Geek

Spectrum VHF handheld programming

A friend gave me two “Spectrum” VHF handhelds. No model number on the radios, the battery packs are “Model N91A”. AI assisted image seach came up with “Kukjae PC-4312”. For what _that_’s worth.

Anyway, I figured these would make good APRS radios for some of my vehicles, provided I could move them to 144.800.

Opening it up revealed a 93C46 EEPROM connected to a header and from there via resistors to the MB88551 4 bit mask ROM CPU. Obviously the idea is to program the EEPROM while the CPU is not looking, while the resistors prevent a clash. Some more digging revealed that the 93C46 is actually a rotated package, just to make life more interesting I guess.

Anyway. Broke out PulseView, hung it on the wires, turned the radio on, changed channels. The Microwire decoder worked fine, but the 93C46 decoder got confused, so I had to read the bits.

On startup (channel switch on channel 9):

     543210 0123456789abcdef 
1 10 001000 0000000000000000 0x08
1 11 111110 0101101110110010 0x5BB2

1 10 011000 0000000000000000 0x18
1 11 111110 0101100101101010 0x596A

1 10 101000 0000000000000000 0x28
1 11 111110 0000000000000000 0x0000

1 10 110000 0000000000000000 0x30
1 11 111110 0010100100000000 0x2900

1 10 110001 1111111111111111 0x31
1 11 111110 1011101110111011 0xBBBB

1 10 110010 0000000000000000 0x32
1 11 111110 1011101110111011 0xBBBB

1 10 010000 0000000000000000 0x10
1 11 111110 0101100101100100 0x5964

1 10 100000 0000000000000000 0x20
1 11 111110 0000000000000000 0x0000

Let me explain. The top line is the data to the EEPROM, “10” is read, then there’s a 6-bit address. The zeros or ones after that don’t matter, this is where the data gets clocked out on the second line. So it’s reading location 0x08, 0x18, 0x28, etc., all in 16-bit mode.

Change to channel 9:

1 10 001001 1111111111111111 0x09
1 11 111110 0101101110101010 0x5BAA

1 10 011001 1111111111111111 0x19
1 11 111110 0101100101100010 0x5962

1 10 101001 1111111111111111 0x29
1 11 111110 0000000000000000 0x0000

Same thing, reading locations 0x09, 0x19, ox29. First guess: receive PLL parameters, transmit PLL parameters, unknown (but zero for all channels) parameters (call ’em “flags” for now).

On startup, it reads the selected channel parameters and then a further 5 parameters. Two of these are the receive VCO frequency and flags for channel 1, maybe it’s like a priority channel. The other three, your guess is as good as mine.

Now to find out what frequencies these parameters map to. Transmit is easy, dummy load and frequency counter. Receive was more tricky, I had to disassemble the sandwich to get to a point on the VCO, soldered a wire there, re-assembled, frequency counter — and found that it was the transmit frequency. Repeated the whole process, found the receive oscillator. Put it all in a spreadsheet, started looking at the data, and found that one channel had the two frequencies separated by 10.7MHz. Ha! This channel is simplex. The other channels were all 7.05MHz split repeater channels.

So now I knew that 0x5D50 and 0x56A0 both mapped to 149.300, with a 10.7MHz difference. The difference is 0x6B0, decimal 1712, and 10.7MHz / 1712 is 6.25kHz, yea I might actually be on to something.

Some more spreadsheeting and the answer is, the parameter in hex is the VCO frequency in 6.25kHz quanta. Also, the first 16 parameters are the transmit frequencies and the next 16 parameters are the receive VCO frequencies.

OK, that was the easy part.

The EEPROM came out easily enough, then I had to solder it to a socket (just like last time, but rotated), stick it in my EEPROM programmer, read the data, edit the data, write the EEPROM, unsolder it from the socket and put it back on the PCB.

0x5A80 and 0x53D0 are the magic numbers I came up with to get to 144.800. And hey, it seems to work.

2026-08-05 by wrm Geek Radio ZS1KE 0

Ringle jock bell Biatches

2024-12-24 by wrm Farting around Geek Uncategorized 0

Peek & Poke

Rijeka is home to quite a large computer museum (as these things go, and measured in number of computers, not floor space). You will find the expected Apple / Atari / Commodore / IBM PC and clones… but those don’t interest me so much. What is interesting is the cold war East Bloc stuff that we never got to see or experience in the West.

Unfortunately a lot of the exhibits are behind glass and don’t photograph well.

This is an Ivel Ultra, a Croatian Apple II compatible computer designed by Branimir Makanec and developed by Ivasim Elektronika (in Ivanic Grad close to Zagreb) around 1984. It has a Z-80 (for CP/M) onboard like Franklin did with the Ace 1200.

The Robik is a Soviet ZX Spectrum clone produced between 1989 and 1994 in the Ukraine.

Spica Ines: A decent keyboard for your ZX Spectrum. And a bare PCB would be easier to import as “washing machine parts” than the whole computer…

Much more interesting (and also an unavoidable self-portrait) is the Galaksija.

In 1983, Voja Antonić designed the Galaksija, using a Z-80 processor, some interesting hardware and some hectic software to render the screen directly from memory using interrupts and code that does nothing in a very specific way while using the Z-80 RAM refresh function to pipe the scan lines to the monitor.

The design was published in the October 1983 issue of Galaksija magazine (hence the name) and at least 8000 of these things were built. At least.

Several versions of the PCB has now been recreated, and there’s even a way to get graphics if you have enough memory.

