Hi Everyone,
1st post here from a new CPC464 owner. I have an Australian CPC464, Board revision MC0001A that I got off a friend just Yesterday, who got 2 of these
from His Uncle who wanted them to go to a good home. Comes up AWA on the screen. One has a Monochrome monitor and the other has the Colour monitor.
As You would expect my friend has the Colour monitor and the good working unit. He also has the Monochrome monitor as I don't want that.
This unit was tried on both monitors first and gives the symptom pictured. I got it working on my GBS8200 easily enough. I am hoping someone doesn't
tell me it's a ULA fault as I'll likely give it back to Him as a spare if that's the case. So far I have reseated the Z80 cpu and pushed down on the ULA chip,
also tried a spare 4164 over each Ram chip but that made no difference to the screen. If this problem was on a c64 I'd suspect one of the 3 ROM chips, but
don't really have much of an idea with this. No dry joints that I can see. I do have a Programmer and 27c256 eproms if it miraculously turned out to be a dodgy FW/basic Rom.
One other thing, the Yellow colour doesn't change, but the colour of the text can be the red/pink colour pictured, or dark or light blue at turn on.
Any help much appreciated.
Hi and welcome to the forum imperious. Unfortunately I am not a hardware expert, so I cannot help you with your problem. However I am sure that one of the forums resident experts (probably Bryce), will post here soon enough with some helpful and friendly advice :)
If you have the pasic promt working, Z80/ROM/RAM are OK.
Looks like the gate array is not working properly. Ink color and mode does not seem right.
The gate array being on socket, you can confirm by swapping it with an other one (well same ref, 40007 on a MC0001A)
Thanks for the information, it's what I feared unfortunately. The motherboard can take a 40010 also, but I won't be paying $50 Aus to get one
here. A couple of Years ago the Exchange rate was a lot friendlier and $30 would have been a lot more acceptable.
The computer is in pretty good nick, so I might hang on to it and see if any cheap ULA's show up.
I'd guess the Gate-array too. However, it may not be actually damaged. Remove it from the socket and clean the pins of the IC and the socket with isopropanol and it might solve the problem.
Bryce.
Quote from: imperious on 13:53, 04 October 15
As You would expect my friend has the Colour monitor and the good working unit. He also has the Monochrome monitor as I don't want that.
Too bad for you you did'nt take the monitors :
- the colour one provide much better image for vintage games graphics than any LCD display currently available, unless you add some expensive video pre-processing hardware. The GBS 8220 is definitely not of these ones. Also remember all vintage graphics were designed for CRT screens, not for the now "pixel perfect" LCDs.
- the green monitor is really good for any serious activity on the CPC. The monochrome image is crispier than on the colour output and, if your are in any serious programming, provide less eye-strain.
Quote from: imperious on 02:14, 05 October 15
Thanks for the information, it's what I feared unfortunately. The motherboard can take a 40010 also, but I won't be paying $50 Aus to get one
here. A couple of Years ago the Exchange rate was a lot friendlier and $30 would have been a lot more acceptable.
The computer is in pretty good nick, so I might hang on to it and see if any cheap ULA's show up.
Have you tried Tot0's site imperious? I have just had a quick look and have worked out that either a 4007 or a 40010 from him should work out at about $32 Aus including tracked and insured postage.
Link here CPC Circuits - Cent Pour Cent (http://www.centpourcent.net/store/c4/CPC_Circuits.html)
Could be an error in the ROM too, so mode 3 gets used instead of 1.
Quote from: TFM on 22:15, 05 October 15
Could be an error in the ROM too, so mode 3 gets used instead of 1.
That wouldn't cause the dodgy text font though.
Bryce.
Quote from: Bryce on 22:23, 05 October 15
That wouldn't cause the dodgy text font though.
Bryce.
Save a MODE 1 switch-on message and reload it in mode 0 (or 3) and you will see just this effect. Of course pen and paper are switched here too. An additional ROM error.
Really? Must try that out.
Bryce.
Yep, as TFM said, that's the MODE 1 startup message in MODE 0 and different colours.
But why aren't the characters mode 0, they look corrupted?
Bryce.
The letters are correct for MODE 1. You can cheat the firmware into thinking you're still in one MODE, while you've switched the hardware to another MODE. The result for MODE 1 letters shown in MODE 0 looks exactly like the screenshot.
So, either - as TFM surmises - the MODE is set in ROM to 0 (with all other parameters still set for MODE 1), or the hardware has some kind of strange and singular glitch and doesn't switch to MODE 1 correctly.
The colour changes irritate me. It looks like it's a hardware problem after all.
Possibly a data bit not making it to the CRTC?
Bryce.
Quote from: Bryce on 10:22, 06 October 15
Possibly a data bit not making it to the CRTC?
It could be the bit 0 stuck at 0.
- Mode is on bit[1:0] of the mode/rom register. if bit 0 is stuck at 0, only mode 0 and mode 2 are possible
- To set the color you have to select the ink register via an index.
