 by Bryce »

Offline Devilmarkus

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Re: Faulty 6128+
« Reply #16 on: 12:37, 24 September 10 »
Well the Joystick was a Compet. Pro.
I changed the AY chip and everything was fine.

I cannot say if chip was faulty or the solder points.
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Offline TomEtJerry

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Re: Faulty 6128+
« Reply #17 on: 14:34, 24 September 10 »
Hi,

I have a 6128+ with a fautly AY, the third voice plays false notes (or maybe it was a Targhan's tune :-))) ).
Never changed it, because I own other + machines...

T&J/GPA

Offline TFM

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Re: Faulty 6128+
« Reply #18 on: 17:36, 24 September 10 »
It's a feature, not a bug.
 
No seriously, Targhan developped an algorithm to chance the microcode of the AY, so it's reprogrammed now for ever :P
 
Really seriously: In case you see one spare AY, just get it and save it. Maybe one day, you'll need it.
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Offline redbox

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Re: Faulty 6128+
« Reply #19 on: 21:00, 24 September 10 »
There's definitely something up with my 6128+ and I'm praying it's not the ASIC or AY...  ???
 
I just get totally random crashes or sometimes just artifacts on the screen.  It's so hard to pinpoint because it won't happen for days but then it'll happen 3 or 4 times in a row.  I thought I'd cracked it when it seemed to not happen when the joypad was unplugged, but now it has happened again without it plugged in so I know it's not that.
 
Guess I'll just have to go over the whole board looking for dry joints etc.  :(

Offline Grim

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Re: Faulty 6128+
« Reply #20 on: 21:39, 24 September 10 »
It's so hard to pinpoint because it won't happen for days but then it'll happen 3 or 4 times in a row.
Dirty/oxidized cartridge contacts can cause this kind of problem. Just switch your Plus ON and touch the cartridge to make it move a bit and see if it crashes the machine. If it does, just clean the contacts on the cart until they are shiny again. Otherwise, well, we'll see.

Offline TFM

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Re: Faulty 6128+
« Reply #21 on: 22:25, 24 September 10 »
Exacty! I had the same problem. Clean the cart contacts with 99% Ethanol (drink the remnants) and then move the cart 3-5 times in and out. That helps usually.
 
Else it's a gremlin hinding under the keyboard  ;)
« Last Edit: 23:04, 24 September 10 by TFM/FS »
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Offline Executioner

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Re: Faulty 6128+
« Reply #22 on: 05:04, 27 September 10 »
steve, You don't happen to have a spare UK keyboard do you?

Offline steve

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Re: Faulty 6128+
« Reply #23 on: 05:21, 27 September 10 »
No, if necessary I will transfer one from a 464+.