Then there are the commercial “home” computers. The Galeb (“Seagull”, codename YU101) was an 8-bit computer developed by the PEL Varaždin company in the early 1980s. Only 250 were produced by the end of the summer of 1984, before being replaced by the Orao. It’s a 6502 machine “inspired by the Compukit UK101” but if this Ferguson Big Board “(C) Mikro Slovenija” is an indication, it might have been very similar indeed.

One of the Galeb prototypes.

The Orao (“Eagle”) replaced the Orao. Still 6502 based, it was developed by PEL Varaždin in 1984. It was used as a standard primary and secondary school computer from 1985 to 1991.

The Pecom 32 and Pecom 64 were 1802-based educational/home computers developed by Elektronska Industrija Niš of Serbia in 1985. Both had 32k RAM and 16k ROM, but the Pecom 64 supported colour while the Pecom 32 was B&W, as far as I can tell.

These used the standard 1802 (CDP1869 + CDP1870) VIS display system.

The GETI 3220 is an AY-3-8500-based pong game made by Gorenje, who is better known for their household appliances (our fridge in Globoka is a Gorenje).

They also have calculators.

Lots of calculators.

I have a Triumph/Adler 108T, that Triumph looks like an 81S.

I also have the exact same Tvornica Računskih Strojeva TRS612 calculator, although mine is missing a few pieces. Made in Zagreb in the seventies.

They also have TVs, and audio equipment, and cameras, and test equipment. And I have the exact same Philips PM2421 Nixie-tube multimeter (top center of pic).

They cram a lot into 300 square meters.

I knew there was a camera, but I never knew there was a printer for the Game Boy. You could take a picture, print it out (in glorious monochrome) — the electronic version of Polaroid.

A bit more modern but still historically significant — the badge for the Hackaday Conference in Belgrade, 2018.

The website mentions that they’re looking for bigger premises. I will have to go back someday.

2023-09-17 by wrm Computers Electronics Europe 2023 Geek Travelography 0

Silicon mumbo-jumbo

So this thing crossed my path.

I suppose that’s as much of a disclaimer as you’re going to get.

Because it’s pure snake oil.

Of course I took it apart and reverse-engineered it.

The battery was a bit dodge so I disconnected it.

Someone else had been here before.

The schematic is very similar to the one on the cs.cmu.edu web page. The power supply is… interesting. Unless there’s an external transformer that I don’t have?

US Patent 3,290,589 issued Dec. 6th, 1966
Here’s a long but interesting history of the e-meter: https://scientologymoneyproject.com/2020/06/03/a-brief-history-of-how-scientologys-e-meter-came-into-existence-parts-1-10/

2023-02-22 by wrm Electronics Geek 0

Welcome Distopia

Sol stopped pedaling and the whine died away to a moan, then vanished. He disconnected the wires from the electrical generator that was geared to the rear axle of the bike, and carefully coiled them up next to the four black automobile storage batteries that were racked on top of the refrigerator.

— Harry Harrison, Make Room! Make Room! a.k.a. Soylent Green

The novel was set in 1999, the movie in 2022. Reality is lagging a tiny little bit behind.

2022-12-07 by wrm Geek 0

Happy Birthday Tom Waits

2021-12-07 by wrm Geek 0

Invader

I found these two on the corner of Dvorni Trg and Židovska Ulica. After that I kept an eye open for them.

Somewhere along the Cankarjevo Nabrežje.

Rijna brv (Fishmarket footbridge).

They’re everywhere.

Seems it’s the work of a fellow who calls himself Invader.

2021-10-02 by wrm Geek Slovenia 2021 0

Redecorating

2021-07-03 by wrm Farting around Geek Guns 0

Really large PCB

If you need an oscilloscope, or you have an oscilloscope that needs a service, Peter is your man*. I bought an Elteknix OS 620 from him, gave him my Hitachi V650F to service.

In his stash of stuff he had a large PCB with a 68000 on it. Obviously an arcade game of some type, I recognised the JAMMA connector. Gave me a bad case of the 10th Commandment. So he gave it to me.

Apart from the 68000 there’s also a Z80, in close proximity to the only surface-mount IC on the main PCB. Said IC is a MSM6295, a sound chip used in many games, so this does not narrow down what we actually have here. But some searching for the text on the ROMs pointed me at this ROM image, and some further searching gave me this auction.

So it’s a bootleg Street Fighter II.

It’s also to far gone to save, IMO.

Interesting mix of chips, very heavy on the programmables, with lots of GALs, an OTP 27512 and three HY18CV8 EEPLDs. I found the array of 74597 shift registers interesting, I wonder whether they shift the content of the rather large (10 Mbit) ROM / EPROM array straight out to video (maybe to create the background).

And interesting to note, it’s all on two PCB layers.

So now I’m conflicted as to whether I should strip it for spares or mount it in a lightbox for display.

*Assuming you’re in the Cape Town area, that is.

2021-04-13 by wrm Electronics Farting around Geek 1

Decepticons

My wife asked why I carry a gun around the house? I looked her dead in the eye and said, “Decepticons”. She laughed, I laughed, the toaster laughed, I shot the toaster, it was a good time.

Or in this case, the dishwasher. It was doing strange things so I took out the controller PCB to look for dry joints, etc…

What’s that at the top left? Looks like a PCB antenna?

It’s a CC2500 2.4 GHz transceiver.

OK, so some smeg products (this is a smeg LVS65W8A for the record) do have built-in transceivers. And there’s an app (terrible, terrible app BTW) to let you control them — but it’s limited to ovens and wine coolers and this is neither.

Maybe they use one controller for all their appliances, to reduce their inventory. But I’m not sure the reduced inventory cost would balance the increased BoM cost.

Or maybe my dishwasher is spying on me.

2020-08-27 by wrm Electronics Geek House 0