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

SiriusHardware 10th Nov 2020 4:24 pm

Re: I found it! A very sorry looking MK14.
 
Can you try testing those ICs as type 7445 instead? Should work I think, the tester should just put pullups on the outputs. Just wondering if the TS200's test algorithm / truth table for 7442 is incorrect/faulty but the one for 7445 is OK?

Buzby123 10th Nov 2020 7:04 pm

Re: I found it! A very sorry looking MK14.
 
Tried testing chips as 7442 and 7445, all test bad.

Lashed up a breadboard, inserted 7442, wiggled d0-d3, ten outputs changed as expected.

So from that we can deduce my TES200 is not as clever as it should be.

TES told me all the other TTL parts are OK, and I'm tempted to believe that, as when I scope the board all the pins I expected to wiggle are wiggling.

But still no nearer to getting Vicky running

The only chips not tested yet are RAMs and ROMs.

Cheers,

Buzby

Buzby123 11th Nov 2020 1:10 am

Re: I found it! A very sorry looking MK14.
 
1 Attachment(s)
I've got dozens of vintage TTL chips, but not a single 7445 among them !.

Although I'm now fairly certain the problems lie in the ROMs or RAMs, I have one last check on the PCB.

I don't know the orignator of this VI board, but there is a number on the back which I think is a fab shop batch identifier.

The number is in tiny print, an inch below the 'S' of science. The number on my board is '2364469A-Y118-200602'. If this matches any known working VI them we know they came from the same production run, and mine should be OK.

A faulty PCB is a real long shot. All the points I've probed with a scope show good signal levels and shapes, and I even dug out my 308 logic analyser ( contemporary 1981 kit !) to see the what the data bus looked like for reads and writes. ( I must learn to use this bit of kit properly, I've had it long enough. )

If I don't get Vicky working, I won't get Micky working either.

SiriusHardware 11th Nov 2020 9:22 am

Re: I found it! A very sorry looking MK14.
 
I'll look when I get home but I know that my board and Tim's came from a one-off batch of five which are all accounted for so yours is not one of them - ours are black, not green.

Whoever had yours made had their own batch of five or more independently made so the PCB manufacturer would have treated it as an entirely separate run with no relationship to our batch. There is no way for us to know whether whoever had yours made made alterations for some reason, although that would not have been a sensible thing for them to do given that the original batch work. Unfortunately you are the first other person that we are aware of who has tried to build one of these PCBs so we can't refer you to anyone else who has at this time.

SiriusHardware 11th Nov 2020 9:50 am

Re: I found it! A very sorry looking MK14.
 
If your problem is ROMs, how unlucky are you to have at least one duff IC in both sets of PROMs? If RAM, how unlucky to have at least three faulty ones out of four? It would have taken some odd kind of catastrophe to wipe all of those out but leave the TTL untouched.

The SC/MP itself, I would imagine you can only really prove by substitution.

Buzby123 11th Nov 2020 3:55 pm

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

Originally Posted by SiriusHardware (Post 1309307)
... how unlucky are you to have at least one duff IC in both sets of PROMs? ...

Yes, that's the story of my life. The only luck I have is bad !.

I started to rig-up a ROM dumper, but then remembered that the MK14 rewires both busses, so I wasn't sure if I was going to get the same values back as expected. I am however going to test the RAMS, at least I know I should get out what I put in.

On order is a new set of TTL parts, so no doubt then about their provenence.

Cheers,

Buzby

Slothie 11th Nov 2020 5:13 pm

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

Originally Posted by Buzby123 (Post 1309461)
Quote:

Originally Posted by SiriusHardware (Post 1309307)
... how unlucky are you to have at least one duff IC in both sets of PROMs? ...

Yes, that's the story of my life. The only luck I have is bad !.

I started to rig-up a ROM dumper, but then remembered that the MK14 rewires both busses, so I wasn't sure if I was going to get the same values back as expected. I am however going to test the RAMS, at least I know I should get out what I put in.

On order is a new set of TTL parts, so no doubt then about their provenence.

Cheers,

Buzby

The MK14 only plays fast and loose with the address lines on the RAM. The ROM address and data lines are wired as specified on the chip.

Mark1960 11th Nov 2020 5:29 pm

Re: I found it! A very sorry looking MK14.
 
If I can find time later today Iíll try running my MK14 with RAM removed, then maybe if you get the same symptoms with no RAM it might indicate your PROMs are ok.

Looking at the monitor code it might not show anything on the display with no RAM, the digit counter is held in RAM so I think should be 0F with no RAM fitted.

