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Hi, Another PC-8012A expansion unit available on eBay US: https://www.ebay.com/itm/155277724197 No idea what expansion cards it has, if someone here buys it please tell us what you get. Regards, John

Hello, I have an Epson FX-80 printer which has an additional board which provides a serial interface. It has several switches (8 DIP and one push button), but I don't have a manual. I'm trying to identify the maker, I've attached a picture but Google hasn't found any hits for the several...

Site back up today!

Hi, Apologies but my site at https://vintagecomputers.sdfeu.org is currently down (been out of service for a couple of weeks now), the sdfeu people emailed to say they were working to restore service. Regards, John

Hi John, Yes I am, I'll PM you. Regards, John

Hi, I can supply and program a range of EPROM chips from 2708 to 27010, and also the MCM 68764 / MCM 68766. Either of these can be used to replace Mostek MK36000 or MKB36000 ROMs and also most 2364 ROMs, where chip enable (CE) is negative (eg in the IBM PC, or some HP or Tektronix equipment)...

Hi, I have a Lucent 2900/260LF terminal, which is a dumb terminal unit with a serial port that uses a VGA screen as display and PS/2 keyboard for input. I found a manual here (appears to be manufactured by Boundless Terminals)...

Hi, I have a small website here: http://vintagecomputers.site90.net/cpm/z100.htm which is currently on 000webhost.com as a free web hosting site. Problem is I hit their limit of 100 unique visitors in a day which resulted in a suspension, and if this happens again (it will!) the site will be...

Spotted on ebay.com (I have no connection to the seller): https://www.ebay.com/itm/NEC-PC8001-N-BASIC-Vintage-Programming-Manual-Z80-Japanese-Computer-Platform/264355940361 If anyone has the English version of this or any other PC-8001 manual please PM me. Thanks, John

Hi, Quick summary - no issues found powers up with all the expected voltages under load. I have a stack of 3 PC-8001 units all with the same power supply. I have never powered these units on, so I thought I would go through and check them over before doing so (as a faulty PSU can damage an...

Hi, I can supply and program a range of EPROM chips from 2708 to 27512, and also the MCM 68764. This can be used to replace most 2364 ROMs, where chip enable (CE) is negative (eg in the IBM PC). MCM 68764C, 8K EPROM, £8 (blank), £10 programmed. 2708 1K EPROM, £3 blank, £6 programmed 2716 2K...

Hi, I've just fitted a new battery (lithium 3V, 2325 size) to my 2MB SRAM Melcard (PCMCIA card), which is working fine. Recognised by XP laptop, can format (FAT) and save and read files. On the back of the card is a space to write a 'Battery Expiration' date, but I have no idea how long a new...

Hi, I have an Osborne 1 which I recently fixed up. I previously used it about 9 years ago, so before powering it up I replaced some capacitors on the power supply. Here's how to get to the PSU board. Place Osborne top side down on a soft surface. Remove 5 bolts from what is now the top half of...

Hi, Are there any plans please to update the forum to be more mobile browser friendly? If you need funds for a vbulletin update then I for one would make a small donation :-) Regards, John

From an email sent to members, non-members welcome (must book as per link), currently 47 spaces left: Welcome to the first meeting of 2018 of the Computer Conservation Society which is on Thursday 18th January 2018 at 2 for 2.30PM at the BCS London offices (see below). Our speaker is Oscar...

Hi, I have a Model 1 Expansion unit with an RS232 board, as per: http://akhara.com/trs-80/docs/model1/RS-232-C%20(1978)(Tandy)(pdf).zip My board is missing the DC converter, which takes 5V input and provides dual +/-12V outputs. The above manual shows the part number is Astec AA4890. Can...

Hi, My mate Doug has ported an Mk14 emulator to run in a web page, written in Javascript: http://www.dougrice.plus.com/dev/seg_mk14.htm Enjoy! Regards, John

Thanks for the replies, Christmas is over for another year so had a play today. I tried tweaking R115 to set the DAC output a bit higher to match gslick's trace, the result was now the same as his: and my IUP now passes the diagnostic test! I can't see a fault with the actual power supplies...

Thanks for the parts list. Yes my IUP-201 has four RAM chips. I haven't had much time this week to look at the circuit, but I did capture the comparator chip (LM339 - U4 and U41) outputs during the POST. U4 was easy, on the three comparators used (1, 2 & 4), all of the outputs went straight to...

I've finally traced out U24 and U25 (74LS74) and U26 and U32 (7407) so can confirm following Yes, except the transistors are driven from Q bar (pin 6 or pin 8 ) not Q (pin 5 or pin 9). I think you meant U25, pin 8 (Q bar) connects to R75 which drives Q17 and Q19. Yes all correct. Also all...