Hello Radio Forum,
I am beginning the restoration of an RCA 66X3 tabletop radio of 1946 vintage or so. Right after I bought this radio I noticed it in a movie. One is clearly visible in the movie Coal Miner's Daughter in the kitchen scene after the family moves to Washington state. No one can miss the tiger stripe grill cloth of this set!


I bought this unit at a yard sale in Denver about 8 years ago. Now it's time to bring it back to life. I have no idea what I am going to find with this one. I have never attempted to power it up or really look at it until now.

It is a 6-tube set and covers the broadcast band a section of the shortwave band. The tuning dial on this radio is pretty unique, with the scalloped glass. This is all intact and not cracked. The dial printing is in good shape, while the dial background is just a gold-painted, curved strip of steel (but may be aluminum. I haven't looked closely yet). The tuning capacitor and indicator needle move fairly smoothly. It should, since it employs ball bearings! The cabinet is in bad need of some TLC. The face seems to be a photo finish, and possibly the sides of the cabinet as well.


This shows the top finish. There is definitely a veneer top layer, but the wood grain is VERY thin. Could this be photo finish grain too?


Image showing a closer view of the veneer top, including some damaged veneer. You can see where the "grain" has flaked off along the edges. (Not the obvious v-shaped chip from the veneer itself) This is what leads me to believe it might be photo finish on top of the veneer.

I believe someone may have had an idea to repair this radio in the past as all six of the screws holding the chassis to the cabinet were missing. The three front-panel knobs were all that was holding the chassis in place. The chassis came out easily, revealing a substantial patch of asbestos heat shielding that encompassed the entire underside of the chassis. This was all safely removed and disposed of outside. The chassis is dusty but seems to have no damage. Underneath revealed what seems to be all original components. I intend to replace all capacitors without question...and will check all resistors, replacing those out of tolerance. The left-most knob is firmly stuck and does not move at all. I haven't begun wire tracing yet, so I am not entirely sure what it's function is yet. The right switch has three positions, and is likely the on/off and band selector switch. The center is the tuning knob. So I am not sure what the left knob does yet!


Rear of the removed chassis.


Underside of the chassis, showing the phono input. A switch for the phono mode is obviously part of the switch mystery! Which one is it though? Time will tell...

I will post my progress here as the restoration moves forward. I can assure you I will need a lot of assistance! I have re-capped a 1941-era Motorola console radio successfully in the past. But this will be my first top-to-bottom restore to include the cabinet work. I have admired from the sidelines long enough! I plan to go slowly and make sure I understand what I am doing before I do it. I fully anticipate this to take some months to complete. It's likely to be summer before it is done! I thank you for your patience!

Bryan

I am looking forward to your progress reports.
Enjoy.

The top is wood veneer. It is normally that thin. You can repair that damaged sports by using wood glue and tightly clamping an oversized patch with the right grain match, then sanding down (slowly and carefully) to excess. The patch will precisely conform to the jagged edge, helping it blend.

[The Dog Bone looking resistors on the band selector switch appear to be wire wound coils. There is a set of contacts on the record player input jack. When the plug from the record player is inserted into the phone jack on the radio the set of contacts will open disconnecting the radio signal from the volume control. This looks to be a very clean chassis. Not a mouse hotel. First replace the dual paper electrolytic capacitor 50mfd and 30mfd @ 150 volt (ref C17 and C18) with a 47mfd and a 33mfd @ 150volts respectively. Turn the radio on .The on off switch is located on the left front knob which is also the volume control. Adjust the volume control up and bring the voltage up slow with a variac. About 70 volts input the panel lights should start to glow and the radio should start to play.

Why leave all of the bad old capacitors? Replace all of them before applying power. Most of the resistors may also need to be replaved, and testing is not worth the time required. Before any if that, check for obvious damage.

The 66X1 is the bakelite version. Below is a video that reveals how well this RCA 6 tube set can play.

https://www.youtube.com/watch?v=2OfWjoGSJjc

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There is one not too far from you on CL: https://washingtondc.craigslist.org/nva ... 69338.html

You might want to do a comparison on this cabinet and yours. You also might want to get it as a parts set.

GL,

Terry

I will check out the local radio. Thanks for the replies! I will hopefully get a chance to dig in this afternoon...

Terry,
I bought the Craigslist unit last night for $20. I am glad I did. The cabinet is in far better shape than my original unit, and the on/off/volume switch at least moves. I'll post some photos soon once I get a chance to give it a once-over.

Bryan

As promised, here are a few photos of the "new" 66X3 I picked up Sunday night. As I noted earlier, the cabinet on this one is in a lot better shape than my original one- especially the left side of the cabinet.


Here is a view of the pair side-by-side. The new unit is on the left.


A closer view of the "new" radio


Rear of the chassis in the cabinet. The "Golden Throat" sticker on the rear panel (not visible) is in better shape on this unit too.

I will begin assessing both radios and figure out a path forward. The first priority is to get the best-of-breed in parts between the two for a fully functioning radio. But unless there is a real showstopper I plan to get the second radio working as well. I figure the second one might be a little easier after having completed the first one! That is, unless there is a component or two that are really destroyed...like a transformer! Time will tell...

