SAM Coupe - a video problem
Hi mates.
Lately I managed to acquire a SAM Coupe 512K.
There are, however, certain problems that - I thought - You might help me with, in a moment of free time.
1) The screen is black/white only. From both: TV antenna output and monitor RGB output. Which I've been told isn't normal for 100%. ;)
2) There is a white little mess in the right/low side of the screen. They blink and slightly change position sometimes. And sometimes they even disappear for a while. What could it be and what causes it?
A small photo:
Several photos of the error, in better resolution:
http://yerzmyey.republika.pl/sam_error.zip
3) The sound is _very_ silent and has no bass at all. Supposedly it isn't normal?
I took sound from the connector described on Wikipedia:
http://en.wikipedia.org/wiki/File:SAM_Coup%C3%A9_rear.jpeg as a "Stereo sound output/Light Pen input".
Yes yes, I know I should write to some SAM Coupe people but I tried and wrote to some guy leading one of the biggest SAM-related WWW sites but he didn't answer for a month or so now, so he will not do it at all.
If anybody could suggest anything, I would be very grateful.
Lately I managed to acquire a SAM Coupe 512K.
There are, however, certain problems that - I thought - You might help me with, in a moment of free time.
1) The screen is black/white only. From both: TV antenna output and monitor RGB output. Which I've been told isn't normal for 100%. ;)
2) There is a white little mess in the right/low side of the screen. They blink and slightly change position sometimes. And sometimes they even disappear for a while. What could it be and what causes it?
A small photo:
Several photos of the error, in better resolution:
http://yerzmyey.republika.pl/sam_error.zip
3) The sound is _very_ silent and has no bass at all. Supposedly it isn't normal?
I took sound from the connector described on Wikipedia:
http://en.wikipedia.org/wiki/File:SAM_Coup%C3%A9_rear.jpeg as a "Stereo sound output/Light Pen input".
Yes yes, I know I should write to some SAM Coupe people but I tried and wrote to some guy leading one of the biggest SAM-related WWW sites but he didn't answer for a month or so now, so he will not do it at all.
If anybody could suggest anything, I would be very grateful.
Post edited by Yerzmyey on
ZX81/ZX Spectrum/Amiga/Atari music: http://yerzmyey.i-demo.pl/
Comments
Can be bad ram (too slow dram chips) or bad ASIC chip (end of lifetime) or can be bug in ROM chip (very old eprom with unstable data).
Can you load any game (not games in basic) or ZX emulator ?
http://velesoft.speccy.cz/samcoupe/snaper/snaper-2010-v0_3.zip (test game EXTREME)
ZX emulator on sam coupe not use SAM rom and run in allram mode. If you will see stable graphic in ZX mode or during games then EPROM chip is bad...
Hold reset button - if reset is active + screen defects continue then is unstable sam coupe hardware (DRAM chips or ASIC chip)
Other colors are visible as grey ? Or you see only white and only black ?
Can be dead ASIC chip. :-(
Thanks a lot for the response and help!!!!!!!!!!!!!!!!!!!!!
> Can be bad ram (too slow dram chips) or bad ASIC chip (end of lifetime) or can be bug in ROM chip (very old eprom with unstable data).
Ah, I see. I was afraid of such a thing, heh.
> Can you load any game (not games in basic) or ZX emulator ?
Yes, all programs and games work fine. I mean - when they're able to load.
I use HxC and not everything want to work.
> http://velesoft.speccy.cz/samcoupe/snaper/snaper-2010-v0_3.zip (test game EXTREME)
ZX emulator on sam coupe not use SAM rom and run in allram mode. If you will see stable graphic in ZX mode or during games then EPROM chip is bad...
Oh. This disk has no DOS. So I can't load it and I don't know too well what to do with it. :(
> Hold reset button - if reset is active + screen defects continue then is unstable sam coupe hardware (DRAM chips or ASIC chip)
I will have to do it later because I've just noticed a strange thing: the more SAM is turned-on, the less "garbage/mess" is visible on the screen. And now, after about an hour it's turned-on, the mess disappeared totally. Odd.
But I will remember what You said and check it out later.
> Other colors are visible as grey ? Or you see only white and only black ?
Yes, shades of grey. I meant: like on black&white TV-set, You know.
Now that's annoying.
OK, will try with "boot 1" then.
Thanks!!
