gemeinsch: VE301W (VE 301 W); Volksempfänger: Tube repair
Here's an update on my RGN-354 repair. I jut touched my soldering iron to the tip of the tube base on what I guessed was the one remaining connected wire. It pulled right out and this is what I found:
The good news is that the other two wires are not broken right where they exit the glass so I should be able to solder to them. Here's what the base looks like:
You can see the end of the pin on top where the good wire came out of. Below that are the stubs of the two broken wires. That's where the next problem will be. They are embedded in this big glob of old very hard glue. I need to get them out to be able to resolder them to the tube. Does anyone have a suggestion on how to remove these wires without destroying either them or the base? I suppose I can replace the wires but that glue has to go. Thanks!
try this: clean and tin the wire endings. Attach extending wires of 5 (at least) to 10 cm (better) on them, first by twisting, then soldering, but keep these connections as slim as possible.
Align these wires according to the base diagram; avoid any cross-over, keep them distant to each other as much as possible.
Remove any wires and tin from the base pins, the pin-tubes should be free and empty inside. It should look as shown here.
Remove any old cement or glue from the base and clean the surface. It may look like this one (or even better), but without of these nasty silicone diodes.
Also clean the glass surface of the tube neck.
Thread the wires into the base pins according to the base diagram, note the mirror-image as seen by the top view. Prevent these wires to move out of the pins, e.g. by twisting their endings together.
Attach new glue around the base collar. Then put the tube vice-versa and move the base towards the tube, care about good covering of the glue to the glass surface of the tube neck. Watch the wires inside the base to stay distant to each other. Make (very) sure the wiring still corresponds to the base diagram.
Keep the tube in vice-versa position and let the glue harden out. Probably you can use tape to fix the base at the tube.
After the glue is rigid, solder the wires inside the pins and cut-off surplus wire. Then test the tube; good luck !
Best Regards, Jacob
Thanks so much Jacob for taking the time to post such a detailed reply. Here's how things turned out:
First I removed the solder from the ends of the tube pins. Then I ran a 1/16" drill up each pin to drill through the glue. This worked very well:
Next I very carefully cleaned the corrosion off the stubs of the two wires coming from the tube using a bit of steel wool gripped in my needle nose pliers. Then I soldered some new wire to the stubs. This was tricky because the wires are recessed in the base of the bulb and there is very little room to work in. The repaired wires are on the left and right below. The one in the middle is the remaining original wimre.
(The tube is sitting inside a box to protect it and hold it steady while I worked on it).
Finally I threaded all three wires back into the matching holes in the base (this was easy since there are only three wires), glued the tube to the base, soldered the wires to the pins, and clipped off the excess.
Fortunately, the repaired wires were from the heater so it was easy to verify the repair just by measuring the resistance between these pins. Next, I will have to see if my newly repaired tube actually works. Pretty cool, huh?
Just a hint:
Don' t use Epoxi adhesive for fixing the valve. Due to the fact that Epoxi is shrinking while hardening it may destroy the valve. Some collectors already had negative experience with that.
You can use a liquid gum adhesive or a wood glue for fixing the bulb.
If there is no residue of the old glue I use a mixtue of Shellac, alkohol and stone dust for glueing the bulb. After hardening in an oven at 100 °C it looks like the original used glue. The original glue was based on stone dust and phenolic resin and also hardened at elevated temperatures.
For the new wires use thinner ones as showed on your pictures to avoid mechnical stress of the old ones. They may bleak at the point where they enter the glass.
Thanks for the advice, Rudiger. I did not use epoxy. I used a clear general purpose adhesive that goes by the unlikely name of "Amazing Goop". It dried OK and nothing is broken so far. We'll see what happens when I try it in the radio.
The wires I used were made from three individual strands of copper wire from no. 18 speaker wire twisted together. That's very close to the diameter of the original wire, although I agree that because of the shadows in the photo, they look larger. I was as careful as I could be to minimize the amount of moving around I did to the wires I was soldering to. I used my temperature-controlled Weller EC-2000 soldering iron set to 650 deg. F (343 deg. C).
When I was done, I measured continuity across them, showing that the tube filament is still intact and the circuit is complete from one pin to the other. I still need to replace a few capacitors before I can power up the radio. Then we will see what's what.
The tube repairing seems to be successful so far, congratulations !
To avoid any risks I like to advice not to use this tube for the first tests with the radio.
For this purpose, use two 1N4007s and a 470 Ohms / 2 W resistor, all in series connection, to replace this rare RGN354. The two 1N4007s are because of the around 350 V AC from the transformer, the 470 Ohms resistor substitutes the internal resistance of the RGN354.
Later, when any repairing works on the radio are finished and the radio works very well, then remove the silicone substitute and put in the RGN354.