1934 AW 15 Electrical Restoration, Questions Please

[Jon Ketron]

Hello all,

I am new to this forum and somewhat new to E.H. Scott Radios.  I have about 10 years experience collecting, restoring, and rebuilding pre WWII radio's back to factory specs., or as close as possible.  I am excited to start an electrical restoration on this early version AW15.  My goal is to re-stuff each and every bathtub style capacitor which will include drilling out each rivet and re-installing new rivets.  I will also re-stuff all electrolytic cans.  The end goal of this restoration is to have an electrically restored factory looking set.  

Has anyone re-stuffed these bathtub style caps before?  Could you please give me any pointers or advice for this procedure?  What style of rivets are used for re-installation and what would be the best tool to use for this as there will be many awkward angles?

You may notice the Olympian cabinet this radio resides in has short legs.  Upon close examination, Norman and myself have decided this cabinet had a new set of legs and stretcher installed at some point during the radio's life.  Whether at the beginning or sometime mid point, I don't know.  The legs and stretcher look to be a custom job and the quality shows as this modification looks to be neat and very difficult to spot upon preliminary inspection.

I would like to thank all of you for any help provided, this looks to be an excellent forum!

Thanks,

Jon

 

[Jon Ketron]

Thank you Mike.  Also, thank you for sharing the control on your unit.  Seems like both of our units are somewhat similar in this manner.  Regarding your post about different manufacturers earlier, I too find Scott quality above most all other makes.  Capehart, McMurdo, Lincoln are three others from research and other member input that are ranked very high in terms of quality.  About the only run of the mill manufacture I have in my collection any more would be a 1933 Sparton Triolian and 1930 Philco Concert Grand.  Where did you find your Scott in Europe?

Jon
 
mike hadley said:

Dave;
It would be interesting to know just how many variants of the aw15 were actually made, it seems that no two sets were alike,
Like johns chassis mine has no rear tone control,
it does have the dual pot on the volume control, the static control is a continuous 'top cut', and it has an antenna switch fitted.
My chassis has this odd business with no bathtub filter on the first if, instead there is a discreet choke and 0.1uf cap to ground,
The psu is a 240v version, and it does have the correct Jensen loudspeaker.
I do like the fact that Jon's chassis is in excellent condition, I am rather envious about that as mine has been stored badly and has rust,
I must commend Jon on his restoration, as Scott radios are something special.

[Jon Ketron]

As Dave mentioned earlier I do have a video of this unit in operation for any whom are interested:

https://www.youtube.com/watch?v=v3MAu9w22UQ

[David C. Poland]

Incidentally, the toggle switch in the middle of the back switches between 2 antennas. And is seen only on the AW-15 Wunderlick sets of 1934. The single black antenna post was for a long wire antenna. The pair of red antenna posts was for the short wave antenna supplied with the radio.

The optional Scott Super Antenna (double-dipole antenna)  with external antenna coupler switch (hung on the middle tube shield) seems to have been introduced Fall 1934 along with the revised AW-15 when 1) the Wunderlick 2nd detector was replaced by the 55 tube and 2) the red antenna posts and rear toggle switch were deleted and 3) the final IF transformer secondary was no longer center tapped for push-pull detection. This same optional Super Antenna with outboard coupler switch continued into the AW-23 run for the 1935  5 knob and much of the 7 knob run until late 1936, when Scott modified the antenna circuit to include internal antenna switching (the Super Shield Antenna  Coupler - per October 1934 Scott News).

[mike hadley]

Jon;
Nice vid, what's the tune you're playing?
I take it that the signal was coming through your own in house transmitter, you seem to have a little hum between tracks.
I have a modified talking house, was a real pain to sort out, the house wiring was picking up the am and the resultant signal was getting through the set rectifier, the solution was simple, Earth the set via the coax outside at the antenna,no hum, superb.
You ask how I got the Scott, it was on eBay here in the uk, being advertised as a theatre prop, I think that it has done the rounds by the amount of previous "restoration" that had been going on under the chassis,
It once belonged to a guy called John Howe, when I contacted him he told me that he imported the set into the uk, odd thing is the psu is a 240v model, fits in with uk mains.
I really didn't intend to buy another set but I kept going back to the eBay listing, and then the voices started in my head, and the rest is history, I rescued the Scott from obscurity.
I think that the next how to I post should really be the speaker rebuild, I had nothing to loose as there was no cone and a badly damaged voice coil, maybe.
Happiness is the smell of a warm radio.

[Jon Ketron]

Thanks for the additional info Dave.  Much appreciated as I continue my research.

Jon
 
David C. Poland said:

Incidentally, the toggle switch in the middle of the back switches between 2 antennas. And is seen only on the AW-15 Wunderlick sets of 1934. The single black antenna post was for a long wire antenna. The pair of red antenna posts was for the short wave antenna supplied with the radio.

The optional Scott Super Antenna (double-dipole antenna)  with external antenna coupler switch (hung on the middle tube shield) seems to have been introduced Fall 1934 along with the revised AW-15 when 1) the Wunderlick 2nd detector was replaced by the 55 tube and 2) the red antenna posts and rear toggle switch were deleted and 3) the final IF transformer secondary was no longer center tapped for push-pull detection. This same optional Super Antenna with outboard coupler switch continued into the AW-23 run for the 1935  5 knob and much of the 7 knob run until late 1936, when Scott modified the antenna circuit to include internal antenna switching (the Super Shield Antenna  Coupler - per October 1934 Scott News).

