CBM 710: Replacing Power Supply - Help Needed

From: Micah Bly <micahbly_at_gmail.com>
Date: Fri, 13 Apr 2018 19:04:24 +0000
Message-ID: <CA+7e1fqkTMj+gTXn2=xHxoRtEN8hLY5UWO6bgysWYhPRegfKGg@mail.gmail.com>
Hi All,

I am trying to get a CBM 710 into working shape. I recently acquired this
from a collector, and my understanding is that is has never been up and
running, it was incomplete from the start. There were a few missing chips
and ROMs, but I think I'm basically down to the last part: new PSU.

I am the US, the machine is from Germany. 240V (or maybe it's 220V) 50Hz vs
120V and 60Hz.

I have enlisted the help of a long-time Commodore technician (I don't mean
he worked for Commodore, I mean he has been repairing them for 20+ years
and has his own shop still). I am entirely useless when it comes to
anything more than the most basic circuit.

I have been reading through a few relevant historical posts on CBM hackers,
and looking through other stuff that Google reveals. So far, we have
assembled the following:
- ELM440 frequency generator.
https://www.elmelectronics.com/ic/elm440/
- NTSC color burst crystal
- Mean Well RT-125B power supply.
http://www.meanwell.com/productPdf.aspx?i=491

The PSU seems like it should be fine for the power side of thing, but could
someone help us with designing a circuit for the timing? I showed this
diagram to the gentleman helping me, and he is scratching his head pretty
furiously about it.
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/b/cbm700-ceag-PSU.jpg

My goal here, aside from getting the CBM II back up and running, is to
document it in case somebody else wants to do something similar in the
future. I don't have a web site, so I am using a blog, here:
http://www.vintageisthenewold.com/not-your-daddys-128-retrochallenge-2018-04-update-1/

Thanks,

Micah
Received on 2018-04-13 22:00:02

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