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Less blurry picture of the 2.1mm socket - note how it just touches the upper case. I've also re-sprayed the metal bracket of this one as it was quite worn and looked horrible. Note that the extra switch is for the kernel, switching between the normal VIC kernel and JiffyDOS (because JiffyDOS doesn't have Datasette support) /Brett

The original VICs used a 9V AC power supply - the 9V was used for the Datasette and expansion port. It was also converted internally to 5V DC (via the rectifier and regulator). So if you aren't going to use a Datasette (or something on the expansion port that needs 9V) then you could bypass the rectifier AND regulator and feed 5V DC directly to where the rectifier would've been outputting its 5V. In my case, I prefer to just add that 2.1mm socket ... I've done it a few ways ... wired directly to the rectifier input (so on/off switch has no effect), wired directly to the regulator input (using a 9V DC only supply, saves wasted heat on rectifier) or, more recently, across the 2-pin power socket. I think I prefer just wiring it across the input socket - on/off switch works, doesn't matter if you have an AC or DC power supply, you still get the protection of the fuse, you can use a Datasette/expansion port. I've made other improvements that reduce the heat/power consumption so don't mind the wasted heat in the rectifier. Hopefully the attached photos are helpful. If attaching the 2.1mm socket, be very careful about positioning ... the top case overhangs the metal bracket by a few mm ... if you position the 2.1mm socket too high then it might get in the way of the top case (not a big deal, just do some small filing). Oh, and in the case of a US two-prong VIC, then I just make up a converter cable using a figure-8 power plug and either a 2.1mm socket or a 9-pin DIN socket (so you can use a regular/modern C64 PSU) /Brett

These are the two final designs I've settled on ... one with a 2.1mm DC power socket so you can use any 9V (AC or DC) plug pack, and also one with a 7-pin DIN socket so you can use an existing modern (or vintage) VIC/C64 power supply. /Brett

I've gotten my VICs down to under 1A (no Datasette obviously) - if you're using DC then the rectifier wastes a bit of power (and waste heat) so I bypass it and go directly to the regulator. But first I always chuck the LM323 (well, I keep them) and put in a modern replacement, saving a bit of power & heat again. The 23xx ROMs are also pretty inefficient it seems - replacing the kernel ROM at least with a 27C128 saves a bit of power & heat yet again. And, I've just got myself a bunch of modern CMOS 6522s so am interested to see if I get reduce power consumption further /Brett

Success! I finally got my 3D printer and printed out the PAL connecter that EMD69 had designed. As the original video was in Italian it took a bit of trial & error but I finally figured it out. I used an M3 nut and an M3 x 12mm countersunk bolt to hold them together - the nut wouldn't fit into the hole for it so I used a longer M3 bolt (say 20mm) to pull the nut into the hole resulting in a tight/permanent fit. For the connectors I broke them out of a terminal block (8mm pitch) and removed one screw from each - the other screw remains to hold the 2.1mm socket lead. I used what I had lying around but it looks like Hylec HYKS-02412PP is similar. Finally for the 2.1mm DC power socket, I used a bunch of pre-made leads from Aliexpress ... search for something like "dc power jack pigtail". /Brett

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!

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

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

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

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

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

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

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

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

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.

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.

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

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 ...

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!

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.

Unknown - I got them off eBay last year, or earlier this year. They didn't immediately work so I put them aside until I had time to try to figure out the problems.

Yep, you're right, now that I look at it closely there appears to be a lot of flux residue around that one chip. All the connections "look" okay with a loupe but will double check it.

Oh wow, thanks! Sorry for my earlier, shoddy photos I've taken a snap of each board, but I'll have a look at those bit you highlighted already. I was wondering whether the pair of transistors near the speaker were for the soft ON/OFF ... maybe a BC237 and a 2N2222A?

Thanks for replying. I gave it a try: [1] Holding down ON button and typing beep<enter> gave no sound or displayed anything other than my original pic [2] Pressing ON then releasing - screen displays then disappears - typing beep again gave no sound or other display I can see the CPU gets +5V when I press/hold the ON button but this disappears when I release it. I'm not familiar with how these "soft" ON buttons work - I'm assuming some sort of transistor is involved - I can see the ON button goes via a transistor to the left of the speaker/ribbon cable ... ? In the picture, the ON button is the two left-most tracks on the ribbon cable (IIRC)

I found my second CC40 (used) and it does remain powered on but shows the same half-screen of characters as this one - so that'll be the second issue I need to fix I guess