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Wards Airline Model 14WG-1108A series 1A48

WG & C series 1A48

This is a new restoration project on the bench at this time.  Information will be periodically added as the project progresses.

Before any work is done general assessment and preliminary cold checks are performed including but not exclusive of:

Test audio OPT
Test all tubes
Test and Clean Controls
Test Voice and field coils
Measure Bias resistors
Test first IF transformer
Test 2nd IF transformer
Test Ant coils
Test Oscillator Coils
Clean and test volume control
Full Voltage test Power Transformer (no load).
Dust all chassis and cabinet areas

 

 

front.JPG (21243 bytes) Before pictures. 

 

 (Jump to Finished)

chassis.JPG (25633 bytes)

lineup.JPG (294009 bytes)

Original underside chassis

IM000051.JPG (95516 bytes)

Original chassis underside.  Note the two brown axial capacitors used to replace the can caps.   

See this link for In the chassis can capacitor modification.

 

 Finished with the underside.

Finishedchassis.jpg (95293 bytes)

This is the restored chassis. Most of the wires were brittle and some were bare.  All paper/wax and electrolytic capacitors have been replace.  

See the reference chart showing the drifted out of tolerance resistors.  It is quite surprising how many are bad.  

You can see the new Hammond audio output transformer in the lower right. 

Component replacements.

I have begun going through and replacing bad components.  This included all wax/paper capacitors, electrolytic capacitors, decayed brittle wires and out of tolerance resistors. The IF can wires get treated to shrink tubing to avoid disturbing delicate windings.  Since this radio will be used perhaps daily, with a 5 CD changer in the phono input,  I will be replacing any questionable wire or component for "Daily Driver" reliable operation.

It is surprising how many resistors are out of tolerance.  Most resistors in this radio have a silver tolerance mark.  That is 10%.  Some one commented that my meter may be bad.  I then got that sinking feeling and went t the shop to verify its accuracy and precision.  Both were easily checked by measuring the replacement resistors and trying a different meter.  

I am surprised at the quantity of bad resistors that I find in all restorations to date.    See below: 

    Part Rating (K ohms)   Tolerance as marked (%) Marked Tolerance (%) Measured (ohms, out of circuit) (k) Calculated Tolerance (%) Replace value (k)
R1 15 10 19.2 28 15.0
R2 16 10 21.4 33 14.9
R3 20 20 18.5 6.5 Good 20.0 (It was clipped out)
R4 5 10 6.84 36.8 4.98
R5 20 10 24.1 20 Good 20.0 (It was clipped out)
R6 50 10 67.2 34.4 50.3
R7 eye tube 1000 20 open infinite 999
R8 80 10 61 -23.8 81.7
R9 2000 20 1080 -46 1999
R10 200 20 296 48 197
R11 500 10 628 26 507
R12 Volume pot -- -- -- Good
R13 490 5 666 36 503
R14 1.5 10 1.91 27 yes
R15 Tone pot -- -- -- Good
R16 100 20 155 55 98.9
R17 100 20 138.4 38.4 98.9
R18 5000 5 7950 59 4950
R19 200 258 20 29 199.2 (41 grid)
R20 200 282 20 41 199.3 (41 grid)
R21 .008 20 .0087 8.7 Good
R22 50 5 70.8 41.6 50.4
R23 150 5 205 36 149.9
R24 500 20 795 59 yes
R25 1000 20 1400 40 yes
R26 .025 10 .0284 13.6 26
R27 2000 20 3060 53 yes
R28 .008 20 .0098 22.5 not replaced
yes=verified but not recorded        good=not replaced

Out of 26 fixed resistors all but five were significantly out of tolerance.  And R28, series plate resistor, is just over the limit was also not replaced.  That yields 76.9 percent of the resistors are bad.  This is not uncommon.  I find out of tolerance resistors in many restoration.  It is an exception when a chassis has in tolerance resistors.  At 4 cents each for the 1/2 watt, in quantities, it makes little sense not to replace the resistors. 

For me there would be exceptions to this rule of mine.  One is if the restoration is a "Museum Show Piece" that is not to be powered up. Leaving original components is only for "looking at", to appreciate the "State of the Art" at the time of manufacture.  Secondly if the technician wanted to rush the device off of the bench and await its quick failure they may choose to leave original caps and resistors. Not to mention the possible loss of irreplaceable components. 

Every resistor (and capacitor) has been verified against the schematic before retention or replacement.  Technicians have been known to "tweak" values to compensate for other weaknesses or failures.  And simply connect stuff up wrong.

