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-   -   I found it! A very sorry looking MK14. (https://www.vintage-radio.net/forum/showthread.php?t=170727)

Slothie 17th Dec 2020 12:10 pm

Re: I found it! A very sorry looking MK14.
 
I'll confess to having bought 4 from him, so thats good news. With the 4 I got from Mark I now have 8 chips, so I should be able to get 4 working ones!

Buzby123 16th Mar 2021 7:02 pm

Re: I found it! A very sorry looking MK14.
 
2 Attachment(s)
Hello All, I'm still here !.

There's been a lot of domestic issues, hospitals and stuff, since Christmas, so I've not had a chance to look at Micky till now.

I've built an 8060 NOPulator, and got one of those 10 logic analysers. From using these tools I've learnt a lot about Micky.

The main thing I've learnt is that every IC socket is rubbish. Not a single one is reliable. This especially includes the 8060 socket.

To replace this socket I will have to desolder most of the ribbon cables that connect the daughter board. However, without these connections there will be missing address decodes that the main board needs.

So I've decided that I'm going to restore Micky back to nearly original, without the extra RAM/ROM and single-step that the daughter board provided.

To do this I am going to replace the dodgy IC sockets, and re-wire all the cut or missing tracks. I'm sure this will be easier than debugging both the main and daughter board together, with not a single reliable socket on either.

What do you think ?.

Cheers,

Buzby

SiriusHardware 16th Mar 2021 7:50 pm

Re: I found it! A very sorry looking MK14.
 
I have to admit those flat-top IC sockets with the square holes in were never my favourites. The only word of caution I would offer is to warn you that the pads on old fibre glass boards of that period are very, very easy to burn off the board because the bonds which keep them attached to the PCB are not very heat resistant now. Lower-side pads which don't have tracks going to them are especially prone to this because there is nowhere for the heat from the iron tip to run away to.

I don't know if you have a 'proper' electrically pump assisted, temperature controlled desoldering gun but I would seriously suggest you might want to invest in one for this job if you don't.

I would say get it working in its original stand-alone MK14 configuration but then gradually take it back to something like its expanded form with the keypad and display extended to the enclosure, and reinstate whatever is needed to drive the binary LEDs and binary switches so that everything on the outside of the enclosure works the way it originally did.

Certain enhancements - like the ability to choose either the new or the old OS - with hindsight, are probably not necessary.

Mark1960 16th Mar 2021 8:03 pm

Re: I found it! A very sorry looking MK14.
 
Tough choice to make as it does remove a lot of the history of your original MK14 and all your custom mods, though I guess you could recreate those again after you have it working.

Mine has been showing some intermittent connection on the ram chips but can still be persuaded to work.

Are those TI IC sockets on yours? They were poor at the best of times and those socket strips were even worse.

Maybe you could try and get a set of cambion ic sockets to keep the period look. Turned pin sockets would look too new, and would be very difficult to replace in future, if ever that was required, without damage to the board.

Did you consider stripping the board to scan both sides? Or is that going to risk damage to other components?

SiriusHardware 16th Mar 2021 8:09 pm

Re: I found it! A very sorry looking MK14.
 
I would say it's not necessary to scan the PCB as it is issue II, I think. What we really want for the archives are scans of an original issue V.

I would second the use of (modern) conventional IC sockets rather than turned-pin, not because of how TP sockets look but because they would be near impossible to remove from an old double sided board, if the need ever arose, without doing damage to the pads.

I used to like the 'low-profile' type where the IC sat really low down and the top of the IC was almost flush with the tops of the sides of the sockets.

circuitryboy 16th Mar 2021 9:06 pm

Re: I found it! A very sorry looking MK14.
 
The bare metal sockets are Molex 'Soldercons' which came in a continuous strip. I used those (versatile and cheap!) for many years/projects. Allowed access to tracks and running wires below each IC.
The basic version was tinned brass. In your picture many are looking grey, oxidised by the unsympathetic storage.
Any further soldering without a (scrap?) IC fitted will ruin the pin alignments.

Timbucus 16th Mar 2021 9:28 pm

Re: I found it! A very sorry looking MK14.
 
Maybe a tin of deoxidiser would be a good first attempt at restoring the sockets? I would be tempted to remove the extra items (after documenting) and then see if you can get it working with the least amount of desoldering after restoring broken tracks and replacing any chips. I have just invested in a desolder gun and wish I had done it years ago...

SiriusHardware 16th Mar 2021 9:39 pm

Re: I found it! A very sorry looking MK14.
 
Briefly OT, which one Tim? I was introduced to them in the early noughties and I wouldn't even think of not having one now.

Timbucus 16th Mar 2021 9:48 pm

Re: I found it! A very sorry looking MK14.
 
I bought the Duratool one which is often offered around 90 (It is currently 150 again on Amazon - just keep your eyes peeled) - I had seen mixed reviews but, had a job (my ZX81 Memopak 16K) that would have been impossible without (The edge connector) and I will likely need to desolder each RAM chip although I suspect not all will be faulty. I have some funny effects - I may create a post on it to help track down the issue. Sadly the first unit I had delivered was faulty but, no quibble another arrived within 4 days and works great as long as you leave it heated and clean the nib before letting it cool.

/END OT/

SiriusHardware 16th Mar 2021 9:52 pm

Re: I found it! A very sorry looking MK14.
 
That's the thing, they are very high maintenance, but worth keeping in tip top condition. One thing you should never do is try to clear a hole which you suspect might have a broken component or IC pin in it, once something like that gets jammed in the narrow channel in the nozzle, it's never coming out.

Timbucus 16th Mar 2021 10:04 pm

Re: I found it! A very sorry looking MK14.
 
