Cost To Date

Tubes, TubeDepot, $23.75
Tube, VacuumTubes, $10.00
Filter Caps, Digikey, $2.05
Filter Caps, Digikey, $3.15
Paper Caps, Digikey, $24.28
Knobs, Bias Pot, IF Xformer Play Things of the Past, $31.35
Speaker Connector, NAPA, $2.96
Transistor, Quest Components, $32.50
Weld Nuts, McMaster-Carr, $2.00
TOTAL $132.04

Saturday, December 21, 2013

Radio Restore Complete!

Installed the last tube, did a complete alignment using the antenna that will be used, and built the speaker cable.

Friday, December 20, 2013

Received Antenna Today

This is the antenna that Brian had drop shiped to me from Studebaker International:

Wednesday, December 18, 2013

Tubes Arrived

Four of the five tubes came in.

New Tube Location Guide

Added a new tube location guide using MS PowerPoint, printing onto photo paper and laminating. It's not very much ike the original but it will do the job.

Tuesday, December 17, 2013

Another Tube Resource

Ordered a 12AD6 from here.

Alignment Info from Antique Radios Forum

Here are the alignment instructions for the similar Motorola CTA8X, which is the one that the SM9T Motorola page refers to for everything except the schematic and the parts list, which you have. A1, A2, A3, A4 are of course the IF adjustments. A5 is the Osc trimmer, A6 is the RF trimmer, and A7 is the antenna trimmer on the back of the radio. This information is from Sams AR-9 and component labels may be different from Motorola labels. My Motorola manual is missing the pages for CTA8X.

Motorola CTA8X alignment.jpg

Sunday, December 15, 2013

Mounting Bracket, New Capacitors, Fuse Holder, Component Vibration Prevention

I made an aluminum mounting bracket so that the radio can be mounted flush with the front surface of the dash:

 High temperature RTV and foam pads added to reduce component vibration. Foam pads will help hold the upside down vacuum tubes in place:

New fuse holder and length of wire for power connection:

1/4-20 screw added for rear mounting:

Friday, December 13, 2013

Cow Pasture

OK, capacitor. I call large capacitors "Cow Pastures". I got this name for them from a an engineer colleague when I first started work at Melpar, E-Systems back in 1977. He was in charge of the AN/UIC-7 Digital Intercom System that was used in all the ground intercept systems. I digress...

To keep the radio looking original I gut the old filter capacitors and reuse the can to hold the new capacitors.

Cow Pasture removed from chassis
 The bandit

 Odd to see a Motorola name on it, didn't think that they made Cow Pastures

 So I start by grinding down the bottom edge to remove the mounting ring, bottom plate, and the guts.

 Here are the three capacitors that replace the guts. Even Cow Pastures have gotten smaller.

 New capacitors installed on the bottom plate. I made another plate from perf board to hold it all together with the help of epoxy.

Capacitor assembly test fitted

Completely assembled and epoxied and ready to go back into the radio after testing.

Thursday, December 12, 2013

Parts From Play Things of the Past

Received vintage bias pots, IF Transformer, and knobs


Second IF Transformer

Three different Bias pots, one intermittent, 100 ohms and on 200 ohms

 One set of back knobs and two sets of front knobs

 Round knobs with back knobs

Flat faced knobs with back knobs

Flat faced knobs on radio
Round knobs on radio

Monday, December 9, 2013

Volume/Tone Control

I took apart the volume/tone control to clean the insides with hopes to clear up the scratchiness. Unfortunately it did not fix it but it helped a bit. This is a 2 meg volume with a 1 meg tap. the tone is 500K.

 Control disassembled

 Both tone and volume wipers are very worn

Volume shaft installed on element
 Switch installed on volume control

 Tone shaft installed on element

Coupling cover installed
 Assembled control

Friday, December 6, 2013

Alignment Tools and Bezel Painting

 I think I bought a few more than I need... Well I'll be covered for any tuning that needs to be done.

Flat black painted bezel parts

Heat Sink

Today I wanted to remove the lone power transistor and check the heat sink compound. I also decided to clean up the area. As suspected the compound was hard and dried up.

 Lone power transistor and heat sink

 Transistor removed

 Parts cleaned and ready for installation of transistor

 Heat sink compound, insulator, and transistor

 Transistor coated, insulator installed and insulator coated

Transistor re-installed.