|[AMRadio] boat anchors heathkit etc|
Merz Donald S
merz.ds at mellon.com
Fri Jun 23 10:28:15 EDT 2006
A small quibble...the light bulb thing is great. But if you're in this hobby, you need a variac and you need to always use it to bring up anything that is unknown.
Going beyond that, my experience is that cap reforming seems to work best when the cap is reformed without a load on it--not using the rig as the power source. I am often to lazy to do this, but I think the right way to do it is to use a Sprague TO-series cap checker (or regulated DC supply, etc.) to apply a varying DC voltage while watching the current flow, keeping it at 1ma or less. As the current falls on the meter, you can increase the voltage until you are at or above the rated voltage of the cap. Then you can see the leakage right on the meter and you know how the cap is behaving under power.
If you have the time and the gear, I think that's the right way to do it. But I frankly don't usually take the time required and just bring the radio ups lowly over a period of 1-10 hours on a variac.
73, Don Merz, N3RHT
From: amradio-bounces at mailman.qth.net on behalf of Phil Galasso
Sent: Thu 6/22/2006 8:51 PM
To: Discussion of AM Radio
Subject: Re: [AMRadio] boat anchors heathkit etc
The safest thing to do when you decide to apply power to an old rig (after
inspecting it carefully for frayed or burned wiring, obviously damaged
parts, and other such problems) is to connect a 100 watt light bulb in
series with the rig. If you have a Variac (variable autotransformer) for
gradually bringing up the line voltage, so much the better. If any filter
capacitors or solid state rectifiers are shorted, the bulb will glow to full
brightness and you won't blow any fuses or burn anything. Bringing up the
voltage slowly will allow electrolytic filter capacitors to "form". It is
usually a good idea to "shotgun" such capacitors, as they do deteriorate
I made up a test jig in a box with a standard light socket in series with a
receptacle. It has saved me a lot of grief.
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