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AETNA 652 manufactured by Walgreen Co.

Just below are the restoration pictures.  This is a beautiful radio.  

IMG_3691.jpg (1001611 bytes)Original colors were found as the damaged finish was stripped off. 
IMG_3692.jpg (989982 bytes)Stain colors were custom blended to match what was found under the original lacquer
 
IMG_3693.jpg (1176614 bytes)Multiple coats of high gloss lacquer applied.  About 7 coats. 
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IMG_3697.jpg (249927 bytes)A PM speaker replaced the open field coil electrodynamic speaker. 
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IMG_3700.jpg (328758 bytes)Flat rubber washers were used to better set the chassis height.

This unit came in with out a power cord.  I like that!  I can and did cold test all the important parts made of Unobtainium.  All the important parts tested good except the field coil of the speaker.  It is open.  I will be researching possible repair of the voice coil.  If not repairable I'm confident a replacement 6.5" electrostatic speaker is available.  Take a look below. 

This chassis matches the schematic for a Walgreen Co., (Aetna) 652 found on Riders 9-1.  The bias cell is shown, the output tube is a 6B5 as installed in the chassis and the two filter 8uf 450 volt capacitors are on both sides of the 1500 ohm field coil making up the Pie filter (as in the symbol for 3.141...).   The schematic is rough but very usable. 

 

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IMG_3489.JPG (295231 bytes)This cabinet will be stripped and refinished.
IMG_3490.JPG (300893 bytes)All the parts are included except one knob.  I think one control shaft was cut off to remove the chassis. 
IMG_3491.JPG (334664 bytes)
IMG_3492.JPG (349806 bytes)
IMG_3493.JPG (329489 bytes)
IMG_3494.JPG (1308935 bytes)All coils and IF transformers ohmed out good. 
IMG_3496.JPG (872916 bytes)I need the schematic to confirm what this is.  It may be a bias cell. I can measure about 168 mv on it. Tracing the circuit will tell for sure what it is. 
IMG_3497.JPG (215200 bytes)
IMG_3498.JPG (932782 bytes)This disk is driven from the tuning shaft.  It needs replaced. 
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IMG_3505.JPG (199578 bytes)Audio output transformer tested good. 
IMG_3506.JPG (246382 bytes)
IMG_3507.JPG (271031 bytes)The black donut surrounded by the brown "U" bracket is the field coil. 
IMG_3508.JPG (242526 bytes)I will follow the lead wires into the coil.  Maybe there is an accessible break in the wire. 
IMG_3509.JPG (311253 bytes)

Unless an electrodynamics speaker economically  becomes available, I think we will go with a permanent magnet speaker and a 1500 high wattage ceramic resistor for the old field coil. Permanent magnets were hard and expensive to come by in the 1930s.  I will mount the audio output transformer on an open space on the chassis. 

 

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Chassis component locations. Green tested good. This should help me determine the model number. 

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Cost estimates are coming in for rewinding the field coil.  There is no easy way to separate the coil from the frame.  It needs to be cut and welded back together.  All that labor on top of shipping, and rewinding costs make repair of the original speaker a poor economic choice.  Replacement is more cost effective.  If this was a classis stand a lone speaker like this one, then the cost may be well worth it.  But this is a common speaker concealed in the cabinet. The search goes on. 

There are three knobs.  I need a fourth.  If there is no match then four new reproductions will be procured.  Some times a new reproduction does not color match the original knobs, exactly.  This could be irritating to most owners.  So it is better to order 4 new knobs then chance it with a miss match.

IMG_3532a.jpg (255079 bytes) 0.49 or 1/2 inch thick
IMG_3531a.jpg (270136 bytes) 0.80 inches wide.
IMG_3530s.jpg (236003 bytes) 20.32 mm
IMG_3529s.jpg (349838 bytes)12.5 mm thick

 

The chassis during restoration:

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IMG_3533.jpg (432864 bytes)High voltage lug missing and a bit of carbon on the chassis.

IMG_3534.jpg (533725 bytes)Epoxy and a new lug. 

IMG_3535.jpg (3957071 bytes)A before shot showing the new HV solder lug. 

IMG_3537.jpg (156572 bytes)This is a dead dry cell.  It provided negative grid voltage for the #75 tube.

