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ABI IC Tester - Fault **SOLVED**

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    Posted: 19 Jul 2011 at 11:35pm
Dudes
 
I managed to get myself an old ABI IC Tester which was supposed to be a bit faulty, indeed it is.  The unit is manufactured in 1986 and uses a Z80 CPU.  I have not been able to find ANY information, references or even images on the web about this unit.
 
Anybody else have one?  I know P-Man has/had an ABI Boardmaster 4000.
 
The unit cycles through the self-test fine, and all functions appear to be working.  However, when I try to test a TTL it always reports them as bad with a FAIL-n message.  With some TTLs it would for example report FAIL-4, when I remove the TTL and run the test again it will say something like FAIL-5, so the unit is seeing the TTL but not reporting success for a good IC.
 
There are two TMS 27128 eproms onboard (although pics only show one, other is in the programmer during shots duh!), I read these eproms successfully, and viewed the data in a HEX editor.  As far as I can tell the data looks good.
 
I noticed that the programmer ceases to run without either one of the eproms, this implies the data must be good?  No other way to check.
 
 
The main board;
 
 
 
The Power Supply, markings say it supplied 5v and 11V, I measured 5v and approx 10v which Im sure is fine;
 
The board which appears to be controlling the keyboard, ZIF inputs and display;
 
 
 
Id really like to get this working to add to my tool arsenal, any ideas guys where to check first?


Edited by Equites - 21 Jul 2011 at 12:04am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote trm Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 2011 at 12:02am
Hi dude. Pretty sure p-man or possibly Backflipper have/had one of these. Will check tomoz when I'm not on my phone and see if I can find some details.

ABI are a bit random when it comes to giving help it seems: some people seem to have luck and others none :( I'm not aware of any schems or engineers guides but yours isn't one of the most complicated models so there is a fair chance of troubleshooting it IMO.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Equites Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 2011 at 11:36am

Thanks Tim

I noticed the 6116 Hitachi RAM, but also the two D8255AC-2 NEC Programmable Peripheral Interface devices.  I do not know too much about the function of the later, do these have flashable memory on board?  I wondering if these contain the IC data to determine if an IC is good or bad??

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Post Options Post Options   Thanks (0) Thanks(0)   Quote PaulSwan Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 2011 at 5:41pm
It's probably not the CPU, RAM or ROM because it's working and you can use it :)
My guess would be it's something to do with IC testing itself. When testing an IC, I'd verify that the IC has power and there is activity on the signal lines going into it. All the IC's will show as bad if they don't have power when they are tested.
 
The 8255's are programmable IO devices that provides a lot of lines that can be programmed as inputs and outputs. Looking at the board, the LS125's look to be buffering some lines. Likely these are programmed to set the inputs and outputs to match the chip being tested.
 
Look for no power and dead lines on the LS125's or 8255's.
 
Paul.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Equites Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 2011 at 5:44pm
Originally posted by PaulSwan PaulSwan wrote:

It's probably not the CPU, RAM or ROM because it's working and you can use it :)
My guess would be it's something to do with IC testing itself. When testing an IC, I'd verify that the IC has power and there is activity on the signal lines going into it. All the IC's will show as bad if they don't have power when they are tested.
 
The 8255's are programmable IO devices that provides a lot of lines that can be programmed as inputs and outputs. Looking at the board, the LS125's look to be buffering some lines. Likely these are programmed to set the inputs and outputs to match the chip being tested.
 
Look for no power and dead lines on the LS125's or 8255's.
 
Paul.
 
 
Thanks Paul
 
That helps a great deal and makes sense, I never even thought about checking for power and signals at the ZIF end, I will do just that and let you know what I find.  I will also check the 8255's for dead lines.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote trm Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 2011 at 7:42pm
+1 for everything that Paul suggested. The datasheet for the 8255 is here http://pdf1.alldatasheet.com/datasheet-pdf/view/119081/NEC/UPD8255AC-2.html but as Paul says they just give you more IO lines.

