ChanServ changed the topic of ##yamahasynths to: Channel dedicated to questions and discussion of Yamaha FM Synthesizer internals and corresponding REing. Discussion of synthesis methods similar to the Yamaha line of chips, Sound Blasters + clones, PCM chips like RF5C68, and CD theory of operation are also on-topic. Channel logs: https://freenode.irclog.whitequark.org/~h~yamahasynths
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<andlabs>
nice
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<cr1901_modern>
whitequark: You mentioned microstepping as a way to position a floppy head finely. Well, this comment doesn't _explicitly_ say it, but seems like Seagate had the same idea for one of their stepper motor drives
<cr1901_modern>
During startup the drive frantically looks for its alignment info by moving the head back and forth between seemingly the same two tracks: https://www.youtube.com/watch?v=vTu-1dLegzI
<cr1901_modern>
(ST-251 is the MFM version, ST-277R is the RLL version)
<cr1901_modern>
I actually have the latter, but no machine to put it in
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<__sen>
cr1901_modern: i watched that without sound and the sound of it played in my head from having heard it so many times back when that was a more current drive :)
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<cr1901_modern>
__sen: It is the best hard drive startup sound, hands down
<andlabs>
okay I must be missing something about how to use an oscilloscope
<andlabs>
I have my probe on the pin I want to probe
<andlabs>
it should be a clock
<andlabs>
I see a random ass sine wave that either dies down or goes insane depending on how i tilt the probe
<andlabs>
if I use the ground alligator clip then it either dies to 0 completely or hovers at around 20 mV (????)
<andlabs>
switching from DC to AC coupling doesn't fix it; switching to GND coupling results in no signal at all
<andlabs>
when my father holds the probe to the pin I see what appears to be the falling edge of a square wave but that's about it; zooming out just produces random noise near 0 and zooming in produces the weird sine wave again
<andlabs>
oh and also the frequency jumps around like mad
<balrog>
andlabs: what kind of probe are you using?
<balrog>
and what is generating the clock?
<balrog>
are you maybe overloading the line?
<balrog>
what is the expected clock level and frequency?
<andlabs>
a 1X/10X probe
<balrog>
ej5: worth requesting the GPL sources? :p
<andlabs>
the clock is coming from a crystal but I am measuring a user of the clock
<balrog>
(probably not)
<andlabs>
not sure about overloading
<andlabs>
not sure about levels either, I assume DC
<andlabs>
but frquencies range between 1Mhz and 16Mhz
<balrog>
is the probe set to 10x?
<andlabs>
(these are multiple clock signals)
<balrog>
is the user of the clock something that you programmed yourself?
<balrog>
this is a good write-up on the difficulties of reading a crystal oscillator output with a standard scope probe
<balrog>
but it's basically what I said -- it's very easy to add too much load to a crystel
<balrog>
crystal*
<andlabs>
oh
<andlabs>
well I'm trying to measure simple Vcc pins now
<andlabs>
and I'm getting weird results still
<andlabs>
600mV straight lines, not 5VDC
<andlabs>
oh and if I tilt the right way I get no reading whatsoever
<andlabs>
progress!
<andlabs>
I set 10X on the scope and measured some other Vcc and I got 5V
<andlabs>
and I measured another chip's clock pins and they look correct!
<andlabs>
okay yeah I think the VIC is dead
<andlabs>
VDC is generating a signal
<andlabs>
and my TV seems to support 15khz (!)
<andlabs>
but I'm not seeing anything so I'm gonna try connecting hte keyboard and having 40/80 pressed on power-on
<andlabs>
*15khz VGA
<andlabs>
nope, still blank, so I'm gonna have to do more torubleshooting.... after replacing the VIC
<andlabs>
thanks again balrog
<balrog>
yeah it's critical that the X is matching between the probe and the scope
<balrog>
10x attenuates the input signal but also does not load down the circuit
<balrog>
(as much)
<andlabs>
not sure why the two Vccs I measured earlier on some 74xx chips read 1V differently in the multimeter and the scope but I'll worry about that later if it becomes a problem