Hi Rob, still enjoying your reports from the workshop.
Its like a day from the radio factory back in 1958!
You are getting a lot of experiance in old radios.
Probably you could run some of the early repairs back through the workshop and look at them in a different light.
Maybe more to finding out exactly how they work and what the designers were up to when they did things a certain way.
you certainly have a huge range of designs to pick from!
Fred.

With the commercial sets, the owner would if commercially viable like it working: Some are dogs and you expect them. Recently one of those in the form of a hacked Airzone 609 chassis only, turned up. It had obviously forgotten the words as all there was, apparently, was hum?

One look at it said do not power. Now with this sort of set you need patience and methodology. There were parts in mid air, which did not appear on the parts list. Cans had to be topped to replace the "Fly Leads" Mains cable was a write off etc. Electrodynamic speaker had cone damage. Topping that one 6D6 fell to bits as the pins were not soldered to the envelope tails. The #80 in it was gassy & the plates bypassed by silicon diodes.

Standard for repairing my sets is the same as commercial: Ruthless. Sets failing quickly are not good for business: Some parts you cannot guarantee: But! you're getting paid to refurbish it properly.

The set currently needs a bit of final adjustment, before sending it home. IF was done early for testing. Actual chassis I have:-

https://www.radiomuseum.org/r/airzone_656_ch_609.html

Marc

Been quiet for a while. The Philips 4-valve mentioned in post #12 did get scrapped today. From it I removed the 2nd IF transformer and put it into the Pye 9-MSW mentioned in posts #22,23 . After that the Pye started working.

Unfortunately the Pye uses some plastic parts and they are well and truly past their use-by dates. One plastic part is mounted on the dial drum and connects it to the tuning capacitor shaft. It's held in position by a screw. The plastic had cracked allowing the drum to turn without adjusting the frequency. I came up with a temporary solution, until the plastic breaks up completely.

Also, there's a knob at the top which lets you turn the ferrite antenna to the best direction. The ferrite is joined to the mounting plate by another piece of plastic which had rotted, leaving the ferrite dangling in space. I put some glue in there with the hope it might join up. I'll find out tomorrow if it works.

While the Pye sat in the garage, the case got a bit scratched and the back cardboard was damaged a bit too.

So, while our glass and metal constructs should last for many years yet, the plastic bits will let us down.

EDIT: The ferrite came loose again, and this time it ripped out the wires, so the radio is once again dead as a doorknob. I don't think I'll bother with it any more.

I have noted as have conservators, that the plastics of the 50's & sixties are not the universal wonder material that they were promoted as.

A lot of it is decomposing. The early Nitrocellulose plastics used in photographic film and other things like radio dials, started decomposing the day it was made and the Nitrates send it brown. If it caught fire in a projector, it was self sustaining and nothing poured on it would stop it.

The picture theatre normally had a fireman as a result. In the one Mum worked in he could be summoned by ringing the local RSL. I see lots of plastic formers, cabinets & stuff breaking up. The decomposition product in some is Hydrochloric Acid which is the catalyst for further decomposition.

Your only hope, where possible is to print, or in the case of diecast a CNC to cut out anew bit.


Marc

Last night I looked at the ancient regenerative radio console, to find out why it had gone silent.

Valves: 24A, 47, 80. Each valve socket has the required tube number moulded into the base during manufacture.

The thing has never worked well, but with that lineup it's no surprise really. You'd have to live among the transmission towers for it to be of any use.

The initial problem was that the wire to the centre terminal of the volume control has fallen off. This caused the 47 to be driven full blast, lucky it didn't break anything. Once this was back on, the grid bias on the 24A was wrong as well. The grid leak resistor was supposed to be 600k, but the 1Meg resistor there measured 1382K, so it was replaced. At some stage the resistor had been bypassed by a diode which was now leaky, so it was removed.

Long ago this radio could pick up the ABC Sydney stations (barely audible), but now the only thing it can get is the station in the house. It can make a tiny whistle on 2BL, but there's not enough volume to work out what they are saying.

Yet somehow I bet some shop sold this trash for huge prices 90? years ago (or whatever) and some sucker bought it.

