Excellent advice here Ian!
Cement-cased power resistors are an abomination...
73
Leigh
VK5KLT
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Ian White
Sent: Wednesday, 26 April 2017 5:09 PM
To: amps@contesting.com
Subject: Re: [Amps] Price per Watt Conversation
K8RI wrote:
>At close to 200W per device, it would require 8 devices in a circuit
>much like the Yaesu Quadra, but with a legal limit out for less money.
>BTW I saw several posts praising the Quadra, but the Quadra has several
>inherent problems in the basic design according to the Yaesu news
>groups.. One is the PS is designed for 220 VAC and not the current
>standard of 240 leading to a number of failures. Another is the way the
>power supplies feed the individual amps. OTOH it is a nice amp and I do
>see a number of hams claiming to be running 1200W out for many years.
I
>have two.
The main problem with the Quadra PS is its tendency to blow the
step-start resistors (R2A, B, C) that limit the startup surge current.
This is caused by two design errors, both of which can easily be
rectified at repair time.
1. Step-start resistors are overloaded by design, but the cement-cased
resistors that Yaesu selected are quite poor at handling surges! If they
fail, replace all three with glass-coated resistors with better
surge/overload characteristics.
2. If the step-start relay fails to activate for some other, unrelated
reason, then the step-start resistors *will* blow because they have no
other protection. Following an idea from Alpha, insert a time-delay fuse
that is rated to blow in several seconds. (This idea will not work with
the existing Yaesu resistors... guess why.)
73 from Ian GM3SEK
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