N_Cook <diverse@tcp.co.uk>: Jan 28 01:23PM
I replaced the triac with similar rating and same symptom.
Runs perfectly smoothly, bypassing the control pcb, feeding 60V,.15A DC
bench ps. Pot and Rs ok, DB3 diac tests ok dropping +/-30V on droppered
35V supply. Even checked the switch current carrying . Just leaves 2
caps, that I've not ESR'd or LCR'd yet.
A better triac match required?
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Clifford Heath <no.spam@please.net>: Jan 29 08:10AM +1100
On 29/01/16 01:52, N_Cook wrote:
> stator, good ESR but only about 50nF.
> Perhaps spark eroded away and now arcing across internally, anyway will
> find a replacement for that and retry on mains
My Dremel sometimes fails to start, but runs ok once push-started. Bad
at low speed. Commutator looks ok, so I was assuming internal shorts in
the armature, rather than problems with the controller. Am I wrong?
A similar problem to yours however...
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whit3rd <whit3rd@gmail.com>: Jan 28 04:24PM -0800
On Thursday, January 28, 2016 at 5:24:00 AM UTC-8, N_Cook wrote:
> I replaced the triac with similar rating and same symptom.
> Runs perfectly smoothly, bypassing the control pcb
Ordinarily, stuttering means the brushes are sticky or dirty,
and not making consistent commutator contact. It could be,
though, that your triac is false-triggering (there ought to be
a gate-to-cathode resistor or resistor+capacitor that prevents
false triggering).
Are you sure that component is a triac? There are similar devices
called 'quadracs' that have an inbuilt trigger.
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Jon Elson <elson@pico-systems.com>: Jan 28 10:17PM -0600
Clifford Heath wrote:
> My Dremel sometimes fails to start, but runs ok once push-started. Bad
> at low speed. Commutator looks ok, so I was assuming internal shorts in
> the armature, rather than problems with the controller. Am I wrong?
If there are shorted turns in the armature, the motor will run slow, vibrate
and get very hot. The shorted turn is acting like a brake. An open in one
wire will make it lose torque, and possibly have a dead spot where it won't
start, but otherwise will mostly run.
Jon
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N_Cook <diverse@tcp.co.uk>: Jan 29 09:25AM
On 29/01/2016 00:24, whit3rd wrote:
> false triggering).
> Are you sure that component is a triac? There are similar devices
> called 'quadracs' that have an inbuilt trigger.
Main control is a Z0409MF triac.
If a short in the windings then it would not work well on DC, even if
only 60V. I'll try a diode on a variac while the pcb is removed to check
for higher V internal arcing.
In a couple of hours I'll put in a new 100nF and crack open the old one
and look for errosion of the film metalisation.
Generally I'm very impressed with this Workzone WCT 135, I bought a
second for a spare luckily. Just 2 safety issues, needs a shroud around
the on/off switch and a brake on the pot knob from vibrating around,
both easily modified.
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N_Cook <diverse@tcp.co.uk>: Jan 29 09:28AM
On 29/01/2016 04:17, Jon Elson wrote:
> wire will make it lose torque, and possibly have a dead spot where it won't
> start, but otherwise will mostly run.
> Jon
no overheating or smoke/smells.
Cold testing showed consistent <>12.5R segment to segment, consistent
<>50R across brushes and <>120R overall, while turning the rotor
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N_Cook <diverse@tcp.co.uk>: Jan 29 12:50PM
With a 1n4006 on a variac, perfectly happy with 70% mains , quasi DC ,
presumably about 180V peaks.
Autopsy on the cap. No obvious smoke trails inside or burning smell,
just a "chemical" hot polyester clothing out of a tumble drier sort of
smell. Minimum metalisation mid way into the bulk of the layup, only 1/3
of width of metal remaining, so presumably local heating there so run
away and the metal there looked very suspect , grey, not mirror and
microscopic pin holes
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"Michael A. Terrell" <mike.terrell@earthlink.net>: Jan 28 01:00AM -0500
> I don't know how you get here, but Google and aioe or whatever seem to be the only free ways to do it. Actually I probably should get a paid service but then, who gets that money ? Originally I got here via AOL but they stopped doing everything I wanted so I got rid of them.
