Help Diagnosing Language Card.

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Help Diagnosing Language Card.

I have a "Promethius Products Inc" language card that all of a sudden stopped working.

My first indication that it wasn't working was when booting to the System Master the system locked up when loading integer basic to the language card.

The only memory test I have is in LocakSmith 6.0, and while it rocognized a 16k card exists in slot 0, the memory test shows all errors.

I have tried putting it into another slot, and while LockSmith recognizes it in any slot, it still shows all errors.  I have mode sure all chips are correctly seated and that the cable is plugged into the motherboard.  It has worked (and tested) fine prior to this.  Any ideas how I can diagnose this?

 

 

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It would appear that the D1

It would appear that the D1 bit is stuck. Not sure which RAM chip that is but you could probably trace it out to the edge connector. Or perhaps just replace all of the RAM.

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Luckily all the chips are

Luckily all the chips are socketed. 

At this age RAM faults are getting common. Msg me if you need some 4116 chips (the top row are 4116 equivalents and interchangable) albeit you can probably source them from Jameco or Unicorn Electronics just as easily. 

 

If your card is the same as my clone card (which it appears to be) then D1 is chip C8. 

If you swap it with the one beside it you should get a different value on your errors and restoring their positions you'll get the error value shown. 

CVT
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I suggest using the Apple ][

I suggest using the Apple ][ RAM test Utility v1.4 with the card plugged in and connected to test just the 48K. This will tell you if there is a problem with the ribbon connection, since one of the chips of the 48K sits on the card. If the ribbon connection is fine, I would suspect one of the two chips on the right: the 74LS244 or the 74LS86. (The first one a lot more than the second.)

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Thanks for the tips, guys.  I

Thanks for the tips, guys.  I found I have some 4116 chips around here and swaping those out didn't make a difference.  I'll get that RAM utility running and see what that shows.  I alos see I have a 74LS86 handy, so I'll swap that out.  I'll look around for a 74LS244, there might be one here somewhere.

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Apple's tests would probably call it a "RAM 00000010" error

The card is returning unreliable values for Bit 1, or the binary bit position 00000010 within a byte.

Locksmith's message "Error writing 00(02)..." means that it stored $00 (bits 00000000) and read back $02 (bits 00000010).

Locksmith's message "Error writing 55(57)..." means that it stored $55 (bits 01010101) and read back $57 (bits 01010111).

The card in your picture is not wired like an Apple Language Card, which attaches its RAM chips directly to the bus.  Your card sends pin 14 (Data Oout) of each RAM chip through a 74LS244 Octal Line Driver at U9, and then to the bus.  So that's another component that could fail, which is not uncommon.

 

So there are three likely components that could be cause that behavior: U2, or U7, or U9

  • Faulty 16K DRAM, one of the MM5290N-3 chips at either U2 or U7, whichever position is supposed to store Bit 1.
  • Faulty 74LS244 Octal Line Driver at U9.

 

There are eight identical RAM chips installed in positions U1 through U8, so you can narrow it down by swapping them around.  If the chips are working normally, swapping them shouldn't have any distinguishible effect -- but if one of them is faulty, moving the faulty part will also move the fault to a different location.

  1. To distinguish whether the RAM chip at U2 is faulty, swap it with the RAM chip at U1 and run the test again.  If Locksmith now starts reporting unreliable values at Bit 0, then the faulty chip is the one you moved into U1.  (eg: "Error writing 00(01)...")
  2. To distinguish whether the RAM chip at U7 is faulty, swap it with the RAM chip at U8 and run the test again.  If Locksmith now starts reporting unreliable values at Bit 0, then the faulty chip is the one you moved into U8.
  3. If you tried both of the tests above without affecting the bit position where the error occurs, then the fault is probably coming from the 74LS244 in socket U9.

If it's a faulty RAM chip, there are plenty of compatible 16K DRAM chips you can replace the MM5290N-3 with.  There's a list of compatible part numbers here, they're widely referred to as the "4116 chips" because that's the most popular part number.  For example, Jameco carries two compatible replacement DRAMs, the 4116-15 and MK4516N-15.

 

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CVT wrote:I suggest using the
CVT wrote:

I suggest using the Apple ][ RAM test Utility v1.4 with the card plugged in and connected to test just the 48K. This will tell you if there is a problem with the ribbon connection, since one of the chips of the 48K sits on the card. If the ribbon connection is fine, I would suspect one of the two chips on the right: the 74LS244 or the 74LS86

 

I would concur those are the two most likely chips, and I'd tend to suspect the 244 more.

 

 

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Here's where I'm at:  I

Here's where I'm at:  I replaced all of the 4116 chips.  It made no difference.  I replaced the 74LS86 and there was no difference.

This is the original 74LS244:

 

Here are the results with the original 74LS244:

 

Here is the new 74LS244:

 

and the results (which are very different, but still not working):

 

While I am enjoying this diagosis, I think I may just have to accept the fact I will need to spend another $50 for a replacement.

 

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Here is something I found

Here is something I found that was interesting.  These are a few of the pins from the 16-pin cable connector:

It had obviously been replaced, and not completely soldered.  I did resolder the pads.

I should check continuity and make sure all pins are working.

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kb0wwp wrote:Here is
kb0wwp wrote:

Here is something I found that was interesting.  These are a few of the pins from the 16-pin cable connector:

It had obviously been replaced, and not completely soldered.  I did resolder the pads.

I should check continuity and make sure all pins are working.

That will certainly affect the operation of the card.  Whoever resoldered that did not apply sufficient heat or flux to ensure a good joint.

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Regardless, fixing the bad

Regardless, fixing the bad soldering did not make a difference.  I've already ordered a replacement. 

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kb0wwp wrote:Regardless,
kb0wwp wrote:

Regardless, fixing the bad soldering did not make a difference.  I've already ordered a replacement. 

 

What other chips did you try swapping out than the 74LS244 and the 4116s?

 

 

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