Search found 10 matches

by klf
21 Nov 2020, 17:35
Forum: Kit assembly gallery
Topic: My Gigatron! It very almost works! (Help!)
Replies: 7
Views: 1257

Re: My Gigatron! It very almost works! (Help!)

Instead of feeding the shift register you could also add a parallel input to your Gigatron. Use a 74HCT574 or 374 octal flipflop and connect its outputs to BUS0..7. Clock (pin 11) goes to SER_LATCH (/VSYNC). Cut the /IE signal where it enters U39/74HCT595 at pin 13 and insert a three-pin jumper here...
by klf
21 Aug 2020, 16:09
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 10838

Re: microtron

Up only: 74xx461, 463, 590, 591, 592, 593
Up and down: 74xx469, 579, 869, 867

74HC(T)590 should be the most common one.
by klf
20 Aug 2020, 17:25
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 10838

Re: microtron

74HC393 is a ripple counter, like the 4040. Better use a 74HC163.
by klf
20 Aug 2020, 14:56
Forum: Escape Meta Alt Control Shift
Topic: Anyone got one for sale?
Replies: 2
Views: 1098

Re: Anyone got one for sale?

There is a Dutch company selling kits: https://www.budgetronics.eu/en/building ... a-25779-20
by klf
17 Aug 2020, 21:44
Forum: Hardware and software hacking
Topic: Ye Olde Gigatron and Gigatronski
Replies: 11
Views: 2497

Re: Ye Olde Gigatron and Gigatronski

Neither works.. The scope shows that it is oscillating, but the output voltage is very low. The propagation delay of these is about the same as the 74C04 according to the specification, but I doubt that would be the problem, as I see it oscillating nicely. Did you try to change the bias resistor? E...
by klf
11 Aug 2020, 18:43
Forum: Hardware and software hacking
Topic: Ye Olde Gigatron and Gigatronski
Replies: 11
Views: 2497

Re: Ye Olde Gigatron and Gigatronski

National Semicoductor's MM74C series has been introduced in 1976. So you could try a 74C04 instead of the '90s 74HCT04. However, it has 50 ns propagation delay and might be at its limit at 6.25 MHz. The CD4069A from the very first 4k CMOS series is even older. -A is the unbuffered configuration, wit...
by klf
28 Jul 2020, 12:36
Forum: Hardware and software hacking
Topic: Issue with building my own Pluppy McPlugface
Replies: 14
Views: 3510

Re: Issue with building my own Pluppy McPlugface

USB keyboards from the transition time, when PS/2 was still common, often support both protocols. Newer ones do not. If your USB keyboard came with a green PS/2 adapter it should work. If no adapter was included it is unlikely that this protocol has been implemented.
by klf
23 Jul 2020, 11:31
Forum: Hardware and software hacking
Topic: Raspberry pi loader
Replies: 14
Views: 5654

Re: Raspberry pi loader

So the first thing to do is to wire up the RPi's GPIO header to a female DB9 connector. You will need some sort of multi-conductor cable with at least 4 unique wires, (I would personally use a strip of ribbon cable for testing purposes and then clean it up later once it's running). Be careful, the ...
by klf
18 Jun 2020, 18:50
Forum: Hardware and software hacking
Topic: PucMon
Replies: 23
Views: 6939

Re: PucMon

This is the access time rating. You will need 150ns or faster. So all three versions should work.
by klf
09 May 2019, 22:22
Forum: Hardware and software hacking
Topic: Oscillator with 50% duty
Replies: 3
Views: 1956

Re: Oscillator with 50% duty

You should use 74HCU04 for an oscillator, not 74HC04. A 74HC04 actually consists of three inverters in a row, therefore it cannot be biased into linear mode (that's what the 1Meg resistor does).