SD2100 Mods

[jtz54]

Looking at modding an SD2100. Haven't found a schematic posted. Does one exist?
Would the crystal mod for the SD2000 work for the 2100 or is the frequency generated another way?
What are the differences between the 2000 and 2100?

[Mechanic]

Hi Jtz,

For the most part the 2100 is exactly the same as the 2000. The major difference is that the timing logic cct on the 2000 is replaced by an eeprom on the 2100. The 2100 doesn't use crystals for its clock frequency, I'm pretty sure it uses an LC oscillator cct. Basically to make frequency changes, set the cap on the board to give you the highest frequency you want, then use a switch to switch more capacitance in parallel to lower the frequencies. It is better having the oscillator this way as emi can be tuned out via the fine tune pot, whereas with the fixed crystals your stuck with that operating frequency.

There will also be some different timings timings stored in the eeprom. There is a jumper there that changes between them, add a switch in place of the jumper too.

Is it the original green 2100? If so, replace all the electro caps.

Cheers Mick

[jtz54]

Thanks Mick, any clue to the location of the LC circuit? I know everything will be covered in white paint.

[Mechanic]

It will be pretty much right next to the eeprom toward the rear end cap in the corner of the board. It will most likely run with a 74hc00 and the 74hc00 will provide the clock signal for a 74hc4040 that switches the address pins on the eeprom.

Cheers Mick

[Altra]

If you have not seen this thread. There may be some useful info, photos ...

http://www.geotech1.com/forums/showt...ighlight=mario