New to Group - All Wave 12

[Lars Edwards]

Hello and Happy New Year !

I am new to the group and just getting started on repairing/restoring an Allwave 12 to operating condition.  The serial number is Y-98 and it has a Napier cabinet that is in fair to good condition.  It has the single large speaker and all the old electrolytic cans on the power supply and radio are still in place.

As far as I know the radio has been in the family since it was purchased and in the mid to late 60's I installed new electrolytics in the power supply only for my uncle and it worked well for a lot of years.

The last time I powered it up, approximately 20-25 years ago, it worked but had a lot of hum.

The main goal here is to get the radio functioning first and then decide if I want to tackle the cabinet.

My strategy is to replace all capacitors in the power supply and the electrolytics in the receiver first then check the power supply, check the radio and if it works at all then replace capacitors and resistors as necessary.

I have pulled a schematic from the archives to use as a guideline.

One question I have is regarding the large 0.1 MFD "bathtub" capacitor assemblies (#8031) that also have a coil (located on back of receiver chassis with red dots).  I have read the information on how to open these up and restuff with a new capacitor and that seems pretty clear.  My question is has anyone determined how to duplicate the coil ?

Any suggestions and information are more than welcome.

Thanks and best regards.

Lars

[Lars Edwards]

Here is where the repair stands:

Electrolytics replaced and bathtubs replaced except the 3 along the back.

Replaced several resistors that were out of tolerance.

Shortwave reception

Radio receives very well and sounds nice on shortwave with the antenna connected to the black antenna terminal. 

When the antenna was connected to the red terminal the reception was very good but tonight I started to get a really loud hum with the antenna on the red antenna terminal.  No hum when the antenna is connected to the black antenna terminal.

Four good 58 tubes were tried in the RF tube position and the hum is the same on all 4 when the antenna is connected to the red terminal.

The switch in the can has been checked and is functioning as it should.

BC band reception

Calibration on the BC band as checked with a signal generator is quite good across the band.

Reception on the BC band is not very good - sensitivity appears to be low overall and even lower on the low end of the BC band.

Antenna is connected to the black antenna terminal.  No hum.

Again the switch in the can has been verified to be ok.

Tried several 56 tubes (oscillator) and am using the one that seems to perform the best.

Any ideas/advice on how to troubleshoot these two problems will be greatly appreciated.

[David C. Poland]

Hi Lars -  

Your Napier cabinet should have the "auxiliary antenna tuner" mounted on the right side of the cabinet. 

Have you reviewed the antenna info in the owners Instruction Booklet?

On your work bench, use a long wire antenna on the black antenna post, for both broadcast and shortwave.

In the cabinet, use the antenna tuner wired as instructed. (Never seen the special short wave antenna.)

Is your AW-12 the AVC model with a blue glass Wunderlich  tube - MFG'd by Arcturus.

Incidentally, the Napier cabinet is a very desirable cabinet, being open style displaying the receiver on top.

If your receiver hum disappears with antenna disconnected, then the source is external. Any number of modern electrical sources for bad hum including florescence lights, electrical motors like a treadmill or clothes dryer, LED lights, those little wall chargers (wall warts) for computers, cell phones,  and light dimmers and especially the track lights that use those 12 volt spots and floods  ... in your house or a neighbor's. Even a failing step down transformer on a nearby electrical pole.  

As for the larger bathtub caps riveted across the rear chassis apron, I have not rebuilt mine n the two I have restored. If you open one up, try to save the coil and replace just the .5 cap.

[Lars Edwards]

David

Thanks for the information.

The Napier cabinet is a very nice design and this one needs a little work in particular around the bottom.  I do have the antenna tuner as well.

This is the AVC model with the Wunderlich tube.

I have reviewed the manuals on the archives and am planning on reducing the length of the antenna (now ~ 100') to better match the recommendations and I also want try to improve the grounding.

My recollection is that my uncle simply had ~ 20' of wire running around the room (on the floor) and did not even have a ground.  BCB and SW reception at night was very good to excellent.

The SW reception here is what I remember but (very strong) but the BCB is only fair on local stations during the day.  The stations within ~ 20 miles are all daytime only.  At night the BCB stations are weak at best and below ~ 1000 kHz very weak at best.

Once I get over the hurdle of the BCB band reception I may elect to not recap those 3 bathtubs.

David C. Poland said:

Hi Lars -  

Your Napier cabinet should have the "auxiliary antenna tuner" mounted on the right side of the cabinet. 

Have you reviewed the antenna info in the owners Instruction Booklet?

On your work bench, use a long wire antenna on the black antenna post, for both broadcast and shortwave.

In the cabinet, use the antenna tuner wired as instructed. (Never seen the special short wave antenna.)