There are a lot of free, or dirt cheap NNTP servers. It is included
with any Earthlink account and I can set up, up to eight Usenet accounts
with my Broadband account. One for each Email account.
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T Wood <f6ceedb9c75b52f7fcc0a55cf0cfbf5d_1028@example.com>: Jan 29 12:37AM
responding to
http://www.electrondepot.com/repair/sherwood-rx-5502-receiver-protection-shutdown-repair-thoug-134725-.htm
, T Wood wrote:
> a month old. I think six months would be good. At least there's a good
> chan
> ce the people are still alive.
If you really care to know--I did a goggle search and found the info on
electrodepot.com. I replied through that web site. I have no idea what Usenet
is. I just know there is at least one ass that like calling people idiots
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thekmanrocks@gmail.com: Jan 28 05:10PM -0800
T Wood wrote: "electrodepot.com. I replied through that web site. I have no idea what Usenet
is. I just know there is at least one ass that like calling people idiots "
Most folks born after 1980 wouldn't. Basically,
usenet WAS the internet. A worldwide "distributed
discussion system" according to Wikipedia:
https://en.m.wikipedia.org/wiki/Usenet
And many traditional Usenet users become very
irate and take it personal when someone - like
me - interacts with usenet groups via Google or
some other non-standard usenet interface.
What they see coming into the group from
a non-NNTP source is out of the ordinary that
the context of the message is lost.
But still, no reason for them to be jerks about it. ;)
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"Mark Zacharias" <mark_zacharias@sbcglobal.net>: Jan 28 06:41AM -0600
"Cursitor Doom" <curd@notformail.com> wrote in message
news:n8cv5k$3i4$3@dont-email.me...
>> mz
> But you still find that exposes every form of damage you encounter in
> practice?
I never said "every form" but it is a powerful tool.
Like oscilloscopes.
Like multimeters.
Like an esr tester. (Even though the "curve tracer" can give a quick check
of esr in many situations.)
It's usable in-circuit and once a person is proficient with it, can VERY
often cut troubleshooting time dramatically. (Test current is
resistance-limited, depends on exact schematic of the curve tracer. There
are many variations.)
We all have our favorite tools and little tricks to help us in what we do.
This is just one more.
Mark Z.
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"Mark Zacharias" <mark_zacharias@sbcglobal.net>: Jan 28 06:46AM -0600
http://www.techlib.com/electronics/curvetrace.html
A sample curve tracer "octopus" schematic.
mz
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Cursitor Doom <curd@notformail.com>: Jan 28 01:34PM
On Thu, 28 Jan 2016 06:46:59 -0600, Mark Zacharias wrote:
> http://www.techlib.com/electronics/curvetrace.html
> A sample curve tracer "octopus" schematic.
> mz
Thanks, Mark. I'll take a look on youtube see if I can find any tips on
how to use these under practical conditions to take in-circuit
measurements. I have more than enough scopes here with x-y/comp tester
inputs.
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legg <legg@nospam.magma.ca>: Jan 28 04:40PM -0500
On Wed, 27 Jan 2016 00:43:30 -0000 (UTC), Cursitor Doom
>> inspection and simple open/short or bias testing.
>> RL
>Nice - but a bit pricey!
Hence the jig on offer. Just add your own uncommited oscilloscope...
You won't want to hook it up and disconnect it every time you need to
switch over.
RL
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jurb6006@gmail.com: Jan 28 04:24PM -0800
We used to make those out of a 6.3 volt transformer and a couple of resistors.
Later I figured out a neater one for caps. You need a 1 KHz square wave of 400 mV with as close to 350 ohms source impedance as possible.
I can check caps with it from about 0.47 uF all the way up. If you can manage to, have the 400 mV square wave ride on 200 mV DC and it will also automatically detect shorts.
It is way faster than any ESR meter out there, even the old Wonderbox. Once you learn how to read it that is. And it is easier to see than almost any analog or digital display.
One of these days I plan on doing a writeup on it but I want to get a bunch of pictures depicting the readings on good and bad caps of a bunch of different values.
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