RE: New small sized MOS8701 replacement

That is another interesting way to do it! A chap on FB solved the problem by giving the SSOP28 its own carrier PSC that gets soldered down to the PCB with the pin headers. 

All three solutions require a different sort of hand tweaking to get the job done 😊

 

Jeff Birt

 

From: Pasi Lassila <pasi.lassila_at_gmail.com> 
Sent: Friday, July 10, 2020 2:54 PM
To: cbm-hackers_at_musoftware.de
Subject: Re: New small sized MOS8701 replacement

 

Nice design. I also just finished my design and ordered PCBs from JLCPCB. It's called neat8701 as it is similar design style as neatPLA  https://github.com/1c3d1v3r/neatPLA

 

It has all parts on the bottom side. You can use an oscillator soldered to the PCB or original crystal on C64 motherboard.

NTSC/PAL selection is done with a solder bridge.

 

I solved the IC width problem by cutting the IC pins a little bit shorter with flush cut pliers. I made a custom PCB footprint for it.

The PCB pins are soldered from the top side. The through hole pads have smaller diameter annular ring on the bottom side to make more room for the IC.

PCB rendered images:

https://imgur.com/a/zcvUqkw  

 

The configuration is "45-55% duty cycle, lowest jitter".

I'll compare it to the "no duty cycle restriction, lowest jitter" configuration which many other uses. I'll change the connection if necessary.

 

Later on the design will be shared at github.

 

-Pasi

 

On Fri, 10 Jul 2020 at 21:21, Jeffrey Birt <birt_j_at_soigeneris.com <mailto:birt_j_at_soigeneris.com> > wrote:

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.