IMG_3536.jpg (161586 bytes)  It is made of Unobtainium. 

IMG_3544.jpg (188404 bytes)A quick trip to RadioShack to find a 1.5 volt lithium cell that fits inside the battery holder.

IMG_3547.jpg (154758 bytes)Wrap it in heat shrink and trim it neat.

IMG_3548.jpg (129784 bytes)The positive outer shell will not short to the old battery holder. 

IMG_3552.jpg (393825 bytes)That's slick baby!  This should last a long time.  But it will eventually need replacement.  

IMG_3554.jpg (354658 bytes)The grid circuit draws about 134ma. (as calculated from the voltage drop on the series resistor).  

When the battery runs down the audio will get distorted.  Measure the voltage across the battery clip with a volt meter.  If it is less than 1.0 volts it is time for a new battery.  It is best to use a battery tester that applies a proper load. 

IMG_3558.jpg (1177288 bytes)All components have been replaced.  All but the parts on order, Tone control and Volume on/off control.  The bias battery is easily accessible in the middle of the chassis. 

IMG_3557.jpg (278756 bytes)This tone control is jammed, will not rotate and is burned. 

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What is the minimum wattage needed for the 50k ohm tone control?  I think is is a wire wound.  The rated output of the 6B5 is 4 watts.  Only a part of that will go through the tone rheostat due to the series capacitor.  So logically something less than 4 watts is needed.

The research came back at a 1/2 watt.  Quite available.  the Xc of the capacitor with the tone control near full bass is about 650 ohm with the 0.05 capacitor from plate to ground.  Good. I have a half watt long shaft on order.   Xc= 1/(2*3.141*R*C) C farads R ohms

 

The 0.03 inch clear plastic came in for the tuning drive mechanism.  

I measured the original and built a cutting jig.  The outer edge is captured by the tuning knob shaft.  It has to be smooth and consistent.  

IMG_3588.jpg (333680 bytes)Determine the radius.

IMG_3589.jpg (2339418 bytes)Razor on 3/4 plywood. 

IMG_3595.jpg (190965 bytes)Just high enough to score the plastic.  Use multiple rotations. 

IMG_3601.jpg (224153 bytes)Move the disk for the inner hole. Remember Measure twice & cut once.

IMG_3602.jpg (181529 bytes)This is the second try. The first disk's inner hold was too big and the brass mounting ring was too small. I could not successfully heat expand the ring.  

IMG_3605.jpg (332777 bytes) The brass retaining ring was opened up a bit with a Dremel tool and epoxy in place. 

IMG_3604.jpg (220300 bytes)The retainer still needed press fitting. 

IMG_3609.jpg (171669 bytes)Tuning knob shaft edge drive. 

IMG_3611.jpg (339633 bytes)This clear plastic disk, driven by the tuning knob, moves the air capacitor veins (tuning capacitor) and the dial pointer. 

IMG_3612.jpg (131375 bytes)Align and paint the indicator.  See the "Dial Scales" page for a high res scan of this dial scale. 

 

 

The cabinet finishing is Done.  I normally would post the completed radio but I wanted to get these preliminary pictures up.  I will add better pictures after reassembly.

IMG_3489.JPG (295231 bytes)  IMG_3485.JPG (282237 bytes)   IMG_3488.JPG (292773 bytes) 

Before.

  IMG_3614.JPG (880518 bytes)   IMG_3613.JPG (786415 bytes)   After with flash.  Three colors of tint was  used to match the original colors.  The colors were carefully chosen to both match the original hue and allow the grain to show through.  The black highlight was one of the colors.  About 7 coats of lacquer have been applied. The wood was stripped and sanded.  

Once complete I will add more pictures with and with out flash and backdrop.

 

IMG_3641.JPG (1060957 bytes)Nice new reproduction grill cloth. 

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IMG_3644.JPG (1118754 bytes)I just need to get the proper size knob in.  The upper right is just a tad too big.  Good for tuning bad for the match. 

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IMG_3646.JPG (635908 bytes)No flash. 

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IMG_3649.JPG (809578 bytes)See the PM speaker.  A 1500 ohm 10 watt wire wound resistor has been installed to replace the voice coil.  

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