ZXmore - questions and answers (FAQ)

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
User avatar
PokeMon
Posts: 2171
Joined: Sat Sep 17, 2011 5:48 pm

Re: ZXmore - questions and answers (FAQ)

Post by PokeMon » Sat Nov 18, 2017 6:08 pm

The battery has no influence normally as it is used for the RTC chip only.
This chip isn't active now.
You both could try to remove this IC (8 pin DS1302).
Any change ?

I will check your pictures right now, dessony. ;)

Shaun_B
Posts: 337
Joined: Wed Apr 22, 2009 9:22 am

Re: ZXmore - questions and answers (FAQ)

Post by Shaun_B » Sat Nov 18, 2017 7:52 pm

Hi PokeMon,

These are the following things that I can remove:

IC4, IC3, IC2, IC26, and IC27.

There also pins on J7, J8, J12 and J16 that I can amend/remove.

What are you asking?

Thanks,

Shaun

User avatar
PokeMon
Posts: 2171
Joined: Sat Sep 17, 2011 5:48 pm

Re: ZXmore - questions and answers (FAQ)

Post by PokeMon » Sat Nov 18, 2017 9:02 pm

I am talking of IC27.
But I don't think that this will make any difference.
J12 (BaseAddr) = A3
J8 set to connector direction
J16 set to connector direction
J7 must be set for power
J12 is NTSC/PAL (set=NTSC, not set=PAL)

dessony
Posts: 149
Joined: Tue Oct 29, 2013 1:26 pm
Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Mon Nov 20, 2017 4:33 pm

Pokemon,

After I looked over a cover of the ZXmore V2: notes for the construction kit, I decided to put a capacitor (471) in the C4's area and soldered it down. Still no change on the screen.

I found a wire with a single female header connector at one end and a single male header connector at another end. I put a female end on one of the 5 male headers on a J12's ground area. I put the male end of the wire on the ROM's A16, which is a pin number 2. The LED lit up blue. But, no change came from the screen, only white screen.

I have a multimeter. :D I checked the ZXmore board's ROM and RAM for their voltage readings.
Pin number 32 = 4.99 vdc
Pin number 16 = same as above but 2 probes were reversed.

Then I removed the ROM, the RAM and the Z80 from the board. The screen was black because I took the Z80 off the board. I, then, put the Z80 back on the board and the screen is now white. The LED lit up blue also with the A16 grounding test. I kept the ROM and the RAM off the board for the time being.

I took out an EPM3064(IC26) off the board. The screen was black also. I tested the A16 grounding test, the LED lit blue. I, then, returned the EPM3064 to its proper socket. The screen remained white.

I took a chip off the board, one chip at one time, Result;
IC5 = No effect on the screen = white screen
IC7 = "many horizontal bars"
IC15 = Black screen
IC21 = Black screen
IC10 = White screen
IC6 = White screen
IC19 = Black screen
IC9 = White screen
IC23 = White screen
IC8 = Black screen
IC17 = White screen

Thank you very much for your comment on my videos of my board, Karl.

Yes, I can check/reprogram the flash ROM (SST39SF040)! :lol: I am using a second socket for a height additional purpose for a ZIF socket. I really also want to use a 2764/27C64/2864 and a 64K SRAM, as a top priority, temporarily for a testing purpose since I also noticed that the board has its 2 different drawing line sizes of the IC3 and IC4. Can we do this one with these smaller ICs on the board? :?: What about a J8?

Do we have any way to test these resistor arrays? Maybe, 180 turn round, cracked open, or short? Measured wrong?

Will the whole original ZX80 case fit the ZXmore board?

I have a logic probe, too. :D


Thank you very much in advance.

Sincerely yours,
Dessony (Wm)

User avatar
PokeMon
Posts: 2171
Joined: Sat Sep 17, 2011 5:48 pm

Re: ZXmore - questions and answers (FAQ)

Post by PokeMon » Tue Nov 21, 2017 12:16 am

So when you temporarily switch to another instance (1=blue colour led) you must always press the reset button, too.
In the ZXmore all ICs work together so it is not easy to just remove one or more ICs and to expect a predictable result. If IC's are removed you have open pins, missing signals. At the end, trial and error is not that helpful in this case.