SiriusHardware 11th Nov 2020 5:57 pm

Re: I found it! A very sorry looking MK14.
 
As Slothie says, although the wiring to the RAMs is scrambled - it was scrambled on the original machines and is scrambled on the issue VI - the wiring to the PROMs is exactly as per databooks so PROM D0 -is- DO, PROM D3 -is- D3, PROM A0 -is- A0, PROM A8 -is- A8, etc. (Bearing in mind that system D4-D7 will actually go to D0-D3 on one of the two PROMs).

I have a device programmer which can read and program most of the PROMs which are pin compatible with the MK14, I have programmed quite a few sets without problems and certainly without having to rearrange the order of bits or addresses in the code. If reading the PROMS you can make your life a little bit easier by making a jig with the high and low PROM wired side by side so you can read the contents of each address from both PROMs as a single 8-bit byte, as that will be easier to compare with the monitor listing (your 'Old' OS PROMs should match the listing in the MK14 V1 manual).

Mark1960 12th Nov 2020 12:31 am

Re: I found it! A very sorry looking MK14.
 
I tried remove each RAM chip one at a time, I only have the standard pair of RAM fitted. Result in both cases was all segments on bright on the rightmost digit and all segments on dim on the second from right. I didn’t want to try leaving it running like that for long enough to take pictures.

When I was first trying to get my MK14 running again, before I replaced the RAM chips, it was still showing four digits and two digits in the correct place but stepping through memory would make it jump to random addresses on the display. I was fairly sure it was a RAM issue, which turned out to be the case, but it was only partially faulty RAM.

Buzby123 12th Nov 2020 5:46 am

Re: I found it! A very sorry looking MK14.
 
With 0,1, or 2 RAM chips I get the same result, 'X XXX XX', where X is a flickering digit.

With no ROMs, I get all digits, all segs.

In a few days I'm getting a set of brand spanking new TTL chips, so I can replace all those vintage bits.

I don't remember having all these problems 40 years ago.

This retro computing was easier when it was cutting edge.

Cheers,

Buzby

SiriusHardware 13th Nov 2020 10:16 pm

Re: I found it! A very sorry looking MK14.
 
1 Attachment(s)
I've dug up my drawing for a 2-PROM to 2716 adaptor (for the purposes of reading a pair of PROMs as though they are a 2716 in an EPROM programmer) - I've tidied it up a bit and thickened all the lines so that it will hopefully still be readable after the forum has crunched it down.

Buzby123 16th Nov 2020 2:36 pm

Re: I found it! A very sorry looking MK14.
 
Well, I've replaced every TTL chip in Vicky with a brand new one, but no change in behaviour.

I've tried every combination of my four 2111s, but no change in behaviour.

The only change comes if I swap 'old' for 'new' ROMs, but neither set gives sensible results.

circuitryboy 16th Nov 2020 11:52 pm

Re: I found it! A very sorry looking MK14.
 
The display pic you posted (for SCIOS?) showed the dominant binary pattern x0F.
What is the different (SCMPKB?) display?
The Display/Keyboard code in both monitors is the same.
From Reset, SCIOS would be outputting '0000__00' and SCMPKB '----__--'.

SiriusHardware 17th Nov 2020 6:01 pm

Re: I found it! A very sorry looking MK14.
 
While we await the outcome of other avenues of investigation, earlier on, you said that you had tried 'exercising' the upper address lines and scoping the _CE signals for activity, which you did see.

I suggest that you now need to specifically check whether address A8-A11 state =nnnn actually results in the expected _CE signal being activated, so,

xxxx1111xxxxxxxx (0Fxx) should activate both _CE pins on the standard RAM ICs

xxxx1011xxxxxxxx (0Bxx) should activate both _CE pins on the extra RAM ICs

xxxx1000xxxxxxxx (08xx) should activate _CE on the RAM I/O

xxxx110100000000 (0D00) should activate the strobe signals to the display output hardware. For this last one you will probably need to assert NWDS low as well once the address is established.

SiriusHardware 4th Dec 2020 8:28 pm

Re: I found it! A very sorry looking MK14.
 
A little update on this - as has been mentioned in PMs, Buzby's PROMs - both sets - turned out to be OK, so I sent them back to him and I've just received his 4 * 2111 RAMs for testing.

Unfortunately all four of the 2111s have turned out to be dud. I have some of the IM65X61 RAMs which the issue VI (only) can use as alternatives and I'll be happy to let Buzby have four of those, but of course he will still need actual 2111s for the resurrection of his original Mega MK14.

