stottlem@ittral.UUCP (Bill Stottlemyer) (02/28/84)
I'm using the Commodore Datasette with my C-64 and encountering quite a few load data errors. I'm using high quality cassettes (Microsette brand) and I've cleaned and de-magnetized the tape heads with little or no improvement in performance. I didn't have this much trouble with my Sinclair ZX-81 using a standard audio cassette. Question: Could I possibly have problems with tape head azimuth alignment. What about problems in the tape drive path? Also, is there a standard reference tape available for checking tape head alignment? Any suggestions short of going back to the Sinclair would be greatly appreciated. Bill Stottlemyer
porter@inuxd.UUCP (J Porter) (03/01/84)
Look at the output from the cassette drive with a scope when playing back a known good tape that you want to be able to load. Then with a small screwdriver, gently adjust the azimuth (through the tiny hole in the top of the drive) (If you have an older cassette unit, you will have to lift up the nameplate). Simply adjust for the best digital looking signal. The front of a program has seven seconds of pure tone before data. This portion should come out looking like a real clean square wave. Happy Hacking. Jeff Porter (inuxd!porter) AT&T Consumer Products Indianapolis
miller@uiucdcs.UUCP (miller ) (03/02/84)
#R:ittral:-37300:uiucdcs:36100058:000:591 uiucdcs!miller Mar 1 16:50:00 1984 A friend of mine had a cassette and found it to be *very* sensitive to the TV. He had to move it far away or he got tons of load errors too. This may not be your problem, but if so it will save you a lot of unneeded hardware debugging. Also on another note, be careful with that grounding wire on the cassette line. If it touches the wrong contact on your expansion or user port, you potentially could fry part of the machine. It is not used on the vic or c64, only for Commodore's business machines. So be sure you tape it down next to the line. A. Ray Miller Univ Illinois
dollas@uiuccsb.UUCP (03/02/84)
#R:ittral:-37300:uiuccsb:16800009:000:1495 uiuccsb!dollas Mar 1 11:50:00 1984 One of the most significant factors is the interference from the TV/monitor screen. Try to keep your datasette far from it (you can even put a metal pan over it to see if this is indeed the problem -so much about technology); if so just make longer cables and ...reach out! If you use a homebrew interface (I use one all the time) it might be sensitive to tone and volume levels. Usually once you've got the proper settings it works fine. In fact with my roomate's SANYO (no, I don't work for them) and TDK SA cassettes (Chromium setting - I don't work for TDK either) we get virtually no loading errors even when the recorder is 1ft off of the TV! The azimuth may be a reason for problems but I would think that it would give problems with both FSK (Sinclair) and PCM (Commodore) coding schemes. On the other hand noise tolerance may be different, by adding noise with frequency components far beyond the ranges it looks for in FSK you may still get good results whereas in PCM it might interpret this noise as transitions thus goofing up. As a final comment you may get better results if you use magnetic 'donuts' at the ends of each wire (that connects the interface to your datasette). Good Luck Apostolos Dollas Dept. of Comp. Sci. U. of Ill. ...!pur-ee!uiucdcs!uiuccsb!dollas