The first article is located on CoCo3.com, and suggests replacing a transistor to fix the negative voltage circuit, which fails at high speed on a stock SSC. This article also provides instructions for adding a mechanical switch so the user can manually set the cartridge to work at the desired speed.
The second article I found is on Robert Gault's homepage and also features a manual switch, but instead of replacing the transistor, Mr. Gault points out that the same effect can be achieved by simply adding a capacitor across R16 (or C26 as in my photo). Beautifully simple, and it works.
The switches are located differently in the two articles, but provide the same function... they provide the sound effects chip with a 2MHz clock, which is normally provided by doubling the CoCo's Q clock. If the CoCo is running at high speed, we no longer need to double this clock.
The AND gate (74LS08) is piggybacked on top of IC3. Make sure to align pin 1 of both chips. Only pins 7 (Vcc) and 14 (Gnd) should be soldered to IC3... all other pins of the 74LS08 should be bent out, preferably removed with the exception of pins 8,9 and 10, a single AND gate. I actually cut my 74LS08 from an old 8088 motherboard with some small diagonal cutters, desoldering only pins 7 and 14.
Connect pin 8 of the 74LS08 to pin 9 of IC3. Connect pin 9 of the 74LS08 to the Q clock at the eyelet under C8 (the blue wire in the photo). Connect pin 10 of the 74LS08 to one pin of a 2 pin jumper plug, the other pin goes to ground.
Finally, take a twisted pair of wires with a 2 pin socket (such as an LED or Reset switch connector from a PC) and connect the wires to pins 6(/Q) and 7(Gnd) of the 74LS74 of the Turbo Light circuit. Make sure you don't plug the connector into the SSC plug backwards or you'll be shorting you're CoCo's Q clock to ground... probably not a good thing.
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