New small sized MOS8701 replacement

From: Jeffrey Birt <birt_j_at_soigeneris.com>
Date: Fri, 10 Jul 2020 13:17:56 -0500
Message-ID: <035e01d656e6$6ff348d0$4fd9da70$_at_soigeneris.com>
I have been working on a MOS 8701 clock chip replacement that is just a bit
bigger than the original so it will fit into a C128 with the RF shield cover
in place.

The design is based on Frank IZ8DWF's design from one of his videos. The PCB
size is about 0.5"x0.9" with the holes on 0.4" centers. This was needed to
make room for the SSOP28 clock chip.



The 0.4" spacing required making a fixture to custom bend some leads into a
'Z' shape. And another fixture is used to align the leads for soldering. To
make it even more fun the resistors and caps are 0603 size which is about as
small as I care to do without a proper microscope. I built the first board
this morning and it works!! It takes a fair amount of time to build one of
them, and you need the special fixtures for the leads, but it was an
interesting challenge.



This version of the PCB uses cut pads to configure NTSC or PAL. I have a new
design that should do this automagically. I should have some of those PCBs
in a few weeks for testing.

 

_at_IZ8DWF - Frank when I am able to confirm that PAL works, I will send you
some completed units, gratis. 

Links to images

 

https://1drv.ms/u/s!AtH4vpaZnzX7kvswntJpVdEm6W-OrQ?e=4wnmac
https://1drv.ms/u/s!AtH4vpaZnzX7kvsts_rsv_eTHoKL7w?e=TlqTnX
https://1drv.ms/u/s!AtH4vpaZnzX7kvsuRF1lVXL5UNJLgA?e=NjEhZa

Jeff Birt (Hey Birt!)
Received on 2020-07-10 21:00:03

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