I've traced back the cut wires, got rid of a bunch that were not connecting actually anywhere.
There are essentially three wires left that could potentially do a ROM switching, one of which is VCC.
I did a bit of rewiring, tidying. Lifted the PROM with an additional socket ( i don't like bent leg solders ).
If I pull one presumably chip/address select line up, the other down the machine starts. 
The modification also involves a 48k RAM upgrade - which is super nice.
Yesterday I brought home this:
I never turn on a machine I didn't saw from the inside first, so:
- PARENTAL ADVISORY SHOCKING IMAGES MAY FOLLOW -
wait, what? why?
First I thought, well I just restore it to the factory state, but there are a bunch of cut traces, patch cables, piggybacked ICs etc...
Also in my opinion the era-specific or post-market modifications shall be preserved as well when possible.
Now I just need to figure out what is missing from the end of the ribbon cable right? RTFM I suppose.
Has anybody ever seen documentation for a CMP Switchboard 3 ?
Thank you in advance,
m.
Yesterday the PET went home, because "it belongs to a Museum!"
I am going through the row. PC-100 check, PET check. Coming up next, Trash-80 to Treasure.
oh no...
Apple //e really rocks. I'll get my 65C02 tomorrow. Can't wait to run some killer //c applications 🙂
Aus dem Platinenschrott ein Motherboard der CBM-II B Serie, vermutlich CBM 710B mit SID.
Schade, dass mir sonst so ziemlich alles fehlt. Wenn jemand mal eine Tastatur davon rumliegen hat...
ooooooh. Platinenschrott? wo? 
Another resurrected Osborne-1.
Final BCD decoder and BUS driver replaced. Case closed.
Eventually there is a configuration file, somewehre - to switch on the second drive option ?
Might be. Couldn't find it though.
I picked up an ATonce Plus yesterday ( along with some trapdoor RAM )
https://bigbookofamigahardware.com/bboah/product.aspx?id=347
Thankfully the disk images are still available at http://amiga.resource.cx/expde/atonceplus .
Today I've popped it into my trusty A500+
Since I don't have a hard drive, I just started the emulation environment as it is.
ATonce BIOS reports 640k base memory, access to Mouse, Serial, Parallel port and VGA video.
Volkov commander ( sorry, my studio is too bright )
Space commanders
It is awfully slow, a lot slower than my PPC512. I don't think it would make much difference if the utilities were installed on a hard drive.
Nonetheless it's a nice working piece of obscurity.
According to the manual, it should support external disk drives, but it just doesn't
Hey,
I wanted to make a composite terminal display for the HX-20 that implements the peripheral protocol, but unfortunately there is something wrong with the port of my HX.
The service manual barely covers the relevant schematic, my guess is that the RS232 level converter is failing. If I'll have some free time I would like to revisit this project. Would anyone be interested?
Trapdoor RAM expansion and Vortex i286 emulator card for A500:
https://bigbookofamigahardware.com/bboah/product.aspx?id=347
ZX Dandanator!
Alles anzeigenAnd both chips show a garbage screen when you place them at G8 ?
My first idea is that they are blocking the address or data bus so that the CPU can not write to the screen memory.
I would check with the NOP generator if the chip selects are still ok.
And with the RAM/ROM board if there are any weak signals on the data bus.
Both tests with G8 in place.
I can look at the schematic later if there could be another cause.
All four chips produce garbage screen when placed to G8.
I'll check with the NOP and the expansion card. Thanks for the tip!
I've bought them from a pinball service, and they claim they test everything before shipping...
I've received today two PIAs for the PET ( MC6821P types instead of the MOS6520 ).
I've got now 2x 6520 chips that are may or may not be working, and 2x MC6821P chips.
I am using the universal RAM expansion to rule out any RAM issues ( as the computer was reporting only 4095 bytes free ).
Without any of the PIAs installed, the full 32k RAM is showing up.
If I place in [G8] PIA the garbage screen comes back. Populating [B8] PIA seems to be indifferent.
Cycling through [G8] all 4 PIA options that I have, one of them presents a black screen, the other three just garbage.
