--- Philip Pemberton wrote: > > The one thing I need to work out is the bias current. 5V Vcc, with a > record/playback head impedance of 92.5mH. Same thing for the erase > head - except that's 92.28mH (yeah, I know, big difference). > Well there are a few things to consider (ehh?). First are you performing FM or standard direct recording, and is your signal analogue or digital. If the latter there is a lot less to worry about. The bias is used to improve the low frequency response of the tape, at the cost of high frequency response. However if you are recording digitally you don't need it and the bandwidth of the tape is much higher due to recording in a narrow frequency range. > I figured it would be for something like that. Might be good for > determining the rotational speed too. Speaking of which, I need to > find out what speed these tapes are usually run at (in normal > rec/play mode). Sounds like you are looking at recording analog? 1.5" IPS for Cassette tape and 0.75 IPS for microcassette tape. The capstan is what you should use to determine tape speed (at least recording speed). Since this is actually fairly precise you can use it to determine tape position relatively well. Unfortunately fast forward and reverse would make that scheme untenable. You might be able to pulse the motor and measure the EMF generated by it when there is no power applied to acruately estimate the speed of the capstan. The worst problem with all tape mechanisms is the drive belts. I can't find replacements for anything anymore reguarding them unless I look at a restoration web site these days, Stephen R. Phillips was here Please be advised what was said may be absolutely wrong, and hereby this disclaimer follows. I reserve the right to be wrong and admit it in front of the entire world. __________________________________ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/ -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist