[Skimmertalk] QS1R regulator mod. by 3B8CW

[Bob Wilson, N6TV]

For those who may be interested, I've uploaded the high res. photo of
3B8CW's QS1R regular mod here:

https://www.kkn.net/~n6tv/3B8CW_QS1R_Regulator_mod.jpg

Details below.

73,
Bob, N6TV

Forwarded Conversation
Subject: QS1R
------------------------
From: Clive Woodlock
Date: Wed, Oct 31, 2018 at 1:12 AM
To: <n6tv at arrl.net>

(snip)

As you will be aware, it is well known that the QS1R, although a trusty
workhorse for many years, suffers from overheating and failure of the
voltage regulators - in particular U6 (I think it is).  This happened to
the QS1R that I have here running the Indian Ocean CW Skimmer, but I have
been able to repair it and bring the receiver back into service with a
relatively simple mod.

Perhaps you can pass the relevant information about this modification on,
via the reflector, for anyone else who might be interested to perhaps
attempt to rejuvenate a "dead" QS1R.

Various solutions have been proposed over time to help minimise the
overheating problems of the QS1R, including drilling holes in the case and
bolting on a fan.

However, the fundamental problem causing most of the failures appears to
centre around the voltage regulator U6.  The load, and thus heat
dissipation, of this regulator can be significantly reduced by running a
couple of high current diodes in series with the +5V supply voltage (this
is to drop the voltage to a more manageable level). In my case the diodes
are mounted on a small heat sink of their own to further help dissipate
heat. The small diode heat sink is then attached to the inside wall the
QS1R case - which in itself is also a heat sink.

To save drilling holes in the case - and potentially allow bugs to crawl
inside (a perennial problem for those of us living in the tropics!) -
external cooling is provide using a low speed Thermaltake laptop cooler,
which has a 120mm slow moving fan.  This does a nice job of keeping the CW
Skimmer installation, comprising the QS1R and an associate LNA, at a
comfortable temperature.

See the attached photo which illustrates the regulator mod. (Note - the
diode block actually has 4 diodes, but only 2 are used).

If you need any further details, then please let me know.

BR & 73,

Clive
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From: Bob Wilson, N6TV <n6tv at arrl.net>
Date: Wed, Oct 31, 2018 at 1:20 AM
To: Clive Woodlock

Very nice work Clive.

I assume you also had to cut a trace somewhere.  But maybe all you had to
do was lift one surface mount lead of its pad?

73,
Bob, N6TV
----------
From: Clive Woodlock
Date: Wed, Oct 31, 2018 at 1:40 AM
To: Bob Wilson, N6TV <n6tv at arrl.net>

Bob,

Yes, you just need to cut the trace of the normal 5v line and in my case
also replace the damaged U6 regulator.

The diode block was actually put together by Paul G8AFC (3B8HE when he is
here), who also kindly build the LNA in his Manchester workshop over in UK.

73,
Clive