Posted By
chudson
on 2012-09-04
17:28:15
|  c16 doesnt work but screen isn't black
Can smomeone help me identify what's wrong with mine ?
Bought it from a person who siad that he hadn't known if it was working. I checked the universal power supply he gave me and noticed that POWER DIODE barely lights up. I changed te PSU to 800ma 9V i had in a drawer and this is what I saw:
http://img607.imageshack.us/im...90002x.jpg
http://img404.imageshack.us/im...090001.jpg
The strange signs blink all the time , no response from the keyboard and no sound.
Haven't heard bout CPU or TED giving up ghost this way.
Any suggestions what to check ?
Thought it might be the BASIC that is broken but have no idea how to check it withouth another chip
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Posted By
crock
on 2012-09-04
18:45:11
 | Re: c16 doesnt work but screen isn't black
Hi chudson - you posted truncated versions of the links so I can't see your screenshots but if you see the normal border and screen colours it means the cpu/ted/pla & kernal are at least partially working. If the symbols on the screen are part of the normal character set, this also indicates the the TED is reading from the kernal and rendering OK.
Easy way to check if it's the basic ROM is to carefully take the chip out of the board and turn the machine on while holding down run/stop. This would normally cause the machine to drop into the m/l monitor.
Let me see the screen shots and I may be able to tell you more. If it is any of the ROM's or the PLA, I have plenty of spares I can send you for the cost of postage.
Rob
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Posted By
retroscener
on 2012-09-04
19:19:35
 | Re: c16 doesnt work but screen isn't black
Fortunately he posted the screenshot links on the Commodore16.com forum too, so here they are again. Unfortunately I have no idea of these kinda problems myself. I'm more a gamer than a tweaker.
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Posted By
chudson
on 2012-09-05
01:21:23
| Re: c16 doesnt work but screen isn't black
Hey thanks for reply. Taking the 318004 and turning the machine on with run/stop pressed does nothing ( BLACK screen ) But when i took the 318006 and turned it on the computer started as on the screens ( no difference whether the chip was in the socket or not )
If I only knew what's wrong I would be glad to buy the corrupted elements from you 
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Posted By
crock
on 2012-09-05
02:50:43
| Re: c16 doesnt work but screen isn't black
Sorry, I should have given you the code for the basic rom (318006-01.) Removing the kernal ROM (318004) will indeed give you a black screen.
As the screen and border have been set, and there has been an attempt to clear the screen the machine is starting the initialization but failing before it gets as far as displaying the start-up message. As such, it never gets as far as the basic ROM so that didn't prove anything.
Judging by the pattern on the screen, I think the most likely culprits are a partially failed RAM chip at position U6 or the address line multiplexer at U8. Unfortunately this will mean desoldering the old chip as neither is usually socketed.
I don't have many spare C16 ram chips but if you want to tackle this yourself, there is usually plenty on ebay (search for "TMS-4416"). The mux (74LS257) is also easily available.
Rob
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Posted By
Hans
on 2012-09-05
03:26:47
| Re: c16 doesnt work but screen isn't black
Hi,
crock wrote:
Judging by the pattern on the screen, I think the most likely culprits are a partially failed RAM chip at position U6 or the address line multiplexer at U8. Unfortunately this will mean desoldering the old chip as neither is usually socketed.
I don't have many spare C16 ram chips but if you want to tackle this yourself, there is usually plenty on ebay (search for "TMS-4416"). The mux (74LS257) is also easily available.
@chudson: If you have, by any chance, an Atari 600 in reach, you could get the chips from that machine. On the Atari board, all chips are socketed, thus no need to fire up the iron for desoldering.
Regards,
Hans.
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Posted By
chudson
on 2012-09-05
06:13:45
| Re: c16 doesnt work but screen isn't black
Bought today the elements on Polish eBay equivalent. twelve TMS4416-15NL for 3euro and 5 Tesla 74LS257 for 2,5 euro. Think I'll add sockets for easier putting them in and out to be abbleto check a few of them. Need to wait for the package and see if it helps.
Would love to fire up the C16 . I've got a 1551 waiting to be tested
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Posted By
chudson
on 2012-09-14
07:17:28
| Re: c16 doesnt work but screen isn't black
Thanks a lot for the help. Changed Ram at U6 solved the problem. Now I have a working C16 and starting to test the 1551 drive
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