Closed MOS8701 clock chip replacement kit or assembled - open source -

[Jeff_Birt]

I borrowed an 8701 out of a C128 and wanted a replacement that would nicely fit in the same area. There are other replacements available but I wanted one that was small, easy to build, inexpensive and 'just works', i.e. you can plug it into an NTSC or PAL machine and it will just work. There are no jumpers and the same PCB will work in either machine.

I started with a schematic from Frank, IZ8DWF which uses the same ICS525 clock chip many other MOS8701 replacements do. I shrunk the layout down to a board size of 0.5"x0.9" (12mmx23mm). Not being able to get the commercial offset DIL lead frames in hobbyist quantities I made my own offset legs. I'll link to a video below where I show how the legs are made and demonstrate building a board.

My original intent was not to sell these but just do an open source project. Since the offset legs require machining a fixture to make, and some folks on Twitter were asking about getting some boards/kits I had some PCBs made up and ordered in enough parts to make up a limited number of kits. I am also selling some boards assembled and tested.

The project is on Github and includes the MOS8701/HB replacement as well as an 8701/crystal testing PCB I made. Link below.

I suggest watching the video linked below to see how one is soldered up.

MOS8701/HB Kit $9.95 for 1, $8.95 for 2+
MOS8701/HB assembled and tested $14.95 for 1, $13.95 for 2+

International shipping ~$6 for kit
US Shipping ~5.00 for kit

Easiest way to order is via my website: https://www.soigeneris.com/mos8701-clock-generator-replacement-chip
Github page: https://github.com/Jeff-Birt/MOS8701_HB
Video about design and how to solder: https://youtu.be/e5o8c656j3Q

 

[Deleted member 14264]

BTW, R1 and R2 are absolutely not needed.

 

[Jeff_Birt]

BTW, R1 and R2 are absolutely not needed.

Just had a question about them from the video so I'll copy my response here...

Let's first take a look at what the ICS-525 datasheet days, "A 33ohm series termination resistor should be used on the CLK and REF pins." The purpose of the termination resistor is to reduce signal reflections. There are several different ways to go about this, if you have have a resistor at each end of the signal line to GND or VCC, this would be parallel termination (the CAN bus uses this type of termination for example). Series termination resistors on the other hand are placed near the signal source in SERIES with the signal, which is exactly what I have done per the manufacturers recommendation. Here is a good article which discusses many types of signal termination: https://resources.pcb.cadence.com/blog/termination-resistors-in-pcb-design

 

[Deleted member 14264]

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[Jeff_Birt]

DUDE, what is your issue? Running all over to make comments about this little board I made because 'someone told somebody something negative' about your TOLB? I don't know who it was and nor do I care!

Do you have nothing better to do than act like a child? Grow up! Leave me alone!

 

[Deleted member 14264]

DUDE, what is your issue? Running all over to make comments about this little board I made because 'someone told somebody something negative' about your TOLB? I don't know who it was and nor do I care!

Do you have nothing better to do than act like a child? Grow up! Leave me alone!

My apologies. Because of similarities, I confused you for somebody else.

Added edit: In fact I was the target of a very stupid prank. I should've known better.