[Collins] kwm-2 fan and outputs

[Dr. Gerald N. Johnson]

Keeping the post rectifier section floating solves my concern. The KWM-2 
can be wired for 6, 12, or 24 volts. Running at home on the original AC 
supplies the heaters are wired for 6 volts. If running off a heathkit 
power supply I think that's 12 volts AC. Most ham mobile unless in a pre 
56 or so vintage car will be 12 volts, but military vintage could be 24. 
With the 12 or 24 volt connection the fan supply might unbalance the 
current distribution a little bit, but I suspect the variations from 
tube to tube are as great.

The voltage doubler circuits that I'm familiar with, half wave, and full 
wave, depend on capacitors in series with the transformer and won't pass DC.

Brushless fans are quieter than brush fans, but if the switching 
transistors switch rapidly with fast rise or fall times, they can make 
noise too and at harmonics of the switching frequency. Bypassing helps 
either fan a lot.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 10/11/2010 12:01 AM, K5GNA at aol.com wrote:
> Jerry,
> ANSWER:
> The 6 to 12 volt doubler for full speed, with the slow speed at a 6 volt
> supply was my design and Dave didn't cover the concept originally.
> The voltage doubler and the fans are actually floating above ground, so
> they really don't care which is chassis ground or not. To guard against
> any possible interference, I have 2 bypass caps on both sides of the
> floating 6.3 VAC input to chassis ground and I also used 2 on both the
> fans negative leads to chassis ground. The board's floating ground is
> bypassed to chassis ground with 4 caps, so it causes no problems. The
> fans are brushless, so they don't generate any electrical noise.
> BACKGROUND:
> My books and equipment are buried for at least the next week or so, but
> I was under the impression that one side of the filament line is
> grounded and the other side either floats are parallels the first --
> depending on whether or not you are on 6 or 12 VDC. Of course if you are
> on DC, the doubler won't work and you only get slow speed at 6 volts DC
> out. AC puts one side of both filament strings at ground. Working from
> memory here!
> When I designed the board, I thought I used the chassis ground side of
> the 6.3 VAC on the NB plug and used it as the (floating) ground on the
> fan supply board. The white striped power wire on my fan assemblies is
> the doubler circuit's floating ground. And I used the shell (not center)
> of the pilot lamp for the same. I don't actually remember if I checked
> to see if the pilot lamp socket was a chassis ground or not -- it sure
> did look like it.
> I have sold almost 300 of them and have had only one complaint and it
> was very recently. He has hum on RX, but I probably have a short on the
> board. But it will be a week or so before I can get on it and resolve
> the problem. Replacing the assembly should do the trick. No other
> complaints in any of the 300 units sold.
> TNX & 73
> Bob
> K5GNA
> In a message dated 10/10/2010 11:08:12 P.M. Central Daylight Time,
> geraldj at weather.net writes:
>
>     Thank you. Dave's page seems to cover the topic well except that one
>     circuit detail bothers me. I see the voltage doubler supply marked as
>     grounded on the negative side, picking off 6.3 volts AC from some
>     filament string in the radio, but that full wave voltage doubler
>     expects
>     a non grounded source which is not the case for the KWM-2. Is that
>     ground not really grounded in the modern power supply assembly?
>
>     I'll post a copy of your answer to the Collins Radio Association list
>     where the inquiry began.
>
>     73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.
>
>     On 10/10/2010 10:20 PM, K5GNA at aol.com wrote:
>      > Jerry,
>      > I have been off of Ebay for a little over a year and working on my
>      > house. Had some Hurricane Ike damage and a lot of bad galvanized
>     water
>      > pipes -- so we have done a complete remodel. I should be back on Ebay
>      > next month.
>      > I made a bunch of fans assemblies for Dayton, but haven't been
>     actively
>      > selling them. I have two types in stock.
>      > The KWM2 version fits on the final cage with 3 original screws
>     and will
>      > plug into the NB socket for power. It is $48.95 plus $8.00
>     shipping and
>      > handling for one and $2.00 shipping for each additional unit.
>     There is
>      > no NB plug on the 32S.
>      > The 32S / KWM2 version fits on the final cage with 3 original
>     screws, as
>      > above, and solders onto the back of the pilot lamp assembly for
>     power.
>      > It is very easy to fit on the 32S since the socket is very
>     accessible,
>      > so it takes just a minute or so to tack it on. On some KWM2's a
>     bracket
>      > blocks the back of the lamp socket and you must first take the
>     bracket
>      > off. It is $39.95 plus $8.00 shipping and handling for one and $2.00
>      > shipping for each additional unit.
>      > The original design for the brackets came from Dave about 16
>     years ago
>      > and I bought the rest of his stock of brackets a few years back and
>      > modified the bracket and built a small PCB to give either full
>     speed or
>      > half speed with a switch (no off) . Half speed is pretty much
>     silent and
>      > full speed is hard to hear at arms length.
>      > The NB mounts in the same space as the fan, but on the lid, so it
>     is one
>      > or the other inside. The cable on the NB is long enough to put the NB
>      > out the rear of the radio if you really want to use it. Some of the
>      > Waters accessories like the Q Multiplier stick up into the left
>     fan, but
>      > if it has a NB, then the NB would also interfere with the Waters.
>      > The bracket I was talking about on the solder in version mounts
>     on the
>      > plastic nuts on the back of the meter, so it is not that hard to
>     remove
>      > and saves you a few dollars if you want to solder it in. I just
>     solder
>      > it into the unused holes on the lamp socket, so there is no trace
>     of it
>      > if you want to remove it and keep it unmodified.
>      > Here is a copy of Dave's original article in Electric Radio in 1996.
>      > http://members.cox.net/daveishmael/KWM2FanBracket.htm
>      > I accept PayPal at this Email address and I am good at QRZ.com.
>      > 73,
>      > Bob,
>      > K5GNA
>      >
>      > In a message dated 10/10/2010 9:25:24 P.M. Central Daylight Time,
>      > geraldj at weather.net writes:
>      >
>      > Google shows several hits referring to epay sales by K5GNA and he has
>      > 2674 comments, but nothing offered at the moment. Might be a direct
>      > request would be in order. I'll carbon copy him with this for a
>      > reaction.
>      >
>      > 73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association
>      >
>      > On 10/10/2010 9:06 PM, Ron Manfredi wrote:
>      > > The Collins web site:
>      > > http://www.collinsradio.org/default.aspx
>      > >
>      > >
>      > > on the Dayton Prize Donors page mentions:
>      > >
>      > >
>      > > *KWM-2A Cooling Fan Kit*
>      > > Bob Seydler, K5GNA K5GNA at aol.com, booth spaces 1310, 1313
>      > >
>      > >
>      > > Could this be what your are looking for?
>      > >
>      > > 73,
>      > > Ron
>      > > WA2EIO
>      > >