Recent content by Hugo Holden

I have attached the diagram what I ended up with in my units with the DB9 connector. I doubt if anyone else would want to make this version, because it means having to have an impedance matching transformer to run an 8 Ohm or 45 Ohm speaker (in this case the design needs to keep the relatively...

I essentially used the manual procedure. For the AD converter calibration you have to monitor the digital output pins on pin 14 to 21 of the board's connector, pin 14 being D7 and pin 22 being bit D0. That can be done in 3 or 4 ways, Just an array of LED's & resistors would work to show the 8...

In the meantime I made some progress getting my D+7A board running and calibrated. It wouldn't quite come into calibration because the 78L05 voltage reference was 4.9V not 5v and it caused R22 to be at the far end of its range, so I had to replace the 78L05. Not having too much luck with the...

Does that mean that CDOS .COM files would be expected to work in CP/M ? If so, and I could get the Dazzler games as CDOS.com files, they should work on my 8080 computer running CP/M ? @palinst : can you post the GDEMO.COM file, and I will try it in CP/M running in my 8080 computer This...

Thanks Ansgar & nullvalue, While I am ok with hardware, I struggle with the software.

On a related topic (if it turned out to be magnetic interference) I was once told by a Physics teacher, that if you were inside a vessel of some kind and couldn't see outside and it was travelling at a constant speed, that you would and could never know you were moving, even if it was moving at...

Mine had A7 tied high, I also reversed it. Also the whole board was set up for -Unipolar operation, so I had to change the resistors too and reverse those other mods with the wires. In the Joystick manual as you know there is the code for Dazzler doodle. Is it obvious from looking at that...

Thanks. It is just that it was not very clear when printed out, I probably need to take it to the print shop and have it printed on a much larger sheet. It is better zoomed up on, on the computer. Yes, I figured out those mods and have undone them on my board. The board was also configured...

They seem to be a lot cheaper coming out of Canada, this seller even supplies it with an eraser which you should also have, but of course there is the shipping. The GQ-4X's seem a little pricey (considering the exchange rate) on UK ebay. https://www.ebay.co.uk/itm/123541441930? I think...

The Source code (at least the one I found) for K.scope runs on an 8080 machine. Perhaps there is some hope that Dazzle Doodle, Dazzle Mation, Gotcha and Life might (or with some modification be made to work) Where is this source code documented? can you post a copy of those if you have them...

In the PET VDU, there is positive feedback around the vertical scan amplifier, it is a common technique to control the linearity of the vertical scan. In the case of the PET it is only just over a critically damped situation, so on these VDU's if you adjust the vertical height, it induces a...

I'm sure I suggested the GQ-4x, which is linked via usb, you won't have any trouble at all. Also, it really does pay to buy something where the makers have bothered to fit it into a professional enclosure. Things on exposed pcb's are just begging to get shorted out by some debris on the bench...

Crystals do deteriorate over time and they age and it is affectionately called, losing activity. In many cases though it does not prevent oscillations. However, many logic circuits that use crystals deploy a sort of fudge to convert a digital device like an inverting gate, into an analog...

Does anybody have a clear copy of the D + 7A board, Revision E ? My board has had some mods, I'm trying to figure out what they were for and to reverse them, but the only clear copy I have of the board is Rev B and it doesn't match rev E in many ways. For example on the Rev E board IC24 is an...

@nullvalue: Do you know how your address jumpers are set on your D+7A card ? Mine have been modified in the past. My board was set up for unipolar operation, so I'm changing it back to bipolar and removing the mods it had. I have finished cleaning up the IC pins & sockets. Most are TI parts ...