ZX81 rebuild

Discussions about Sinclair ZX80 and ZX81 Hardware
User avatar
1024MAK
Posts: 1799
Joined: Mon Sep 26, 2011 9:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX81 rebuild

Post by 1024MAK » Sat Oct 07, 2017 9:25 am

More about transistor switch off times.

The bits in the datasheet that you are looking for are:
  • Max. Storage time (ts or tstg)
  • Max. Turn-off time (toff)
Both meaured in nanoseconds (ns).

Links to the datasheets here:

http://hardware.speccy.org/datasheet/ztx313.pdf
https://www.onsemi.com/pub/Collateral/BC182-D.PDF

As you can see, the BC182 datasheet does not even list the storage or turn off times...

Mark

User avatar
1024MAK
Posts: 1799
Joined: Mon Sep 26, 2011 9:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX81 rebuild

Post by 1024MAK » Sat Oct 07, 2017 10:30 am

Although I don't have a plastic cased through-hole transistor to recommend, a 2N2369 or 2N2369A should work. There was a plastic version PN2369A but this is harder to find/buy. They are also not cheap compared to most plastic transistors in TO92 packages.

Mark

Lardo Boffin
Posts: 656
Joined: Sat Nov 26, 2016 1:42 am

Re: ZX81 rebuild

Post by Lardo Boffin » Sat Oct 07, 2017 11:08 am

Thanks Mark.

I did find some new old stock on ZTX313’s eBay but they are somewhat lacking in detail...

https://m.ebay.co.uk/itm/QTY-10-ZTX-313 ... Ciid%253A1
ZX81 iss 1 (bugged ROM, kludge fix, normal, kit)
Iss 3 with ZXVid, another in nearly perfect box
TS 1000 iss 3, ZXPand AY, ZX8-CCB & ZX-KDLX
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Spectrum 48k
Toastrack + DIVMMC future

User avatar
gammaray
Posts: 283
Joined: Sun Apr 17, 2016 1:44 am
Location: Texas

Re: ZX81 rebuild

Post by gammaray » Sat Oct 07, 2017 9:27 pm

Just a note. Ferranti does not manufacture a PNP complement to the ZTX313 for use in a "WHYWAIT" circuit. That I could find anyway.

Personally, I love the ZXmore and ZXblast and modifying a Zeddy-bear but would like to see a new OEM-style ZX81 PCB V.4 made that includes some of these transparent add-ons like the signal enhancer for tape play, whywait and maybe 2000-4000 RAM/ROM (FLASHROM) selectable on-board memory configuration,50hz or 60Hz, ...

I got to get busy!
Finish what you start. Truth is over the mountaintop or six feet under.
4 x TS1000, 2 x TS1500 , 2 x timex 2040 printer, 1/2 x timex 2020 cassette deck, ZXPAND, ZeddyNET, ZXBlast..., unfinished Spectrum...Still no life!

axtelle
Posts: 11
Joined: Sun Sep 10, 2017 5:37 pm

Re: ZX81 rebuild

Post by axtelle » Sun Oct 08, 2017 2:24 am


gozzo
Posts: 444
Joined: Fri Jul 08, 2011 7:52 pm

Re: ZX81 rebuild

Post by gozzo » Sun Oct 08, 2017 3:45 am

😱 sacré merde..£17.80.. 😱 i wish i'd bought a load at 50p each when i had the chance ...d'ohh!!

gozzo
Posts: 444
Joined: Fri Jul 08, 2011 7:52 pm

Re: ZX81 rebuild

Post by gozzo » Sun Oct 08, 2017 3:46 am

oh, and 2N2369 plastic version... MPS2369 ...i have at least one zx81 that has these in...

User avatar
1024MAK
Posts: 1799
Joined: Mon Sep 26, 2011 9:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX81 rebuild

Post by 1024MAK » Sun Oct 08, 2017 6:44 am

gozzo wrote:
Sun Oct 08, 2017 3:46 am
oh, and 2N2369 plastic version... MPS2369 ...i have at least one zx81 that has these in...
Yep, but in my search yesterday these were even harder to find... :(

Mark

Lardo Boffin
Posts: 656
Joined: Sat Nov 26, 2016 1:42 am

Re: ZX81 rebuild

Post by Lardo Boffin » Sun Oct 08, 2017 8:26 am

1024MAK wrote:
Sun Oct 08, 2017 6:44 am
gozzo wrote:
Sun Oct 08, 2017 3:46 am
oh, and 2N2369 plastic version... MPS2369 ...i have at least one zx81 that has these in...
Yep, but in my search yesterday theses were even harder to find... :(

Mark
I have just bought 5 MPS2369 (https://m.ebay.co.uk/itm/MPS2369-Transi ... Ciid%253A1) new old stock from eBay. I don’t really like buying components from there but sometimes...
ZX81 iss 1 (bugged ROM, kludge fix, normal, kit)
Iss 3 with ZXVid, another in nearly perfect box
TS 1000 iss 3, ZXPand AY, ZX8-CCB & ZX-KDLX
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Spectrum 48k
Toastrack + DIVMMC future

User avatar
1024MAK
Posts: 1799
Joined: Mon Sep 26, 2011 9:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX81 rebuild

Post by 1024MAK » Sun Oct 08, 2017 10:34 am

Yeah, note that I was only searching RS, Farnell, Rapid, ESR, Bowood, Mouser etc...
I normally only use eBay for semiconductors and some other electronic parts if said parts are unavailable from normal electronic suppliers / businesses.

Although some eBay sellers are proper honest businesses and do supply genuine parts.
So far, the only fake parts that I have received (as far as I know) are:
  • EEPROM chips (won't "burn", all address locations just read as 0xFF) [more info on StarDot],
  • a 65C02 (which tests as a NMOS 6502, NOT a CMOS 65C02, and this is from a UK based seller),
  • and some SRAM chips, which all have different moulding marks/stamps, but all have the exact same screen printing, but they all work in a ZX80.
I also have some other CPUs, and it's possible that some of these are fake or more likely are 'pulls'. The most common issue with cheap chips from overseas, is that they are sold as 'new', but are actually used 'pulls' that have been cleaned up and the pins re-tinned. I don't mind if they are honest in the listing, but some either don't say, or they are listed a 'new' :evil:

Oh, and I'm not including chips that I bought knowing that they are 'pulls' (and work fine) in the list above.

Mark

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest