Scott AW 15 Antenna Switch

[Michael J Boessen]

Hi, All:

Working on a Scott AW15.  One problem I've been working on is terrible short wave sensitivity.  This morning I have found what I think is the problem, but have no idea how to fix it.  See the attached photos.  This is part number 43 on the parts list.  I believe it is what the schematic calls S101, but these numbers on the schematic don't seem to relate to the parts list.  

Anyhow, I have a shaft that is geared to the band switch, and has a phenolic cam on it.  The cam is situated 'way too low to engage the switch contacts, and doesn't rotate such that it would change the switch even if it did.  It rotates from the position you see in the photos clockwise, toward the shield can base and never gets anywhere near the switch contacts.  If I am reading the schematic correctly, when I rotate the band switch from BC to SW this cam should open the normally closed contacts and close the normally open contacts.  I cannot imagine any way for the cam I have on the shaft to accomplish this.  

I suspect that what I am seeing here is not what I am supposed to have.  Can anyone help me with what this switch actuator should actually look like and how it works?  I can't see any way for what I am encountering here to do the job.

Any help greatly appreciated!

Best

Mike

[Michael J Boessen]

Forgot to add the picture that shows the location of the antenna switch

[Michael J Boessen]

Forgot to add the picture that shows the location of the antenna switch

[Kent King]

You are correct - the cam should leave the switch open on the AM band and be closed for all 3 SW bands as the switch is rotated. Someone did what Scott tells you not to do in the service data - while the coil assembly underneath the set is off the spindle - do NOT move the wave change. Someone did move it, and it sounds like you may be 180 deg off with the wave change switch. In addition to this switch, there is one on the wave change shaft just behind the front apron, it may be "off" as well. I've redone several sets where the restorer got the bandswitch out of position, it's not difficult to fix but takes a few minutes to tear it down. If you'd like help, let me know, my direct email is [e-mail]

Kent

[Michael J Boessen]

Hi, Kent:

Well, what you just said makes sense.  I may have "fixed it wrong".  I took the little cam off and rotated it 180 degrees, which made the switch work correctly, but I have other problems, mostly with the oscillator.  I'm thinking what you have described is more likely what happened, so I may have to "unfix" the little cam and take a look at what is beneath the chassis.

Heading out to golf.  I'll look at it again when I get back.  You might just have the solution to my problems.

Thanks for the help.  I'll be in touch later today.

Mike

[David C. Poland]

I would assume the wafer switch behind the apron on the band switch shaft was not messed with with respect to the shaft.
The broadcast band is the full counter clockwise position - about 7:30 (clock face) - so the metal pointer knob points to the white diamond of the band escutcheon.
There is a stop that limits the range of the band switch rotation to about 300 degrees, for the 4 bands.
There are detents on the coil wheel for each band - in the form of spring loaded cups (don't loose the springs).
The band shaft has a flat side, so the knob's D shaped knob hole positions the knob properly on the shaft.
As long as the casting containing the angle gear has not been dismantled, the orientation of the control shaft to the vertical shaft (to the coil wheel and overhead switch) should be OK. (If not, have fun - been there, done that.)
The vertical shaft holding the the coil wheel (and holding the fibre cam above) is flat sided, so the wheel may be mounted 180 degrees wrong. But if you are getting some reception, the coil wheel is probably correctly mounted. (Bottom cover holes should align with padders)
The fibre cam should operate the antenna coil switch, without binding on the can skirt. I too experienced one fibre cam mounted backwards. It should operate the switch freely.
Also, concerning the big tuning capacitor, the mounting screws securing it may no longer be quite well enough grounded after all these years and affect reception. So, loosen and retighten each of the 3 (as I recall) mounting bolts.
*
Scott radios of the 1930's were custom built - each upon receipt of an order and shipped in about 3 to 5 weeks usually. And Scott was chasing performance so most models evolved during the model run .... especially true of the AW-15 with several circuit diagrams and a given example details may straddle 2 diagrams. The Riders AW-15 diagrams are only the later versions using the 55 tube for 2nd detector. The Scott Enthusiasts web site has the earlier AW-15 diagrams using the Wunderlich tube for 2nd detector.

[Norman S Braithwaite]

The vertical shaft can be 180-degrees out of phase with the horizontal shaft without the gear box being dismantled.  Furthermore the wafer switch behind the front panel may be 60-, 120-, 180-, 240- or 300-degrees out of phase if one had removed the gear box (without dismantling it) at some time past.

Norman

[David C. Poland]

Yeah, so true. hoping Michael's set had not been that brutalized.

One AW-15 I acquired had the metal band pointer so difficult to remove from the shaft, that past efforts pulled the shaft out of the gear box before I acquired it. 

I was able to use the overhead antenna switch action as an aid to help get the control shaft gear properly re-engaged with the gears box.  And I had an AW-15 wood panel that AW-15's are shipped with, so I was spared  having to repeatedly put the receiver in the cabinet to get the pointer to align with the escutcheon detail. Still was a bit of trial and error, but succeeded.  

footunately