Wednesday, 6 November 2013

ZX Spectrum +/48k - Lower 16K RAM Repair

So my spectrum's lower 16K RAM failed about a year ago. Basically the machine would not load programs properly and sometimes freeze on power on (Black screen with grey border). Initially I thought the internal power circuit was playing up causing instability, but I checked it wasn't. All the voltages were present and stable. Next I replaced all the 30 year old electrolytic capacitors thinking this would sort the problem. But still the same issue persisted. Lastly I did the "PRINT PEEK" basic commands stated over on the Spectrum repair guide, and confirmed that the one of the lower 4116 DRAMs had failed.





















The lower 16k RAM is implemented across 8x "4116" DRAMs at the bottom left of the main board. (See picture above) IC: 6,7,8,9,10,11,12 and IC13 on my Issue 4S board. As you can see I've already de-soldered them! Soon as I confirmed the lower rams had failed I removed them all ready to see if I could replace them. 

The removed RAM 4116 IC's:


    

















With my spectrum sat in storage unable to use. Nearly a year later I found a suitable replacement for the failed RAM. Over on zx.zigg.net newly manufactured memory modules designed as a drop-in replacement for the lower 16k RAM are available to buy! I brought one straight away. The module is a small pcb that is soldered in where the original DRAM's sit.

The module soldered in to my spectrum board:





















The DRAM's can be replaced with IC sockets then the module installed on to them, but I soldered mine directly to the board. I left a 5mm gap between the boards to avoid short circuits. 





















A quick power up test with the the new ram and the system booted as normal again:




















Games load perfectly again!


















The repaired system reassembled. Running Bomb Jack 2 from divide 2k11 interface.




















Links:

http://www.worldofspectrum.org/SpectrumRepairGuide/

http://zx.zigg.net/


1 comment:

  1. Thanks for sharing this post.
    Om Nanotech offer complete range of Non-ECC DRAM modules. We are DRAM Components Supplier Distributor in India Delhi/NCR.

    ReplyDelete