- border is OK (index is 16, bit 0 = 0)
- ink 0 is wrong (index is 0), but has color of ink 1
- ink 1 is random (index is 1), looks not initialised
So a check/cleanup on GA IC and socket may help. IC115 (74LS244) may also be the problem.
Thanks for doing the analysis, saves me from doing it :)
Bryce.
@bryce: You can do the MODE 0/MODE 1 effect even in BASIC:
10 out &7f00,&84
20 goto 10
Execute this on the start screen and it'll look quite like on the picture (colours are different obviously). It won't be perfect because interrupts get in the way (which set colours and mode back to the current values of the firmware variables).
Cool, I'll try it tonight :)
Bryce.
Quote from: Bryce on 10:22, 06 October 15
Possibly a data bit not making it to the CRTC?
Bryce.
The CRTC generates addresses, so more likely is the Gate-Array.
Quote from: gerald on 10:36, 06 October 15
- border is OK (index is 16, bit 0 = 0)
border is selected if bit 4 is set to 1, bits 3..0 can be any value. So bit 0 could still be 1.
16-31 will also select border.
at reset time, I believe only border is set to black. So clearly it's initialised here and initialised correctly too.
All other colours could be random.
Border is good colour, so the hardware colour number used will be one of:
4 or 16.
At reset time mode will be set to 0, lower and upper rom will be enabled. Screen will be written to ok because you can write to ram under the rom.
The colour for pen 0 shown here is probably hw colour 3, but may be coincidence.
Bit 0 could be stuck at 0.
What happens if you try to change the mode from basic?
Quote from: arnoldemu on 13:02, 06 October 15
The CRTC generates addresses, so more likely is the Gate-Array.
Yes, but it receives data from the databus.
Bryce.
Quote from: arnoldemu on 13:05, 06 October 15
border is selected if bit 4 is set to 1, bits 3..0 can be any value. So bit 0 could still be 1.
16-31 will also select border.
I was wondering, but did not make any test. Good to know ;)
Either a problem in the GA or in the ROM. Check / clean them first. :)
Quote from: Bryce on 13:40, 06 October 15
Yes, but it receives data from the databus.
Only when reading/writing to it's registers.
CRTC generates an address the gate-array reads the data from that address and outputs it as pixels.
CRTC address is also used for ram refresh, gate-array doing the read performs the refresh.
1st of all thanks for all the replies everyone. I Will pull the unit out of my cupboard and try what has been suggested.
QuoteHave you tried Tot0's site imperious? I have just had a quick look and have worked out that either a 4007 or a 40010 from him should work out at about $32 Aus including tracked and insured postage.
I just found that today whilst surfing for Amstrad parts, so looks like I will definitely be fixing it anyway :)
QuoteToo bad for you you did'nt take the monitors :
- the colour one provide much better image for vintage games graphics than any LCD display currently available, unless you add some expensive video pre-processing hardware. The GBS 8220 is definitely not of these ones. Also remember all vintage graphics were designed for CRT screens, not for the now "pixel perfect" LCDs.
- the green monitor is really good for any serious activity on the CPC. The monochrome image is crispier than on the colour output and, if your are in any serious programming, provide less eye-strain
I realise CRT's look better, had my c64 running on one last week. Unfortunately I don't really have the room for it, mostly due to a retro computing habit getting a bit out of control :) . I am only really interested
in games on it so a Monochrome monitor won't cut it. If I had grown up with one it might be a different story.
QuoteI'd guess the Gate-array too. However, it may not be actually damaged. Remove it from the socket and clean the pins of the IC and the socket with isopropanol and it might solve the problem.
QuoteEither a problem in the GA or in the ROM. Check / clean them first. :)
The only socketed IC's are the Z80 and the Gate Array (ULA). I already tried reseating the Z80 but will remove, clean, and try the ULA tonight.
Just out of curiosity, is the 40010 ULA any better than the 40007? this board has provision for either, so if the ULA proves to be faulty then I could remove it
and fit the 40010, in a socket of course.
Quote from: arnoldemu on 17:32, 06 October 15
Only when reading/writing to it's registers.
CRTC generates an address the gate-array reads the data from that address and outputs it as pixels.
CRTC address is also used for ram refresh, gate-array doing the read performs the refresh.
And aren't those registers used when setting modes and colours?
Bryce.
Quote from: imperious on 04:23, 07 October 15
Just out of curiosity, is the 40010 ULA any better than the 40007? this board has provision for either, so if the ULA proves to be faulty then I could remove it
and fit the 40010, in a socket of course.
There are slight differences between 40010 and 40007.
- they do not have the same pinout, so put it on the right socket ;)
- the 40010 have a minor display difference in mode 2 where the display start one pixel clock earlier.
- the 40010 consume less than 40007
If you can choose, go for a 40010
Quote from: Bryce on 08:23, 07 October 15
And aren't those registers used when setting modes and colours?