I would appreciate any inputs on this matter,
thanks
Moin moin,
I know you are an experienced restaurateur so I will just write down what I did repairing my Data East Time Machine:
0. Study the documentation, make your own photographs, look for post factory modifications etc...
1. Contact fluid bath or massive spraying on the corroded IC legs that sit in sockets. ( ~2-3 hours rest time )
2. Gently remove all socketed components and put them into a small tank that is filled with antioxidants ( 2 hours in WD40 will do, toothbrush them )
3. Put the PCB into the washing machine ( short program 30-40 degrees 30-45 minutes ) - I know, but still.
4. Leave it dry as long as it needs to, you can use pressurized air to get rid of excess water more swiftly ( recommended )
5. Use flux and lead based solder wire to refresh the solder joints on all components you would like to replace ( all sockets, and polarized capacitors )
6. Desoldering station is a must, take your time on all pins, be careful not to damage the tracks, use hot air to help the component to leave
7. You can wash the the flux off with 99% isopropyl alcohol.
8. Test the semiconductor components that you have removed. Try to dump the contents of the ROMs, compare them to factory binaries if you can.
9. Repopulate the sockets and capacitors. Use quality components only. ( e.g. precision dip sockets )
10. Reassemble and cross fingers. Then debug. And debug, and ...
I hope this is more helpful than common sense.
oh. so it seems like there is no way to set the extended fuse to 0x07 and the TL866 GUI has no options, because there are no such options (?)
The oscillator won't start. My suspicion was that the extended fuse bit's are not set correctly as the TL866 GUI has no options for the lower 5 bits.
I've set up a Dragon as Parallel Programmer for the Atmega328p:
Programmer Type : DRAGON_PP
Description : Atmel AVR Dragon in PP mode
Vtarget : 5.0 V
SCK period : 8.00 us
Writing | ################################################## | 100% 14.91s
avrdude: 17942 bytes of flash written
avrdude: verifying flash memory against sdisk2.hex:
avrdude: load data flash data from input file sdisk2.hex:
avrdude: input file sdisk2.hex contains 17942 bytes
avrdude: reading on-chip flash data:
Reading | ################################################## | 100% 14.48s
avrdude: verifying ...
avrdude: 17942 bytes of flash verified
avrdude: safemode: lfuse reads as DE
avrdude: safemode: hfuse reads as D9
avrdude: safemode: efuse reads as FF
avrdude: safemode: Fuses OK (E:FF, H:D9, L:DE)
I am not able to set the efuse to 0x07 as required, not with TL866 not with Dragon-ISP or Dragon-PP...
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.15s
avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: safemode: lfuse reads as DE
avrdude: safemode: hfuse reads as D9
avrdude: safemode: efuse reads as FF
avrdude: verifying efuse memory against 0x07:
avrdude: load data efuse data from input file 0x07:
avrdude: input file 0x07 contains 1 bytes
avrdude: reading on-chip efuse data:
Reading | ################################################## | 100% 0.05s
avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
0xff != 0x07
avrdude: verification error; content mismatch
avrdude: safemode: lfuse reads as DE
avrdude: safemode: hfuse reads as D9
avrdude: safemode: efuse reads as FF
avrdude: safemode: Fuses OK (E:FF, H:D9, L:DE)
High voltage serial programming is not supported on m328p. Any tips?
Moin moin,
I have built the original Nishida (2013) version of the SDISK// and I am wondering what could be the magic trick that would make it tick.
Thanks for your help in advance,
nils
Ich hatte das Glück, über eBay Kleinanzeigen einen sehr gut erhaltenen Rockwell AIM-65 in Originalverpackung, zu einem humanen Pries zu erwerben.
Der Verkäufer war sehr kompetent und freundlich. Er hat mir das Gerät in einer sehr stabilen Umverpackung geschickt, damit der schon etwas mitgenommenen Originalverpackung nicht passiert. Ausserdem hat er noch drei Rollen Thermopapier, zwei Steckleisten, ein Usermanual und ein Schaltplan dazugepackt.
Der AIM-65 ist mit 4kB RAM und den zusätzlichen Assembler und BASIC ROMs ausgerüstet.
Incredible Glück!
A bit more explanatory images on what went wrong in this PET ( just a couple of things really )
Now I am looking for two 6520 chips, both are fried...
The problem was with two address tracks, that the NOP generator method recovered. It didn't boot up with 2k of RAM, so I used the RAM expansion and enabled 4k and that did the trick.
Thank you all, again!
fyi https://informatik2022.gi.de/ ( We are planning to put up a little retro show for the GI conference with Horst. )
