Thursday, April 09, 2009
Spectrum+ keyboard & new membrane
Some of the keys were intermittent. For example, the " key took a minute or two before it would work.
I noticed that SYMBOL SHIFT + A did not give me the STOP command while I was writing a simple BASIC program to monitor the Kempston joystick on port 31 which is what jogged my memory (i.e. not getting the STOP command!)
Then, I remembered something about a 22K resistor from the Spectrum+ upgrade manual so downloaded the PDF, saw I was right and the keyboard is now OK after putting a 22k resistor in parallel with R68 on the motherboard.
The resistor calculator was useful to make sure I had the right resistor to hand - it's been a LONG time since university!
I noticed that SYMBOL SHIFT + A did not give me the STOP command while I was writing a simple BASIC program to monitor the Kempston joystick on port 31 which is what jogged my memory (i.e. not getting the STOP command!)
Then, I remembered something about a 22K resistor from the Spectrum+ upgrade manual so downloaded the PDF, saw I was right and the keyboard is now OK after putting a 22k resistor in parallel with R68 on the motherboard.
The resistor calculator was useful to make sure I had the right resistor to hand - it's been a LONG time since university!
Labels: 22k ohm resistor, IN 31, intermittent key, Kempston, R68, resistor colour chart calculator, Spectrum+ keyboard, STOP
.jpg)
