XM1541 cable question

[commodorejohn]

Okay, so I want to build myself an XM1541 cable to make life easier. But that requires four 1N5819 or BAT85 diodes, which my local Radio Shack doesn't have. And from what I can find, it's difficult to buy them online in small quantities without getting shafted on shipping costs. So what I'm wondering is, what is the difference between these and the diodes Radio Shack does have? The purpose is just to prevent current from flowing one way, right? So, theoretically, any old diode should work. Is it a question of how much current they can block? If so, what tolerances should I look for on the other kinds?

[hydrophilic]

This is from memory, so the actual numbers are problaly off a bit.  A standard diode has a voltage drop of 0.7 volts and those listed have a considerably lower drop (I'm thinking Schottky diodes have a drop of 0.3 volts).  The Commodore uses TTL logic which means the 0v level should be less than 0.8v (0.8~2.4v is undefined).  In an ideal world, a standard diode should work just fine.  But reality includes things like inductance and capacitance in the line, and not 0.0v from the PC to the diode.  These things tend to push the value read 'up' to 0.8v or more.

So if your PC is grounding a line through a standard diode, your Commodore will see a value close / within the undefined range and may read the wrong value.

Maybe I have this backwards.  The PC does not use TTL so maybe it requires less than 0.8v.  Anyway, I hope you get the idea!

I've never ordered from them so I can't recommend them, but Jameco Electronics carries a huge selection of stuff.  They have these for $0.10 each at quantity of 10+.  That's only $1.  I don't know what their minimum order is, but they have so much stuff, you're bound to find something you need if a $1 order is too small.  Anyway, here's a link to one of their 1N5819 diodes.

P.S.  Got the cassette connector so now I have to stop procrastinating!

[RobertB]

Okay, so I want to build myself an XM1541 cable to make life easier.

There is the XE+XM1541 adapter at NKCElectronics.com   Go to http://www.nkcelectronics.com/commodore-xexm1541-ada1541.html

              Truly,
              Robert Bernardo
              Fresno Commodore User Group
              http://videocam.net.au/fcug

[Andrew Sutton]

Okay, so I want to build myself an XM1541 cable to make life easier.

There is the XE+XM1541 adapter at NKCElectronics.com   Go to http://www.nkcelectronics.com/commodore-xexm1541-ada1541.html

              Truly,
              Robert Bernardo
              Fresno Commodore User Group
              http://videocam.net.au/fcug

That's the way to go. I made the simple X1541 cable, which is a pain in the rear at times. I think I'll go with the XE+XM1541 adapter next. Really, I need a MMC2IEC and Ethernet!

[RobertB]

I think I'll go with the XE+XM1541 adapter next.

I've bought several MMC2IEC/SD2IEC boards from Tony Kim at NKCElectronics, and I've always had quick shipping from him (though having him respond to e-mails is hard to do).

Really, I need a MMC2IEC and Ethernet!

Though still listed at the site, the MMC2IEC/SD2IEC board is out-of-stock as Tony considers making another run of them.

                      Truly,
                      Robert Bernardo
                      Fresno Commodore User Group
                      http://videocam.net.au/fcug
                      The Other Group of Amigoids
                      http://www.calweb.com/~rabel1/

[sirmorris]

I built my mmc2iec on some proto-board. If you're confident with a soldering iron and you get some practice in with kynar wire then you shouldn't have too much of a problem. Take your time, and make sure there's plenty of light!