Zenith 6-S-128


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Zenith chassis 5634 six tube three band radio.  This chassis fits models 6-S128, 137, 147, 152 and 6-S-157.  This chassis came in dead.  Two tubes were bad (the audio output and an IF), and the out put transformer primary was open.  The cloth covered wire is in good shape.  There appears to have been a new IF transformer installed.  I replaced the crumbling tape on the I wire splices with heat shrink.  Most of the resistors were way out of tolerance.  

First on the restoration list is to replace the audio output transformer.  A Hammond Single Ended universal replacement was procured.  This replacement transformer has a DC bias current rating of 60MA and 8 watts of power.  The chassis output spec is 4 watts.  Looking at the 6F6 output tube's cathode current helped select this transformer with a bit more capability than the original.  I have seen Zenith failed output transformers before.   The old transformer rivets were drilled out, a metal strap was fabricated to accommodate the larger transformer.  Then the whole thing riveted back on to the speaker frame.  The appropriate secondary wires were selected for a 10,000 ohm primary and a 4 ohm secondary.  This is the closest match to the 6F6 output tube and the 3 ohm voice coil.  The 6F6 audio output tube was dead.  So a new one was installed.  

See the pictures below for more details. 

IM000001.JPG (1131063 bytes) Original underside. IM000002.JPG (1186521 bytes) Close up of Candohm resistor.   IM000005.JPG (212811 bytes) This is the dial lamp reflector.  Quite dirty and stained.    IM000009.JPG (257706 bytes) The origonal paint was stripped.  Then repained.  The back bare metal has been lacquered to stop surface rust.  IM000010.JPG (220594 bytes)
IM000011.JPG (285415 bytes) Looks good with new pilot lamp shades.  IM000012.JPG (321208 bytes) Nice. IM000008.JPG (176333 bytes) These are the "sacrificial" pilot lamp shades that are burned.  The dial scale would burn if these did not.   IM000007.JPG (245604 bytes) Mark Oppat posted this hint.  Fabricate new shades from white or beige mini blind slats.  Thanks Mark!  
IM000006.JPG (149637 bytes) These standoffs are shot. I used a heat gun to remove them in large pieces. 

A new belt will go around the big pulley shown to under the chassis tuning control shaft. A belt kit is on order.  

IM000016.JPG (234753 bytes) A trip to the hardware store.  I used the orange pipe as a spacer through the chassis whole.  The toilet tank washers go on the top and bottom side of the chassis.  This also centers the indicator in the dial lamp reflector.  The white plastic hose goes inside the orange pipe.  I reused the existing inner Bakelite standoffs.  IM000015.JPG (208203 bytes)  You can see the orange hose with the standoffs inside.  The flat washers fit over the standoffs.  IM000013.JPG (225817 bytes) Second shot.  I will get a shot of the new under chassis and the new variable air capacitor standoffs to post later. . 
IM000017.JPG (247269 bytes) Tuning gang drive belt. IM000018.JPG (618962 bytes) New dial glass installed with new gasket. IM000019.JPG (216013 bytes) NICE! IM000020.JPG (196648 bytes) New output transformer.  The cardboard held on with gum bands are to protect the speaker cone from bench damage.   



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