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looking for two M5L2716K Memory IC for mc-4
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author looking for two M5L2716K Memory IC for mc-4
sleestack808
I have two chipped IC's in my MC-4 the fits two on the CPU board E and D labeled M5L2716K. They are discontinued. Know where I can find a couple? Anything I should know? Are they standard? Im no expert so experts please help would be appreciated
Synthiq
2716 is a 2kx8 EPROM memory made by many manufacturers and are mostly pin and functionally compatible but at least some TMS2716 from Texas Instruments used 3 supply voltages instead of the usual +5V so avoid these. These memories came in different speed ratings but anything faster than 450ns would be compatible with M5L2716K. There is also the 2816 EEPROM, equally obsolete but functionally identical when read but can be erased electrically instead of with UV light.

These memories were used to store the software controlling a microprocessor so just buying the memory will be of no help unless you have access to the original program and a programmer to copy the program to the memory.

You can find 2716 on ebay of unknown quality and Jameco also sells refurbished 2716.
sleestack808
Ok, So what is the black covering on top of the chip? Is it just a ceramic cover? I have two of those IC's that have chipped off black stuff (like plastic).
Synthiq
UV erasable EPROMs all have a glass window on the top so the UV light can reach the chip. The window may be round as in the picture below or square. To prevent the memory from being erased by mistake from ambient light it is normally covered with a label or some other means.
Modulart_JP
1st off, keep in mind that those chips are EPROM's and therefore they have data programmed in them.
If you replace them you have to program the new chips with the same data.
Any 2716 EPROM will be compatible.
However I'd recommend 27C16 instead. (CMOS version of the EPROM drawing far less current)
In fact, it would be even better to replace them with 28C16 EEPROM's.
They are compatible and since they are EEPROM's, not EPROM's, you can erase them and reprogram them without the need of a UV eraser.
And they might be cheaper and easier to source as well.
sleestack808
yeah, these are covered. Two of them the black plastic is chipped off. Just little bits. But the center where the chip sits is fine. And covered by a sticker. Im just wondering if they'll be ok with e black plastic top slightly chipped. I have the MC-4 apart and might try and put it back together and power it up later,
Synthiq
sleestack808 wrote:
yeah, these are covered. Two of them the black plastic is chipped off. Just little bits. But the center where the chip sits is fine. And covered by a sticker. Im just wondering if they'll be ok with e black plastic top slightly chipped. I have the MC-4 apart and might try and put it back together and power it up later,

It sound like they should be fine as long as the package itself isn't damaged.
sleestack808
Finally powered up the MC-4. Works ok until about 5 seconds then I get a flicker show in the leds and screen. Strange symbols, triangles etc.

I might need an MC4 tech. Not sure if they exist.
Synthiq
Maybe a stupid question, but did you make sure you placed each memory in the original socket so they didn't get swapped?
sleestack808
I haven't removed anything. Just did some cleaning.
sleestack808
It's weird, The flickering starts exactly maybe 8 seconds after starting. So it must be one thing.
sleestack808
Modulart_JP wrote:
1st off, keep in mind that those chips are EPROM's and therefore they have data programmed in them.
If you replace them you have to program the new chips with the same data.
Any 2716 EPROM will be compatible.
However I'd recommend 27C16 instead. (CMOS version of the EPROM drawing far less current)
In fact, it would be even better to replace them with 28C16 EEPROM's.
They are compatible and since they are EEPROM's, not EPROM's, you can erase them and reprogram them without the need of a UV eraser.
And they might be cheaper and easier to source as well.


I’m pretty sure the EPROMs are the issue, I just have know idea how you could program them.
sleestack808
Could a synth tech program them? It sounds really proprietary. I’m getting hopeless about it
roglok
sleestack808 wrote:
Could a synth tech program them? It sounds really proprietary. I’m getting hopeless about it


as outlined by Modulart_JP it is possible to replace/reprogram the chips but obviously you'd need access to data dumps from an uncorrupted set of EPROMS. as the data doesn't seem to be floating around the web it might become difficult to find someone to do the readouts for you. there's a thread somewhere on this forum by a guy who is working on a clone of the MC-4 - maybe try your luck there...

that said, why are you so sure your problems are down to the EPROMS? it could be many other things (like a power issue for example). as others stated, a chipped UV cover is not an indicator that the chip is broken...
sleestack808
Here is a pic of the proms. I don't know. I guess Im assuming the worst. I dropped the cpu board on a hard floor like the klutz I am.

jorg
OK you did chip the ceramic. It's possible that's the problem; I think there are printed traces between the layers of ceramic, to connect the pins to the chip. If you cracked a trace, the chip is effectively dead, though it might still be partially readable.

I'm sure you could find a programmer device to program a fresh set of chips. The hard part (as pointed out by everybody here) is finding a copy of the code - at this point, most likely only inside a working MC-4. Maybe buy a programmer, then advertise to find an MC-4 owner. Of course, the best option might be to buy another MC-4. :-(
sleestack808
I need a tech to fix this. There must be one out there that can specialize in this.
Synthiq
The missing pieces are definitely part of the package itself and not a cover over the UV window which is situated under the white label. This is called a CERDIP package consisting of a top and bottom ceramic piece with some lighter gray cement holding them together. It looks bad but the lead frame that connects the pins to the bond wires are buried in the cement and doesn't seem damaged so the chip can very well be intact. But any force large enough to break the package can also do internal damage like a loose chip or a broken bond wire, or for that matter a broken track or solder joint anywhere on the board.

Unfortunately the EPROMs are soldered to the board. Otherwise I would have removed them and tested them to see if they contained any data.
sleestack808
Id love to send the board to someone. This is beyond me.
I refuse to throw it in the trash over a couple eproms.
Graham Hinton
sleestack808 wrote:
I need a tech to fix this. There must be one out there that can specialize in this.


I can copy, erase and program these devices.
The standard format for the data content is an Intel Hex File which is ASCII and so may be emailed. All good programmers could dump and load this format between a computer, usually over RS232.

It would be a good idea to create a repository of EPROM contents in this format that people could download. If you know the data you can always put it in a larger EPROM and make a site adapter to the 2Kx8 footprint.

jorg wrote:
I think there are printed traces between the layers of ceramic, to connect the pins to the chip.


No. There is a metal lead frame that goes to the centre and then gold wires are ultrasonically bonded between the ends of the leads and the silicon. If you peel off the label you can see this through the window.

I doubt if chipping the ceramic is responsible for this fault, but if you dropped it to cause that who knows what else you have damaged? You may have fractured some of the bonds, but you could see that with a microsope through the window.
sleestack808
Yeah, Maybe bonds in the other eproms. Who knows.
Can I send it to you? It would rule out a huge issue. Everything else seems regular tech worthy.
jorg
I agree with Graham; it's been a long time since I used devices like that and I'd forgotten how to spot the differences. The package in the photo has leads that bend as they exit the package, implying there's a lead-frame that continues in to the chip well. Other ceramic variants welded flat leads to the edges of the package and had printed leads inside ("side-brazed" was the term of art).

Also, yes it's possible the EPROMs functionally survived, hard to say for sure, but that much of an impact could have cracked a trace on the board, or a resistor, or a capacitor...

Because it boots a little bit, my guess is there's one fault somewhere, rather than many. Just a guess.
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