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[AMPS] Power Supply Question

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Subject: [AMPS] Power Supply Question
From: (Phil Clements)
Date: Wed, 12 Jul 2000 16:27:23 -0500
> I had everything disconnected, I put the Sencore on the AC
> filter choke. I was surprised to note that instead of 8 Henrys
> inductance (per schematic)it was 6. The surprise was because
> there were no signs of windings shorting out, like charring,
> stink, seepage, etc.

I would venture to say that 85-90% of Henry failures are the choke.

> So, you power supply gurus. I'm not certain of the Q of that trap,
> but is being 10% off frequency enough to compromise effectiveness?
> Is it normal for high inductance devices to change their value by
> 25% over time? This amp is around 20 years old.

My guess is that turns are shorted internally. Call Henry to see
what the resistance should be.  (No Guru here...I stand in awe of
"tuned choke" filters!)

> I have contemplated adding a third .1uf 7.5Kv cap in parallel with
> the existing two, or replacing them all with a .3uf 7.5Kv cap.
> .3uf x 6 Henrys = 119 Hz
> Any input would be appreciated before I jump in.

Bad will not be curing the problem, only prolonging
total failure. Bite the bullet, and buy a choke. There is a delicate
balance going on here. To get that great regulation with a 16 mfd cap,
you need all of that choke working. If you get just a bit off with the
"tuning," you will have serious problems.

Just my idea on how to do it right.

Phil, K5PC

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