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New Digtal Group Toys

Hi All;

Brad, I just looked, I have a Rusty 11.98MHZ, but NO 5.99 MHZ crystals..
For Now, I would take an 11.98 hook it up to a 74LS393 and Divide it down and use that for Now..
Or, Maybe You could take a 6.00 MHZ and with some caps it might work, I don't know as I haven't tried it..

THANK YOU Marty
 
falter said:
Yeah.. I'm interested. Wish I was more skilled. Working on it. :) I have three keyboards that would at least be plausible for a DG system of that era -- 2 are Decision Data 8010 punch keyboards, and one is a Univac punch keyboard from 1970. Obviously would need a major rewiring and some kind of encoder built. I'm not sure exactly if I understand how ASCII works -- ie if I were to take one of Lancaster's 7 bit ASCII encoders.. if the output from that is just a matter of wiring correctly to the DG system, or if the 'format' will still be something the DG isn't expecting.
Click to expand...

I was thinking of building a PS/2 converter for it, is that something interesting to you?
 
Marty said:
Hi All;

Brad, Here are a couple of things to try..
First as many of us have Said Before, You NEED a Scope, Even a Lower Frequency one would work in a pinch.

THANK YOU Marty
Click to expand...

Brad and Marty and all,

the following Micro USB oscilloscope & logic analyzer is probably a great low cost start at around Aus$150 so most likely cheaper in USA.

BitScope Micro USB Oscilloscope & Analyzer and Micro Analyzer

They don't come any smaller than this!

This is one model of their fully featured mixed signal test & measurement systems, being a mixed signal scope in a probe! www.bitscope.com

BitScope Micro functions as an oscilloscope and logic analyzer simultaneously; it is a mixed signal oscilloscope.
Note: Oscilloscope Probes and Adapter shown below are NOT supplied.

20 MHz Bandwidth.
40 MSps Logic Capture.
2 Analog Scope Channels.
2 Analog Comparator channels.
6 Logic/Protocol Analyzer channels.
8 & 12 bit native analog sample resolution.
Decodes Serial, SPI, I2C, CAN and more.
Windows, Linux, Mac OS X & Raspberry Pi.
Built-in analog waveform & clock generators.
User programmable, C/C++, Python, VM API.
Tiny, light weight (14g) and water resistant.
BitScope Micro would not be complete without the ability to generate waveforms and drive clocks.
BitScope Micro is also a powerful real-time mixed domain (time and frequency) spectrum analyzer too. It can be used in baseband or narrow band (RF) applications.
We call it BitScope Micro, a go anywhere problem solver that fits in the palm of your hand.

mixed signal scope.jpg

Bitscope works on Win XP/7/8, Mac OS X 10.6+, Ubuntu (Debian), Fedora (RedHat) and Linux Generic.

above taken from ebay seller darkwire (NOT ME)
http://www.ebay.com.au/itm/Bitscope...3TR16WMWNUfSLxNapF9Ow%3D&orig_cvip=true&rt=nc
 
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Hi all,

Just realized that my reply post yesterday on Martys comment about Brad needing a scope, by posting about the bitscope was maybe to long. All I did was a cut and tuck from that finished eBay listing. I looked today at the www.bitscope.com and may have been more appropriate to have just mentioned a few lines and posted that web link.

Sorry guys.
 
Hi All;

Inotarobot, You still could go in, in Edit mode and take some of the Lines out and leave what You think might be appropriate..

THANK YOU Marty
 
Marty said:
Hi All;

Inotarobot, You still could go in, in Edit mode and take some of the Lines out and leave what You think might be appropriate..

THANK YOU Marty
Click to expand...

Hi Marty, valid point. I went back in an edited out +40% of it and moved the makers web link up near top. They do have quite a range of measurement product, that is certainly giving the traditional Scopes and Logic Analyzer a run for their $'s (bucks). BTW I have NO affilliation to them.
regards
David
 
Okay so I think the TVC 32 card for now is kaput until I find a crystal. Also, its character generator is shot -- I had it swapped into the spare TVC 64 board which was not working at all and now is sort of working... forgot I had swapped the char gen and when I fired it up -- lines through everything.

Anyway, last night to occupy some time I decided to try to fix the second TVC 64 board. And I managed to get it to a prompt, but this is what's happening with the sync on the screen:

https://www.youtube.com/watch?v=fHKHwUjNsCo

I can get it to stabilize a little bit but never completely. And the display itself is dimmer than my other TVC 64 board. Now, there are two things I've noticed that differ with these boards. One of them is on the non-working TVC 64, on the left side there are variable resistors in two locations. On my working board, there are just regular resistors. The other thing I noticed is there are four capacitors (top right) on my working TVC, but only 3 on the non-working. I'm not sure if that is on purpose (due to modifications) or if something broke off.

I did follow the DG group instructions for vertical sync issues and changed out IC7 and IC8 with known good, but to no effect. I'm not sure at all what those variable resistors are supposed to do.. turning the little dials doesn't change anything. Here's a pic of the cards side by side.. working TVC to the left, non-working to the right.

20160718_103115.jpg
 
Hi All;

Brad, "" And the display itself is dimmer than my other TVC 64 board. ""

Change out the Transistor..

"" One of them is on the non-working TVC 64, on the left side there are variable resistors in two locations. On my working board, there are just regular resistors. ""

That was to get a closer tolerance on where they are wired.. If You want , Just change them to what You have in Your other Board..

"" The other thing I noticed is there are four capacitors (top right) on my working TVC, but only 3 on the non-working. I'm not sure if that is on purpose (due to modifications) or if something broke off. ""

Broke off, and is Missing, It needs to be Replaced for the Cassette Read to Work Properly..