Bryan

these are two of my favorite sets.

I did them a few years ago.

great performers too once aligned.

steve

Steve,
From what I have been hearing and reading, I am looking forward to getting these sets back in action! Thanks for the photos. I am pretty fond of wood cabinets, but your 66X1 looks pretty good too! Is that the original grill cloth?

Bryan

hi bryan,

yep, all original.



steve

Tonight's update...tube testing! All 12 of the tubes from the two radios tested good with my trusty old Sylvania 620 tester. I acquired that when I lived out in Denver 10 years ago. It was completely restored by Dave Boyle, the Colorado Radio Club president at the time. He put it up for bids at the annual club auction and I was lucky enough to win it! Later on I also bought an Eico 320 sig gen from him...also restored. I'm sure that will show up somewhere along the line in this thread eventually!

One of the chassis' had a substitute for the 35L6 audio amplifier tube. Instead, it had a 50L6 in the socket! I can't imagine that would work with a 15V difference in filament voltage. From what I've read, including a thread here on this forum, they are both beam power amplifiers and basically comparable except for the filament voltage. I have no interest in modifying circuitry to accommodate the extra 15V requirement for the filament. So, I'll be getting a proper 35L6!


Here is a photo with a 35Z5 rectifier tube under test...


And another of the entire tester.

From here on out for a little while it will be grunge work cleaning and tracing out wiring and components...

Until next time!

Bryan

That’s a pretty common tube substitution 50l6 in place of 35l6. Many prefer to do it due to today’s higher line voltage. There are several threads on it in the past if you want to look them up. If it were mine I would leave it.

Life has intervened, keeping me from doing much this week. However, I do have an update and a question for the group. In my original post I mentioned that the radio had an asbestos sheet beneath the chassis. That really didn't make any sense to me as any heat issues would be noticed on the top of the cabinet above the tubes in the chassis, not below it! This pad is actually referenced in the schematics. It is not asbestos. It is a dielectric material called fish paper. I had never heard of this prior to reading it in the schematic. It seems it was used as an insulator between the chassis and the cabinet. So now the questions...

Why would there need to be an insulator between the chassis and a wooden cabinet?

In the references I could find on the Internet about fish paper, it does not seem that it contains asbestos. What is it actually made from? And more importantly, now that I have thrown it away, do I need to replace it in the radio?! Grr...

Bryan

NOTE: I just realized this thread is probably in the wrong thread. If the moderator wants to move it to the Restoration thread, that probably makes sense!

Now on with the show. I had a brief hiatus for Christmas vacation and then a mild heart attack right after New Year's! But, I'm back at it again finally. I have finally begun verifying circuitry and have immediately run across a couple of variances from my schematic! First question is, does anyone have a newer version than what is on Nostalgia Air where I believe I got mine from? I started with the circuits around the 35Z5 rectifier tube.
Here is the schematic for this section as printed:


Here is the schematic showing how C16 is actually in the circuit:


And this is the cap in the chassis. C19 was removed by the previous owner and is not visible:


It seems the factory upsized the filter caps as well. And the values and configuration are different between the two chassis' I have on-hand! One of them actually has the specified 50uF/30uF "can". However, the 30uF cap has an additional 20uF/20uF in parallel piggybacked on it. The values of the filter caps in the other chassis are 80uF and 50uF! They both appear to be factory installed. Here are some photos showing this:




Which values should I go with when I replace all these capacitors? Per Schematic or as-installed?

I would dearly love to have the updated schematic. I have a sneaking suspicion that there will be a lot more variances the farther along I get if this is any indication!

Bryan

Update: I just received updated factory schematics for this set from ARF advertiser Steven Johnson and these do have the as-built circuit configuration I painstakingly (idiotically?) detailed earlier for capacitor C16. With these schematics I should be able to get to work in earnest!

Bryan

Progress continues...
I have completed the tracing of all the circuits in the schematic. All had the correct continuity and resistance readings where appropriate. I have located and marked each component for ease of finding them later. This is mostly done using a printed photo of the chassis annotated with the component enumerations. I've begun cleaning up the chassis and have removed the variable tuning capacitor and speaker from the chassis to help this process along. Here is the stripped down and partially-cleaned chassis:



Once the chassis is completely cleaned, I intend to use a clear finish on the steel chassis components. I'll mask off the IF cans (which are aluminum), tube bases, and other openings for this. Since there was no fancy finish on this chassis, I am not going to paint it. I'll probably clear coat the frame of the tuning capacitor as well, but I'll mask off the vanes and other critical areas for this.

First, I will be replacing a bunch of components! It's time for the old wax/paper and electrolytic capacitors to go. I will likely replace many of the resistors as well. If their values are way out of tolerance, they look burned or flaky, or I just think they should be replaced, I'll be pulling them.

Here is something I could use some help in locating:


Where can I find replacement rubber grommets for the variable tuning capacitor mounts? These are the same on top and bottom of the chassis. A steel threaded stud extends through the middle for the mounting bolts. Any help locating a supplier will be greatly appreciated!

Bryan

An update: The two white "dog bone" devices turned out to be capacitors! There are a few turns of wire wrapped around either end of the plastic cylinder. I will admit to never seeing a capacitor like these before.