Search found 43 matches

by psmart
Tue Aug 11, 2020 9:35 am
Forum: Off-topic
Topic: Introduction
Replies: 36
Views: 10221

Re: Introduction

I will have to check later, I stripped it down completely about a a year ago but too long ago to remember!!! One of the things I keep planning to do, but never get around to it, buy belts for all the machines I have, all are still on original!! My MZ80A is fine reading and writing tapes it makes but...
by psmart
Thu Aug 06, 2020 10:10 pm
Forum: Off-topic
Topic: Introduction
Replies: 36
Views: 10221

Re: Introduction

Just to add, check out the service manual for the MZ80B https://original.sharpmz.org/mz-80b/download/mz80b_sm.pdf section 24, this gives fault finding instructions for the tape deck. Looking at the schematic it has a sensor to detect tape motion and a micro switch, do the drive cogs turn when you pr...
by psmart
Thu Aug 06, 2020 10:04 pm
Forum: Off-topic
Topic: Introduction
Replies: 36
Views: 10221

Re: Introduction

Good luck, best to strip it completely down and give everything a clean at the same time. The screen is actually quite easy to get off. If you unplug all the cables that are coming down from the screen onto the motherboard, then looking from the back, at the left and right side are two brackets, tow...
by psmart
Thu Aug 06, 2020 9:51 pm
Forum: Hardware
Topic: [MZ series] Overclocking Z80
Replies: 12
Views: 205

Re: [MZ series] Overclocking Z80

Looking at the LSI you have Phi-out and Phi-in. On the MZ80A it is similar, the main crystal is divided down by the MB14298 gate array and fed into 2x74LS04's, one feeds the CPU and the other is used for timing. On the MZ-700 it looks like they are doing the same thing, feeding the clock driving the...
by psmart
Mon Aug 03, 2020 10:55 pm
Forum: Hardware
Topic: [MZ series] Overclocking Z80
Replies: 12
Views: 205

Re: [MZ series] Overclocking Z80

So which case is the two-clock source doing in the schematic? Just re-reading your information, the clock circuit is operating asynchronously of the Z80, the two clocks can be out of phase and frequency. When a switch occurs the MARK is elongated so in turn whatever the Z80 was doing at the time of...
by psmart
Mon Aug 03, 2020 10:24 pm
Forum: Hardware
Topic: [MZ series] Overclocking Z80
Replies: 12
Views: 205

Re: [MZ series] Overclocking Z80

BTW. The below image is the new board Im making for the MZ-700, still being worked on as it depends on information I gain from the MZ80A Video Module which Im currently assembling, but basically it combines the tranZPUter SW v2.1 and the Video Module 2.0 into one board which fits into the tight spac...
by psmart
Mon Aug 03, 2020 10:18 pm
Forum: Hardware
Topic: [MZ series] Overclocking Z80
Replies: 12
Views: 205

Re: [MZ series] Overclocking Z80

Second photo, for some reason attaching two photos the second one doesnt show!

The green trace on this picture is M1 in relation to the clocks.

If you need a trace of any other signals let me know and will see if I can snapshot them.
by psmart
Mon Aug 03, 2020 10:17 pm
Forum: Hardware
Topic: [MZ series] Overclocking Z80
Replies: 12
Views: 205

Re: [MZ series] Overclocking Z80

Hi, I've attached below two photographs from my scope, the ground wasn't good as I used the frame rather than the actual 0V connection but it shows the frequency switch. The top yellow trace is the MZ700 3.58MHz clock, the blue trace is the 8MHz 2nd frequency, the purple trace is the actual Z80 Cloc...
by psmart
Mon Aug 03, 2020 2:19 pm
Forum: Hardware
Topic: [MZ series] Overclocking Z80
Replies: 12
Views: 205

Re: Introduction

My MZ-700 running the with the tranZPUter SW v1.1 board, the software needs some tweaks which Im working on and also will soon make a board which fits in the MZ-700.
by psmart
Mon Aug 03, 2020 2:17 pm
Forum: Hardware
Topic: [MZ series] Overclocking Z80
Replies: 12
Views: 205

Re: Introduction

Hi Hlide, Good to hear from you. Back in the days, I overclocked my MZ-80A to 4MHz (cant remember quite how I did it, but it involved cutting tracks!!!). Fast forward to today, my tranZPUter SW v1.1 board uses a variable 2nd frequency and will reliably run at 11MHz (the limit is on the decoder I use...