Greenspring Rackmounted Macintosh II help

[YersiniaPestis]

I have this Greenspring RM1200 Macintosh II that I am having trouble with finding any info about.

I am able to jump start it using a coin battery but it powers on with no chime and no power to hard drive. It most likely needs a recapping, but what confuses me is the key mechanism that is attached to the power supply circuit, turning the key counter clockwise shuts down the mac entirely. yet turning it clockwise seemingly does nothing, and doesn't lock the key in that position. The cables for this was disconnected so I'm unsure if I just reconnected them improperly.

I have tried connecting the power supply with this board out of play, but it seems to have wires soldered somewhere to the board, and it wont power on with it disconnected at all. I'm assuming its on the underside of the board.

Motherboard is an 820-0228-A.

I wanted to try to get more info about this machine before I start ripping it apart and looking into a recap and seeing whats wrong with the traces pointed out in the photos.

 

[bigmessowires]

Is this the normal push-button power switch, or something custom? I'm not sure about this version, but the case itself is an integral part of the locking power switch mechanism on the IIcx and IIci. It doesn't work if the logic board is removed from the case. If this rack mount conversion doesn't have the same plastic nubbins in the case surrounding the power switch, then that feature might not work.

 

[YersiniaPestis]

Is this the normal push-button power switch, or something custom? I'm not sure about this version, but the case itself is an integral part of the locking power switch mechanism on the IIcx and IIci. It doesn't work if the logic board is removed from the case. If this rack mount conversion doesn't have the same plastic nubbins in the case surrounding the power switch, then that feature might not work.

There is a power switch in the back of the unit, but it seems to do nothing. It is sadly covered by the metal box with the power connectors in the top right of the first image. I am unfamiliar with Mac II's so I'm unsure if this is original.

 

[YersiniaPestis]

Also I know I am missing the 3.6v battery for the power on circuit, I moved the PRAM battery which is still good there and connected the coin battery via terminals to the pram slot but still didn't power on with the power button. I am receiving new 3.6v 1/2 AA's sometime today to see if that changes anything, but doubtful

 

[Phipli]

There is pretty much always cap damage to the power on circuit on those. There is one particular trace that crosses the board from near the power button all the way over to the Nubus slot area and it always has at least one break. The power circuit is documented online... I'll find the link...

 

[Phipli]

Downtown Doug Brown » Explanation of the Macintosh II/IIx power on/off circuit

www.downtowndougbrown.com

Thank you @dougg3

 

[YersiniaPestis]

There is pretty much always cap damage to the power on circuit on those. There is one particular trace that crosses the board from near the power button all the way over to the Nubus slot area and it always has at least one break. The power circuit is documented online... I'll find the link...

Yeah I figured the power on circuit is shot, hence why I was powering it on by attaching a battery to pin15. I'm more curious as to why I'm not getting anything past PSU powering on though. I was thinking it could be the traces that look damaged in the photos but I'm unsure, I'd hope there'd at least be a chime. Past those I imaged, i didn't see anything else wrong with the board.

 

[Phipli]

Yeah I figured the power on circuit is shot, hence why I was powering it on by attaching a battery to pin15. I'm more curious as to why I'm not getting anything past PSU powering on though. I was thinking it could be the traces that look damaged in the photos but I'm unsure, I'd hope there'd at least be a chime. Past those I imaged, i didn't see anything else wrong with the board.

There is damage visible in the photos. It needs recapping and trace repair.