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For 2k games you have to cut the A11 line (pin 6, front, from the right) between the cartridge port and R1, as I had difficulties otherwise selecting D1. You can paint nail polish over A11 or even a piece of tape for a more non destructive solution...

What do you know, it worked right away. Tested so far with 8x2kb rom games that required no RAM. Used 4k7 for the pullups. Even if I shut it off before switching games, I have to reset it again after poweron, otherwise some games don't load. Used this site to look up the games and stuff.

Unfortunately I don't have any double or quad density disks. In 1541-II drives the masterdata HD ones worked most of the time, if not, I "helped" them with a speaker magnet. The CP/M I wrote on such a HD disk 15 years ago still works today on a C128. Cleaned the head in the 8050 with IPA...

I'm trying to format a brand new HD disk (I still have like 200 masterdata ones): HEADER "test",D0,I12 are you sure? yes ready The ready reply in instant. Same for D1. Even if I put a piece of paper instead of the disk should do more with it I believe, so it's not the type of the disk. There...

Surprisingly easy fix so far just with two diodes, a bad led driver logic and a capacitor needing reforming.

Reformed the 23000uF capacitor overnight through a 5w 3k3 resistor and 15V. This morning connected it directly to a PSU and slowly raised the voltage to 15V and left it until it draw less than 5uA. I believe for now this is all it was needed after 25 years of rest. CR5/6 are warm, but not hot...

As I've edited above, I'm fairly sure the one of the rectifier diodes CR5/6 blew/crack, while still remaining operational. Both measure as diodes with a multimeter... Here are the chips fitted in the board: UH1 901482-06 2364-091 ROM DOS 2.5 rev. C000-DFFF UL1...

I have a 8050 drive in my collection for about 25 years, now that I have a working PET 8032-SK, wanted to see if the two will work together. After a bit of a cleaning, powered it up, middle led stays green, Drive 1 led lights up long, goes off, lights up short, then stays off. Drive 0 led...

4 DRAM memory chips replaced until PETTEST completed 16 full memory test cycles. "New" CPU and CPU socket, two new filter caps, all from aliexpress. It has some rust over the oscillator cover and inside the case, some dust here and there. Case says 4032 on the back, has a 12" display and...

With a multitool I've cut about 15mm from the left plastic mounts, 8mm from the middle mounts, and case closed (literally). The motherboard sits slanted a bit, that's not seen from the outside, the tape port is where it should be and accessible. Now I have to figure out why the keys write all...

Got away easy by replacing only 5. Only 3 needed to be unsoldered. Two were already in a socket. Passed the PETTEST memory test about 0x12 times. Now Supersoft HR80 board added, everything works Just that I can't close the case. The transformer in the 8031-SK is mounted under the monitor...

nevermind, this time piggybacking worked, and replacing UA10 now PETTEST is passed the ROM test, now is running the RAM test throwing some more mem fail messages

Another PET 8032-sk, board assy 8032030, pettest gave initially: Bad between characters 64 and 127, that was a D6 issues, so I replaced UA6 and UA7. Then it passed Page0/1, however now gives this weird screen repeating "k dram memory test" and monitor high voltage shuts off in a few seconds...

Found in the attic an Audio Sonic 1392 Advanced Programmable Video System made by Radofin (sold also as Acetronic, Prinztronic, Fountain, Grandstand, Hanimex and Lansay in other parts of the world). Have no idea where or when I got this, but I have no cartridges to test it so I designed one and...

Replacing the CPU socket fixed all remaining issues... I remembered the original CPU I removed about 20yrs ago had the legs fall off. It's interesting that I still have that CPU now :biggrin: Just look at that blue and black oxidation on the socket pins.

The scratches read OH then below 3ZG or 3Z6 crossed over with an X. Pencil marking say 154, and there is also a small paper label 154 topside. Printed with black is 518-006 154-8 on the side. Will search further into the PDP-11 direction, thanks!

Bought this early 90s in the market, when everything that was movable was sold beside fruits and vegetables by people coming from former soviet member states. For the ram chips K155RU7 that are TTL, their pinout, and that they are analog to F93425APC, haven't found much else. Would be...

Kernal UD6 - 901465-22 Basic UD8 - 901465-21 Basic UD9 - 901465-20 Basic UD10 - 901465-23 Char UB3 - 901447-10 For the edit ROM I've wrote edit-4-80-b-50Hz.901474-04-0283.bin About the cursor, I've found that if I put my hand on the top of the 6502, blinking stops/slows. I can't know what...

Sorry, UA14, a 4116 DRAM, hard to see on the printed schematic. I saw something like this on the screen (was changing): The clue was the first 4 characters read back, usually d,e,f,g (even if the photo shows d,e,n,g). When I realized the PETSCII "d" is 0x44 or 0b01000100, that seems a stuck...

After switching R11/10, and replacing UE14, the 32KB DRAM test passed at least 0x20 times. I'm so happy! I've learned that PETSCII is not ASCII, thus managed to not replace more RAM chips than needed. Thanks @daver2 , you do a great job helping the community here. Before adding back the...