A copy of the drive manual can be found here if you don't have one:
http://www.samcoupe-pro-dos.co.uk/sammanual.html
RGB output can't work in BW mode without colors. Problem is in your TV...
We sent the SAM to Lotharek first. He said he was using monitor RGB output and he had a black&white screen. He said he could do nothing about it, didn't find any way to fix it - and he sent it back to me.
I connected it to the TV-set via antenna port - and have the same problem: black&white screen only. All other computers work in colour.
So it's not TV-set.
Btw - how should I load this http://velesoft.speccy.cz/samcoupe/snaper/snaper-2010-v0_3.zip ?
The effects changing while heating sounds like loose solder joints that warm up.
F9 is a function key that by default will BOOT <enter> is the same as typing BOOT and pressing enter. This will load the DOS from disk and load the auto boot file (if it is normal samdos). BOOT 1 does the same, but will not load the auto file.
Note that a DOS.must be the first file on the disc (or at least start on track 4 sector 1).
SIMcoupe will automatically switch a boot disk in place if the disc you are attempting to boot from does not contain a dos to load dos and then put your disc back in drive 1.
> Hold reset button - if reset is active + screen defects continue then is unstable sam coupe hardware (DRAM chips or ASIC chip)
I tried it today: when the reset button is being hold, the bug (white mess) disappears.
So the DRAM and ASIC could be OK then, I gather...?
> RGB output can't work in BW mode without colors. Problem is in your TV...
Another TV-set, another connection -
I'm not a hardware guy, I'm just a regular humble user, so I just took a cable and connected the SAM into the second TV-set, this time via RGB/monitor output (which is SCART) and that's what I can see:
Stefan:
> Defect ASIC? Colin Piggot at www.samcoupe.com should know more.
I'm afraid that's the guy I mentioned in the first post, I recognize the site.
> The effects changing while heating sounds like loose solder joints that warm up.
Ah, that's more comforting. :) I will remember about it too.
> F9 is a function key that by default will BOOT <enter> is the same as typing BOOT and pressing enter. This will load the DOS from disk and load the auto boot file (if it is normal samdos). BOOT 1 does the same, but will not load the auto file.
So that's what I do and the file http://velesoft.speccy.cz/samcoupe/snaper/snaper-2010-v0_3.zip doesn't work ("no DOS" requester).
> Note that a DOS.must be the first file on the disc (or at least start on track 4 sector 1).
SIMcoupe will automatically switch a boot disk in place if the disc you are attempting to boot from does not contain a dos to load dos and then put your disc back in drive 1.
That's what I've been told.
Would anybody be so kind and send me the "boot disk" or the DOS file that must be the first file on the disk?
One might think they're the most popular files in SAM world. While looking for DOS files, I can't find anything that wouldn't scream: "no DOS" while loading.
ASIC make only digital RGB signals then on system connector(expansion bus) you can see logic levels of each R,G,B pins. For test you can connect led diode between +5V and "RED1" pin. In basic write:
1 BORDER 0:PAPER 0:PALETTE 0,0:CLS:GOTO 1 - this basic line set black screen and LED diode on system connector is OFF.
1 BORDER 0:PAPER 0:PALETTE 0,34:CLS:GOTO 1 - this basic line set red color and LED diode on system connector is ON (active).
For load my disc image with snaper you must as first write DSK image to real FDD via SAMDISC utility. Next step is boot dos from any other fdd via "BOOT 1". And now you can insert diskette with SNAPER and press F9(boot). In menu load file with name EXTREME or any other..
Your BW screen and low sharpless on TV can sign video mode without colors (problem with XTAL 4.43MHz or CHROMA COIL L1)
Is it not too much trouble to send me the DSK with the dos to boot?
The easiest way would be to point the file on Internet.
Hi Yerzmyey, I replied to your email on 4th March! I'll resend my email via PM to you just now.
Colin
Hardware, Software, Magazines and more for the SAM Coupé
Website: www.samcoupe.com
Twitter: QuazarSamCoupe
The first thing to try is to swap the two DRAM from the SAM motherboard with that on the little 256K expansion that's plugged into it. If the flickering doesn't appear you'll know one or both of the lower DRAM is faulty. If it still appears, then chances are there is something more severe. It could be the ASIC.
As for the B/W signal via RGB, this would depend on the TV I think in this case, the RGB signal is generated via a few crude resistor DACs from outputs from the ASIC. As per my email, a B/W output via Composite video or RF could depend on a few other factors - mainly the circuitry with the MC1377 colour encoder.
