16k Issue 2 board and DivIDE load errors

Johan1973 · August 2012

I today got an Issue 2 16k board (thank you PMSR) that i added the logic and ram on to get a 48k machine. However, I am unable to load software from DivIDE. I get a lot of R loading errors, and sometimes the machine wants to reset randomly. Any suggestions?

napoleonblownaparte · August 2012

I got similar errors when using my Divide with an (apparently faulty with replacement en route) Kempston interface with an Issue 4 board - dunno if that helps :).

Johan1973 · August 2012

Some keys work, and some dont. And some just resets the machine.

Update, specifically keys 6 to 0 is not working.

Johan1973 · August 2012

Keyboard problem was due to a small damage on a trace. It is fixed now. However, can not load from DivIDE. Have tried replacing the ROM with one I know will work on DivIDE. Still it wont load tap files.

Johan1973 · August 2012

The Sinclair logo is randomly screwed up when I turn it on with DivIDE connected. :(

Johan1973 · August 2012

It is also unable to load from PC soundcard.

pmsr · August 2012

Ah that's a bit of bad luck there, Johan. Does the tape loading work without the divide? I didn't test that board loading from tape before I sent it. Just plugged it in to the tuner and did some brief tests. But I expected it to be working. I remember loading Horace & the Spiders and Planetoids before I put it in storage.

/Pedro

Johan1973 · August 2012

I am trying to load JetPac, and it simply wont load it. Seems signal is way to weak, which is strange, since my 4S loads from this signal without problems. And my other issue 2 board did as well before it was "borked".

Might he problem with loading from audio source through EAR and loading .tap files from DivIDE be related?

Anyway, thank you for the board Pedro. It is beautiful. Much better condition than the Issue 2 I had picked up and was working on :)

Johan1973 · August 2012

Finally I got it loading from EAR and from PC. Had to crank volume much higher than usual for this machine to load from external source.

Johan1973 · August 2012

Loading any .tap results in the machine resetting, and any .z80 provides an unresponsive keyboard. Suggestions?

ingo · August 2012

Johan1973 wrote: »

Finally I got it loading from EAR and from PC. Had to crank volume much higher than usual for this machine to load from external source.

This might be a sign for a dirty supply voltage. If supply voltage is dirty with ripples or hum, the tape input needs more signal to identify the pulses correctly.
Did you check the 7805 output voltage? is it really 5.0 +/-0.1V? Is there an undesired ripple? If possible change the 7805 against a new/different one. Is the 12V line ok? is it about 11 ... 13V? Are the electrolytic capacitors cool? if there is a warm or deformed electrolytic capacitor change it.

Ingo.

rwap · August 2012

Have you tried loading a 16K .tap file - if the .z80 causes an unresponsive keyboard, I wonder if it might be a faulty ram chip somewhere....

Johan1973 · August 2012

Replaced the 7805 with a new one. Did not change anything.
I have tried to load 16k .tap files, does not matter, it immediately resets when trying to load a .tap file.

Johan1973 · August 2012

Now it is working, one or more of the chips I had put as high ram had failed, I dont know why. need to test each of them individually later. It even works with DivIDE now.
YAHOOOO!!!!
Thank you Pedro,RWAP and all others who replied to this thread.

Johan1973 · August 2012

And just to give a small update. This issue 2 have now socketed 4164s in place for lower ram. I can take a photo and show it here if someone is interested. Running cool and problem free. Picture quality from the output on this board with the simple composite mod is better than any other ZX I have had.

Thank you again Pedro for an excellent quality board.

pmsr · August 2012

You should post a photo, especially because of that cardboard shielding the board had. I have two other 48K, one of them also an issue 2, and have never seen it. Maybe others know if this was common when shipped from factory or it was an after-thought.

/Pedro

Johan1973 · August 2012

The PCB with socketed CPU, ROM and Lower RAM (4164s I find to be much more reliable as they dont die if you have a failure in the power circuit).

The mentioned paper/aluminum "shield". I think the first ZX I ever owned had something like this, but I have not seen it again until now.

Machine in its case with new keyboard membrane and DivIDE up and running :)

BloodBaz · August 2012

Nice looking Speccy and setup there Johan1973!

Johan1973 · August 2012

BloodBaz wrote: »

Nice looking Speccy and setup there Johan1973!

Thank you. But was easy to work with such a prime example as PMSR sent me :) It was in perfect condition. All I did was changing cpu to a Zilog Z80, socket the ROM, put 4164's as low ram (cutting -5V and +12V track and route +5V to where +12V used to connect on lower ram). Put logic chips and 4164s as high ram. Add a buffer transistor to the beeper to increase volume.

I love my DivIDE. Before it I loaded software from PC sound card. Which was quite a pain compared to how I do it now :)

Johan1973 · August 2012

Since I have heard that it is a rarity, I give you photos of my 4S machine as well. :)

I have made all the ICs socketed, to make it easy to test chips and do tests. This machine will keep its 4116 memory modules and be kept in original configuration to have a reference machine for any future projects.

Johan1973 · August 2012

I could not resist, just because I love LEDs, you here get my DivIDE light show :D

Johan1973 · August 2012

One final addition. The issue 2 is plagued by very low volume on the beeper. I used to have just a buffer transistor. But this was not enough. I removed the beeper and took a speaker from a headset which are a bit easier to push. Then I hooked up a diode to the 9V pin on the 7805, and from that a 22 ohm resistor to the collector of a BC546 transistor. The base of the transistor connects to the lower (closest to edge) pin for the speaker (no longer connected to speaker). The emitter connects to the speaker.

This circuit might be far from ideal. But it provides more than enough volume from the buzzer without causing distortion (at least with the speaker I use).

pmsr · August 2012

Johan1973 wrote: »

The mentioned paper/aluminum "shield". I think the first ZX I ever owned had something like this, but I have not seen it again until now.

This. Has anyone else seen it? Was it factory installed?

/Pedro

Johan1973 · August 2012

I guess it is a cheap EMI shield. And I guess it is factory installed. Because as I said, my first ZX I ever owned had one.

pmsr · August 2012

Dealt with quite a few boards over the years but this 16k was the only I saw with it.

/Pedro

Johan1973 · August 2012

Well, I dont remember what Issue my first ZX was, I dont have it still. Unfortunately I sold it back then. After that one I have only handled 2 issue 2 (one from you), one issue 4S, and one Issue 3 128k +2 board. Thats what I have here. So my experience only goes so far.

1024MAK · August 2012

I know that computer equipment intended for export to the USA had to have EMI screens fitted in order to meet the requirements of the American law. For example Timex Sinclair TS1000's had conductive paint on the inside of the case.
Some other countries may have had similar requirements in their laws that made such a screen necessary.

Mark

16k Issue 2 board and DivIDE load errors

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