Getting closer to the end, just working through the consoles. There's 2 Radiola octal consoles that look almost identical apart from one having a tuning indicator. This one picked up nothing and crackled a lot.

Valves: 6U7G, 6A8G, 6U7G, 6G8G, 6F6G, 5Y3G, unknown tuning indicator possibly 6U5G. The rectifier had been changed to a 5AS4 - I changed it back to a 5Y3G to save 5 watts.

The first 4 valves have blue-painted metal shields - they must have been really worried about unwanted feedback. The paint is colour-coordinated with the speaker frame and all the transformers. The speaker has a spider-thing in the voice-coil and is dynamic.

When the volume was turned the radio cracked and made squealing noises. After replacing a few parts to no effect I opened the control and gave it a good clean. That fixed it.

Next, the original crackling noise was still there. Removing valves showed the problem was around the frequency changer, but trying new valves made no difference. The local oscillator was running fine, and suddenly I could pick up my house station, even though I didn't do anything. Tuning around picked up other stations on the MW band. The SW band was dead, but I wouldn't expect much with a 6A8 anyway. Flicking the bandswitch showed it had troubles, after doing that a few times the crackling seemed to be gone.

Next I thought I'd see if alignment might do something. Almost immediately I found that the IFT1 has a number of issues. The bottom adjuster makes not the slightest difference. Bumping the transformer changes the reception level. And it was wobbly in the chassis. That part I could fix. So alignment had to be limited to what I could get with the bottom coil not adjustable.

So, in the end, even though I'm not sure what was actually wrong, it's working pretty well on MW, as long as you don't touch the bandswitch. If SW had been working I might have upgraded the 6A8 to a ECH33 or something to improve the performance.

EDIT: After running for several hours, the crackling returned - but receiving of stations still worked.

Rob, reading about the reaction set with the 24A, 47 and 80 made me smile.
Do not write it off yet!
Having gone through the trials of making a reaction set work I can tell you such a set can be " deaf" if the reaction circuit is not working fully.
The gain of the front end is entirely dependant on the feedback working properly.
Without feedback the set will be about as good as a crystal set and match the way yours is working.
For sure it will be a "metropolitan" set build and no match for a superhet long distance but once the feedback is operating the front end gain will go up by 100's lifting the sensitivity and selectivity hugely.
I would tip your reaction is not working. You should be able to smoothly adjust the reaction feedback through a sudden increase in sensitivity all the way into oscillation squealing and set it for just spilling over.
Then the set comes alive.
My set with 57 front end, 57 + 47 audio, "80" line up will receive all Sydney stations up in the mountains at Springwood at full volume with a 30 foot aerial.
Your reaction may need a good look and hours of fun for the whole family experimenting.
Fred.

Hi Fred, yes I had arrived at the conclusion that the feedback wasn't working, however the circuit is so simple that I can't see why it stopped. The voltages were measured as being where they should be, nothing's changed in that area. On the very odd occasion that feedback is attained it is very distorted, not the smooth squeal that it originally had.

I've unplugged the 24A so often that it has developed cracks in the glass around the top cap. It hasn't gone right through yet, but it's only a matter of time.

One thing that I discovered that is definitely not part of the original design, is if I hook an alligator clip to the grid, then drape the alligator cord near the output valve, it induces a bit of positive feedback (at audio frequencies) which makes the audio louder. So, I made the grid lead pass by the output valve to do the same thing.

But still, in the end, it takes a lot of space that I need for other things, and it may as well not work at all for all the good it does.

I've now repaired the other Radiola console, an easy one for a change.

It's the same chassis, with everything in the same place, but the valves are pre-octal equivalents, so 6D6, 6A7, 6D6, 6B7, 42, 80. There's a wired-up socket for a tuning indicator, but there's no hole in the cabinet to see it, so obviously no valve fitted. I guess the indicator would have been a 6E5 or 6U5 - a 6-pin type.

This radio has collected a few modifications over the years - there's a Radio/Gram switch on the side, also under the tuning indicator socket there's a RF gain control, which is quite effective. The IFT1 has been replaced - I suppose the original died.