Bryce.
No, the colours and modes are registers inside the Gate-Array.
For CRTC you control the size of the display, it's position and the timings (vsync and hsync).
Ah, good to know. That's where my lack of programming knowledge lets me down :(
Bryce.
I removed, cleaned, and reinserted the 40007, made no difference unfortunately. Unless there is a real chance of it being the 74ls244 (I can get one in Jaycar just 3 minutes away by car)
I will order a replacement ULA.
I also did some resoldering on the Rom, Audio, Video IC's.
The smudging effect around the characters on screen definitely changes colour at switch on. It can be pink (might be light red), red, dark blue, light blue. The Yellow always stays the same though.
Quote from: imperious on 14:09, 07 October 15
I removed, cleaned, and reinserted the 40007, made no difference unfortunately. Unless there is a real chance of it being the 74ls244 (I can get one in Jaycar just 3 minutes away by car)
I will order a replacement ULA.
I also did some resoldering on the Rom, Audio, Video IC's.
The smudging effect around the characters on screen definitely changes colour at switch on. It can be pink (might be light red), red, dark blue, light blue. The Yellow always stays the same though.
Did you check/clean the socket ? D0 is on pin 24.
Quote from: imperious on 14:09, 07 October 15
I removed, cleaned, and reinserted the 40007, made no difference unfortunately. Unless there is a real chance of it being the 74ls244 (I can get one in Jaycar just 3 minutes away by car)
I will order a replacement ULA.
I also did some resoldering on the Rom, Audio, Video IC's.
The smudging effect around the characters on screen definitely changes colour at switch on. It can be pink (might be light red), red, dark blue, light blue. The Yellow always stays the same though.
Blindly ordering and swapping parts can be an expensive passtime. Do you have any test equipment, even a cheap multimeter to test what's actually broken?
Bryce.
Quote from: Bryce on 14:46, 07 October 15
Blindly ordering and swapping parts can be an expensive passtime. Do you have any test equipment, even a cheap multimeter to test what's actually broken?
Bryce.
Sorry, I should have mentioned that I'm an electronics Technician, with over 25 years experience. I have a Multimeter and Oscilloscope. I do consider having spare parts to be a worthwhile expense,
especially with this hobby with 30+ year old IC's that can die at any moment.
Just let me know what You want me to test. It's midnight here, so it will be another 17 hours or so till I can check anything.
Ok, then I don't need to explain how to test these things: I'd start by testing the bits going to the GA to see if any bits are stuck at a particular value. Same with the outputs of the 244.
Bryce.
OK, Had a bit of a poke around the Data lines, inputs and outputs of the 244 looked the same, nothing seemed to be stuck
at a zero or a 5v level anywhere.
Is it normal for VCC2 on the 40007 to be about 3.5v? The two 6 ohm resistors are ok. The +5v rail is good at 4.97v.
Quote from: imperious on 13:46, 08 October 15
OK, Had a bit of a poke around the Data lines, inputs and outputs of the 244 looked the same, nothing seemed to be stuck
at a zero or a 5v level anywhere.
Did you check that all data bit are toggling on the 40007 itself ? You can safely remove the heatsink for the test.
Board schematic are the wiki (http://www.cpcwiki.eu/index.php/Schematics)
Quote from: imperious on 13:46, 08 October 15
Is it normal for VCC2 on the 40007 to be about 3.5v? The two 6 ohm resistors are ok. The +5v rail is good at 4.97v.
Yes !
The Data looks the same on the 40007, ls373, ls244, and D0 on IC120. Nothing jumps out at me as unusual.
I did get a 74ls244 from Jaycar and was going to socket all chips on the 40007 side of the D0 line but it took me ages
to remove IC120, so will order a solder sucker from Ebay as desolder braid takes too long.
I've ordered a 40010 from Cent Pourcent as well as a tape drive belt. My cpc has this motherboard File:Z70200 MC0001A TOP.JPG - CPCWiki (http://www.cpcwiki.eu/index.php/File:Z70200_MC0001A_TOP.JPG)
Thanks to everyone who helped, and especially Richard at "Cent Pour Cent" who reposted the ULA and drive belts I ordered due to the 1st package getting lost somewhere in
the mail system.
The ULA was the culprit and all is fine now with a 40010 in place instead of the original 40007 (board has provision for either). I put 2 copper heatsinks on it for
good measure. The original owner was a smoker and despite cleaning it still smells of it, although only if You get close enough. It looks a whole lot better though.
I did the 200x speedup and used a car cassette adaptor to load some games which works well mostly.
Also captured StarWars via my GBS8200 and Vga to hdmi adaptor into my Avermedia card on my PC. The video is a bit less sharp due to processing for Youtube.
For sure the CPC looks very good on my LCD monitor, far better than nearly all my other 8 bit machines. The stereo sound also is very nice to have.
Well done
Ray
Congratulations.
Bryce.
Good news!