[Jon Ketron]

Mike,

The tune is from 1934 and by Clarence Williams.  Fitting music for this machine at the time of brand new purchase.  In the video I utilized an SSTRAN AMT3000 low power transmitter.  It is a great kit and has solid state components within.  There is an AC line hum present.  Only the Scott seems sensitive enough to pick it up so well.  I need to change the filters or re-evaluate the AMT3000.  Neat story on your Scott.  I like some of the stories behind these Scott radio's.  Norman has some great write up's on some of his units.  Sadly the customer does not have the story behind this unit, purchased at an auction some time ago.  The recent topic on the AW27 has an interesting story behind it, and a very interesting cabinet too.

Jon
 
mike hadley said:

Jon;
Nice vid, what's the tune you're playing?
I take it that the signal was coming through your own in house transmitter, you seem to have a little hum between tracks.
I have a modified talking house, was a real pain to sort out, the house wiring was picking up the am and the resultant signal was getting through the set rectifier, the solution was simple, Earth the set via the coax outside at the antenna,no hum, superb.
You ask how I got the Scott, it was on eBay here in the uk, being advertised as a theatre prop, I think that it has done the rounds by the amount of previous "restoration" that had been going on under the chassis,
It once belonged to a guy called John Howe, when I contacted him he told me that he imported the set into the uk, odd thing is the psu is a 240v model, fits in with uk mains.
I really didn't intend to buy another set but I kept going back to the eBay listing, and then the voices started in my head, and the rest is history, I rescued the Scott from obscurity.
I think that the next how to I post should really be the speaker rebuild, I had nothing to loose as there was no cone and a badly damaged voice coil, maybe.
Happiness is the smell of a warm radio.

[mike hadley]

Jon;

I have attached a before and after photo of the underside of my chassis, only four caps are unstuffed, the two 3uf bolt electrolytics, surprisingly these are still ok after all of these years, and the two bathtubs that are located under the audio transformer, it would have meant removing the transformer to recap, I didn't want to do this as i didn't want to damage anything.

none of the caps fitted by the previous owner were fastened to the chassis, just hanging in mid air,

and the soldering was appaling, still this is what you find with these older molested sets.

I found the song thanks, will add to my collection of old music.

Mike

[Jon Ketron]

Mike,

Nice work on your AW15 Tuner chassis.  I noticed across both electrolytic's on my tuner chassis, there is a power resistor across both positive terminals.  I know this must be a factory change as the power resistor is of the same fit and finish as the large voltage divider it sits next to.  I would recommend replacing those two original electrolytic's on your tuner chassis.  These type of capacitors are always prone to failure due to dried electrolyte within the can.  If those were to fail you risk damaging your power transformer.  Performance of your set will also increase with fresh electrolytic's installed.  Your replicated resistors look very nice!

Jon 

[mike hadley]

Jon;

Thanks for the compliment, as you can see I have a little more rust than you do, the damp storage caused the psu transformer to develop a fault, so unfortunately that's not original but under the shroud who would know.

Both of the 3uf caps were removed and tested on our cap tester at work, it applies current limited dc (halfwave) to the cap while measuring both applied voltage and leakage current, there is also the facility to overrun the applied dc voltage, history has found this to be a really accurate test.

both caps are in really good shape, showing around 5-6v of ripple at 300v, I have thought of changing these for a larger value, perhaps 8uf like the main caps.

I notice that you have used 10uf, so there is room for improvement here, although making the set caps too big can strain the input rectifier during warm up.

Mike

[Jon Ketron]

Mike,

I see your reasoning and fully agree.  I didn't realize you performed extensive leakage testing on the tuner electrolytic's.  That is great they still measure good after all these years.  I see why you are still utilizing them.  I swapped out my original's for 10 MFD to add a bit more filtering.  I must admit I did not perform extensive testing or calculation as to whether or not this value of electrolytic would strain the rectifier during warm up.  I typically never deviate from the value's shown on the schematic when performing all electrical restorations.  If I do deviate as in this instance, I only increase MFD value by a small margin.  It would be wise to measure strain on the rectifier if I ever decide to increase value on future restorations.  Thank you for the advice regarding this suggestion.

Jon

[mike hadley]

Jon,

I only performed the test because the caps could be removed from the chassis and I has access to the test equipment, otherwise I would have restuffed.

I'm still thinking about replacing the caps as I can easily find some cans to fit and maybe going up a size or two on the value,

set was on today china network really strong, but there does seem to be a lot of religious stations in the usa, maybe because it was sunday afternoon here and am in the us,

if I get a chance I will sketch the circuit for the cap tester, scan it and send it over.

Mike

[Jon Ketron]

Mike,

I am interested in a diagram of the circuit if you get a chance.  Speaking of reception, this entire week between 9AM and 10AM I have been able to pull in Radio China on the customers AW-15.  My location is Lexington Kentucky here in the United States.  I don't know Radio China's exact broadcasting location.  Many religious stations on the local broadcast band and U.S. shortwave these days.  Much of AM in the United States has been taken over by religious stations.  I utilize my SSTRAN AMT3000 low power AM transmitter most of the time as a result unless DX'ing.  I listen to local news and evening talk shows on occasion.  As an amateur radio operator I have been working to set up a 136 ft. dipole antenna facing North/South.  I eventually plan on using this antenna for my 350/450 Watt AM tube transmitter once restored.  When not utilizing my amateur equipment, I plan on using this antenna for my standard consumer receivers.  I look forward to test the results after restoration on a Scott as I have an AW-23 and early AW-15 heading my way this week.  I may not be quoting exact text next, I have read within E.H. Scott literature that anything more than an 80ft antenna will produce unsatisfactory results.  Anyone here on the forum ever experiment with antenna's regarding Scott receivers?  What about results with various antenna lengths?

Jon