Allwave Deluxe: Question regarding power supply variation

[Ken Carr]

My AW Deluxe has 9 tubes in the tuner section and 3 in the power supply / amp. It has the pedestal speaker.

The power supply drawing showing one speaker is most like the PS I have. There are some variations though and I would like to determine if they are factory changes or later repairs.

The drawing (CIRCUIT DIAGRAM OF SCOTT ALLWAVE DELUXE POWER AMPLIFIER) shows a total of 4 capacitors. I have 5:  three 8 MFD cans mounted on top of chassis, one bathtub capacitor mounted on on chassis wall (measures 1.755 MFD), and cube-shaped box mounted on the chassis wall that measures 10 MFD (the positive lead goes to the center tap of the transformer section that supplies filament voltage to the 80 rectifier tube).  So, the bathtub capacitor seems to be the one not shown on the diagram.

There are also some resistors in the power supply. A single wirewound resistor (2.0 Megohm) links the first and third can capacitors. Two other resistors go from the no. 80 tube plate supply center tap to terminals on the earphone jack.

All of  these items (unless maybe the 2 MOhm resistor) appear to be factory installed even to the point where the 10 MFd and 2 MFd capacitors are riveted to the chassis.

So, does this all look correct? Photo attached.

[David C. Poland]

KEN  -  Yep: 9 +3 for 12 tubes for the single dial ALLWAVE DELUXE. The Pedestal (Jensen) speaker indicates the AVC model with the later tube line up using 58 for IF and Wunderlick 2nd detector (3rd tube back on the left side).

The black cubical cap underneath is familiar. The Deluxe diagram (with the twin speakers) shows it to be it as 2 MFD. Be careful with polarity unless you use a non polarized cap. The filament winding center tap travels to one of the the 2 speaker fields as part of the bias circuit for the 45's.

*

FYI - the twin speakers are electrically equivalent to the 12 inch Jensen pedestal speaker which was the Spring 1933 speaker upgrade. The twin speaker diagram with Wunderlick tube is correct for the later 1933 DELUXE sets with AVC as long as only 5 of the 6 pins of the Jones plug are used.

However, if the 6th Jones pin IS being used, then it is the 6 th wire that carries the audio signal from 2nd AF to the interstage transformer of the amp. (I have this really late version  Deluxe w AVC ((early 1934?) - for which no Scott diagram has ben found yet.

[Ken Carr]

I will stick to non-polarized capacitors for replacements (other than the filter capacitors). Thanks for the tip. I need to investigate more regarding the pins on the Jones plug. It is of the six pin variety. I was mostly ignoring the diagram with twin speakers but will look at it more closely now. It shows a 30 Henry choke between two of the filter capacitors. I wonder if the blue item that I thought was just a resistor is actually a choke?

And just for reference, my voltage divider is on the tuner/receiver chassis. Sure wish Scott was better at making drawing  changes!

As always, thanks for the help.

David C. Poland said:

KEN  -  Yep: 9 +3 for 12 tubes for the single dial ALLWAVE DELUXE. The Pedestal (Jensen) speaker indicates the AVC model with the later tube line up using 58 for IF and Wunderlick 2nd detector (3rd tube back on the left side).

The black cubical cap underneath is familiar. The Deluxe diagram (with the twin speakers) shows it to be it as 2 MFD. Be careful with polarity unless you use a non polarized cap. The filament winding center tap travels to one of the the 2 speaker fields as part of the bias circuit for the 45's.

*

FYI - the twin speakers are electrically equivalent to the 12 inch Jensen pedestal speaker which was the Spring 1933 speaker upgrade. The twin speaker diagram with Wunderlick tube is correct for the later 1933 DELUXE sets with AVC as long as only 5 of the 6 pins of the Jones plug are used.

However, if the 6th Jones pin IS being used, then it is the 6 th wire that carries the audio signal from 2nd AF to the interstage transformer of the amp. (I have this really late version  Deluxe w AVC ((early 1934?) - for which no Scott diagram has ben found yet.

[Joseph W Strickland]

Ken;

Some of these older radios indicated certain resistors with a capitol M following the numeric value indicated. It was an older approach to shorthand for 1000 (Roman numeral system), so instead of it being a 2 Megohm wire wound resistor it would be a 2000 ohm or 2Kohm resistor. A 2 Megohm resistor in a power supply would normally only be used as a bleeder resistor to bleed off any remaining B+ after the set is turned off. Early schematic conventions were different in that respect and later on the industry began to standardize on abbreviations used on schematics and parts lists.

One source for accurate filter capacitors is the metalized polypropylene film capacitors that are used for electric motors. They are not polarized since they are designed to be used in AC circuits. They have very low ESR and the AC voltage rating is much lower than the actual DC voltage rating. I tried a 16uF of that type in the power supply of my 800B and it worked fine. They often are less expensive than electrolytic capacitors.

Joe

[Ken Carr]

Joe, that is interesting about the metalized polypropylene film capacitors. I have seen them offered and will consider them in the future. Interesting that you mention ESR. I got an ESR meter a while back and find it useful to do a functional check on capacitors even when they are still in the circuit.
The resistor I mentioned is unmarked. It is just painted blue. The values are missing. I unsoldered it and measured directly with a multimeter. I'll check it again but I think that is the right value. I was not able to find the resistors in any of the power supply drawings so I don't know what it should be per E. H. Scott.
Thanks for the suggestions.

[David C. Poland]

The 30 henry choke is mounted on top of the amp chassis. It is encased in chrome an looks a lot like a transformer. Sits between the row of filter caps and one of the 45's.

