[Engineer]

Hi, Vacuumlanders,
I've been dumpster diving again...
My company just threw out 1/2 dozen or so obsolete switching P/S's so,
with the help of a pack-rat technician in the dept, I salvaged them
from the skip.
Here are the components I found with possible uses (not ranked):
1. Each unit has two high value electrolytics of 200 VDC working.
These can be used directly in North American AC/DC receiver ("AA5") B+
filters where the peak unloaded B+ cannot exceed 170 VDC. Value is way
overkill (250 to 600 MFD) but a small series resistor from the
rectifier cathode to the capacitor will limit the ripple current. Use
in AC receivers (and some audio amplifiers) is also possible - put two
in series (still high net capacitance) for 400 VDC working (bypass each
with 1/2 megohm to equalize voltage) but DO NOT do this if the power
transformer exceeds 280-0-280 VAC for a peak unloaded B+ of about 400
VDC. This excludes use in most audio power amplifers with, for
example, a 350-0-350 VAC transformer where peak B+ could be nearly 500
VDC. I've been meaning to try 3 caps in series for 600 VDC working for
this application but I've not done so yet. BTW, any ESR issues here? I
can't measure ESR easily.
2. Power rectifiers - there's a 4 diode, 400 volt PIV, bridge in these
switchers, OK for up to 282 VAC input. If you use one to replace the
1/2 wave rectifier in an AC/DC receiver don't forget that the chasis is
now "live" for both positions of the 2 pin AC plug. The only time I
did this I used a spare 1:1 mains transformer to isolate the radio.
3. HF chokes. Here's a new idea I've not tried yet! These switchers
each have three toroidal chokes, abut 2 inches in diameter, wound with
thick wire on permeable cores. I don't know the inductance values but
they may be usable as speaker X/O chokes. I plan to put 3 of them on a
wood board in series with the taps accessible. Then, using an audio
sig. gen, a VTVM, a power amplfier, an 8 ohm load rsistor in series
with the "choke tree", find if there is a combination that gives a -3
dB point at a useful X/O frequency, say 3 KHz. I also plane to try an
cab. mounted 8 inch woofer and SPL meter to verify - might be a
surprise! More on this later...
4. Small physical size elect. capacitors - there are many 100 to 1000
MFD caps in the 25 to 35 VDC working range. Useful for low voltage
cathode decoupling all over radios and audio amplifiers.
5. Other caps: several 0.01 MFD, 1,600 VDC working disc ceramics found.
Apart from simple 0.01 MFD use (overkill on voltage) they seem to have
a useful role in RF decoupling of an AC/DC radio chassis' to the main
AC input, also across the AC line - very safe!
6. Tiny Si diodes - there are some 1/2 dozen of these per switcher.
Use them for LED protection when you use LED's as dial lamp and tuning
pointer lamp substitutions on vintage receivers (I've done this several
thimes.) Problem: these small diodes are a bit hard to get off the cct.
board (small, not much lead to get hold of.)
Tutorial:
For those who do not know, LED's have a very low PIV rating, about 5
VDC. For AC use you MUST put a reverse-connected diode across the LED
to absorb the other 1/2 cycle - and don't forget the series resistor,
calculated to give 2.5 volts across the LED at 20 mA forward current
(R = (Vs-2.5)/20 KOhms.) You can use two LED's in parallel, reversed,
of course. 7. A very small power transformer: 120 VAC to 16 VAC at a
few mA. With a FW bridge you could get about 22 VDC for bias supply
for, say, a 2 x 6V6 P-P amplifier. Use 2 in series for higher voltage
(don't forget, they're free!)
8. Misc. nut bolts, stand-offs, etc: throw into spares box.
Most of the above applies to discarded PC power supplies, too. Never
pass up the chance to part one out! Or use it to run those "battery
dead" 3.3 volt cordless screwdrivers off the 5 VDC output - lots of
torque, and the motors don't seem to mind!
Merry Chistmas, friends.
Cheers,
Roger

"Reclaim, repair, refurbish, rebuild, reuse, recycle"
Reply to: analogdino "at" rogers "dot" com

[robert casey]

Engineer wrote:

Hi, Vacuumlanders,
I've been dumpster diving again...
My company just threw out 1/2 dozen or so obsolete switching P/S's so,
with the help of a pack-rat technician in the dept, I salvaged them
from the skip.
Here are the components I found with possible uses (not ranked):
1. Each unit has two high value electrolytics of 200 VDC working.

2. Power rectifiers -

3. HF chokes.
4. Small physical size elect. capacitors -
5. Other caps: several 0.01 MFD, 1,600 VDC working disc ceramics found.

6. Tiny Si diodes -

I salvage dead CRT computer monitors for similar parts plus some high
voltage poly whatever caps used in the horizontal and vertical
deflection circuits. I take the circuit boards and toss the CRT and
cabinet.

[Ian Bell]

robert casey wrote:

Engineer wrote:

Hi, Vacuumlanders,
I've been dumpster diving again...
My company just threw out 1/2 dozen or so obsolete switching P/S's so,
with the help of a pack-rat technician in the dept, I salvaged them
from the skip.
Here are the components I found with possible uses (not ranked):
1. Each unit has two high value electrolytics of 200 VDC working.

2. Power rectifiers -

3. HF chokes.
4. Small physical size elect. capacitors -
5. Other caps: several 0.01 MFD, 1,600 VDC working disc ceramics found.