 

Problem Found:

The Output transformer (lower right) has an open primary on one side of the center tap.  It is a Stancor universal replacement.  Obviously it has failed once already.  The two 41 output tubes check good on a Heathkit emissions tester. One strong and the other one just in the green above marginal.  So this radio had played for its current owner. But, I doubt it sounded clean.

I pulled the back the first few layers of insulation to see if the winding came loose from the lead wire.  But no such luck.  The primary is open some where inside the windings.

The Challenge:

Specify a replacement Output transformer to handle the power output, bias current and yield the correct plate impedance.

The Data:

 

Schematics

A more accurate schematic of this particular chassis is Rider's 13-7, 13-9 Montgomery Wards chassis 04WG-1108A.

Note:  I believe the schematic on the above 13-7 link is mislabeled as -1100A and should be -1108A.

 

41.jpg (133356 bytes)

41 referenced to 6K6

41 base 6B.jpg (64242 bytes) Base 6B

6K6  41c.jpg (88205 bytes)

6K6 data

shem 32.jpg (197265 bytes)  p609.gif (143083 bytes) p611.gif (161106 bytes) p612.gif (129400 bytes) p613.gif (168658 bytes)  p614.gif (83019 bytes)   

There seems to be some difference between this schematic and the chassis.  One is the Oscillator tube is a 6J5 and not a 76. There are some other details a bit different.  The RF stage has an RC network on the input grid and circuitry through the phono switch which may be used to suppress the input when in phono.   All other components seem to be the same.

41 output plate voltage is specified at 225 volts, grounded cathode.  Manufacture's output specified at 5 watts (5.5 distorted). 

Documents and schematic courtesy of Brian McAllister from original equipment documentation.   Brian was a great help determining the manufacturer of this chassis.  See his site at http://oldtech.net/.

Thanks Brian! 

 

 

 

Conclusions:

bulletThe Plate to Plate impedance for a Push Pull configuration is 12,000 ohms (see data).  
bulletSpec operating plate voltage is 225volts.  Therefore, the full maximum output of the tubes may be reached.  So the transformer should have a power capacity of about 8 watts (estimated).  The tube spec (6K6GT) is 10.5 watts at 285 volts plate.  The radio manufacturer's output spec is 5.5w distorted (5w undistorted).
bulletThe Plate bias current is 55 ma (value for two tubes at plate = 285v).  So the transformer should have equal or greater DC bias current capacity.
bulletThe speaker and hum bucking impedance is unknown at this time.  The sum of the DC resistance is 1.7 ohms.  The output impedance will have to be measured or calculated separately to properly tap the secondary of the transformer.
bulletSome tube curves would be nice to better spec the output transformer's capacity.  I will search the net for some curves. 

 

The Solution:

HAMMOND UNIVERSAL
PUSH-PULL TUBE OUTPUT TRANSFORMERS

I found this at www.Radiodaze.com.  These guys treat me well!

The owner want to hook up a five disk CD player to this radio utilizing the phono input.  I want to spec a healthy and reliable output tranny to handle the long run times with out worry.  This Wards Airline radio will have the respect of a  "daily driver".   

125 Line Art

Click picture for link to specifications.

125 Schematic

Looks like the HX125C will do the trick..

Secondary pins 1 and 3 for a 3.2 ohm speaker impedance to yield a 11500 ohm plate to plate impedance has been selected.

     See it installed under the chassis.  Lower right side.

  Alignment

Alignment was successful today.  After chasing a run-a-way oscillator (above 15 MHz) the problem turned out to be skewed alignment trimmer capacitors.  The interstage and Oscillator trimmer caps interact to some unpublished degree.  Opening the caps up wide and finding a known good primary frequency allowed the tracking of the signal up the band.  

Establishing a good primary signal entails a week signal properly centered about the intended oscillator frequency.  I found it useful to follow the signal generator up the dial to the specified alignment point when the tuning gang is wide open.   This unit was operating (Police and SW bands) on a higher image of the oscillator and input signal.

This deserves repeating......

What is not mentioned it the interaction between the Interstage and the Oscillator capacitor trim controls.

Once aligned WWV showed up exactly on both bands at 5, 10, and 15.  The SW band is huge 5.350 - 18.300 MHz (see schematics).  

 

Fully aligned, receiving strong, operational chassis.

IM000082.JPG (233407 bytes)

 No flash photo showing original eye tube.  The pilot lamps look like spot lights.  An STSP switch on the B+ has been added to conserve phosphor life.  No need to burn the eye tube during extended listening.

