Thirties Radio Ambition

[Nowhere-Man]

Some months back I started work on a late thirties TRF Halycon radio. The schematic is so faded, even on the printed version, it's not easy to read all of the words.

The radio is powered at 120 volts H.T. When I started work on it, I'd not had much experience soldering. I did get quite far but was reluctant to test it as I was feeling I'd maybe cut too many corners as access to solder joints was tricky on that set. Anyway, I dug the chassis out yesterday and I think I should totally overhaul it and take it more fully apart to get at the soldered wire on lugs. To do this I'd need to remove the dreaded dial string mechanism and remove the plate beneath. Then I could totally remove the last remains of threadbare wire and use all modern wire.

It's really a far simpler radio than any I've worked on to date. Detection is a grid leak and the valves are quite bulky. Some of the valves are loose also on their bases and the hope is industrial superglue might fix that problem.

It actually has the original metal rectifier. This seems to have been added by a fifties or forties engineer to save the bother of messing with accumulator batteries.

All in all, it would be fun to try and get it to work. Even more fun to restore the cabinet which is a big black ugly box but no woodworm.

Below a pic of a typical TRF Halycon.

[Refugee]

Never use superglue on glass. After a few days it will crack the glass.
I have actually seen a photo of a car windscreen where the rear view mirror had been glued back with super glue and the class was badly cracked where the super glue had been in contact with the glass.
Two part epoxy is the norm for valve bases.

[Murphyv310]

I would say that the problem with super glue is its inability to expand. Fast setting epoxy never fully hardens so it can expand along with the glass and won't make it crack.

You can get super glue for glass though and it doesn't make screens crack, wouldn't use it on valves though.

[Nowhere-Man]

Never use superglue on glass. After a few days it will crack the glass.
I have actually seen a photo of a car windscreen where the rear view mirror had been glued back with super glue and the class was badly cracked where the super glue had been in contact with the glass.
Two part epoxy is the norm for valve bases.

I'd heard people were using superglue but if there are doubts about it, I'll discard that idea. Hopefully the valves haven't lost any internal gas but I'll guess I'll find that out later on.

[Refugee]

I'd heard people were using superglue but if there are doubts about it, I'll discard that idea. Hopefully the valves haven't lost any internal gas but I'll guess I'll find that out later on.

Valves have no internal gas to loose. The problem is air getting in and filling the vacuum.

[Alan Douglas]

US octal valves come loose from their bases frequently but it makes no difference to their operation. PVA ("white" glue or Elmer's) works for reattaching them and isn't strong enough to break the glass. Cyanoacrylate "super glue" has definitely been known to break the glass on 1920s UV-199s. I know of two instances and the owners weren't happy. Glass is weak in tension and the glue can pull it apart. Some epoxies are too strong also. The wrong type, on a rear-view mirror, can pull a divot out of the glass.

[ppppenguin]

In the UK most people seem to use Araldite 2 part epoxy. The fast set type may be better. I've only ever done a couple of valves so don't have much experience.

[pwdrive]

There's always the original recipe....

Lawrence wrote some time ago on this forum "This apparently was the standard RCA recipe for basing cement, yealding 200lbs, enough for a lot of valves....

Coarse marble flour 170 lb.
Orange flake shellac 19-1/2 lb.
Durite phenolic resin LR275-2 7-1/2 lb.
Medium-color (grade G) rosin 3-1/4 lb.
Denatured alcohol 9 liters
Malachite Green aniline dye 10 g."

Lawrence.

[Crackle]

I have used superglue on many valves to reattach them to their base, but I only put a couple of small drops on either side of the base, not had any problem with cracking.
Araldite is so messy and does not run well, and always seems to stay gummy even when mixed well.
PVA glue is another favourite of mine and mixed with a blob of superglue sets to a jell in a matter of seconds, and then sets hard in a few hours. Whilst it is in its jell form it can be moulded to a degree.

Mike

[Nowhere-Man]

US octal valves come loose from their bases frequently but it makes no difference to their operation.  PVA ("white" glue or Elmer's) works for reattaching them and isn't strong enough to break the glass.  Cyanoacrylate "super glue" has definitely been known to break the glass on 1920s UV-199s.  I know of two instances and the owners weren't happy.   Glass is weak in tension and the glue can pull it apart.  Some epoxies are too strong also.  The wrong type, on a rear-view mirror, can pull a divot out of the glass.

Here is a pic of what there is so far. I wasn't happy with a few things so decided I'd go over some of my work and just rewire everything with new wires. So, the heat-shrink and soldered wire-to-wire joints will be going. This is really a very simple radio and it may well be persuaded to work again. My work so far was a bit amateurish but, of course, I was only a beginner at the time and soldering takes practice. In order to do a better job I need to take off the tuning chord and plate and try and get access to valve pins in awkward spots.
The big yellow cap is new and was bought some months ago. Some of the valves have been taken out but I still have them. Nothing has been lost. It just wants tidying up and the circuit checking carefully before supplying 100 volts or so HT.