This Arvin 544 came out in 1946 and was owned by Vonna’s father who got it after returning from WWII. It had not been working for many years. In the early ‘80s I did some work on it for him by replacing a tube and fixing a broken wire. Then, apparently while we were living overseas ‘93-‘98, it stopped working again and got put in a closet. A decade later after he had passed away I ended up with it and has been in storage for another 20 years.
Let’s check it out.
The label on the bottom showing the 5 tube layout. A typical “All American 5” style transformerless, series tube filament style radios. These were made by the millions for decades and have a dangerous design.
One of the wires to the wall plug is tied to the metal chassis back when plugs and receptacles were not polarized. So when plugging in the plug could go in two ways. One way would attach the Hot lead to the chassis. So the cabinets were made of wood or plastic with wooden or plastic knobs. But the screws on the bottom could have high voltage on them.
Using pliers to remove the cardboard back cover.
First look. Notice the antenna coiled and glued to the inside of the back cover.
A better view. Functionally the radio dial would not move when the knob was turned. I can see why now…
There is supposed to be a light bulb for lighting the dial. It is not in its socket, but I can see it lodged between the front of the chassis and the front of the cabinet. Turns out it was wedging in and blocking the tuning pulley from moving.
Removing the chassis screws on the bottom. In use, these have a 50-50 chance of being connected to the Hot lead in the wall. That will get fixed.
Chassis out of the cabinet for the first time since I worked it in the early 80’s, or is it?
One of the former inhabitants.
Wayward light bulb.
Under the chassis… Wait a minute.
I see three capacitors that are not from 1946 in there. I didn’t put those in when I worked on it in the ‘80s.
Who else has been in there? Was it before or after I was in there? I think after me, but we will see.
Those dark brown cylinders are wound paper and wax dipped capacitors from the original build. They are brown because the paper is acid based and turned brown like an old book. The acid ruins the electrical characteristics of the capacitors and they turn into resisters which cause burned up tubes etc.
They have to be changed.
Electrolytic filter cap which does not look original. These will also be dried up by now and need to be changed. This actually has two caps inside. One is 60 and the other 30 microfarad.
Let’s see how it performs before surgery. But you ought not just plug these in because they could have a short and even cause a fire or shock.
So I have some specialty power supply equipment on the shelf on the left side.
Most of the rig I use to safety bring power to old electronics.
The red box with the knob on top is a variac which allows me to bring voltage up slowly looking for problems.
Behind that is a set of transformers I use to isolate the power going to the radio away from the house power leads. Isolates ground from being part if the return. (Turns out to not be very good at this so I am getting a new isolation transformer unit)
The 150W light bulb is wired in to the line opposite to the way they are normally in that metal box. It is wired in series, not parallel, so all current goes through the bulb. If there is a short, the bulb glows brightly and limits the current to prevent damage. (Called a dim bulb tester)
Not shown is a box I have that displays voltage, current and wattage going to the radio.
Ok let’s put a light bulb in and see how works. I brought the voltage up very slowly until the meter showed 120VAC.
You can see where I also check the power draw in watts. The 150W light bulb glows with the current running to the radio. If there was a short circuit, that light would be very bright and would also limit the current going to radio which could cause damage, or a fire.
The bulb wasn’t as bright as the camera makes it look.
Very poor reception to say the least. So let’s agree the radio needs work.
Time for close inspection.
Some of the wires are rubber insulated, and the rubber has deteriorated and is falling off. Look where the black lead goes through the chassis and is bare, ready to short to the chassis.
Years of use in the kitchen resulted in an oily coat and adhered dust.
The cap in the center has gotten so hot the wax is bubbled up.
Took 150 pictures during this repair to record what went where, and what changed. Here you see the electrolytic cap with the red and blue leads as it was…
And here it is removed along with its mounting bracket. I cut the blue and red wires to know where they went.
To the right of where the bracket was, I have mounted a terminal strip to mount some of the new wiring I will be installing.
Let the work begin.
Found resisters that had been so hot they crumbled when touched. So those were replaced. Notice the insulation on the green wire crumbling, exposing bare wire as it goes through the chassis. That will get changed, too.
Here you can see two new electrolytic capacitors installed and using the terminal strip for mounting them.
Below them, you can see a fuse block that was also installed. There was no fuse in this circuit, on top of the hot chassis mentioned above. Wow.
The power cord will be replaced with one which is a reproduction cloth covered cord with a polarized plug. The wiring has been changed so that the Hot lead will go first to the fuse and then to the switch. The neutral will go to the common return so the chassis is also closest to the neutral.
