Digest for sci.electronics.repair@googlegroups.com - 12 updates in 4 topics

Dumas.Walker@f10.n1.z312.fidonet.org (Dumas Walker): Jan 15 07:43PM +1200

>changed out of all recognition, that living with old tech is not practical.
>That ain't so at all
> in many areas. Half a century old is a bit modern for me.
 
In my mind, if you can still repair/get parts for it, and it still does the
job you require of it, why not? :)
 
---
* SLMR 2.1a * DalekDOS I/O Err: (I)Obey (V)ision impaired (E)xterminate
tabbypurr@gmail.com: Jan 16 07:18AM -0800

On Wednesday, 16 January 2019 04:15:10 UTC, Dumas Walker wrote:
 
> > in many areas. Half a century old is a bit modern for me.
 
> In my mind, if you can still repair/get parts for it, and it still does the
> job you require of it, why not? :)
 
There are plenty of parts available for those Hoovers. For older stuff the usual thing is to repair the parts. It's far easier than it would be to do that on modern kit. And usually quicker than searching for & waiting for a replacement part.
 
 
NT
"pfjw@aol.com" <peterwieck33@gmail.com>: Jan 16 07:49AM -0800

On Tuesday, January 15, 2019 at 11:15:10 PM UTC-5, Dumas Walker wrote:
 
> In my mind, if you can still repair/get parts for it, and it still does the
> job you require of it, why not? :)
 
What is revealing is going over any given carpet, room or area rug with say... a Kirby in excellent condition, then going over the same location immediately thereafter with something like a TOL Dyson. For many years, we would keep the "new" vacuum at home and transplant the old one to our summer house. Until, 12 years ago, we got a Dyson.
 
As to R&M, I have replaced the filters, internal hoses and brush-bar on the Dyson - all in, about 20 minutes work and less than $75 for OEM Dyson parts. Otherwise, it has managed 4,800 square feet, two long-haired cats, a golden and a Scottie without any trouble from purchase to-date.
 
Peter Wieck
Melrose Park, PA
Phil Allison <pallison49@gmail.com>: Jan 15 09:13AM -0800

Look165 wrote:
 
 
> And then put in an under-pressurized "bubble room" for completing the
> process.
> When there was no more bubbles, the process was over.
 
** The process is commonly known as " vacuum impregnation " - completed transformers are placed in tank of resin or varnish and the air pressure reduced until all air pockets are filled.
 
Not always done with bobbin wound transformers but standard practice with layer wound and old style cloth insulated toroidal mains transformers plus any tranny that handles substantial voltages.
 
.... Phil
 
 
 
 
Look165 <look165@numericable.fr>: Jan 15 07:41PM +0100

Excuse my English, I am French.
 
Phil Allison a écrit le 15/01/2019 à 18:13 :
Fox's Mercantile <jdangus@att.net>: Jan 15 12:51PM -0600

On 1/15/19 11:13 AM, Phil Allison wrote:
> ** The process is commonly known as " vacuum impregnation "
> - completed transformers are placed in tank of resin or
> varnish and the air pressure reduced until all air pockets > are filled.
 
Actually, the vacuum allows the bubbles to expand enough to
float to the surface and pop.
 
I did this with hand wound transformers at TRW using Poly
Urethane, and in my shop mostly with casting resins.
 
The vacuum chambers at TRW were nice, but I found that using
a modified pressure cooker works fine for the size jobs I have.
 
 
--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
Look165 <look165@numericable.fr>: Jan 15 08:26PM +0100

For me, it was telecom transformers for SNCF.
 
Fox's Mercantile a écrit le 15/01/2019 à 19:51 :
whit3rd <whit3rd@gmail.com>: Jan 15 08:42PM -0800

> I remember a lot of old transformers, particularly the power
> transformers on the old TV sets, were coated with tar.
 
There are mechanical forces between wires carrying current, and in addition
to making 'hum' that puts some metal fatigue into the mix. For
reliability, especially for switchmode, vacuum impregnation or some other
secure-the-wires provision is common in power inductors. At low
frequencies, you can get away with oil and paper. Or thick oil (asphalt, tar...).
Look165 <look165@numericable.fr>: Jan 16 10:31AM +0100

That's true, I forgot the magnetostriction.
 
But it's only true for LF ; with HF (some 10 kHz), the inertial forces
are too strong and too much low in movement.
 
whit3rd a écrit le 16/01/2019 à 05:42 :
Rob <nomail@example.com>: Jan 16 12:50PM

> of the steel laminations. Yet, it seems the practice of using tar
> vanished for the most part in the 70s and later. Yet I have not seen any
> untarred modern transformers chatter......
 
It would be partly for that reason, partly because voltages tended to
be higher and insulation materials could be hygroscopic.
 
From the 70s, voltages in typical equipment dropped due to use of
semiconductors (although of course in a TV set the B+ still was there)
and the materials available for insulation changed from impregnated paper
to plastics and resins.
bruce2bowser@gmail.com: Jan 16 03:08AM -0800

> > wrote:
 
> > Suffice it to say that using a substance for a purpose not mentioned on the container's label just isn't what you want. Go to a trusted computer or parts retailer and specifically ask for 'parts cleaner', 'head cleaner' .. etc. Because it beats re-inventing the wheel, being adventuresome, gambling, etc...
 
> You won't do very well in life with that attitude.
 
I humbly disagree.
dplatt@coop.radagast.org (Dave Platt): Jan 15 11:56AM -0800

In article <0lkq3etgnf7ud9l1o3eqedpvqs3285ih38@4ax.com>,
>>fitting, and a lathe-job threaded tube, 3/8-27 to 38-32, to mate the threads.
 
>>I'm not sure I've ever encountered 3/8-27, but I have taps for 3/8-24./ -26. /-32
 
>Pogo pin???? What's that?
 
A two-piece (concentric cylinders) electrical contact. Think
"piece of brass rod, slid into a brass tube, with a spring at the
base".
 
See https://www.ebay.com/itm/261897100962 for one example of how
they're used. This is a JTAG connector with 8 pogo pins. It can be
pressed down onto an 8-pad through-hole pattern on the board
(preferable one populated with a machined-pin socket, although you
could probably make it work just with plated-through holes).
 
https://www.ebay.com/itm/SOIC-8-Spring-Loaded-Pogo-Pin-Adapter-Jtag/250464158353
is similar, for a SOIC pattern.
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