Does anyone know where they, or AMD AM9111s can be had for sensible money at the moment?

Mark1960 4th Dec 2020 10:24 pm

Re: I found it! A very sorry looking MK14.
 
I did have the Am9111bpc in my cart at utsource but I just checked and its no longer there. I think they were listed at usd $2.70. Tried searching again but the price was up to usd $5.33 and showing as certified used. Best option now is listed under P2111A-4 for usd $2.83 also certified used but shows picture of AM9111BPC. I placed my order with ten of these included, take a chance on what I get.

Last set I ordered didnít originally state certified used but in my order history this is now showing, but the parts looked unused to me.

Local shop has AM9111BPC at cad $15 each, AM9111CPC at cad $7 each and SYP2111A-2 at cad $7 each. Iíll consider this if the utsource parts are no good but donít think its worth shipping to uk at those prices.

Utsource also list the AM27S13/BEA as third part original at usd $2.13 each so Iím taking a chance on ten of those too.

Shipping cost is a bit high and then probably customs handling and duty, but I have lots of other things included to help absorb that overhead.

SiriusHardware 4th Dec 2020 10:31 pm

Re: I found it! A very sorry looking MK14.
 
I notice that Cricklewood (a respected old component supplier in the UK) have them:

https://www.cricklewoodelectronics.com/2111.html

That's pretty expensive, though. What I found interesting is their statement that the 2111 is an equivalent of the TMS4035NL - that's an equivalent I had not stumbled across until now.

Edit: Information from circuitryboy, the information above is incorrect, the TMS4042NL is the 2111 equivalent device, not the TMS4035NL as stated above and on Cricklewood's website.

Buzby123 4th Dec 2020 11:56 pm

Re: I found it! A very sorry looking MK14.
 
All thanks to Sirius for testing my PROMs and RAMs.

I can get Vicky working with 6561s, and I don't mind that. For Vicky, function is more important than form.

Micky will need 2111s, but I've still got other work to do before I need to fit RAM.

This project has been a real PITA. I've spent lots of time and money on it, and the end result, if I ever get there, will be my 42 year old 'computer' working just as it did 42 years ago.

Why am I doing this ?

SiriusHardware 5th Dec 2020 12:29 am

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

Originally Posted by Buzby123 (Post 1317530)
Why am I doing this ?

Simply this:-

>the end result will be my 42 year old 'computer'
>working just as it did 42 years ago.

There is no higher or more noble reason. ;)

Joking aside, if you get Micky working either in its highly customised form or just in its original single-board form, the increase in the value of that machine should greatly outweigh what you've spent on new TTL etc, and actually all of that new TTL can stay in the replica which will then have a re-sale value in its own right.

circuitryboy 5th Dec 2020 4:24 am

Re: I found it! A very sorry looking MK14.
 
Best I can find for 2111 offers:

https://www.ebay.co.uk/itm/254633994435 (Germany)

SiriusHardware 5th Dec 2020 11:42 am

Re: I found it! A very sorry looking MK14.
 
Circuitryboy, thanks for that very fast and specific response. I've ordered a set of four myself as spares for my two machines, so I'll test them on arrival and give them the thumbs up / thumbs down according to how I find them.

Timbucus 5th Dec 2020 11:47 am

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

Originally Posted by Buzby123 (Post 1317530)
I can get Vicky working with 6561s, and I don't mind that. For Vicky, function is more important than form.

Micky will need 2111s, but I've still got other work to do before I need to fit RAM.

Why am I doing this ?

The 6561's work fine unless you try to use the SOC VDU - but the OrtonView modern VDU should work fine with them.

Good luck on Micky - it will be wonderful to see it fully running.

Because - why have I built so many clones of machines from back then... Because as Sirius says keeping this relatively unknown bit of British computing history alive for the next generation is vital.

SiriusHardware 5th Dec 2020 12:03 pm

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

Originally Posted by Mark1960 (Post 1317512)
Utsource also list the AM27S13/BEA as third part original
.

What exactly does that mean? Obviously any PROMs described as second hand or used / pulled are virtually certain to be programmed already.

Mark1960 6th Dec 2020 12:39 am

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

Originally Posted by SiriusHardware (Post 1317614)
Quote:

Originally Posted by Mark1960 (Post 1317512)
Utsource also list the AM27S13/BEA as third part original
.

What exactly does that mean? Obviously any PROMs described as second hand or used / pulled are virtually certain to be programmed already.

