#'Budgie' chip
12 messages in this thread
The clocks are generated by the 'Budgie' chip, from a main oscillator.
That osc is 28.63696 mHz for NTSC and 28.37516 for PAL. The NTSC color
burst is generated from it, so I'd say that you'd have to have the right
crystal to generate NTSC *composite* video. The power supply only supplies
DC, so there's no way the system could decide pal vs/ ntsc that way. It
must be internal… Now that I look at the prints again, I do see the
jumper. it's R203, which grounds a signal called \ntsc. Looks like you'd
have to move R245 to R246 as well. Then you'd have to change the RF
modulator- it's a sealed can. If you only wanted composite video, you
could get away with the 3 jumpers & changing the main osc.
At least, that's what I think after looking over the schematics. It's been
a while since I opened up a 1200.
-Jim
MOS via Autopilot & Amiga
From what I read I though that you could get a clock from the power supply, I
suppose if it is dc then you can't. I will check the docs again…….
Phill
The 2000's power supply supplies a line frequency 'tick' signal…. but
the 500 and 1200's do not. .
-Jim
MOS via Autopilot & Amiga
Ah, that must be it, I assumed that all power supplies had this, I wonder why
the 2000 has it but no others….
Phill
That I don't know. I do know it's a jumper option in the 2000, whether to
use the power supply tick line or vsync (what the 500 uses). But I never
heard a good explantion as to why you'd want one over the other.
-Jim
MOS via Autopilot & Amiga
What are 2000's jumpered for normally the power line or vsync?
Phill
They're set for power line. There was a CBM tech bulletin warning that
some 2000's were set wrong at the factory. They said that this would cause
problems with 3rd party genlocks… but that's all they said.
-Jim
MOS via Autopilot & Amiga
Strange that they work off the power line, that must be one of the least exact
timing methods you can get, maybe that's why cbm chose it 🙂
Phill
Actually, I think the power companies hold the power line frequency pretty
closely. That's what lets them buy power from each other… And a drifting
power supply frequency would cause havoc with clocks and other syncronous
motors. Back when I was a field engineer with Burroughs, a drunk took out
the power & backup to a customer's data center. They tried to power the
place with a trucked in diesel generator. Unfortunately, the thing
couldn't hold a frequency under changing loads. All the disk drives in the
place went nuts, cuz their motors were changing speds.
-Jim
MOS via Autopilot & Amiga
In the uk the power line frequency shifts quite a lot, it averages out over the
day though, which is why clocks manage to keep time.
The uk power supply is also never exactly 240 volts, we checked a volt meter at
work the other day and got 245 volts. It wouldn't suprise me if at some times
of the day it drops to 235 as well.
Phill
> In the uk the power line frequency shifts quite a lot, it averages out
over the day though, which is why clocks manage to keep time.
The uk power supply is also never exactly 240 volts, we checked a volt
meter at work the other day and got 245 volts. It wouldn't suprise me if
at some times of the day it drops to 235 as well.
Phill,
Motors and other electrical equipment are usually rated to run on plus/minus
10% of their VOLTAGES. The frequencies remain constant. In the US it's 60hz
and in Europe (I believe) it's 50hz. The voltages can fluctuate, but the
frequencies should stay relatively constant.
Wolf Pup
— Howlin' in the Waves…
Phillip,
<The uk power supply is also never exactly 240 volts, we checked a volt meter
at work the other day and got 245 volts. It wouldn't suprise me if at some
times of the day it drops to 235 as well.>
Same thing is true on this side of the pond (at least here, in northern
California), though the numbers are different…:) That's one of the reasons I
got a line conditioner for my A1000 many years ago, and have my A2000/040
hooked up to a UPS. Not only does it protect me from surges and spikes and
uneven electrical current, but it also gives me up to 20 minutes after the
power is out completely, to gracefully close down my system.
Asha
@}–,–`–