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1 Meg Super AMS Discussion Thread

TI-99/4A 1MEG SAMS AMS

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#251 arcadeshopper OFFLINE  

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Posted Sat Jun 2, 2018 9:41 PM

what's the total assembled so far?  


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#252 Ksarul OFFLINE  

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Posted Sun Jun 3, 2018 10:44 AM

So far, I've put 75 SAMS boards into circulation. I've personally built 51 boards from the 2016 Edition of which 46 are in the hands of other users (I have two of the 51 in my systems and three more on hand and available for sale), the others were sold through your storefront as bare boards or sent to individuals that wanted a bare board from me. Note that Mike Dudeck put another dozen or so from the last group buy into circulation within the last year as well. There are also about 200-250 boards out there from the SW99ers, Asgard, and the 2004 group buy. Lastly, there are eight that Dan Eicher and I made as test boards before the group buy. I have another 40 or so bare boards on hand, and will continue making more of them for as long as I remain with the hobby. The choice between a SAMS card and the regular 32K card is no contest--the price is about the same (when considering PEB boards), but the increased capability can't be beat.



#253 RickyDean OFFLINE  

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Posted Thu Aug 2, 2018 6:04 AM

Well guys, I believe I finally solved it. The board I built last year, has not been working. I have picked it up and tried going over the solder points time and again, reheating, wondering what could have gone wrong. I bought another unit to test the 612 chip and perform other tests, to determine if I had defective parts.

I finally downloaded the schematics, the other day and started doing point to point continuity tests, to see if I I had cold solder joints, starting at the led side of the board and working over. I determined last night that the signal was not making it to the ram chips at the pin 20, on the ram chips.

There was continuity between the chips, but not to pin 17 on the 74LS245, but the circuit from pin 17 to the 612 chip was good. This was about 11:15 PM last night, at 11:30 PM, after throwing on a hasty set of wires, I had the SAMS testing good on my TI. There apparently is a bad trace or via, probably during the production process, between the hole going from the negative side of the capacitor setting between the 612 and upper ram socket, to the hole, just below pins 12 and 13 on the ram chip, that service the pin 20's on both rams.

Attached Files


Edited by RickyDean, Thu Aug 2, 2018 6:12 AM.


#254 RickyDean OFFLINE  

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Posted Tue Aug 7, 2018 6:32 AM

       Well, last night due to being rained in, I watched BladeRunner and sat there cleaning up one of the scanned images of the Geneve layers that Paul Charlton did back in the day. I was doing this so that I could have a clearer view of the holes and traces to repair the Geneve, I recently got from the Insane one.

       While I was there I was using my high magnification specs, and found the issue with the  trace on the Sams board, shown on the prior posting. Apparently when I had added the the 32 pin Ram socket at the top, I went ahead and trimmed down a machined socket to add the additional pins for the possibility of upgrading to the full capacity of the board in the future, making 36 pins. In that trim down process I had set the 4 pin socket extension down and trimmed off some excess plastic, on the board. In that process I seem to have went down on the board and sliced the trace.

      I will post a picture tomorrow, had it on my phone, but forgot it when I came to work this morning. I had blamed the manufacturer of the board in my post above, so wanted to set the record straight. Should be repairable at the slice point, but it is so small, you can barely make it out, at least with my old eyes.



#255 Ksarul OFFLINE  

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Posted Tue Aug 7, 2018 4:57 PM

Finding a minor cut trace can be a real pain, especially when the board has been worked on several times. Ask @arcadeshopper about the weird traces I found on a disk controller board last year. There were a group of cut and shorted traces under the EPROM sockets. . .I cleaned them up and the board worked perfectly.



#256 RickyDean OFFLINE  

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Posted Wed Aug 8, 2018 5:57 AM

Well, I got the traces cleaned back, about an 1/8th of an inch on both sides and then soldered the trace. She's testing well, no more wires. The pic here is what I said that I was going to show yesterday... The circled area is where the trace was knicked.

Attached Files


Edited by RickyDean, Wed Aug 8, 2018 6:00 AM.


#257 --- Ω --- OFFLINE  

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Posted Wed Aug 8, 2018 7:55 AM

I'm envious of those with younger eyes,  I simply would never have found the problem.  It's actually irritating not being able to tackle projects once taken for granted.



#258 RickyDean OFFLINE  

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Posted Wed Aug 8, 2018 8:39 AM

I'm envious of those with younger eyes,  I simply would never have found the problem.  It's actually irritating not being able to tackle projects once taken for granted.

I'm probably older than you, born 1959.  :-D



#259 --- Ω --- OFFLINE  

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Posted Wed Aug 8, 2018 8:58 AM

I'm probably older than you, born 1959.  :-D

 

Yeah, you got me beat, but not by much. 



#260 chue OFFLINE  

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Posted Wed Aug 8, 2018 9:17 AM

I'm envious of those with younger eyes,  I simply would never have found the problem.  It's actually irritating not being able to tackle projects once taken for granted.

 

I use a couple of tools to help me work on boards.

 

One is a USB microscope ($30), which I use for soldering.  The only trick is that it doesn't give me 3D vision so it's hard to tell where my soldering iron is sometimes. 

 

The other tool I use is a proper digital camera.  I take photos of boards and then view (inspect) the results on my large monitor.

 

The attached photo is a shot from my microscope.  Just to give you a sense of scale, the grey squares on the left are 5 x 5 millimeters each.

Attached Files


Edited by chue, Wed Aug 8, 2018 9:55 AM.


#261 Ksarul OFFLINE  

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Posted Wed Aug 8, 2018 6:30 PM

That's really nice for fine-pitch soldering. As to the age thing, I have Ricky Dean beaten, but also not by much. What's a year between friends?  LOLOL



#262 atrax27407 OFFLINE  

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Posted Wed Aug 8, 2018 6:42 PM

Young "whipper-snappers"!







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