Quote:

Originally Posted by SiriusHardware (Post 1354181)
That's the thing, they are very high maintenance, but worth keeping in tip top condition. One thing you should never do is try to clear a hole which you suspect might have a broken component or IC pin in it, once something like that gets jammed in the narrow channel in the nozzle, it's never coming out.

You will laugh then when you see the video - almost every pin from the chopped off edge connector de-soldered from the expansion board at the back as well as the hole and got sucked into the channel - luckily as they were fat and cut off they jammed poking out and a pair of pliers allowed them all to be removed... luck rather than judgement.

Buzby123 16th Mar 2021 10:24 pm

Re: I found it! A very sorry looking MK14.
 
Thanks for your ideas.

Regarding losing my 'custom mods', the 5mm LEDs and switches on the panel connect to the 8154 via the edge-connector, so they will still work.

The 7-seg display LEDs are connected with a plug and socket, so they will still connect as before.

The keyboard again is on the normal edge connector, so no change there.

The only part of the daughter board that affected the front panel was the single-step switch, and as none of the toggle switches were labeled, I don't see that as a major problem.

Regarding removing the IC sockets, using a powered desolderer definately sounds like the best route. I'll look into them.

Also, I've found the original manual, the instructions for the cassette interface, an update leaflet for the 'revised' monitor, and a few other pages about programming.

To top that, I found my notes for building the daughter board, including a description of the 32 way connector.

I'm back on track again !.

Cheers,

Buzby

Timbucus 16th Mar 2021 10:27 pm

Re: I found it! A very sorry looking MK14.
 
Excellent that you have found the documentation - especially the daughter board.

I shall look forward to more updates on the project... and I am sure we will all render opinion as needed :)

Tim

Quote:

Originally Posted by Buzby123 (Post 1354199)
Thanks for your ideas.

Regarding losing my 'custom mods', the 5mm LEDs and switches on the panel connect to the 8154 via the edge-connector, so they will still work.

The 7-seg display LEDs are connected with a plug and socket, so they will still connect as before.

The keyboard again is on the normal edge connector, so no change there.

The only part of the daughter board that affected the front panel was the single-step switch, and as none of the toggle switches were labeled, I don't see that as a major problem.

Regarding removing the IC sockets, using a powered desolderer definately sounds like the best route. I'll look into them.

Also, I've found the original manual, the instructions for the cassette interface, an update leaflet for the 'revised' monitor, and a few other pages about programming.

To top that, I found my notes for building the daughter board, including a description of the 32 way connector.

I'm back on track again !.

Cheers,

Buzby


Mark1960 16th Mar 2021 11:14 pm

Re: I found it! A very sorry looking MK14.
 
I was looking for one of those solder suckers recently but could only find the 240v version on amazon. 240v is available here, but uses two 120 v live supplies with 180 degree phase, maybe not a good idea to try and use uk 240v powered items.

ortek_service 16th Mar 2021 11:50 pm

Re: I found it! A very sorry looking MK14.
 
If you really want to replace those TI sockets, then the easiest thing to do to minimise damage to PCB tracks is usually to pull the tops off first, leaving the pins behind. You can then just heat each pin up and pull out one-by-one.

Back in the 80's, I used this to remove lots of these from some surplus PCB's, and then reassembled the sockets to reuse as I didn't have any stocks of sockets (well I was still at school then, and Maplin shops had only just started to open around the country / didn't want to pay Tandy's prices!)

You may also be able to clean pins and carefully push the tops back on.

Although these TI sockets never had tight grip pins, I didn't have any trouble with them back then. And I still use some very similar looking DIL16 & DIL14 Cambion ones (with 2 Kapton tape strips on underside to stop solder going into socket contacts, rather than single white plastic piece on TI ones), that I bought a few hundred for a few pence each from a surplus place in the early 90's.

Some contact cleaner spray into sockets, and cleaning of IC pins may also work quite well. Even just lifting IC's and re-inserting a few times may work for a while.

Buzby123 20th Mar 2021 8:48 pm

Re: I found it! A very sorry looking MK14.
 
Hi All,

I've got the crappy IC sockets off, and only lifted one track !. The TI sockets are gold-plated, so I just cleaned them with a squirt of isopropanol and an electric toothbrush.

Now, before I fit the new sockets, I need to re-make the tracks I cut 42 years ago.

Are there scans of the Issue 2 board available anywhere ?.

Cheers,

Buzby

Timbucus 20th Mar 2021 8:58 pm

Re: I found it! A very sorry looking MK14.
 
1 Attachment(s)
Not seen a clean scan but, snatched the attached clean-ish photo from a bay sale in 2019

Timbucus 20th Mar 2021 9:01 pm

Re: I found it! A very sorry looking MK14.
 
1 Attachment(s)
Don't forget that it would be worth leaving the approved mods on the board to create the memory hole and remove the SCIOS images...

Timbucus 20th Mar 2021 9:06 pm

Re: I found it! A very sorry looking MK14.
 
Obviously the top will be harder to get a clear view of

Buzby123 20th Mar 2021 10:28 pm

Re: I found it! A very sorry looking MK14.
 
1 Attachment(s)
Unfortunately it's the top I'm having the most trouble with !.

I've cut so many tracks around ICs 16 & 17 it's difficult to see what they were originally. I'll probably have to use the circuit diagram to work it out.

Regarding the 'official mods', I'm not sure if I did them as per the instructions posted in this thread.

These are the instuctions I followed, from the 'Instructions for Revised Monitor' leaflet. There is no mention of swapping C6, and mine is still in it's original postion. These instructions applied to the Single-Step, and are described as resolving a conflict between ROM data and status during NADS.

I'm not too bothered about the duplicated ROMs anyway. Micky is not going to be used for any further experiments, I've got Vicky for that.

Cheers,

Buzby


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