6. Tiny Si diodes -

I salvage dead CRT computer monitors for similar parts plus some high
voltage poly whatever caps used in the horizontal and vertical
deflection circuits. I take the circuit boards and toss the CRT and
cabinet.

What goes a round comes around. When I was first starting in electronics in
the 1960s I joined the local radio club. Parts were hard to afford for a
teenager so the club secretary said he could help me out. I went round his
house and he showed into the back garden. There, in the middle of the lawn
was a 10ft high pile of scrap TV chassis (he ran a TV repair shop). Help
yourself lad, he said.

Happy times.

Ian

[- - : R A T B o y : - -]

Ok... so how many of us have tried to salvage used solder (from old circuit
boards and light-bulb ends)? As a 10 year-old I'd gotten into electronics
but had no allowance money. Our old television set and anything electronic
I'd find were immediately stripped.

At one time I even used old cardboard boxes (with holes strategically poked
into them) for point-to-point project boards. You'd be surprised how well
they hold up... I was even able to mount pots, speakers and variable
capacitors to them.

[thomas]

How do you deal with the problem of too short leads on parts salvaged
from PC boards?

[Eeyore]

- - : R A T B o y : - - wrote:

Ok... so how many of us have tried to salvage used solder (from old circuit
boards and light-bulb ends)?

Never

[Eeyore]

thomas wrote:

How do you deal with the problem of too short leads on parts salvaged
from PC boards?

And how about the distortion because they weren't new ?

Graham

[robert casey]

I've see cheap wall warts made that way inside. The material is
thinner and a bit more rigid than plain cardboard but it's the same
technique.

I think that paper product is known as "Fish paper" in the electronics
industry. Seen as early as the fifties.

[robert casey]

How do you deal with the problem of too short leads on parts salvaged
from PC boards?

No biggie. J hook some wire (with or without insulation) to the "too
short leads", or if you're replacing some old wax paper caps, just cut
its leads at the body of the wax cap, and J hook the new cap to them.


And how about the distortion because they weren't new ?
That won't matter. Unless they were blown up.

[Dersu Uzala]

I wish I hadn't thrown all those tubes at the town dump just to hear them pop,
while I was scavenging bicycle parts circa 1970. Who knows how many Telefunken
12ax7s and various 6sn7s I could have collected from the hifi and tv sets just
lying around.

[Eeyore]

robert casey wrote:


I've see cheap wall warts made that way inside. The material is
thinner and a bit more rigid than plain cardboard but it's the same
technique.

I think that paper product is known as "Fish paper" in the electronics
industry. Seen as early as the fifties.

Your fish paper was very thin I expect.

Elephantide.
http://www.plasticshimsandgaskets.co...lephantide.htm

Or Presspahn
http://www.krempel.com/krempel_2002_gb/pressspan_gb.htm

Some Fender amps use this style of material with brass eyelets to solder the
component leads into.

Graham

[Engineer]

thomas wrote:
How do you deal with the problem of too short leads on parts salvaged
from PC boards?

Easy. Take about 4 inches of 26 gauge tin-plated copper hook-up wire.
Holding one end against the component, wrap 2 or 3 turns around the
short stubs on the removed PCB component, solder quickly (avoid
prolonged heating, especially of semiconductors), clip off the back bit
you were holding and, voila, you have a "new" part for point-to-point
wired projects. You can, of course, do the same to reclaim new
PCB-ready components that you find on the cheap.
Cheers,
Roger

[Güs]

Dersu Uzala wrote:
I wish I hadn't thrown all those tubes at the town dump just to hear them pop,
while I was scavenging bicycle parts circa 1970. Who knows how many Telefunken
12ax7s and various 6sn7s I could have collected from the hifi and tv sets just
lying around.

Hindsight is a bitch.. When I was a teenager I used to live 1/4 mile
from a TV station's transmitter. They put all the used tubes in a pile
next to the building. Hundreds of them!
Geez..

[robert casey]

Might be. I didn't pay a lot of attention to it at the time as I was
scavenging parts. I do remember it was dull reddish/rust colored,
thin, and stiff but still relatively flexible.

The stuff I remember was like you describe, but grey.

--
Posted via a free Usenet account from http://www.teranews.com

[Engineer]

Engineer wrote:
Hi, Vacuumlanders,
I've been dumpster diving again...

(snip)

3. HF chokes. Here's a new idea I've not tried yet! These switchers
each have three toroidal chokes, abut 2 inches in diameter, wound with
thick wire on permeable cores. I don't know the inductance values but
they may be usable as speaker X/O chokes. I plan to put 3 of them on a
wood board in series with the taps accessible. Then, using an audio
sig. gen, a VTVM, a power amplfier, an 8 ohm load rsistor in series
with the "choke tree", find if there is a combination that gives a -3
dB point at a useful X/O frequency, say 3 KHz. I also plane to try an
cab. mounted 8 inch woofer and SPL meter to verify - might be a
surprise! More on this later...

(snip)

Merry Chistmas, friends.
Cheers,
Roger

"Reclaim, repair, refurbish, rebuild, reuse, recycle"
Reply to: analogdino "at" rogers "dot" com

I've just done some measurements on these chokes: 1) with an 8 ohm
resistor, and 2) in an ad hoc X/O. Not bad at all, they are in the
ball park for X/O use.
If anyone wants the numbers, email me. I'd post them but they are
downstairs in my lab book!
Cheers,
Roger