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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 19th Feb 2016, 5:18 pm   #1
jay_oldstuff
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Default 4116 DRAM Tester.

Hi all, anyone know of any plans for a simple 4116 dram tester I have lots of used 4116's and would like to weed the bad from the good. I have in the past used a zx spectrum with a socket in place of one of the lower ram ic's for this. trouble is the failure mode in some 4116 ic's is to draw excess current on one of the supply lines which tends to kill one of the transistors in the spectrum's power supply circuit.

I'm sure there must have been a tester circuit published in one of the electronics mags in the early 80's (I have projects for simm testers from the 90's) but unfortunately I didn't start buying electronics mags until the early 90's.

Jay
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Old 19th Feb 2016, 10:48 pm   #2
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Default Re: 4116 DRAM Tester.

I've been looking for something similar for some while - without success. There is a blog post I found that looks promising as a start - http://axlecrusher.blogspot.co.uk/20...m-testing.html

This is for 4164, but I would thing some tweaking of the code plus sorting out 12v, 5v, and -5V rails may be fairly straightforward.

It's on my to-do list, but I probably won't start for at least a month or so...
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Old 20th Feb 2016, 2:44 am   #3
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Default Re: 4116 DRAM Tester.

How about using a PC I/O card, or the GPIO pins of a Raspberry Pi, to interface (almost; the Pi will need some additional parts, as it uses 3.3 V logic) directly to the data and address lines of the memory IC? Use fusible resistors on the power lines, and maybe some spare inputs to prove their integrity?

EDIT: A 4164 just has an extra address line compared to a 4116; so it has twice as many columns, twice as many rows and therefore 4 times the capacity (64K bits a.o.t. 16K bits).
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Old 20th Feb 2016, 9:58 am   #4
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Default Re: 4116 DRAM Tester.

This might be feasible, but getting the signal timing correct would be tricky. To ensure that the 4116 is correctly refreshed, all 128 rows must be accessed every 2 milliseconds. This means that a read, write or refresh cycle to each row must occur more frequently than one every 15 microseconds.

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Old 22nd Feb 2016, 2:06 am   #5
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Default Re: 4116 DRAM Tester.

Quote:
Originally Posted by jay_oldstuff View Post
I'm sure there must have been a tester circuit published in one of the electronics mags ...
There was a DRAM tester construction project published in the May 1991 edition of Radio Electronics magazine:
https://archive.org/stream/radio_ele...ge/n0/mode/2up

Unfortunately, 64K is the smallest size DRAM that it can test. Nevertheless, as the description is quite detailed, it may be possible to modify the design for 16K devices.
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Old 22nd Feb 2016, 7:47 pm   #6
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Default Re: 4116 DRAM Tester.

Lovely the way it's been presented online as a readable 'magazine' but unfortunately that project uses a couple of programmed PALs.

The logic diagrams for both are given but not everyone has the required combination of editing software and hardware programmer to make their own, especially now that so much time has passed.

At the time they were probably available from one or two third party suppliers much like parts, PCBs and programmed devices for Elektor or Wireless World projects often were.

Mid to high end eprom programmers often included a 'universal tester' function most commonly able to test 7400 and 4000 series logic ICs, but some could also test SRAM and DRAM ICs as well. Might be worth keeping an eye out for something like that.
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Old 22nd Feb 2016, 11:50 pm   #7
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Default Re: 4116 DRAM Tester.

I've been pondering this again and I'm considering hacking my test spectrum some more basically isolate the 12v 5v and -5v lines from the lower ram and feed those from a separate current limited supply (I know the 4116 is picky about the sequence its supply lines are disconnected in but that's not insurmountable) this would leave the spectrum to run a simple ram test program. In fact (and I'm thinking out loud hear) I've a couple of ZX81 16k ram packs that use 4116's wonder if one of those could become the basis of a tester. I have spare edge connectors and the circuit is simple enough to trace out and modify. And it would be a cool practical use for one of my XZ81,s

Jay
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Old 13th Mar 2016, 12:46 pm   #8
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Default Re: 4116 DRAM Tester.

I now have working a very simple tester for 4164 RAM, and am waiting for delivery of several components to setup -5V and +12V supplies from the 5V rail. Once these arrive, I'll modify the code to try and test 4116 RAM.

In the meantime...

Has anyone got any known faulty 4164 RAM? I could do with a couple of faulty chips to make sure I get error handling right and a suitable 'Fail' message to appear on the (not yet fitted) LCD screen.

Many thanks

Graham
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Old 14th Mar 2016, 7:51 pm   #9
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Default Re: 4116 DRAM Tester.

Well done on the project - (I spy an Arduino?)

Running your test without a device in the test socket ought to produce a 'fail' result so you can see your failure message routines working, or you could force specific errors for test purposes by bending a selected address or data pin out horizontally so it doesn't make contact with the test socket. (Or just pull the relevant wire out of the breadboard)

Have you included some kind of overcurrent detection / protection? From what Jay said, this is likely to be something which will come up from time to time.
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Old 14th Mar 2016, 10:08 pm   #10
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Default Re: 4116 DRAM Tester.

I'm using an Arduino Mega at the moment, as I have one that I bought for a different (unsuccessfull) project a while back, and I'm slowly teaching myself how to use it! I am currently having what I think are timing issues as I am trying to cycle through memory addresses - a 4132 I found is still testing good as a 4164! When I was testing using a single address, it seemed to work OK, so a bit more work is obviously needed!

I haven't thought about power yet - once I have the 4164 tester working reliably (assuming I ever do!), I will work on the 4116 version. Then look at overcurrent issues as a final step.
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Old 14th Mar 2016, 11:05 pm   #11
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Default Re: 4116 DRAM Tester.

I have loads of dead 4164 and 4116's if you want any. I keep dead ones in a jar for a friend to make jewellery out of.
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Old 15th Mar 2016, 1:04 pm   #12
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Default Re: 4116 DRAM Tester.

Thanks - I'll get back to you once I'm confident that the algorithm I'm using is working reliably. I would be particularly interested in any ICs that draw excessive current as I suspect they will be the biggest challenge to test.
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Old 16th Mar 2016, 12:09 am   #13
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Default Re: 4116 DRAM Tester.

I have plenty of 4116's that draw excess current on at least one of the voltage lines its used as the lower 16k of ram in a 48k zx spectrum and this very fault condition usually results in TR4 and TR5 biting the dust.

Jay
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Old 16th Mar 2016, 10:27 am   #14
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Default Re: 4116 DRAM Tester.

Excellent - if you could keep a couple aside for me, that would be brilliant. I'll let you know when I'm further forward, but probably won't get back to this for about a week.
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Old 16th Mar 2016, 7:47 pm   #15
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Default Re: 4116 DRAM Tester.

Ok no probs, however i go to china on the 25th for six weeks.
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