PhilCs blog / the latest things hes broken(fixed)

[stephen_usher]

How well do the keyboards map?

[PhilC]

@stephen_usher it works pretty well. It’s not like for like totally, there are 4 maps to choose from, 2 for c64 and 2 for C128. The keypad, cursors etc and most of the function keys work as original.

[PhilC]

Retro things have been a bit quiet lately but I did manage to sneak in a few things this week.

Firstly I managed to get the Apple //e connected to my VGA monitor using the V2 pcb that @rubber_jonnie sent me (thanks RJ!)

Then after getting that working I’ve dug out my non working TI-99/4A. I was doing a whole lot of nothing when plugged in. I’ve made a bit of progress by swapping out a faulty oscillator and now we get a blue screen that glitches every so often. A bit of Googling later and I think it might be the MC6810P ram chips at fault but ironically they are about the only ram chip I don’t possess.

So tomorrow I might get a chance to get the ram socketed and will hunt for some more 6810s. I think my Sharp MZ-711 has a couple of them, so may try the TIs chips in the Sharp and see if that boots ok with them.

Anyone got a couple of spare MC6810P chips handy?

[rubber_jonnie]

Retro things have been a bit quiet lately but I did manage to sneak in a few things this week.

Firstly I managed to get the Apple //e connected to my VGA monitor using the V2 pcb that @rubber_jonnie sent me (thanks RJ!)

You're welcome

[PhilC]

I don’t know why but lately the broken computers I end up having to fix all seem to have lots of blown chips.

With this TI-99/4A so far I’ve had to replace all 8 VRAM chips, a couple of 74LS244 and a 74LS04. It’s also looking like the TMS9929A VDP chip is also dying. There’s no R/W signal out of it but RAS & CAS all work fine. So either the ram killed the VDP or vice versa.

Other than that it looks like the computer is running from all tha activity on the data lines.

[Tomswork]

@PhilC
@rubber_jonnie

I have started to see more ttl failing from age power cycling and corrosion getting inside the package i know one brand i see more often but I forget what is was


Tom

[PhilC]

@Tomswork these are all TI chips, I know MT ram has a high failure rate for 8 but stuff.

[Tomswork]

@PhilC

These are brands like mitsubishi and Samsung ttl mos brand for sure

Tom

[PhilC]

The Memotech MTX512 arrived last night and here it is in all its glory.

IMG_2682.jpeg (738.83 KiB) Viewed 920 times

First impressions are that it is a very well made machine with the good quality aluminium case and proper keyboard.

I’ve got no power supply for it but have ordered a few bits to do a DC PSU conversion to it.

[stephen_usher]

Welcome to the club!

This is the best information resource: http://www.primrosebank.net/computers/mtx/mtx512.htm

The key switches are the same as used on the BBC Master. If some don't work properly squirt Electrolube EML down the stem and work them up and down.