ASR 33 buzzing
vintagecomputer at bettercomputing.net
Fri Oct 14 01:02:38 CDT 2016
Yeah I'm sure we must have bad cap(s) here. I think pretty much everything is original on this thing. I've no idea how old it is.
I'll have to read through the manuals and figure out where the cap is. I'm assuming it must be round.. although directly under the fuse is a little black box connected to it.
I note when I plug it in on Line sometimes there's a single metallic clack from the PSU area and sometimes it's multiple..lioe someone's operating a telegraph.
I was rotating the motor and seeing how things work (hard to believe it doesn't just fly apart given how intricate it is). I was able to push keys.. however now I have the top row locked down and the keyboard cover won't fit back on.. heh. Hoping I'm not breaking things as I go.
Sent from my Samsung device
-------- Original message --------
From: "drlegendre ." <drlegendre at gmail.com>
Date: 2016-10-13 10:17 PM (GMT-08:00)
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
Subject: Re: ASR 33 buzzing
Tony's suggestion is the best at this point - look for issues with the
motor start and/or run caps. A shorted (or open..) cap can certainly cause
this issue. Shorted and it draws excess current in the cap, open and it may
prevent motor starting / running which likewise draws excess (stall)
current, but in the motor windings.
Also, it shouldn't be too hard to isolate the motor assy. itself from the
rest of the circuit - lift the correct lead(s) from the AC power
distribution system. It may be much easier if you can deal with the motor /
cap assy. as a single entity, rather than within the rest of the complexity.
This is just generic advice from a guy who's never fixed a 33. But assuming
yours has the standard AC synchronous motor, it should all apply. Motors
only draw excess current for a very few reasons - overload / stall, shorted
windings, bad start / run caps and possibly associated start / run relays.
On Thu, Oct 13, 2016 at 11:34 PM, tony duell <ard at p850ug1.demon.co.uk>
> > The buzzing definitely seems to be coming from the motor. I put a
> > tool to the casing and could feel it vibrating. However, I can turn it by
> > hand (clockwise) and see all the gears and striker mechanisms working.
> Should the motor be running in the 'Off' positon of the switch, though?
> If the motor is buzzing and taking a high current (which blows the fuse),
> what about the motor run capacitor (the one on the mechanism chassis
> itself, wired to the motor)? Maybe it has failed.
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