Jump to content


New Members
  • Content Count

  • Joined

  • Last visited

Community Reputation

14 Good

About asdf87

  • Rank
    Space Invader

Profile Information

  • Location
    Port Macquarie, AU
  1. I'm just using simple 23-to-27 adaptor boards ... works well for the kernel (2364 -> 27C128) but I've had no luck swapping the character ROM out ... tried replacing the 2332 with a switchable 2764 that had both VIC and C64 fonts ... got some weird effects. https://github.com/SukkoPera/Open2327RomAdapter Good note about the opcodes ... will bear that in mind!
  2. Next step will be to replace the 6502 and 6522 with CMOS equivalents - this should reduce power consumption further, and no need for heat sinks? 6522: W65C22N6TPG-14 6502: W65C02S6TPG-14 (needs an adaptor board ... https://github.com/TheByteAttic/6502-to-W65C02S-adapter) And finally, as the two remaining 23XX ROMs seem to be quite power hungry, replace them with 27-series versions too? Keen to see how much the power consumption reduces to then. Sorry @MAC-42 ... I didn't mean to hijack your topic
  3. Final result - replaced the 2364 kernel ROM with a 27C128 ... down to 0.87A (when doing nuthin'). I've put the rectifier heatsink back on as it still generates a bit of heat when using the normal input socket (AC or DC). /Brett
  4. Greetings from 2021! So you can now 3D print replacement plugs for the two different types: Divided version: https://www.thingiverse.com/thing:4678324 Open version (i.e. can also use figure-8 plug): https://www.thingiverse.com/thing:4658989 I've also done the following mod. - added a 2.1mm socket which bypasses the rectifier and goes straight to the regulator - as I've also replaced the LM323 with a switching equivalent, there is no more heat being generated by either the regulator or the rectifier. And it draws under 1A (if not using a datasette). You lose 9VAC on the User Port, etc. but I still have the option to use a normal power supply if I ever need that (unlikely?). /Brett
  5. Oh, I just remembered another option - getting one or more ROM-el replacements. For an additional £5 they will program it with whatever ROMs you want. Not sure if you can use it to replace the 2332 for the character ROM though. /Brett
  6. Getting off topic ... this is a two-prong VIC20 where I replaced the LM323 with a PSU7 (not PSU5) from ezsbc.com ... it's higher power but a small drawback is that it won't turn on if the input is above 2V ... this will happen if you switch the VIC off then back on quickly (i.e. changing cartridge) because the big 4700µF smoothing capacitor still has a lot of charge, keeping the input voltage above 2V for some time as it slowly discharges. So my workaround was adding in a push-button with resistor to dump the capacitor's charge quickly. So I've switched to the PSU5 instead of the PSU7 to avoid this problem. /Brett
  7. Happy to help out if you're interested (posting from Australia) ... although I've just blown the UV lamp in my eraser because I forgot about it and left it on for several days. Waiting on a replacement ... I've been experimenting with adding the C64 character ROM to the VIC - did a short video - weird behaviour at the moment ... the VIC20 ROM results in a two column display and the C64 ROM has a six column display ... ohhhkay ... been fiddling with other stuff so haven't done any investigation into where I went wrong yet ... sticking the original VIC20 character ROM back in works fine. I also replace the LM323 regulator (and heat sink) in the two-prong versions with a PSU5 from ezsbc.com, and am investigating whether replacing the rectifier with a modern version can do away with the massive heat sink it also has (just use a small square heat sink) /Brett
  8. I've found Aliexpress to have the best prices - US$15-17 per 6561 ... search for "mos6561" ... but 6560s seem to be around US$40 everywhere I've looked (okay, just ebay and Aliexpress) /Brett
  9. Ahh, my question too. I've got an NTSC VIC with black screen, so suspecting the VIC chip - I've got spare 6561s but no spare 6560s - I can see a single one on Aliexpress for $46 (yikes) - more than double what the more plentiful 6561s go for (12 sellers when I checked just now). But reading the thread it looks like I won't be able to convert it to PAL (although it seems possible to go PAL -> NTSC). For the ROMs, I've been replacing mine with 27xxx versions using some 23-to-27 converter boards I got made using SukkoPera's design. Works a treat and allows me to also install a switchable original/JiffyDOS kernel ROM. If the ROM is already socketed then I can just put the adaptor board in the socket, or I'll remove the ROM or socket and just solder the adaptor board into the motherboard as I'm never going to put a 23xx back in there. /Brett
  10. I use Element 14 here in Australia as they do free, overnight shipping (if they have it in stock). https://au.element14.com/c/power-line-protection/power-supplies/dc-dc-converters/linear-regulator-replacements I went for the open-PCB type for the 12V as I could de-solder the right-angle header pins and solder on straight-through pins if I wanted to "lie it flat". The enclosed ones usually have pretty short legs so you are limited to how you can mount it if space is a consideration. The -5V one from Traco is actually pretty tall compared to others I've had but luckily there is space in the case for it.
  11. Oh, certainly! The 12V one is a Multicomp Pro MP-K78L12-1000R3, but there's a few you can choose from that output 12W/1A. The -5V one, not much choice (i.e. pricey) - went for a Traco TSN 1-2450 - it's also 1A (5W) output. The linear regulator version lies horizontally on the board and is riveted in - not a big deal, just need to snip off the rivet on one side and then pull it through the other, once you've desoldered everything. But the replacement has to stand vertically because of the short legs - not a problem though as there's still a few mm gap between the top of the regulator and the underside of the case.
  12. Hello! I'm quite new to 99's but have been curious for years. Finally have a bunch that I'm restoring to their proper glory. Finally finished refurbishing a power supply from the black model - replaced all the electrolytics, replaced the "boring" red LED with a "futuristic" clear blue one, re-applied heat sink compound to the transistor and replaced the 12V and -5V linear regulators with switching equivalents (no more coffee warmer). And it still works. I've got more 99's than power supplies, and we use 240V instead of 110V here in Australia, so am reading with interest the other thread about using a Mean Well GP25A13A-R1B as it'd be handy for my BBC Model Bs too. /Brett
  13. Ahh, good to know! I'm just going off my own experience - never saw one growing up ... Apples, Microbees, Amstrads, Commodores. I've now got an original black example and the newer cream coloured one with a US PSU - it seems the original uses both the 8.5VAC and 18VAC from the PSU but the newer one only uses the 18VAC - I've got a step-down transformer, but was thinking of either trying to replace the transformer with a 240V->18V version (Jaycar MM2011, but it'll only handle 1A), or just adding a 2.1mm socket and feeding the cream version with 16VDC ... not sure what to do about the black model ... but this is probably getting too far off-topic. I'll have a look if there's a hardware 120V->240V modification thread ...
  14. Indeed, there probably were! It was a thing, back then, for people visiting the US to come back with a suitcase full of sneakers (because they were so cheap) - I can imagine people also coming back with exotic computers like the TI ;) I've now got three - I just love the keyboard - and am planning on a few more. Definitely a fan!
  15. Hi - is there an up-to-date collection of both classic and modern ROMs for the FG? It seems the WHTECH one on p1 is from 2017 ... and we're now onto p56 of posts. I've just gotten my first 99/4A (they were never a thing here in Australia) so would love to get into it more. Thanks Brett.
  • Create New...