Anyway, the problem was simply a dry joint in the AGC circuit - easy to get to, easy to repair. As usual the SW bands produce nothing, but MW works very well indeed, pulling in a number of country stations.

A whistle is a dead giveaway of oscillation. Neutralisation & reaction can play a large part in that. The fun starts whenyou have a TRF like Lyric 70 series which starts off with four stages. There tends to be tendency for people to forget, or not understand that like an IF, or TRF stage, If like the gang of four, if the four coils are not on the same frequency, you are going to get attenuation on a grand scale.

Marc

That regen radio has been packed away, and since it has a extra full-sized shelf under the speaker, it's now storing my collection of old hard drives.

Now, on to the next console. Unbranded, line-up is 57, 58, 57, 2A5, 80. No AGC. The volume control progressively shorts out the aerial, and it also adjusts some DC parameters. The dial is the circular 0-100 type, with a friction drive (both Radiolas have friction drives too, but with proper dials).

Problem seemed to be insensitivity. The aerial coil is in a can and has no adjustments. The aerial terminal on the back can be used for a large aerial, but is inadequate for a smaller one. In this case joining the aerial directly to the top cap of the first 57 works wonders.

Anyway, a few adjustments were a bit out, after that it could pick up many country stations where before it was struggling. Didn't need the soldering iron.

Now, just one console to go. Its 2A5 is missing, so I'll need to borrow the one from this console.

While I was working on these last couple of radios, I took the chance to test my meager collection of pre-octals. Unfortunately these valves are very old and getting gassy. One 58 failed, one 57 failed, one 6B7 failed. Out of 3 spare type 80, only 1 works - the other 2 lit up in a brilliant pink/purple discharge, indicating gas. All 3 of type 42 work.

A console that was hiding in the corner which has never worked since the day I bought it. The dial says Watson, and the dial light is a 25W 240V small globe (so there's 25 watts wasted right there). Dual band. Unfortunately almost every part is broken in some way, including the dynamic speaker. Valves: 6K8G, 6U7G, 6B6G, 6F6G, 5Y3G. The output valve had been replaced by a 6V6GT. The spigot of the 5Y3G has broken off. The top caps of the 6K8 and 6U7 had been soldered to the flywires.

The only things known to work were the power transformer, the valves, the dial cord, the wasteful dial lamp - and the nice 3-core power cord. I rigged up a speaker with transformer, and jumpered the safety thing on the speaker plug. When powered on the 6K8 resistor (with integrated fuse) that replaced the field coil got very hot and melted its fuse. There was no sound at all. I could have replaced the filter caps, but really, every single component needs replacing, and I couldn't be bothered. Another one bites the dust.

The last console has been living in the laundry for years, and exposed to the weather. The chassis and many other parts have been painted green. It has a clapped-out friction 0-100 dial, so I have to turn the tuning cap by hand. There's a socket on the back for a SW converter (never seen one, I just know they existed). Valves: 57, 58, 57, 2A6, 2A5, 80 - in other words, just like last week's console but with an extra valve (2A6 is electrically equivalent to a 6SQ7, but with a large top cap and 2.5v heater). The 2A5 was missing, and I don't have spares, so I borrowed the one out of the other console.

The original speaker was completely missing, so a choke had been fitted to the back. A temporary substitute speaker had been lounging around, unattached, at the bottom of the cabinet.

Amazingly, when powered on, it worked just fine. The 2A5 gets quite hot though.

If I knew something about cabinets etc I'd like to get this one up to scratch. I also have no idea how I'm going to fix the friction drive. As far as I know, the usual remedy was replacement. And since a 2A5 hasn't appeared for years, I might have to fit a small 6.3v transformer and use a 42 or a 6F6. I really don't know.

And, that's the end of this absolutely fascinating series.

Hi Rob, enjoyed reading about the various battles with old electronics.

Now all you have to do is go back to the first set and re-repair it, and all the others, with the added knowledge you have gained?

lots of laughter..................

Cheers, Fred.

And thats the end of this absolutely fascinating series lol! I DON'T THINK SO!