Search found 378 matches

by Martin A
20 May 2019 19:03
Forum: MEMOFEST 2019
Topic: A bit early.
Replies: 5
Views: 35

Re: A bit early.

Crazyboss wrote:
20 May 2019 15:32
If its Cambridge, I looks like there is an airport nearby, but its seems like its closed, at least its not possible to fly there from Copenhagen :)
Try flights to and from London Stanstead - that's got a direct train to Cambridge, takes about half an hour according to the time table.
by Martin A
18 May 2019 20:54
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 210
Views: 1741

Re: Resurrecting an MTX500.

I only mentioned the TIP as that was a problem with one of my MTXs. I spent 2 weeks chasing a "timing problem" of random crashing and inability to run programs for any length of time, which turned out to be nothing to do with the timing. Anyway, if the big 10R resistor R62 next to rom B isn't hot th...
by Martin A
18 May 2019 09:58
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 210
Views: 1741

Re: Resurrecting an MTX500.

Silly question, did you replace the TIP2955 in the power regulation section ?

(20 pages of thread is a lot to re-read, so I'll just ask instead :oops: )
by Martin A
16 May 2019 20:39
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 210
Views: 1741

Re: Resurrecting an MTX500.

I've used the 10mhz CMOS Z80 (Z84C0010PEG) in my MTX's for years, with no issues. In fact we found out it works better with the CFX2 than the NMOS version. The only reason one of them has the NMOS chip back in it is for testing. As Dave says we've found a lot of fakes marked up as the 20mhz part (Z8...
by Martin A
16 May 2019 17:49
Forum: INTRODUCE YOURSELF
Topic: Hello
Replies: 13
Views: 71

Re: Hello

One advantage of de-soldering rather than clipping legs is, if the 32k onboard is made up of the 3732H part, you potentially have replacements for the video ram. The trick for replacing a 4116 with a 4164 ties A7 high to reduce the chip to 16k x1 which would in theory work on the high bank 32k chips...
by Martin A
16 May 2019 16:59
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 210
Views: 1741

Re: Resurrecting an MTX500.

Something to consider, the RUN type games usually load and run at #8100. REV.RUN is 14k in size so fits entirely into the paged memory area between 8000 and BFFF STAR.RUN is 18k in size so overflows into the unpaged memory at C000 onwards CPM has all of it's drivers in the top 4k of the unpaged area...
by Martin A
15 May 2019 20:47
Forum: NEW HARDWARE
Topic: CFX
Replies: 44
Views: 6103

Re: CFX

If I'm reading the schematic for the RS232 board correctly, Rom decode for the FDX is potentially as much of a problem as the I/O port decode. Whist the DART is compatible with the CFX it looks like the communications part of the board isn't. So I've come up with a GAL design that enables just the D...
by Martin A
14 May 2019 23:35
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 210
Views: 1741

Re: Resurrecting an MTX500.

I'm guessing the diag ROM merely writes and then reads, which will only detect one type of error. The daig rom writes an XOR of the high and low bytes of the address to each location as it fills the memory, then reads back to check the correct value is present. The early version wrote a fixed patte...
by Martin A
12 May 2019 21:21
Forum: NEW HARDWARE
Topic: CFX
Replies: 44
Views: 6103

Re: CFX

But it works fine when the RS232 board is not fitted? OK, I have found one issue. The machine's stable when in BASIC and running games. The machine boots into the CFX menu fine and as long as you enter BASIC within about 10 seconds everything is fine. If I leave it any longer then the machine will ...
by Martin A
12 May 2019 20:55
Forum: NEW HARDWARE
Topic: CFX
Replies: 44
Views: 6103

Re: CFX

Mmm, that’s odd. Martin, any ideas? The PAL on the RS232 is the usual 14L4. Looking at the pal-assem code for that in the phoenix manual: Pin 14 is the direction pin for the LS245 buffering the data bus Pin 15 enables the DART I/O ports, it's fully decoded so shouldn't clash with the CFX's I/O rang...