When I was about 7 or 8 I took apart my parents record player because I wanted to see how it worked. I had a few parts left over when I put it back together. It took the technician 2 weeks to sort out whatever I had done. I'm much better at putting the things I take apart back together now.

I am lucky that I still have this. There are a few hundred floppies that I wish I still had. I think I have most of what was on them but would like the opportunity to go through and check for any long lost projects that I might not still have.

You've given me some things to think about. I need to investigate that NVRAM a bit more and see if there is more on it.

Ahh, you are right! The first part of that memory does have some interrupt addresses that are setup by the monitor. I did not realize that the interrupt table goes all the way to 03FF. I may have repurposed it but I don't remember if I did that 30 years ago.

The first bytes of hex are:

00FF  000F  1400  E85C  00B0  34E8  7500  BA06
00E8  5100  B034  E86A  00BA  0100  E846  00B0
06E8  5F00  BA01  00E8  3B00  B00E  E854  00BA
0100  E830  00B0  01E8  4900  BA04  00E8  2500

which when disassembled doen't make sense for the start of a program.

I just need to figure out if I used an offset from the beginning of user space for the start of the program. The data I found is only about 380 bytes long so it isn't anything huge. And there are some obvious text fragments in it.

The NVRAM covers the 00000-03FFF address space of this system with user program space starting at 00100. There is a EPROM at F8000-FFFFF which contains a monitor program that communicates over RS-232. That is what I used to extract the data from the NVRAM. I still have the source for the monitor.

That looks cool. I should add some LEDs to mine. I was able to read out the NVRAM though I haven't been able to make sense of it yet. I've tried disassembling the hex dump but haven't found an obvious program yet. There are a couple of text strings in it so there is obviously some data.

I don’t know if this is helpful but here is a thread on Mastodon talking about DIY tape heads. tech.lgbt/@nina_kali_n...

I am really happy with my Rigol DS1054Z. Currently going for about $350 which doesn't seem too bad for a 4 channel scope. If I did it over again I would probably get the version that has the logic analyzer built in. There are a few times that would have been handy for the work I do with it.

Those things are beautiful!

Reverse engineering this old project while waiting on parts. It’s amazing the number of issues I’m finding with the design. Floating inputs. Unused address lines -> the ability to address peripherals in multiple blocks. The things I didn’t know then. But it works so I am happy!
#retrocomputing

I already unlocked that achievement. I'll have to find a different resolution.

That’s cool! I wonder if it might be possible to etch the solder mask with the fiber laser or with a CO2 laser. That way you wouldn’t have to deal with alignment of the artwork or with potentially pealing off solder mask with the artwork.

I have a Greenlee DM-510A that has lasted me 7 years and is still going strong. You might have a look at them.

I became interested in space when I was 3. As a teenager I took an astronomy course where I hand built a 6 inch reflector that I still have. I have worked nearly 30 years in mission planning, mission design, and navigation of spacecraft. I guess I have always been in love with space and astronomy.

That is what I was thinking. Thank you for the response.

Thank you!

I’ve had good luck using Plastruct Plastic Weld to glue 3d printed parts together.