Colin
Hardware, Software, Magazines and more for the SAM Coupé
Website: www.samcoupe.com
Twitter: QuazarSamCoupe
Thanks a lot, I've got it now.
So it must have been lost (I've checked it out now - no incoming letters in 04.03).
More and more idiotic advertisements on the Internet but quality of regular works gets worse every year, I agree.
> The first thing to try is to swap the two DRAM from the SAM motherboard with that on the little 256K expansion that's plugged into it. If the flickering doesn't appear you'll know one or both of the lower DRAM is faulty. If it still appears, then chances are there is something more severe. It could be the ASIC.
Ah, I see. We will try to do that.
if the 256K on the motherboard is broken and if I replace them with those from 256K expansion - is it safe to leave those broken ones on the expansion, or should I just get rid of them at all?
> As for the B/W signal via RGB, this would depend on the TV I think in this case, the RGB signal is generated via a few crude resistor DACs from outputs from the ASIC. As per my email, a B/W output via Composite video or RF could depend on a few other factors - mainly the circuitry with the MC1377 colour encoder.
Thanks. So first I will try to obtain the cable mentioned by Velesoft. It will be the final test for the b/w screen from my side. If it doesn't work (and I suspect so), then I will have to give the SAM to fix, to somebody.
> I only know of one SAM user who has used the HxC floppy drive emulator. It
was connected to his SAM using one of the disk drive interfaces I build -
customised with longer cables. I have attached a photo of his setup using my
interface.
How do you have your HxC connected?
Oh I don't know, but it works now.
Lotharek made some connectors probably based on Your ideas that was suggested by Velesoft, if I recall.
First it wasn't working but then it appeared the newest 'server-prog' for PC is required.
Now almost all programs load just fine.
Btw, could anybody provide a DSK/SAD/MGT disk that would allow me to boot diskettes with no DOS? If it's not any 'SAM community secret'. :) :)
___________EDIT_____________
Thanks Quazar, testing it now. :)
.
You can use big part of DSK images here:
http://velesoft.speccy.cz/download.htm
If you swap the DRAM - and the flicker stops, then you would still need to replace those DRAM that you had just swapped from the expansion to the motherboard.
The SAM can use any of it's memory for the video display, so the dodgy DRAM may still give problems if the SAM then uses lower memory for video.
Also, I do keep a list of compatible/not compatible DRAM that the SAM can use - can you give the numbers from DRAM chips in your SAM?
I've been making RGB Scart cables for the SAM for many years, if you are looking to buy one it can be ordered direct from myself via PayPal or via my sales on eBay. I can also offer my services for checking/repairing the SAM if needed.
Colin
Hardware, Software, Magazines and more for the SAM Coupé
Website: www.samcoupe.com
Twitter: QuazarSamCoupe
Thanks a lot, and thx Quazar.
So -
Velesoft:
> Can you load any game (not games in basic) or ZX emulator ?
http://velesoft.speccy.cz/samcoupe/s...-2010-v0_3.zip (test game EXTREME)
ZX emulator on sam coupe not use SAM rom and run in allram mode. If you will see stable graphic in ZX mode or during games then EPROM chip is bad...
The "EXTREME" game behaves totally normal. Looks normal and sounds normal. Everything's OK.
What would it mean? It's not so bad, huh?
Then at 90% are unstable DRAM chips, else EPROM chip or unstable ASIC.
Different graphic modes use different speed of reading video data from memory. Can you test in basic commands:
MODE 1 - switch to ZX graphic mode
MODE 2 - switch to multicolor ZX mode (similar as TIMEX)
MODE 3 - switch to hi-res mode 512x192
MODE 4 - sam coupe graphic mode 256x192/16 colours for each pixel
Please test if screen bugs are visible in all this modes.
Actually that's what I'm starting to think about very seriously.
Especially that I managed to make one song for the machine - and the SAA has died (probably the song was THAT bad).
Without SAA it's no point for me to have a SAM, so when all the other ways will end (soon) I will write You a PM via WOS.
Thx a lot.
The computer is pure fun (even if not necessarily the tracker), and when it's fixed, I will surely get back to it.
That tune is amazing, I hope you get your Sam fixed!
(Although small correction - "SAM" actually stands for "Some Amazing Micro" - at least according to Alan Miles :-))