Is your AW-12 the AVC model with a blue glass Wunderlich  tube - MFG'd by Arcturus.

Incidentally, the Napier cabinet is a very desirable cabinet, being open style displaying the receiver on top.

If your receiver hum disappears with antenna disconnected, then the source is external. Any number of modern electrical sources for bad hum including florescence lights, electrical motors like a treadmill or clothes dryer, LED lights, those little wall chargers (wall warts) for computers, cell phones,  and light dimmers and especially the track lights that use those 12 volt spots and floods  ... in your house or a neighbor's. Even a failing step down transformer on a nearby electrical pole.  

As for the larger bathtub caps riveted across the rear chassis apron, I have not rebuilt mine n the two I have restored. If you open one up, try to save the coil and replace just the .5 cap.

[Lars Edwards]

In looking at the schematic in the archives for the Deluxe with AVC there is a significant difference for the sensitivity switch.

I know that running changes were made and I've outlined the differences in the attached file.

Thanks in advance for any advice.

SN_Y98_1.pdf

[David C. Poland]

Chronology observations and a question.

My earlier AVC model DELUXE (small serial number tag) has the 3 position sensitivity control and my later version (large serial number tag) has the 5 position control. Not to say the the serial number tag was simultaneous  with the control change)

The early AVC owners booklet (dated 1932 and Wellington cabinet on cover) shows the twin speaker set and mentions the special short wave antenna. The later 1933 booklet shows the pedestal speaker (Scott decal but is a Jensen) and shows only a longwise antenna, 60 to 80 feet including the lead-in. Too long an antenna wire degrades performance.

Yes, a short indoors antenna still works well, but may pick up more household electrical interference than an outside long wire.. 

Remember, Scott was a custom set builder and made small running changes as a model evolved in pursuit of performance. Each radio was built upon receipt of an purchase order. A deviation from a diagram may be legit.  

Question - Inspect the wiring of the amp at the 6 in socket.   are 5 wires only used?   or 6 wires, (which is the final version with alternate audio path to the amp)? 

[Lars Edwards]

Dave

The radio has the pedestal speaker.

On the round socket to the speaker one pin goes to ground and the others have wires.

On the rectangular socket all 6 have wires.

We've been having a lot of electrical storms but today we got a break and now the antenna is 70' including the lead-in.  This may have helped a little but the BCB signals are still weak.

This afternoon/early evening I was using a station about 20 miles away as a "reference" while trying some troubleshooting.  I was making some small improvements and then the station signed off for the day ! 

I guess I'll just use the signal generator.

I'm going to recheck voltages and the signal path starting from the antenna post. The sensitivity switch is also a bit touchy on the highest sensitivity position so I will try cleaning that again.

[David C. Poland]

Turn the band switch several times so the built-in silver polishing felt block wipes the coil contacts several times. Also work the band switch off the broadcast position and back on a few additional times.

Also, clean the contacts on the coil wheel with alcohol - Do not use any kind of abrasive of any sort on the silver plated surface of the spring loaded contacts. Always position the coil wheel on the broadcast band and leave it in the position while the coil wheel is dismounted. Inspect and clean the contact switch in the antenna coil coil can - the coil directly behind the tuning dial - may be a bit of a pain if the grid cap wire goes through the side of that coil cover,

[Lars Edwards]

Again, thank you for the interest and sharing the information.

The contacts on the coil wheel have been cleaned with alcohol and the switch in the antenna coil can has been cleaned and has been tested for continuity.

Cleaning the contacts on the coil wheel helped a bit in that the switch is a bit better in that it does not require much if any toggling to get good contact.

The strength of the BCB reception is still weak.

I'll update you as soon as get a few more measurements and observations.

[Lars Edwards]

David

I've checked voltages and all appear to be reasonable meaning within +/- 10%.

With the 5 position sensitivity switch there are of course a couple more readings than those listed in the documents on the archives.

The surface of the spring mounted contacts on the band switch look really clean and have a mirror finish.  You mentioned a built-in silver polishing felt block.  I do not recall seeing this when I had the turret off.  Where is this located ?

Hopefully I'll get some time to continue work on the AW12 this week.

[David C. Poland]

You can't miss the two felt blocks. Both attached to the coil wheel between certain coil wheel contacts.

Dark red and 1/4 inch thick riveted to the coil wheel - so as to wipe the spring loaded, silver plated contacts when turning the band switch.

[Norman S Braithwaite]

Except possibly for some of the last ones made, the coil wheels for the AW-12 Deluxe did not have the felt bars for cleaning contacts.

Norman

[Lars Edwards]

David and Norman

Thank you for the replies and information.

It appears that the AW-12 Deluxe here does not have this.

Have a great 4th of July.