[Hammarlund] Possible problem source

[Bob Camp]

Hi

One of the interesting things about having a bunch of radios from "days 
gone by" is that you build up a bunch of data. That does not mean that 
the data is being correctly interpreted, only that there is a bunch of 
data.

Having built a fair number of Heathkits back in the good old days and 
having a variety of Hammarlunds, Drakes, and various mil gear I will 
make a *guess* at what's going on here.

I have not seen the problem you describe in military gear. That 
includes stuff that like your radio still has the original tubes in it 
from back in 195x. I also have not seen it in stuff like HQ-170's that 
are the same approximate age as your SB-110. I have seen a number of 
similar problems in Heath SB-301/401's.

As I recall my approach (back in the 1960's) to building these radios 
the focus was on getting it done and on the air. If the manuals had a 
step for cleaning the rosin off of a solder joint I must have missed 
it. I also don't remember there being any kind of flux cleaner (like a 
bottle of alcohol) coming with the kits.

My suspicion is that the commercial and military radios got a better 
cleaning job when they were made. A little bit of rosin and a lot of 
years could create some issues.

The other possibility is that somebody used a cleaner on the tube pins 
back a while. Some of these cleaners don't get washed off totally and 
they will corrode the area. Bottom line is that if you do a cleaning 
process be sure you don't leave anything behind other than lubricant 
....

	Take Care!

		Bob Camp
		KB8TQ

On Feb 17, 2005, at 12:25 AM, Glen Zook wrote:

> Tonight my Heath SB-110A 6-meter rig developed a
> couple of problems.  First of all, I tightened all of
> the screws that hold the printed circuit boards to the
> chassis.  Then I took a paint brush and cleaned
> everything on top of the chassis.  Finally, before
> disconnecting the rig and taking it to the service
> bench I started unplugging and then plugging in again
> the tubes in the circuit "area" that the problem was
> occurring (the push to talk circuit was "hanging" for
> several seconds after releasing the microphone).
>
> When I removed the 6AZ8 that controls the relay the
> unit returned to receive.  Of course I had to return
> the tube to its socket before the unit would operate
> again.  I "wiggled" the tube, I removed and replaced
> it, and so on.
>
> Finally, I actually removed the tube, removed the tube
> shield, and took a good look at it.  Frankly, the tube
> pins had corroded over the years and just were not
> making a good connection to the socket.
>
> Since I keep a jar of Goddard's "Silver Dip" around to
> clean various items (like coax connectors) I "dipped"
> the tube pins in the solution.  After a good rinse at
> the sink and a good dry with a towel I replaced the
> tube.  Problem solved!
>
> I then checked the other tubes and all of their pins
> were showing various signs of corrosion.  Thus, I
> cleaned them one-at-a-time.  Of course most of the
> tubes in the SB-110A are actually original, and since
> the unit works perfectly, I haven't replaced a tube in
> years.
>
> I now plan on cleaning the tube pins, along with
> tightening all of the hardware that holds everything
> in place on any boat anchor that I work on that had
> intermittent problems.  In fact, I really think that
> it would be a good idea to actually clean all of the
> tube pins whenever I work on a unit for someone else.
>
> Corrosion on tube pins is not something that you
> immediately think about when troubleshooting a "boat
> anchor".  But, it certainly can be a source of
> problems.  Often we clean the sockets as well as
> switches, potentiometers, and so forth.  However, how
> often do we think of cleaning the pins on the tubes?!!
>
> Glen, K9STH
>
> =====
> Glen, K9STH
>
> Web sites
>
> http://home.comcast.net/~k9sth
> http://home.comcast.net/~zcomco
>
>
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