I think third party in this case refers to the various alternate suppliers listed on utsource.

Utsource started including four different categories of components earlier this year. This is the four categories with the additional description :-

Utsource certified original, Original products offered by Utsource. New guaranteed.

Third-party original, Original parts offered by the third-party.

Utsource certified used parts, Used and refurbished parts offered by Utsource are guaranteed can be used normally.

Third-party used parts, Used parts offered by the third-party.

I usually avoid the last two categories.

Third-part original doesnít specify new, but I have had success with parts in this category, previous orders appear to be unused, so I thought it worth taking a chance on the am27s13bea, also I think these are ceramic. If not blank then I can probably still make some use of them in trying to test a programmer.

SiriusHardware 6th Dec 2020 12:25 pm

Re: I found it! A very sorry looking MK14.
 
Thanks for that clarification, Mark.

Circuitryboy has pointed out that the statement on Cricklewood's website (and therefore in my post #118, where I said the TMS4035NL appears to be equivalent to 2111), is incorrect, that IC is actually a 2102 clone.

The correct TMS equivalent to 2111 is apparently the TMS4042NL. My thanks to the mods for making an appropriate edit to post #118.

Buzby123 7th Dec 2020 5:34 pm

Re: I found it! A very sorry looking MK14.
 
1 Attachment(s)
Vicky is ALIVE !!!!!

With the greatest thanks to Sirius, I can now show my Slothie board running.

And, it gets better ......

My ceramic SC/MP is working !.

Can't do much on it tonight or tomorrow, but I'll use the manual for some bedtime reading. Got to re-learn all the stuff I forgot from 40 years ago.

Cheers,

Buzby

EDIT : That's not a wire link from SC/MP to a 157. The wire is on SC/MP pin 5, but I can't remember why.

Slothie 7th Dec 2020 5:40 pm

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

Originally Posted by Buzby123 (Post 1318423)
Vicky is ALIVE !!!!!

With the greatest thanks to Sirius, I can now show my Slothie board running.

And, it gets better ......

My ceramic SC/MP is working !.

Can't do much on it tonight or tomorrow, but I'll use the manual for some bedtime reading. Got to re-learn all the stuff I forgot from 40 years ago.

Cheers,

Buzby

EDIT : That's not a wire link from SC/MP to a 157. The wire is on SC/MP pin 5, but I can't remember why.

Yay! Thats good news. What was the problem in the end? At least you now have a reference for signals to compare when fixing up Mickey,

Buzby123 7th Dec 2020 5:43 pm

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

Originally Posted by Slothie (Post 1318426)
Yay! Thats good news. What was the problem in the end? At least you now have a reference for signals to compare when fixing up Mickey,

Look back a few posts, ALL my RAMs were duff !.

Timbucus 7th Dec 2020 6:41 pm

Re: I found it! A very sorry looking MK14.
 
Nice Ceramic SC/MP II only ever seen the PMOS V1 in the Gold and Ceramic.

Pin 5 NBREQ is supposed to have a resistor pulling it high to VCC which is R1 / R2 depending on JMP/MKIV - not checked originals or ML

SiriusHardware 7th Dec 2020 6:50 pm

Re: I found it! A very sorry looking MK14.
 
Oh, what a relief. ;) So that's at least four built and working issue VIs we know about now, three among us here, and one elsewhere. Another one here imminent, hopefully.

All of Buz's original 2111s were dud, so he was on a hiding to nothing trying to get either of the machines working with those. Vicky is currently running with 4 * IM6561 RAMs, good job Slothie designed that ability in. He must have wondered, when he did, whether anyone would ever use it.

The supplier for the German-source AM9111s circuitryboy flagged up is telling me to expect them on Wednesday this week which will be pretty quick, if so. I'll test mine the moment they arrive and let everyone know whether they are OK.

Buz, don't forget your manual (Version 1?) describes the operation of the machine with the 'old' OS fitted. There is a .PDF of the V2 MK14 manual on Martin L's site here:-

https://www.8bity.cz/files/MK14/mk14ManualV2_OCR.pdf

..which describes the operation of the machine when the 'New' OS is fitted. It's a nice quality scan but be aware that page 88 - part of the 'Moon Landing' game listing - is missing. Really needs someone with the know-how to reinstate the relevant page from the V1 manual.

Buzby123 7th Dec 2020 7:03 pm

Re: I found it! A very sorry looking MK14.
 