The EPROMs will contain the chip test info - probably some form of bit patterns that have the input states and expected output states. When you mention that you get a fail-n with an IC present and then a different code, is the failure code when a given IC present consistent or will the fail code change even if the IC doesn't? It's not critical at this stage - more of a curiosity.

Also, the top-down photo of the main board makes it appear as though a lot of the through-holes aren't soldered very well: the legs don't appear to have wicked the solder up and through to the top. If this is just an artefact of the photo then ignore but if the soldering does indeed appear dodgy I'd be tempted to reflow them. Unfortunately I'll bet this was made with leaded solder so if you do reflow and don't have any leaded solder you're probably better off removing the existing solder before cleaning and reflowing with lead-free. 

This will obviously put a bit more thermal stress on the board so if it looks better than the pictures then I'd probably be tempted to leave this for a while (especially as you're probably going to have to pull some ICs).

IC8 appears to be a keyboard/display IC and the tracks suggest it's interfaced straight to the keyboard/display sub-board connector so I'd ignore that for the time being as you've clearly got some degree of keyboard/display functionality.

Finally, the ZIF socket and keypad soldering look rather fluxy. Is this widespread or localised - if localised it could be an indicator that somebody has done work on the sockets? Could be that if the ZIFs have been replaced for whatever reason that somebody has vaporised some tracks so I'd consider a beep test between each "slot" in the ZIF and the track somewhere closer to the interboard connector - maybe one of the vias, just to check you have electrical continuity.

In terms of general troubleshooting process I'd suggest picking one socket, mapping out which 8255 it's wired to and stimulating test activity on that socket and see what you find. I'd be a bit surprised to find that all of the 8255s have popped so if you can find some bit that is working you'll have an idea of what to expect.

Good luck and it should be a very interesting fix!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Equites Quote  Post ReplyReply Direct Link To This Post Posted: 20 Jul 2011 at 11:53pm
Dudes
 
I checked out the 125's and the 8255 as Paul/Tim suggested, but these checked out good.  Then I remember what Tim said about the soldering work on the PCBs, and had a look.
 
I was suprised at how bad the soldering was, especially for a electronics company specialising on repair equipment lol, so I removed both PCBs and reflowed, once I had cleaned up the flux and replaced the PCBs this was the result;
 
 
It works!!
 
Only problem I found is that all the ZIF sockets plates are badly tarnished, and occasionally (especially the 20 pin ZIF) reports a bad TTL even though it is good.  Just budging it a bit resolves the problem though.
 
So new ZIF sockets are on order!
 
Thanks guys for all the help.


Edited by Equites - 21 Jul 2011 at 12:03am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote guddler Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jul 2011 at 12:36am
Excellent! Glad you got it sorted. Unfortunately, that's pretty typical for old ZIF sockets
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Post Options Post Options   Thanks (0) Thanks(0)   Quote trm Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jul 2011 at 1:04pm
Nice work dude Big smile It'll definitely be a useful tool.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Macro Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jul 2011 at 3:04pm
as long as you didn't have my problem - making a test lead up for an ABI DIT-24 and it kept telling me pin 6 was bad - after much checking of connections / swearing and generally getting annoyed, I tested the IC in another tester - yep, it was actually bad (despite being new out of a tube)
 
still, that has gone to another member here now as I have a boardmaster 4000 to play with.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Equites Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jul 2011 at 4:53pm
Originally posted by Macro Macro wrote:

as long as you didn't have my problem - making a test lead up for an ABI DIT-24 and it kept telling me pin 6 was bad - after much checking of connections / swearing and generally getting annoyed, I tested the IC in another tester - yep, it was actually bad (despite being new out of a tube)
 
still, that has gone to another member here now as I have a boardmaster 4000 to play with.
 
Lol - Yes been there, now I never assume an IC fresh from a tube is good, been caught out a few times.  This is why this IC Tester is so useful.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote karlcdoe Quote  Post ReplyReply Direct Link To This Post Posted: 01 Aug 2011 at 1:11pm
Originally posted by Macro Macro wrote:


still, that has gone to another member here now as I have a boardmaster 4000 to play with.


Yes, quite an entertaining toy so far though I'm glad I didn't have to knock up the cable in the end Big smile

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