Working my way one tube socket at a time across the chassis changing caps and testing resisters to change them if needed. Checking against the schematic as I went.
The schematic I got from two sources, one is free online from Nostalgia Air of the old Riders books but it did not show the component values. I was able to buy a schematic from Sam’s for a pdf with complete info. I followed the Sam’s pdf as it was clearer.
You can see where I had written numbers on the caps as I worked to sort through which cap was which on the schematic. It was a little confusing in this old style point to point wiring.
Finally worked over to the other side and am having a problem seeing where wires are going as it is not obviously following the schematic. Seemed like I was missing one, and another that was the wrong value and in the wrong place. What’s going on here?
I ended up taking the Sam’s schematic and a highlighter and followed every wire. So can also see all my notes.
The area on the left just didn’t match.
Added a cap for the audio transformer that wasn’t in the radio at all but was on the schematic.
Labeled the capacitors trying to figure out the schematic issues.
After all the work was done on the tube sockets can now put in the power cord and have it wired in. Both leads go to the terminal strip. Hot goes to the fuse then on to the on switch.
Scratching my head, I look at the schematic again…
Wait just a darned minute…!
Not fair! Sams schematic on the left, Riders on the right. They are different!
On left, see the red wire pointing at the bottom of the tuning capacitor lead tying onto the AVC circuit. I could not find that connection! See, it wasn’t highlighted in yellow confirming it.
On the right, the blue wire shows the tuning capacitor going to ground. And there is another capacitor added you see I have circled. Ugh!
Relooked at the radio, yup it is wired per the Riders, not the Sams. Circled in green wire on the Riders is a schematic about the schematic on early production units, which IS per the Sams. Ok so there was a change. Let’s go back to the radio.
So I took a picture and added notes about what needed to be changed and where the ‘missing’ capacitor goes.
With the capacitors replaced I will now align the radio’s IF section (intermediate frequency – as used in these superheterodyne sets) by adjusting the 4 adjustable capacitors in the IF transformer cans.
This is a kinda interesting pair of videos which shows some of the test equipment being used.
Let’s see how it sounds. A lot of ‘static’ and seems to be reaching for a signal.
I’m going to go after the tuning capacitor – had hoped to avoid that.
On top of the two tuning capacitors are two adjustable capacitors for tuning the variable caps. The two plates of each are separated by a small sheet of mica. These can get to where they need cleaning.
Here is one before being cleaned.
Here it is after cleaning. Looks better huh? But still dirty inside where it goes.
Back together it still sounds poor, and also the tuning cord cannot turn it. It too tight.
Ok, let’s go ahead and take a risk…
Built a homemade signal tracer to see where the noise is originating. Can’t tell. Let’s get the tuning cap out.
Pulled off the needle and then carefully removed the dial face.
Disconnected the dial cord, unsoldered the capacitor leads from under the chassis, and then removed the tuning capacitor.
Look how grungy this is.
Check out this video showing the tuning capacitor condition.
Tuning capacitor into the ultrasonic cleaner. A mix of hot water and a little Dawn degreaser.
After: Compare this with the ‘grungy’ pic above.
Check out the gleamy bearings now. Turns a bit easier now.
This video shows the results of the tuning capacitor cleaning.
Also revealed are these wires that look partly melted, partly corroded and maybe having intermittent shorting to the frame.
These wires were easily replaced with the tuning capacitor out.
Race now uses the equipment to tune the two mica caps on top of the tuning capacitors. The one on the right tunes the oscillator, and the one on the left tunes the antenna.
The replaced components
Looks finished. Nice cord, cleaned and polished the cabinet.
But, after the radio is run for a while, the power to the tubes drops out.
Watching the wattage, the power draw drops to zero. It is not a short. I think I need to change some tubes. I suspect the audio output tube. It had acted strange on the tube tester.
New (apparently never used) tubes from the past have arrived finally.
Put them in the 1946 Arvin and put through a test run on the Variac.
How’s this for almost 75 years old?
(Away from all the interference in the house, wifi and switching power supplies)
Colt45s No hitter. Loel and Elston with an interview with the 45s pitcher at the end.
Yeah I think the only audio output tube (50L6) I had that tested ok, but then developed a problem when it warmed up and played for a bit. Its a fault a tester can miss, just had to diagnose with a replacement tube.
All good now! Enjoying listening to it.
Handsome looking and working great.
A huge amount of work and learning.
See more of Mark’s projects here.