• PDP11HackPlus

    PDP11 Hack+ Bus display

    Well I got the PCB and assembled it, and first off when I powered the board up it caused my PSU to go into over current protection. After a little investigation I realised I had grounded the left and right dots, which are not logic inputs like the rest of the chip for some reason, they are the cathodes of the LEDs. So I was basically putting a whole bunch of LEDs between 5V and 0V, oops. So having fixed that, it does indeed light up. The next problem is that I forgot to include the enable line for the memory so that it only displays memory data/addresses rather than…

  • PDP11HackPlus

    PDP/11 Hack+

    I’m really pleased to say that over the holiday I managed to get some time and built up my RAM/ROM/Text Display PCB for my DCJ11 system. First power up (just RAM) worked, I could write and read from the memory, YAY! Next up I added the display and that also worked (you can see the block on the right hand most character), however I couldn’t then write to the UART memory address, after a bit of digging I’d got my PAL code wrong for the memory address decoding. I forgot that the DCJ11, despite being a 16 bit chip, can only access 16bits of address. A quick bit of rework…

  • PDP11HackPlus,  Personal,  Synths,  TTL CPU

    Time & motivation

    I am still struggling with my mental health, though it is getting better slowly. I’m getting a bit more motivated and I’ve been some work for Isla Instruments, which is a refreshing change. I’ve had an idea for another synth, curse my head, so I’ve jotted it down and put it in the “laterbase”.My current plan is to get the Synth Voice module I designed completed and running (I have PCBs), work on the Isla Instruments project (which will be on going) and do some bits on Epsilon when I get stuck with that and need to free my mind up a little. I’ve put a self imposed ban on…

  • Uncategorized

    Mojo and Epsilon

    Things have been really bad for my mental health over the last month or so, to the point I even had to take some time off work because I can barely function. Some function is returning, but my mood is still very very low, and it’s exhausting. I have been working on Fusion 360 to figure out how to make sheet metal and how to make a case for Epsilon, so after some work here are some pictures. This picture shows the underside of the PCB assembly, showing 10 voice cards and one effects module. I’m glad I put these PCBs all together in Fusion before ordering them because a…

  • Personal,  Synths

    Better late than never?

    Well, It’s been a while and yeah I’m failing at updating this blog regularly. First an update on synth stuff, I’ve been working on a front panel for my synths, I’m currently fed up with the sound of the analogue synths I’ve heard (though I will say the GS e7 sounds amazing) and I want to build one for myself, this isn’t a product I plan to sell. I’ve designed the voice, using two SSI VCO chips and an NJM2069 VCF/VCA (as I have a few), I’ve got the PCBs for that but haven’t got around to building any yet. The front panel also uses a lot of the same…

  • Delta,  Synths

    Synth stuff

    It’s been a while since I posted anything to do with synths, and that’s largely down to some family issues (my partner not being well, but she’s getting better now) and my mood taking a massive dive. The recent news about Modal hasn’t helped, it’s a huge shame and I do hope that a solution can be found going forward. I thought it was time to give a quick update on my polsynth, currently known as ‘Delta’. I’ve been thinking it through and I think I got carried away which has meant that some of the bugs are now really difficult to find (read I have no idea). So I’m…

  • PDP11HackPlus

    It’s ALIVE!

    Well, the new version of the DCJ-11 board worked!!! Here you can see some output from the ODT console (this is me typing “R0/” and it returning the value in octal for that register). you can also inspect the memory, but as it has no RAM yet you get gibberish back. Here is the assembled board; And here is a picture of it all “lit up”, the two buttons are “reset” and “halt”, both with built in LEDs. And finally with it mated to, and powered from, the back plane board It’s currently running with an 8MHz crystal in, and in all honesty for what I’m likely to do with…

  • PDP11HackPlus

    PDP11 Hack plus V2

    It’s been a while, life has been difficult of late for a number of reasons which I won’t go into. However I’m slowly getting my electronics Mojo back, so I’ve been working on the PDP11-Hack board With the previous version I think I tried to put too much in too quickly, so I’ve gone back to basics. The new board (V2) has replaced the discrete glue logic with a PLD and I’ve removed the 16bit RAM and address decoding, again, trying to keep it simple and make sure everything works. A PDF can be found here. The PLD code was written by my partner as she’s done a number of…

  • Delta,  PDP11HackPlus,  Personal,  Suzi,  Synths

    LTNT (long time no type)

    I am trying to keep my blog (this thing) updated regularly, but I’m failing so here are three updates in one! PDP11 Hack Plus I’ll give a quick update on a number of things, firstly with the PDP11 Hack plus board I’ve been doing. Basically I can’t get it jump into the onboard monitor or ODT (Octal Debugging Technique). Whilst I can see a clock and I can see at power up some address and data lines change as if it is looking for a boot strap of some kind, but I cannot get it into the ODT. Mr Usagi Electric has kindly offered to test my DCJ11 chip for…

  • PDP11HackPlus

    PDP11 Hack Plus board, part 2

    So my PCBs arrived (I opted for black, just because) and I built one up run tests. Now the 6402 and the DCJ11 are in sockets as they’re hard to find. The two buttons are Reset and Halt, as I couldn’t fit all the LEDs and their driver chips on the board I opted for breakout pins for things I thought I might need to monitor. First problem was a 6402 that was faulty and as a result killed the 1.8432MHz module, somewhat annoying, but in this day and age of chip shortages and fakes sadly not unexpected, so swapping out another 6402 and a new clock module and the…