Search found 16 matches

by SchmitS
21 Nov 2023 10:18
Forum: HARDWARE
Topic: MTX512 - Screen Trouble
Replies: 8
Views: 87593

Re: MTX512 - Screen Trouble

Hello

It works again, I exchanged VRAM 4116 by 4164.
-5V is no more needed.
I also repaired 2 defected keys.
MTX512 - VRAM.jpg
MTX512 - VRAM.jpg (2.04 MiB) Viewed 87354 times
MTX512 - Board.jpg
MTX512 - Board.jpg (3.13 MiB) Viewed 87354 times
MTX512 - Alpha.jpg
MTX512 - Alpha.jpg (1.47 MiB) Viewed 87354 times
MTX512 - Graphic.jpg
MTX512 - Graphic.jpg (1.22 MiB) Viewed 87354 times
by SchmitS
29 Sep 2023 12:43
Forum: HARDWARE
Topic: MTX512 - Screen Trouble
Replies: 8
Views: 87593

Re: MTX512 - Screen Trouble

Thank you for your replies I found the same result that bit 6 was corrupted at 1 on some adresses. I was hesitating between CPU or VDP RAMs. This means that BASIC uses VRAM as a buffer for keyboard inputs. Now I have to find new one to replace them. Have a nice day. 6=36h >> v=76h MTX512 - wrong cha...
by SchmitS
29 Sep 2023 10:56
Forum: HARDWARE
Topic: MTX512 - Screen Trouble
Replies: 8
Views: 87593

MTX512 - Screen Trouble

Hello

When I turn on my MTX there is a character displayed instead of a space on a few lines of the screen.
Before going further into research, RAM or decoder, have any of you already encountered this problem ?

Thank you in advance for your good advice.

Best regards

MTX512 - Trouble.jpg
MTX512 - Trouble.jpg (1.55 MiB) Viewed 87593 times
by SchmitS
09 Aug 2022 08:34
Forum: HARDWARE
Topic: Commodore 64-128 Chips
Replies: 0
Views: 82618

Commodore 64-128 Chips

hello I'm the owner of an MTX512 + FDX and during my research of spare parts I found theses chips for Commodore 64-128 in the store of a 80s repair shop. Commodore 64-128 Chips.jpg Just one 8721 was installed, the other chips are "brand new". I have no possibility to test them. I don't nee...
by SchmitS
08 Apr 2021 18:21
Forum: HARDWARE
Topic: MTX-512 Retrofit (2021)
Replies: 2
Views: 3334

Re: MTX-512 Retrofit (2021)

Some pictures more
by SchmitS
08 Apr 2021 18:17
Forum: HARDWARE
Topic: MTX-512 Retrofit (2021)
Replies: 2
Views: 3334

MTX-512 Retrofit (2021)

Hello If this can help someone, this is a the report of the actions I did to change the power supplies and to exchange old components on my FDX and MTX. This is to solve bad behaviors due to the aging time. 1: In FDX (See drawing on PDF) A: New power supplies and load resistors (+5V, +/-12V, +24V) B...
by SchmitS
23 Mar 2021 16:18
Forum: HARDWARE
Topic: MTX-512 Board Revision 4000-06
Replies: 13
Views: 9467

Re: MTX-512 Board Revision 4000-06

Thank Martin

I will also clean the edge connectors.

I saw also that some ceramic capacitors have a rather old exterior appearance, what's happen inside ?
New ones are just for some cents.

Best regards
by SchmitS
23 Mar 2021 15:08
Forum: HARDWARE
Topic: MTX-512 Board Revision 4000-06
Replies: 13
Views: 9467

Re: MTX-512 Board Revision 4000-06

Thank you Mark

At that time My MTX is disassembled ...

When my supply upgrade and retrofit are completed and the MTX in one piece again I will post the result.
I just hope it's for the better.

Best regards
by SchmitS
22 Mar 2021 17:16
Forum: HARDWARE
Topic: MTX-512 Board Revision 4000-06
Replies: 13
Views: 9467

Re: MTX-512 Board Revision 4000-06

Dave The RESET signal is coming down, but has no effect to restart with or without the FDX. MTX alone, only ribbon cable removed, has also the same trouble occurrences. It doesn't always start at first power-on. RAM "failure" gives no result back, it just stoppes. I'm more confident that s...
by SchmitS
22 Mar 2021 15:53
Forum: HARDWARE
Topic: MTX-512 Board Revision 4000-06
Replies: 13
Views: 9467

Re: MTX-512 Board Revision 4000-06

Hello Dave I always monitor the 2 video outputs. At power-up if it doesn't start most of the time the both are blank or sometimes only the BASIC 40 columns is launched. When the RAM test is completed the boot starts correctly, but sometimes the RAM test failed. The RESET Keys has no effect to reboot...