"" I did follow the DG group instructions for vertical sync issues and changed out IC7 and IC8 with known good, but to no effect. ""

Just change out All of the other Ic's one at a time, until You find the troublesome IC..

THANK YOU Marty
 
I swapped the entire top row with the row from my good card. The very first 74193 proved to be part of the issue. Soon as I changed that.. it stabilized. But here's the weird thing. I started borrowing 74193s from the 32 char card.. went back to not being able to hold sync again. It would *only* work with this one DM74193 chip. The other chips work great in my good card. I've no idea what thats about.

Meanwhile.. I removed and replaced *all* of the 32 char ICs with no change. Only thing that works is to tap the crystal and only for a little while. So I'm going to dig around for a 5.990 somewhere and hopefully that'll be that. I'm thinking that explains why tape performance was so erratic.. I got it dialed in enough to load 8080 op sys once.. but it crashed and then no matter how i adjusted the resistor it either could 'hear' nothing from the tape or heard things when nothing was playing.
 
Hi All;

Brad, keep on plugging away and eventually You will get there..

"" It would *only* work with this one DM74193 chip. The other chips work great in my good card. I've no idea what thats about. ""

Are they all Plain 74xx OR are some of them like 74LSxx ?? If I remember correctly DM is National.. Sometime things can be very Mysterious..
Here is where a scope Would do You Wonders..

"" I got it dialed in enough to load 8080 op sys once.. but it crashed and then no matter how i adjusted the resistor it either could 'hear' nothing from the tape or heard things when nothing was playing. ""

The cause of this could be two fold.. One on the 32 Character card there is only one Variable Resistor Left and that IS for adjustment of the Cassette Reading Section and Has Nothing to do with the Video Section.. Fiddling with that once it is adjusted will make it so it does just as You have Described..
The Other Possibility is the Frequency from the crystal is varying too much and makes it so It won't Read correctly..
Like I said before, Take one of Your 11.98 MHZ Crystals and use something like a 7400 (cross coupled), or a 7474 or a 74393 and Divide it by 2 to get Your Stable 5.99 frequency.. IT may look messy, but it will provide Your stable Frequency that You need to read Your Tapes..
Also, IN the Tapes, I sent You there is one Labeled TONE, it should have all "ONES" on one side and if I remember correctly all "Zero's" on the other side to help You align the Cassette Reading Section of Your Cards.. Or it is all 'Ones' on both sides..

THANK YOU Marty
 
Thanks Marty.. do you know anywhere with diagrams etc on how to do this division thing with the crystal? I've never done it before so no idea what I'm doing. But I can figure just about anything out with a visual aid.
 
Last edited:
Hi All;

Brad, If You look at a Data sheet or Data book like TI for example for the 74393..
It's a 14 pin Package, Power on pin 14, ground on pin 7.. One side of the crystal to ground the other to the input of the '393, pin 1..
Tie pin 2 to ground, and You'LL get Your output on pin 3.. Pin 3, then goes to where the crystal used to attach..
If You don't have a 74393, please let me know what You do have..

THANK YOU Marty
 
I don't seem to have any 74393s in my search thus far. But I do have tons of 7474, etc.

On the minus side.. I fired up lunar lander last night to make sure my original z80 setup was still okay.. and it loads and runs but crashes randomly now (freezes right up, or screen blanks and goes back to non-responsive menu). Ugh! I'm hoping it's just an IC on the TVC board I forgot to swap back. Could be bad RAM again maybe but there's no indication of faults during the load process.
 
Might have found it. Was a 7430 I think I forgot to swap. When I swapped it back in I had the weird video stuff on the right side going on that was going on before. Really need to learn how to properly test these chips.
 
Hi All;

Brad, "" I don't seem to have any 74393s in my search thus far. But I do have tons of 7474, etc. ""

OK, It is a 14 pin Ic, Power to 14 and Ground to 7.. Tie pins 1 and 4 high (+5), as well as pin 2..
Pin 3 is Your Clock, so it goes to the Crystal and Output on pins 5 or 6, If that doesn't divide it by two then just tie it to the second flip-flop on on that IC..

THANK YOU Marty
 
Hi All;

Brad, I just saw Your Latest Video on Your Digital Group machine..

Great Video !!

Also, You Do Not have to shut the machine OFF to Load in a Tape, You should be able to press "1" (Read), and it will Load in the program..
I will just load in the numbers, it will not show the sign-on message..

THANK YOU Marty
 
Thanks Marty! Thought Digital Group deserved some representation.

I have found loading tapes via the Read command sometimes doesn't work.. I don't know if its the memory occupied by the first OS load? I found with my Lunar Lander game I had to shut it right off.
 
Hi All;

Brad, "" I don't know if its the memory occupied by the first OS load? "'

A qualitative no, all or most Programs Load above the Operating System something like page(s) 10 or 11 0ctal..
But, if the Operating System is a different Version that what You have in there at the present, it might affect it..
But, I think it loads both the Operating System and the Game program, no not unless You change a few memory locations, Come to think of it..
So, Lander is loaded at the higher pages, as stated above.. And if it hooks into certain Operating System Memory Locations and they were changed by an earlier or later Version then it would not work right..

So, to keep The Operating System Version the same as what the program wants, then Yes, You need to turn off the Machine..

THANK YOU Marty
 
Yeah. I know for sure there are some programs that don't seem to have the OS attached somehow and they load off the load command.

Tonight I'm going to start figuring out how to handle those tiny jumper wires and start working on getting the Phideck going. Really would like to see that do something, even if it doesn't work. Not having much luck with the crystal divide for the 32char board... I'm still too novice-y to figure it out. But I'm trying.
 
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