CZ1500/TS1500 Board and electrolytic miss marking

[bola_dor]

This is a Czerweny CZ1500.. its an argentinian rebranded TS1500 but running at 50Hz

It reached me with a dead LM7805 and now I am going to recap it ..


I found this electrolytic marked the wrong way in the board.. I don't know if this is already documented elsewhere..
This must be a later board issue as I ve seen in the net another layout with 4116 ram..

[Paul]

This is very interesting.
My TS1500 has 4116 an only runs at 60hz.
Would you be so kind and dump the ROM-content for me?
I'm also interested in higher resolution Pics if possible. Maybe you can mail them to me?
Kind regards Paul

[bola_dor]

This is very interesting.
My TS1500 has 4116 an only runs at 60hz.
Would you be so kind and dump the ROM-content for me?
I'm also interested in higher resolution Pics if possible. Maybe you can mail them to me?
Kind regards Paul

Hi Paul,
I have some pictures here, https://www.dropbox.com/sh/bhlzym5l590g ... 4jNMa?dl=0
I can take more if you want me to.
About the rom I have no means to do that But I guess is the exactly same rom used by Sinclair and Timex . They didn't make any modification in software.. only some minor hardware modification in later series as the CZ1000 Plus, CZ1500 plus CZ SPECTRUM (the first ones were called CZ2000 and had a TS1500 like case but in black and an issue 6A board) ..

[Paul]

Hi, thanks for the pics.
I ask for the ROM because I didn't find out how to change to 50hz by hardware so I just changed the ROM in order to have 50hz.
I wonder if they did the same trick or if it's possible to change by hardware.
If it's done in Hardware I need to analyse all tracks in your photos in order to find out the difference between yours and mine.
Kind regards Paul

[1024MAK]

If the machine is working: As the vast majority of the ROM is likely to be exactly the same, I would have thought that a simple BASIC program to PEEK the relevant memory locations and print the values on the screen may be enough.

Alternatively a machine code program could be used to copy the ROM in chunks to RAM, then these could be saved to a PC or similar as a WAV.

In the photos, it does look like a typical ZX81/TS1000 ROM chip.

When I investigated a TS1500 that I have, I was not able to work out how to signal the “ULA” to change the state of the 50/60Hz signal. But then I was not aware of this topic which has the schematic for the TS1500.

Mark

[bola_dor]

Looks like you are looking for ULA pin 21.
I'll look and take pictures of that..
Tje schematics are about the other board issue with 4116 RAM.. but ULA should be the same

[bola_dor]

looks like pin 21 is connected to pin 18 that seems unconnected on the other TS1500 pictures Ive seen and don't has a cleear function on the ULA 's pin description
(Edit: I'll check continuity to GND)
https://www.sinclairzxworld.com/viewtopic.php?t=2404

[1024MAK]

Or this can be used to report back on the state of bit 6 of the “ULAs” input port, bit 6 being the 50/60 Hz input bit.

Code: Select all

HEX DEC Code          Comments
=== === ============  ================================================
 DB 219 IN A,(254)    ; input data from port 254 and store in register A
 FE 254               ; data for above instruction
 E6 230 AND 64        ; mask off 50/60 bit (bit 6)
 40  64               ; data for above instruction
 4F  79 LD C,A        ; transfer data from A register to C register so it is returned by the USR function
 06   6 LD B,0        ; clear B register
 00   0               ; data for above instruction
 C9 201 RET           ; return to BASIC

1 REM 123456789        must be at least 9 characters long
10 FAST
15 LET A=16514
20 POKE A,219
25 POKE A+1,254
30 POKE A+2,230
35 POKE A+3,64
40 POKE A+4,79
45 POKE A+5,6
50 POKE A+6,0
55 POKE A+7,201
60 SLOW
70 LET D=USR A         The byte that the Z80 read from the input port is returned and stored in D
80 PRINT D

Mark

[bola_dor]

Or this can be used to report back on the state of bit 6 of the “ULAs” input port, bit 6 being the 50/60 Hz input bit.

Code: Select all

HEX DEC Code          Comments
=== === ============  ================================================
 DB 219 IN A,(254)    ; input data from port 254 and store in register A
 FE 254               ; data for above instruction
 E6 230               ; mask off 50/60 bit (bit 6)
 40  64               ; data for above instruction
 4F  79 LD C,A        ; transfer data from A register to C register so it is returned by the USR function
 06   6 LD B,0        ; clear B register
 00   0               ; data for above instruction
 C9 201 RET           ; return to BASIC

1 REM 123456789        must be at least 9 characters long
10 FAST
15 LET A=16514
20 POKE A,219
25 POKE A+1,254
30 POKE A+2,230
35 POKE A+3,64
40 POKE A+4,79
45 POKE A+5,6
50 POKE A+6,0
55 POKE A+7,201
60 SLOW
70 LET D=USR A         The byte that the Z80 read from the input port is returned and stored in D
80 PRINT D

Mark

I don't konw what does it exactly means but returns 64 ...
I am absolutely sure its running at 50Hz as argentinian broadcast is and was PAL-N ...

[bola_dor]

Hi, thanks for the pics.
I ask for the ROM because I didn't find out how to change to 50hz by hardware so I just changed the ROM in order to have 50hz.
I wonder if they did the same trick or if it's possible to change by hardware.
If it's done in Hardware I need to analyse all tracks in your photos in order to find out the difference between yours and mine.
Kind regards Paul

I've added new pictures from the front and back of the board..
I do confirm that ULA pin 21 and 18 have full continuity with GND..