64Kbit DRAM equivalent

Hi Kenny,

Hope things are well!

One of our guys here plays around with Rolands too. I think he modded the Roland to take another sort of DRAM. I'll point him in this direction.

There was also an obscelesence guy posting here befor. I'll try look him out,

Ally 

Hi Ally,

Things are hectic, which seems to be the norm now.

I have some 8-bit DRAM chips in my bins (can't remember the exact part number just now) so I could replace the 4 x 4bit ones with 2 x 8 bit ones - but I'll have to check the schematic to make sure that will work :-), or I could just use 4 of them, and tie the unused 4 bits down. They have more pins though, so I would need to vero board them.

Might just do that anyway for the fun(!) of it.

There must be loads of old 80's equipment out there with old DRAM going dead which you can't get hold of any more.

I saw one guy on eBay selling MN4264 chips for £15 each!!!

Kenny,

Yep, I know that busy feeling!

I found Carl's original notes here http://www.element14.com/community/blogs/Picman/2010/10/12/roland-d50-hacking-time. I know he did complete the project so he should come back with more details

I did find one sellerhttp://www.brokerforum.com/electronic-components-search-en.jsa?originalFullPartNumber=mn4264-12&hasNoSearchCriteria=false&searchPartNoLabelValue=Search+Part+Number but as you say, probably very expensive.

Ally

Hi Kenny

These old chips are like gold dust nowadays. I must have thrown many of them away still stuck in the PCBs from old gear.

I will have poke around my loft and see if there are any old boards from old video cards / samplers etc.

I stopped the rework of my D50 memory for a while as a few personal issues were more important. In-between the rework even my Roland D5 developed a fault in the keyboard scanner gate array chip. These are also very rare, so I might need to make up a gate array 'hack' for the failed scan line using descrete CMOS chips.

It's a shame your memory chips weren't SRAM as these would have been easier to hack other RAM chips to.

ta

Carl

Hi Carl,

Thanks for the information.

The unit in question is a Roland D110, and the fault is in the reverb section.

I managed to obtain a full schematic for it, directly from Roland UK, so I'm hopeful of hacking something together. :-) Of course, as soon as I fix that, something else will go wrong with it!

do you have many of the schematics for old music equipment? I have an Akai S1000 with a duff SCSI interface and I have been meaning to fix it for ages now. I had to give up on an old Roland sampler for the same reason, that and also because the previous owner had already botched the motherboard with some poor soldering with the gate arrays.

Ps I saw some 4264's for sale at $1.00 each here:

http://www.bigdaddy-enterprises.com/electronics/e_ics.htm#ic-proc

ta

Carl

I don't have many schematics for old stuff like that unfortunately, only for a Roland D110 and a Roland EP880.

I saw the BigDaddy stock but I wasn't sure about it because he describes them as '1 bit' which is true for the 4164, but the 4264 are definitely 4-bits wide.

Hi Ken

there was also this:

http://www.mikes-hobby-shop.com/servlet/the-5175/RAM--4264-dsh-15-/Detail

the supplier still describes it as a 1 bit x 64, but as the picture is definitely a 4264, he may just be mistaken

Is it worth a try?

Carl

I tell you what Ken

I have been looking at the data sheet timing diagrams for the 4264, I almost reckon that I can simulate the DRAM with a suitable SRAM, an 8 bit latch and a couple of logic chips. Could you forward the unit's schematic? I could do with knowing how wide the data bus is and how the memory has been implemented.

ta

Carl

Hi Ken

any chance of a copy of tha schematic for the D110?

thanks

Carl