2 Attachment(s)
I've just been in the attic looking for my manual.

Of course, it's not where I expect to find it, so I have to look everywhere else !.

I did find this though. Has anyone else seen what SoC were planning ?

SiriusHardware 7th Dec 2020 7:10 pm

Re: I found it! A very sorry looking MK14.
 
I think Tim had already tracked that information down way back in one of these threads but it's nice to see the original letters, you should keep those safe as part of your MK14 'library'. The general consensus was that the plans for expansion of the MK14 were overtaken by the development of the ZX80, and the rest, as they say, is history.

Timbucus 7th Dec 2020 7:26 pm

Re: I found it! A very sorry looking MK14.
 
https://drive.google.com/file/d/1UvE...ew?usp=sharing

With the missing page added back in.

The Center for Computing History has those letters (Product 73300 and 104831) and it is the basis of my assertion that we need to get as far a NIBL and a proper keyboard on the KB Expansion connector... but, as Sirius says that is a great addition to your collection.

SiriusHardware 7th Dec 2020 7:36 pm

Re: I found it! A very sorry looking MK14.
 
Thanks for doing that - very quick! I don't know if I'm just not patient enough but when I follow your link and try to view it I just get a Whirly Circle Of Doom and the document doesn't appear. Check permissions?

It might be a courtesy to forward the restored version to Martin L so he can put it up on his site as well. I did point out the missing page to him a long time ago but he's a busy man with many interests - however, I'm sure that if he was presented with the 'repaired' version he would be glad to put it up.

Timbucus 7th Dec 2020 7:40 pm

Re: I found it! A very sorry looking MK14.
 
Seems to work OK and is set to anyone on the internet - maybe just replication time to whatever cloud server you are directed to?

Good idea - I will drop him a mail maybe I will mention the OrtonView and ask if his mate is prepared to share the code for the Squash game as well!

SiriusHardware 7th Dec 2020 7:52 pm

Re: I found it! A very sorry looking MK14.
 
Hmm, first time it would not appear at all, second try just now it appeared in seconds. I've got it now, thanks.

We're drifiting into general MK14 territory again now, let's keep this thread mainly focused on Buzby's 'Micky' machine, as and when he is able to make progress on it.

Timbucus 7th Dec 2020 8:15 pm

Re: I found it! A very sorry looking MK14.
 
Yes that is what I am looking forward to as well - as it is such an unusual custom modification - good news on the Replica though as that is a basis for testing in parallel.

Buzby123 8th Dec 2020 2:38 pm

Re: I found it! A very sorry looking MK14.
 
Sad news, Vicky has died !.

Last night I managed to get an hour free, so I swapped back to a plastic SC/MP and typed 'Message' in to Vicky. It worked Jolly Fine.

This morning, powered up again, but was met with a single digit. A few more power attempts gave either a blank screen or a single digit.

Not tried any diagnostics yet, but I suspect the SC/MP. Will try a new one tonight.

As I've said before, the only luck I have is bad luck.

SiriusHardware 8th Dec 2020 3:45 pm

Re: I found it! A very sorry looking MK14.
 
What's the single digit, a reverse 'C' or a '0'?

If '0', would suggest the system is being held in reset.

Buzby123 8th Dec 2020 4:33 pm

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

Originally Posted by SiriusHardware (Post 1318732)
What's the single digit, a reverse 'C' or a '0'?

If '0', would suggest the system is being held in reset.

Sometimes it's a T-dot, the exact opposite of reverse 'C'. Sometimes it's 8-dot, sometimes it's just a dot. !

Can't do any testing on it till later.

SiriusHardware 8th Dec 2020 4:38 pm

Re: I found it! A very sorry looking MK14.
 
Hmm, actually, you only get a single 'O' (or with the old OS, '-') if the system is held in reset after it has been running correctly, since the segment output hardware remembers the last character which was sent to it.

Edit: Just caught your response. Sorry to have to ask, but you've checked the +5V rail is spot-on volts wise?

SiriusHardware 8th Dec 2020 6:33 pm

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

1) Visual inspection, no cut-off component leads curled over and getting to know each other on the track side of the PCB? (The sort of thing which could happen after the PCB has been pressed down on a few times).

2) Check the regulated supply voltage if not already done.

3) Remove and check all ICs for possible folded-over pins. While doing so, use your IC tester to re-check all the TTL (except the 7445 which it does not seem to do correctly)

4) Try all possible combinations of two of the four RAMs in the 'standard' RAM sockets, which on the issue VI are the two closest to the PROMs.

