upper ram tacks / TR4 socket...

https://photos.app.goo.gl/MkqzRCuNCV3EPr9E7

you can only replace that pesky TR4 so many times .... surprises me that with TR4 not in place or when it blows,, that the specie still boots and almost works only when certain keys are entered does start protesting ... i thought it would just fry the lower ram again .. this is one board that should never work looks like somebody attacked the upper ram with a black and decker.. any sugestions for replacing the upper ram tracks ?

Comments

  • edited September 16
    Well, the last Sinclair DC-DC modification helps with the reliability... see here.

    The ULA does not care about the lower RAM, it will just grab whatever ‘data’ there is and display it, whether it is useful or garbage makes no difference. Regarding the Z80 however, well the ROM program does need some working RAM...

    If there is too much damage, then you may want to use a upper RAM replacement module. But before fitting, make sure the ULA side of the data bus lines are complete (no broken connections), all the wanted RAM address lines are connected and the +5V and 0V/GND lines are okay. You can then ignore the now unused broken pads/tracks.

    To repair broken plated through holes, use a couple of strands out of a piece of stranded 7/0.2mm wire. Thread around the component leg (before putting it into the board) and solder (just a little bit, just enough so the strands are soldered to the leg/pin), poke the strands through the hole as you place the component on the board. Solder the underside. Then test that the connection is good with a meter ;-)

    Mark
    Post edited by 1024MAK on
    Thanked by 1harriusherbartio
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