IM000080.JPG (295706 bytes)No flash shot of the chassis.  You can see the #80 rectifier glowing on the right.  IM000083.JPG (224728 bytes)This is with a new 1629 eye tube.  The 1629 is the military version eye tube with a 12 volt filament.  An adaptor that doubles the filament voltage and changes the 6 pin to an octal keyed socket is used to facilitate the substitution.  No rewiring was needed. This tube and voltage doubler combination was purchased from www.dialcovers.com.
IM000081.JPG (320427 bytes)With flash.  The pilot lamps look dimmer than actual. IM000084.JPG (240982 bytes)A second shot of the subbed in 1629.  

 

Finished and playing loud and clear.

IM000074.JPG (55183 bytes)

New veneer on kickplate

IM000079crop.JPG (36218 bytes) Completed IM000078.JPG (48111 bytes) Different lighting

(Most realistic cabinet color).

IM000085.JPG (19234 bytes)

  Close up of dial with out lights.

 

Second Chassis in the shop.

This unit has the appropriate documented tube line up unlike the one above.  Companies will make substitutions near the end of a model line with the spare but equally functional inventory in house.

Preliminary test on the bench reveal all transformers and coils test good with an ohm meter.  All but three tubes are good and strong.  Two 6D6 tubes tested bad.  One is week and one has a heater short.  The eye tube is dark.  No illumination.  That is expected.  These eye tubes only have a 1500 to 200 hour life expectancy.  If you have a "Daily Driver" a switch can be inserted in the B+ line to extinguish the illumination on most eye tubes.

Most if not all the under chassis wiring is brittle as sugar.  It will need replacing.  The top side eye tube insulation is also cracked.  With the given room under the chassis this task should take about an hour and a half.  The IF transformers will be addressed with heat shrink as well as the power transformer as necessary.  Slipping a piece of heat shrink over the existing insulation, will restore the insulating characteristics of the wire.  Hopefully the Power transformer will not have to be disassembled.  It is not tough to do but adds time to the repair.  

Here are some before pictures:

IM000338.JPG (304348 bytes) Need a new glass.  This is plain glass that can be found at your local Hardware store.  IM000339.JPG (369810 bytes) It looks much more Green in person.  That can capacitor, near the power transformer, has 230 volts on the case.  You can verify that if you touch it. Ouch.  That has been removed on the restoration.  IM000340.JPG (942603 bytes) Lots of room.  This unit had work done.  The electrolytic capacitors have been replace the proper way and not soldered across the bad can capacitors.   It has been a while since I have seen this proper technique in an unrestored  chassis.
IM000341.JPG (321198 bytes) Three bad tubes. IM000342.JPG (211420 bytes)The insulation is like sugar.  Crumbles and needs replaced.  This is not only a functional issue but there will be 450 volts or more on these wires during  warm up.   IM000339.JPG (369810 bytes)  IM000039.JPG (839673 bytes)Before cleaning.

After.

 

A Restored Unit.

 

IM000041.JPG (701560 bytes)New Dial glass, straightened & painted frequency indicator.   NOTE:  The position of the dial lamps.  These are stowed for shipping.   IM000039.JPG (839673 bytes)Chassis after Clorox Clean up and a Scotch pad. The paper labels have been lacquered. See the adaptor for the 1629 military grade eye tube. An original 6 pin eye tube can be installed.   The can capacitor near the power transformer has all wires disconnected for safety.   IM000038.JPG (709288 bytes) Antenna Trimmers.  Adjust these once the internal cabinet antennae have been connected.  Tweak the SW if a long wire is added.  IM000040.JPG (684672 bytes)  Underside shot showing the new components and replaced wires.  Lots of replaced wires. You can see the insulating terminal strip installed near the black transformer to take the 230 volts off of the can capacitor.  terminal strip.JPG (87237 bytes)
IM000007.JPG (847912 bytes) Nice eye tube.  The dial lamps are behind the metal for shipping.  The dial lamps will be shipped in this position.   IM000008.JPG (797580 bytes) Shaded dial lamps in position.   Position the dial lamps so they shine on the dial scale before placing chassis in cabinet.   IM000009.JPG (182105 bytes) Tube glow.   IM000011.JPG (37646 bytes) Expanded tube glow.  You should hear the great sound!

I forgot to mention.  This chassis sounds great with a CD player plugged in the Phono jack.  I tested it with a DVD player's audio output, a Stereo to Mono patch cable and a music CD.  Just move the slide switch on the left rear chassis from Radio to Phono. 

 

       

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