5) Try your other PROMs

6) Try another SC/MP.

Buzby123 8th Dec 2020 9:13 pm

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

1) Visual inspection, no cut-off component leads curled over and getting to know each other on the track side of the PCB? (The sort of thing which could happen after the PCB has been pressed down on a few times).

No curly leads.

2) Check the regulated supply voltage if not already done.

4.96v

3) Remove and check all ICs for possible folded-over pins. While doing so, use your IC tester to re-check all the TTL (except the 7445 which it does not seem to do correctly)

I sent the TS200 back, going to buy an identical cheaper one. No bent pins.

4) Try all possible combinations of two of the four RAMs in the 'standard' RAM sockets, which on the issue VI are the two closest to the PROMs.

Not doing that yet.

5) Try your other PROMs

Yup ! '---- --' works, but '0000 00' doesn't !.

6) Try another SC/MP.

Not yet.




Arggggh !

SiriusHardware 8th Dec 2020 10:06 pm

Re: I found it! A very sorry looking MK14.
 
I listed those checks in 'risk order' hence trying the PROMs and SC/MP last as they are the most unique parts which you wouldn't want damaged by, ie, undetected faulty TTL IC.

So it's looking like you have failure of your new-OS PROMs now? If you want, send just those ones back to me and I'll check them again. If one has now failed I can try to over-programme it (reprogram it with the same code) on the off chance that one of the fuses might have managed to re-grow (apparently that can happen, they have a similar problem to the well known 'tin whisker' disease which commonly affects certain types of germanium transistor).

Buzby123 8th Dec 2020 10:46 pm

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

I was surprised to find the ROMs had failed, but that was the easiest test to do first.

The 're-grown whisker' problem, is it related to absolute age, or to hours in action ?.

I'll pop them in the post again, just to see if a reprogram fixes it.

One day I'll have a stable Vicky, then I'll move on to Micky.

Cheers,

Buzby

Edit : If you remember, I put labels on the ROMs. These were from a thermal printer, and the '2o' label is discoloured more than the '1o' label. Maybe this is clue to something, but I don't know what. It will be intersting to see which nibble ROM has failed.

SiriusHardware 8th Dec 2020 11:48 pm

Re: I found it! A very sorry looking MK14.
 
To be honest I'm not sure what the failure mode or mechanism is.

If one of them appears faulty there would be nothing to lose by trying to over-programme it to see if it recovers. You do, as you say, seem staggeringly unlucky sometimes - worked fine for me here and then for you for the space of just one evening.

There is one relatively high-risk stunt you could try, the 'rap' method which is sometimes used to clear tin whiskers in germanium transistors. Put each IC in turn at one end of a longish piece of IC tubing (with a bung in the tube at the same end), hold the tube by the other end and rap the IC end of the tube smartly on a bench top. This supposes that any regrown whisker will be much more fragile than the links which were never intentionally blown, and will break open.

The risk is that too much shock force may break one of the 'good' fusible links, and if you do manage to shatter the (assumed) regrown, unwanted link there is no telling where the remnants of it could end up.

Using a programmer to try to re-blow a suspected regrown link is a much more targeted and less stressful method.

Buzby123 9th Dec 2020 12:37 am

Re: I found it! A very sorry looking MK14.
 
Hmm ?. I don't think I'll try that, knowing my luck I'll probably break the table !.

I don't know the detailed structure of a fusible PROM, but from reading how the programming machines work ( multiple little shots at the same fuse, not one big shot ) it does look like there is a possibilty that a re-program might work.

Although, knowing my luck, it's possible a fuse has gone open by itself. No chance of recovering that.

Before you re-program, maybe take a copy of the faulty code and see if you can deduce which bit(s) have gone wrong.

At a very long shot, it might be possible to re-program a slightly different, but functional code, by blowing existing fuses to make NOPs or a GOTO to skip the bad code. It would lose some functionality, but maybe nothing that would matter short term.

As it is, as long as my '---- --' ROMs keep working, I've got enough to start on Micky.

Cheers,

Buzby

SiriusHardware 9th Dec 2020 2:13 am

Re: I found it! A very sorry looking MK14.
 
Yes, if the IC in question is not completely duff I'll try to see where it differs from what it should be. Will let you know when they arrive and what I find.

Buzby123 9th Dec 2020 2:27 pm

Re: I found it! A very sorry looking MK14.
 
It's a good job you took file copies before this failure !.

Can never have too many copies of these old ROMs, just can't tell when they might come in useful.


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