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clouduster(at)austin.rr.c
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 Posted: Wed Mar 28, 2007 7:57 am Post subject: Fwd: Re: re: Capacitors for Whelen strobe power supply |
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I want to thank everyone for the information on strobe capacitors. I
have ordered some from Digi-key and will let the list know how they work.
Dennis H.
Robert L. Nuckolls, III wrote:
| Quote: |
<nuckollsr(at)cox.net>
Here's a note I received on one fellows success with
replacing flash-rated capacitors with plain-vanilla
electrolytics.
His confirmation of my past experiences suggests that
the experiment is worth repeating.
> Hey, Bob, I'm just a lurker in the archives, but I have replaced the
> electrolytics in two Whelen strobe supplies.... Worked fine then and
> is working fine now. Some spray-on conformal coating helps cut down
> on the high-voltage corrosion in the units.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
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clouduster(at)austin.rr.c
Guest
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| Posted: Mon Apr 02, 2007 5:31 pm Post subject: Fwd: Re: re: Capacitors for Whelen strobe power supply |
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I was asked how the repair of the Whelen strobe power supply has gone.
The strobe is Model A413A,HDA-DF-14
The power supply is working but it took some luck. I'm pretty much an amateur when it comes to electronics.
I used the P11920-ND capacitors from DigiKey. These were recommended by James Foerster - Thanks James!
The capacitors are the correct electrical size but are much smaller physically than the original caps.
After installing the new capacitors, the strobe flashed erratically and the large transistor mounted on the aluminum heat sink got quite hot. I believe the transistor controls the high voltage transformer primary windings but I'm not sure.
I would discharge the capacitors with an insulated screwdriver before inspecting the unit. Only one cap. had a charge. A test with a voltmeter showed the second cap. was not getting any voltage. The high voltage windings on the transformer charging the caps. is a center-tap winding. The center tap is connected to the + on one cap. and the - on the other. I disconnected the dead winding output wire (read cut it off 1 inch from the circuit board with a dike) and hooked it to my Harbor Freight $4.00 volt meter. Powered up, it had several hundred volts A/C so I assumed the transformer was OK! That was good news because if the transformer was bad I'd give up. I looked at the circuit board and the next component on the board where the transformer wire connected was a diode - marked EDA - BR8M5. I tested it with the HF meter and it was open!! I could not find any data on the BR8M5 diode but I had a pack of RadioShack IN 5404 diodes rated at 400 V. Soldered one in and the power supply came alive - And the transistor is now running Cool!
Hope this helps someone else rejuvenate a strobe power supply. I hate to see them thrown away!
PS: If you want to get your Grand kids attention - discharge one of the capacitors while they are watching!
Dennis Haverlah wrote:
[quote]--> AeroElectric-List message posted by: Dennis Haverlah <clouduster(at)austin.rr.com> (clouduster(at)austin.rr.com)
I want to thank everyone for the information on strobe capacitors. I have ordered some from Digi-key and will let the list know how they work.
Dennis H.
Robert L. Nuckolls, III wrote:
| Quote: | --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr(at)cox.net> (nuckollsr(at)cox.net)
Here's a note I received on one fellows success with
replacing flash-rated capacitors with plain-vanilla
electrolytics.
His confirmation of my past experiences suggests that
the experiment is worth repeating.
| Quote: | Hey, Bob, I'm just a lurker in the archives, but I have replaced the electrolytics in two Whelen strobe supplies.... Worked fine then and is working fine now. Some spray-on conformal coating helps cut down on the high-voltage corrosion in the units.
|
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
|
[b]
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