On Sat, Feb 10, 2018 at 11:35 AM, Mia Magnusson <mia@plea.se> wrote: > Den Fri, 9 Feb 2018 22:21:10 +0100 skrev Francesco Messineo > <francesco.messineo@gmail.com>: >> On Fri, Feb 9, 2018 at 3:39 PM, Bill Degnan <billdegnan@gmail.com> >> wrote: >> >> >> The belt looks ok. It's a bit weak, but it doesn't slip. I might try >> to substitute it out of desperation. > I finally replaced the belt with the one coming from a hopelessly broken 1531 and that made a huge difference indeed. It now reads and writes quite well, though isn't "perfect" as my other 1531s where I could correctly adjust the azimuth. I'm not saying it's an azimuth problem, but still the old drive can't read everything. > > If you follow my idea of hooking up the electronics of an audio cassette > player to the rec/pb head of the datasette, you should easily be able > to judge how it sounds. well yes, that could tell me there's still some mechanical problem maybe, but I guess it was primarily the old belt that was probably slipping slightly. > > Do you have an oscilloscope? > I have a few... > Noise could be from bad decoupling capacitors on the 5V DC line, or > maybe noise from the motor (bad decoupling inside the motor). capacitors were the first I've replaced as the ESR wasn't terribly low. But it wasn't the problem anyway. > > Is the recording level about right? You can check that by recording a > bit with the problematic datasette and also a bit with a known good > datasette, and check the level indicators while playing back the tape > on an audio cassette deck. If you don't have any audio cassette deck > with meters you could hook up an AC volt meter or oscilloscope to the > speaker output of a simple audio cassette recorder. (But if you have an > oscilloscope, you might aswell measure the signal to and from the > rec/pb head). that's fine as theory, but you should concentrate on this particular schematic: the write circuit is: head - 10K - 2 x TTL gates at 180 phase degree difference. Gates were replaced (and checked), 10K is ok, head must be ok since it reads fine at the same level as my other tape drives... > > Have you tried cleaning the rec/play switch? That is by far the most yes, one of the first attempts at fixing this thing. I've also checked the correct operation of all the switch's sections. > common problem in general on old (two head) tape recorders. Usually it > helps at least temporarily pressing rec-stop-rec-stop many times in a > row, but in the long run some contact cleaner that also lubricates is > the way to go. (Without lubrication it usually gets better for a short > while but the switch might wear out faster). > >> I would very much like to try a head azimuth adjustment. All the other >> tape drives I have, needed a bit of tweak to read/write reliably after >> all these years. I think the hole could be under the label, but I'm >> afraid it would bend if lifted... > > In general, on cassette recorders for audio usage, in some cases you > have to remove the lid completely, usually by bending it in a certain > way. A safe work-around is to remove the mechanics from the cover and > run it naked. That works as long as the tape ends up in the correct > place even without the case - not always the case. (Pun intended ;) ). the adjustment screw isn't visible from the tape opening, I've already checked that. It must have a hole either under the Commodore label or needs the complete mechanism to be taken out of the shell. And I will never do that anyway. Frank Message was sent through the cbm-hackers mailing listReceived on 2018-02-10 15:00:02
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