Russian PCB ZX80 clone problem
Russian PCB ZX80 clone problem
Hello, I am back, with my "Russian ZX80 PCB" build.
I am done building ZX80 kit (the one bought from Ebay, so-called Russian PCB), but it just does not start. I checked the following
1. Crystal, it is 6.5MHz
2. 2732 ROM modification, the PCB already has some
3. I did 555 based back porch generator
I got some sort of picture, so I presume CPU is working and it does read ROM, but something wrong with any of the rest of ICs. Unfortunately, I have no oscilloscope, so maybe there is a quick solution like replace IC 11 or IC 20 (for example). All chips are 74LS
Here is a video of the powered board, any advice would be welcome!
https://www.youtube.com/watch?v=6ulOMmdu0Dw
I am done building ZX80 kit (the one bought from Ebay, so-called Russian PCB), but it just does not start. I checked the following
1. Crystal, it is 6.5MHz
2. 2732 ROM modification, the PCB already has some
3. I did 555 based back porch generator
I got some sort of picture, so I presume CPU is working and it does read ROM, but something wrong with any of the rest of ICs. Unfortunately, I have no oscilloscope, so maybe there is a quick solution like replace IC 11 or IC 20 (for example). All chips are 74LS
Here is a video of the powered board, any advice would be welcome!
https://www.youtube.com/watch?v=6ulOMmdu0Dw
Re: Russian PCB ZX80 clone problem
I have one of these but haven't finished it yet. Is that just a plain socket under the ROM? Are you sure the ROM is right? The kit that I got included a ROM chip (2732) but there was no data on it. I have a 2732 to 2532 adapter for when I make mine.
I'm Chris, a Brit in Germany (Chr$ on the QL forum). https:\\QXL.WIN < QL related collection.
Re: Russian PCB ZX80 clone problem
Can you provide a link to the website of the producers?
Was there any documentation with the board? We need to know what modifications compared to the original board were implemented.
Kind regards Paul
Was there any documentation with the board? We need to know what modifications compared to the original board were implemented.
Kind regards Paul
In theory, there is no difference between theory and practice. But, in practice, there is.
Re: Russian PCB ZX80 clone problem
I can't speak for the OP, but I got mine on ebay from a Russian (who seemed to have Chinese connections). It seems very well made and as far as I can tell, it's (in terms of traces) an exact copy of an original. Here are some pics.
It came with all the IC's and crystal, most of which look 2nd hand - certainly the Z80, which has a 1994 date stamp. As mentioned, it included an EPROM (2732) that was non-programmed. I can't find any details on the producer or specific documentation.
I'm pretty sure the EPROM pinout isn't right for the board, i.e. the board has the same connections as an original, so I have an adapter for that. I'm going to steal a modulator box and the 3.5mm sockets from a spares ZX81, when I get round to it!
It came with all the IC's and crystal, most of which look 2nd hand - certainly the Z80, which has a 1994 date stamp. As mentioned, it included an EPROM (2732) that was non-programmed. I can't find any details on the producer or specific documentation.
I'm pretty sure the EPROM pinout isn't right for the board, i.e. the board has the same connections as an original, so I have an adapter for that. I'm going to steal a modulator box and the 3.5mm sockets from a spares ZX81, when I get round to it!
I'm Chris, a Brit in Germany (Chr$ on the QL forum). https:\\QXL.WIN < QL related collection.
Re: Russian PCB ZX80 clone problem
Thanks for the pictures.
I can send you new 3.5mm connectors (original) . No need to slaughter a Zeddy for this.
Just pm me your address.
Kind regards Paul
I can send you new 3.5mm connectors (original) . No need to slaughter a Zeddy for this.
Just pm me your address.
Kind regards Paul
In theory, there is no difference between theory and practice. But, in practice, there is.
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Re: Russian PCB ZX80 clone problem
Hello
Do you have a multimeter? If yes, what type / model?
Do you have a logic probe? If not, are you prepared to buy one, or make your own simple one (I can post up a schematic).
When you say “2732 ROM modification, the PCB already has some” do you mean that you think that the PCB track layout is designed for a 2732 EPROM, or do you mean that you have modified the PCB so that a 2732 EPROM should work?
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: Russian PCB ZX80 clone problem
If the board has the same track layout as an original ZX80 then the 2732 EPROM just requires a simple mod as per the picture, I have tried this and it does work.
- Attachments
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- eprom2732.jpg (38.01 KiB) Viewed 4661 times
Re: Russian PCB ZX80 clone problem
It seems he does not sell ZX80 clone anymore and gone for Wilco PCB instead
But it was on his eBay store, here
https://www.ebay.co.uk/itm/PCB-DOUBLE-C ... 3175822007
No additional info was supplied, just an IC kit, no passives and PCB
Re: Russian PCB ZX80 clone problem
I did some multimeter testing and concluded the PCB already modified to accommodate 2732 ROM.
But the fact that kit may come with empty ROM is very interesting
Re: Russian PCB ZX80 clone problem
Yes I do have Bort BMM-830-A
Hight precision digital one
None at the moment, but yes, I am willing to do one, please send me a schematic
I checked PCB with the multimeter and according to the schematic on Grants site that PCB already modified to accommodate 2732, no modification required
Thank you for your reply