I am currently in the middle of development of something new and exciting, and writing lots of posts about that for my Patreon supporters. I can't post any of them on here until it's complete, so today I am raiding the Patreon archives again. This time a post from January 2023, with some 2024 updates at the end. As the Penultimate +2 Cartridge was being developed, I was sent an interesting bundle of boards from TFW8b.....
Since the Penultimate Cartridge was launched in 2016, there have been very few problems. Most of the ones we have seen have been down to VIC20s themselves, and when the dubious 245s or in most cases 138s were replaced, all was well again.
For example:
- http://blog.tynemouthsoftware.co.uk/2022/11/vic-20-repair-the-vic-that-did-not-like-cheese-and-onion.html
- http://blog.tynemouthsoftware.co.uk/2017/02/vic20-repair.html
- etc.
and also
All boards are tested at several stages during production, so we can be confident of them working, and I think of the few original Penultimate cartridges returned, none were actually found to be faulty.
A few boards failed programming or testing, or were rejected due to physical damage (we lost a few buttons on the corners of the boards).
And here they are. The entire total of rejected Penultimate Cartridge boards from the millions we have sold*.
* OK, not millions, but still quite a lot.
A total of 9 bad boards over 7 years. That's not bad going is it?
Some have been reworked, or raided for parts already, but TFW8b has sent them all to me to see how many I can actually get going (or ultimately raid for parts for PU+2 prototype boards).
I can rule one of them out at the first stage. It has had it's microcontroller and RAM removed, so it does not appear to be worth investigating further. I'm having those buttons though to fix one of the other boards.
So that leaves 8 boards.
I thought the best place to start was trying to program the microcontrollers, see how many of those were good.
I did make a nice pogo-pin programming jig, but it's been so long since I dealt with one of these boards, I couldn't find it, so I made a bit of a lashup with a cut down ZX Spectrum edge connector (and I have actually been using this since then, never did find the old one)
Of the 8 boards, 7 programmed correctly. One failed to detect the chip.
Not detecting the chip either means a bad connection, bad microcontroller, or possibly a bad crystal.
Straight off the reel, the chips are set to use the internal oscillator, but when programmed, are set to use an external crystal. If the crystal is bad, they will program the first time, but then do not run and cannot be reprogrammed.
That had clearly had some rework done (a previous revival attempt?). I probed around and found the crystal wasn't oscillating. Probing further found no continuity between the crystal pin at the top and the microcontroller.
I carefully removed the crystal and checked underneath, and the trace was broken where it connected to the pad. I lifted it at the corner to make it easier to see. (cleaning the chip has also made it easier to see the 2014 date code, so this must have been one of the very early boards, possibly one of the hand assembled prototypes?)
I scraped away a bit of the trace and soldered it back to the pad and carefully fitted a new crystal in place. May as well since the previous one had been trough several heat cycles.
(you can just see here the edge of sticky tape I had put on the boards to protect them from scratches from the edge connector. That is what I was writing on, I wasn't directly graffitiing on the boards.)
Success, that's now 8 boards that have programmed correctly, so time for the next stage of testing.
I'll start with the four boards with all the parts intact.
I installed known working chips in the sockets on the first board and fired up the VIC20.
That's a good start, so I exited to BASIC and ran the test program (this was before the days of the built in self test)
I left that running for quite a few cycles with no problems. I also ran through several games to test some of the different modes (Cheese and Onion, a text adventure and an Atari game).
And the next two did the same.
Three working boards.
The final one of the four failed the memory test.
I spotted a fleck of what looked like hot glue? on the back, that might have stopped it getting a proper connection on that pin. With that cleared, it passed the test. (the very early "Caramac" coloured cases were hot glued together, the second revision hold together fine without even needing the screw. This must be another early board.)
All of those four are now working, one more needed only a reflow of the pins and a clean up.
Next, two boards with sockets, but with some damage and no buttons.
Both had modifications to the ROM socket for some reason or other, so I couldn't test that, but I was able to run the board with just the RAM enabled. With the correct series of magic POKEs, I was able to enable the RAM.
They both passed the RAM test designed for the Max RAM boards.
Finally, two boards with the sockets removed. The microcontroller had programmed, so these were a potential good source of parts. I decided to fit some sockets for the GAL chips and test those to make sure the microcontrollers and RAM was working.
Again, they both passed, so more chips for harvest.
So after all that. All the boards actually worked, or could be made to work. All the damage was mechanical, either boards damaged in transit, or ones with bits removed.
Goes to show, if anyone does have a problem with a Penultimate Cartridge it really isn't likely to be the cartridge itself at fault.
2024 Update.
The parts from those boards went to make the Penultimate +2 Cartridge prototypes, (this is my development version of the PCB, with thinner traces, bigger parts, no gold edges and a different fonts etc.)
Which as usual, started off looking quite neat.
But it doesn't last long.
And indeed, that mod didn't last long, and later got reverted. I remember being very pleased with the track repair.
And rather disappointed when I turned out I had to undo it again.
One or two other mods on this one.....
Since the release of the Penultimate +2 I think there has been one return which turned out to be a flaky crystal. It would work for about half an hour, then start acting up, but other than that, we can still be very confident of all the production boards that go out.
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The Penultimate +2 Cartridge is currently at £49.99+VAT
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Q:Would you like £5 off a Penultimate +2 Cartridge? (or anything else from TFW8b.com)A:YeahYeahYeah
Well, use the code "A:YeahYeahYeah" at checkout.
See this (sort of) helpful diagram drawn by Rod himself.
There is also my store with the full range of Minstrel and Mini PET kits and accessories, things are on the change there, but best just to contact me using the link top right of the blog page, and tell me what you want and where you are and I can send you a PayPal invoice. Hope to have a better solution soon.
All the links can be found here:
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You can support me via Patreon, and get access to advance previews of posts like this and behind the scenes updates. These are often in more detail than I can fit in here, and some of these posts contain bits from several Patreon posts (they also got an extra post covering the development of this board). This also includes access to my Patreon only Discord server for even more regular updates.