For the Jones plug, probably only 5 of the pins are wired up - turn the amp over and look to see pin 6 is unused. If pin 6 is used, you have a very late version like mine.

Blue item? In the amp?

[Ken Carr]

Dave, there is an attachment to my first post above. It shows what looks like a wirewound resistor between the first and third filter capacitors. That is the blue item that I thought was not original since I don't see it on a drawing.

The only thing I do see on the drawing is the choke which you have confirmed is part of the item that looks like a transformer
There are also two more resistors that are attached between the center tap of the plate supply of the no. 80 rectifier and the earphone jack. I am not sure why they are there.

Pin 6 on the Jones plug is not used. That terminal goes to chassis ground and nothing is wired to it.

[David C. Poland]

Ken,

Can't identify your blue item from looking at my amp. But my last version amp is somewhat different from yours.

The earphone jack is not shown on the Scott diagrams, but the earphone jack seems to be standard. The several I have seen all have one. The two dogbone resistors you mention are also standard (mine are 100K: brown body,, black end and yellow dot multiplier = 100,000 ohms). 

The DELUXE Jensen and the twin speaker set are interchangeable. Looking at the Scott Deluxe amp diagram with the twin speakers (your Jensen has 2 field coils) and same 6 pin plug wiring,  perhaps this overview will help:

The high voltage circuit from the 80 tube filament winding center tap: passes 1st filter, through the 30 henry choke, passes 2nd filter, to 2500 ohm speaker field and back to amp, passes 3rd filter and also branching to 1)  Jones pin 4 to provide B+ to the receiver and 2) through the primary of the interstage transformer to Jones pin 5  not only to provide B+ to the plate to the 2nd AF 6J5 tube but also carry the audio signal back to the primary of the interstage transformer that drives the output 45 tubes. The earphones jack is wired into the audio circuit but I have not traced it in detail.

The filament negative bias for the 45 tubes begins with chassis ground at pin 1 of the speaker socket, then though the other speaker field coil (875 ohm) and (being now negative with respect to chassis ground) back to speaker pin 6 to the amp, passes the 2 MFD filter and on to the  center tap of the 45 tube filament winding - thus giving a negative bias to the 45 tube filaments with respect to chassis and further increasing the voltage difference between each 45 tube filament and plate.

I suggest you make a copy of the amp/speaker diagram and color code the wires: red B+, green bias circuit and yellow for the filament circuits. Then compare part by part with the diagram and sketch into the diagram any other part you find. (Some years ago, that is what I did to figure out the very late version amp and receiver that uses all 6 pins of the receiver Jones plug. )

[Ken Carr]

David,

Thanks for the explanation of the circuit theory. I like your idea of mapping it out myself. That is what I have been doing, though not in the most disciplined manner. I am redrawing the circuit so as to get a handle on what might have been done to it and to compare it with the Scott drawings. And yes, those two resistors in the power supply are the same value as the ones in yours. Now I know they belong there.

I fully opened the tuner section today. That has to be the most interesting underside of a radio I ever saw. All those colorful large antique dogbone resistors and the band change turret in the middle that looks like an air-cooled radial engine on an old biplane! Not a technical description, I know, but it is an impressive sight.

The voltage divider resistor may have a problem since one of the terminals has solder on it but no lead. My plan is to continue with drawing up 'the real circuit', replacing capacitors, and finally powering up slowly. A series of voltage tests will likely answer a lot of questions.

I really appreciate your in-depth analysis. Thanks for all your input!

David C. Poland said:

Ken,

Can't identify your blue item from looking at my amp. But my last version amp is somewhat different from yours.

[David C. Poland]

Ken - you have to remove the coil wheel to get at some of the caps for replacement.

It is critical you first move the band switch to Broadcast band position (full counter clockwise) before removing the coil wheel. And do not turn band switch until after you remount the coil wheel. The band switch also works a switch in the antenna coil above the coil wheel gear drive. If you get that switch out of position with respect to the coil wheel you will break that switch.

Study the technical service data pieces available in the set folder for the Allwave Deluxe.

[mike hadley]

Hi,
On reading your notes on capacitors I would like to add my penny worth,
motor caps are an execellent choice for filter caps, you can safely multiply the ac rating by 1.5 times on dc,
Non polarised and easy to come by and will fit inside most cans for re-stuffing,
just make sure you use motor run type as these are continuously rated where motor start caps are not.

The audiophile guys hav been doing this for years, fit and forget,
Mike

[Ken Carr]

Thanks for the advice, David. I have seen where you mentioned this elsewhere. 

It's always good to prevent a problem.

David C. Poland said:

Ken - you have to remove the coil wheel to get at some of the caps for replacement.

It is critical you first move the band switch to Broadcast band position (full counter clockwise) before removing the coil wheel. And do not turn band switch until after you remount the coil wheel. The band switch also works a switch in the antenna coil above the coil wheel gear drive. If you get that switch out of position with respect to the coil wheel you will break that switch.

Study the technical service data pieces available in the set folder for the Allwave Deluxe.

[Ken Carr]

Mike,

Thanks for the additional hint. I will keep my eyes out for the

motor caps also. 

mike hadley said:

Hi,
On reading your notes on capacitors I would like to add my penny worth,
motor caps are an execellent choice for filter caps, you can safely multiply the ac rating by 1.5 times on dc,
Non polarised and easy to come by and will fit inside most cans for re-stuffing,
just make sure you use motor run type as these are continuously rated where motor start caps are not.

The audiophile guys hav been doing this for years, fit and forget,
Mike