Hi,
After a long gap (moved house) am finally getting round to fixing all three of my Sharp MZs (K,A,B) as all have failed caps in the PSUs.
The K is now working almost as it should, screen, tape and board all working but all I get on screen is a mixture of checkerboard and - patterns. I suspect this might be a failed RAM but has anyone any better ideas and any way to test which RAM (of three full banks) is faulty? I have access to a logic probe and an oscilloscope so testing is not a problem. Have tried the service manual but it references a RAM tester I don't have.
Many thanks
Greg
Fixed Sharp but not yet!
Re: Fixed Sharp but not yet!
What do you have as facility to load a program apart from the tape player? I guess it'll be harder with MZ-80 K because it has no external EAR jack.
There could be several issues:
-DRAM (16Kbyte/20KB/24KB/32KB/48KB): well, it has nothing with the screen but it may lead to bad code execution and some garbage with distinctive characters on the screen.
-VRAM (1 KByte): some garbage with distinctive characters though.
-CGROM (2 KByte): garbage with NO distinctive characters.
-ROM(1KB): same as DRAM.
If you think DRAM is faulty, I made a program: https://sharpmz.no/forum/viewtopic.php? ... 7c0ebcc825.
The issue is how to load this program. If you only have the inner tape player and have an MZ-700, use the MONITOR of MZ-700 to input the bytes and then save them on a cassette. And play this cassette with the MZ-80 K.
There could be several issues:
-DRAM (16Kbyte/20KB/24KB/32KB/48KB): well, it has nothing with the screen but it may lead to bad code execution and some garbage with distinctive characters on the screen.
-VRAM (1 KByte): some garbage with distinctive characters though.
-CGROM (2 KByte): garbage with NO distinctive characters.
-ROM(1KB): same as DRAM.
If you think DRAM is faulty, I made a program: https://sharpmz.no/forum/viewtopic.php? ... 7c0ebcc825.
The issue is how to load this program. If you only have the inner tape player and have an MZ-700, use the MONITOR of MZ-700 to input the bytes and then save them on a cassette. And play this cassette with the MZ-80 K.
Re: Fixed Sharp but not yet!
If you have a program to type bytes and save them :
Code: Select all
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 0123456789ABCDEF
D000 FF BD 00 12 FE 00 11 10 0F ED 53 71 11 2A 04 D0 ..........Sq.*..
D010 7D B4 F5 2F CD C3 03 F1 ED 4B 00 D0 2A 02 D0 C5 }../.....K..*...
D020 E5 E5 D1 13 77 ED B0 E1 C1 ED A1 20 0A EA 29 D0 ....w...... ..).
D030 21 04 D0 CB 06 18 CF 2B E5 7E 2F CD C3 03 E1 CD !......+.~/.....
D040 BA 03 C3 82 00 .....
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- Posts: 27
- Joined: Tue May 29, 2018 5:38 pm
Re: Fixed Sharp but not yet!
Thanks. I do also have an MZ700 so shall try that. I am assuming that although the screen is garbage the tape will still load if I press L?
It is extremely regular garbage. If you imagine that # is the checkerboard pattern and - is the centre graphic line then it looks like
#-#-#-#-#-#-#-#-#-#-#-#-
-#-#-#-#-#-#-#-#-#-#-#-#
etc etc.
Greg
It is extremely regular garbage. If you imagine that # is the checkerboard pattern and - is the centre graphic line then it looks like
#-#-#-#-#-#-#-#-#-#-#-#-
-#-#-#-#-#-#-#-#-#-#-#-#
etc etc.
Greg
Re: Fixed Sharp but not yet!
Normally, the program is loaded at the first bytes of the VRAM. If VRAM is not okay, it won't work. If CGROM is not okay, it won't work because the RAM test relies upon having a working screen. I suggest you to try another program which only outputs a music: I already tried it by curiosity upon ùy MZ-80 K. That's way you know if ROM (loading the program) and DRAM are working.
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- Posts: 27
- Joined: Tue May 29, 2018 5:38 pm
Re: Fixed Sharp but not yet!
Just got back off holiday to some new VRAM chips. Have socketed the board and replaced and ...... (builds up tension ......)
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no change . *?!!!****???!!!
The next option must be the boot ROM (EPROM?) but I don't have an EPROM blower so a bit stuck. Anyone any ideas or can help me out?
Greg
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no change . *?!!!****???!!!
The next option must be the boot ROM (EPROM?) but I don't have an EPROM blower so a bit stuck. Anyone any ideas or can help me out?
Greg