If you are able to read the ROM content (SST39SF040) it would be good if you compare its content to the attached rom file (unzipped 512k).

I would avoid to experiment now with other ROM/RAM sizes.
Anyway there is the option to send the board for a factory view to my home address to help you finding the problem. ;)
Attachments
ZXM-DATA.zip
(51.77 KiB) Downloaded 5 times

dessony
Posts: 149
Joined: Tue Oct 29, 2013 1:26 pm
Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Tue Nov 21, 2017 7:17 am

I found out that my original ROM content (SST39SF040) was corrupted! I finally saw a welcome screen after I downloaded a file from you in the behalf of this forum. But, it was like more corrupted characters and a few black columns! Do you want a video of the screen itself? Any suggestion on checking on a few ICs creating these characters in black? Do you still want the corrupted file from me or whatever?

I hate to repeat the same questions but here are questions:

1) Do we have any way to test these resistor arrays? Maybe, 180 degrees turn round, cracked open, or short? Measured wrong?

2) Will the whole original ZX80 case fit the ZXmore board? What about a 3d printing job or file for the ZX80? I really need a board support and its stabilization for the board.

Thanks,
Wm

User avatar
PokeMon
Posts: 2171
Joined: Sat Sep 17, 2011 5:48 pm

Re: ZXmore - questions and answers (FAQ)

Post by PokeMon » Tue Nov 21, 2017 12:10 pm

Sorry - first your questions:

The ZXmore will fit into a ZX80 case in general but some connectors on the rear side do not match. I think the video output changed and the USB has to be cutted out. Not sure if anyone did a mod to the ZX80 3d printer data published somewhere. The edge connector is in the same position and the power connector will fit (maybe matches to EAR or MIC).

I don't know what you want to test in the resistor arrays - I think you checked the orientation already. I never hat a broken resistor array. In general you could measure every pin against pin 1 of array (common pin) and should give the value except the 2.2k arrays with single resistors. Here is pin 1 and 2 one resistor, pin 3 and 4, pin 5 and 6, pin 7 and 8 and pin 9 and 10.

And didn't you tell you saw the welcome screen after reprogramming the flash rom ? So it is running then ?

dessony
Posts: 149
Joined: Tue Oct 29, 2013 1:26 pm
Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Wed Nov 22, 2017 4:22 am

Pokemon,

It is now running. I could press a few instances with few different colors showed up at the multicolored LED. But, I still saw some "trashed" characters showed up some of the screen. I need your help in finding a few ICs responsible for its black dots generating section. I need to ensure most of the ICs have, within the certain section, their clean contacts and break an oxidization by pulling out and pushing in a few ICs within its sockets a few times.

Thanks,
Wm (Dessony)

User avatar
PokeMon
Posts: 2171
Joined: Sat Sep 17, 2011 5:48 pm

Re: ZXmore - questions and answers (FAQ)

Post by PokeMon » Wed Nov 22, 2017 8:50 pm

Please post a picture of such a screen.
I guess it is only a line counter mismatch with characters starting with line 1 and ending with line 0 instead of starting with line 0 and ending with line 7 (scanlines). This is controlled with R26 and C9 (47nF). What values are used for this ? R26 has changed over the time from originally 8k2 to now 5k6.

dessony
Posts: 149
Joined: Tue Oct 29, 2013 1:26 pm
Location: Indiana, USA

Re: ZXmore - questions and answers (FAQ)

Post by dessony » Thu Nov 23, 2017 12:00 pm

My board has a 6k8 [blue/gray/red] resistor for the R26. :? Please excuse my American mind!

My oscilloscope setting: AC/v1/ms2/auto/int with a contact between R26 and C9 near the IC11 socket's left side.
ZXmore results 11_23_2017.zip
Results
(160.29 KiB) Downloaded 3 times
Seems like I am seeing a half of each characters in the screen! :(

Cheers,
Dessony

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests