Thanks Harold, Ian is a great ideas man, I just hit things with a hammer until they look like something.
Helping the project along are the suggestions from other members.
Any comment is welcome for any of my threads, just post it guys there is always a diamond in there somewhere.

I am now waiting on APO to deliver the Kriesler chassis.
When I get that I can test the coils for passband response, get a baseline in normal operation and then see how they react to being used by the single valve.

More to come.

Fred.

I have received my 11-99 and its a great little set, performance wise.
Despite being fitted with dripping wax caps and those terrible IRC carbon resistors (any size you like) the set has voltages within 5% of the circuit. The coils and power tranny are in good nick.
I will now "run the rule" over the set to get a base level of performance and then strip out the 9 pin parts and wire up Ian's suggested 10 pin circuit and see what happens.
My cabinet is looking a bit sad, nothing a bit of epoxy and a coat of fire engine red cannot fix!

Standby.

Fred.

Are you going to experiment with the 11-99 loopstick Fred or has that ship sailed?

Hi Dave, I will leave the coil set exactly as it is.
Hopefully the oscillator coil will work with the 6Y9 autodyne circuit with no changes and the loopstick should need no change at all.
The coil set is very selective as it is and the sensitivity is good enough for the loopstick alone to feed the convertor.
They do have an external aerial terminal for the set to work in country areas.
I'm hoping to do some more work on biassing the autodyne section of the 6Y9 at a point where it has gain but still runs as an oscillator.
There is a bit of a balancing act there.

Fred.

Hi all, work is proceeding slowly on the 1 valve project.

I have converted the 11-99 to one valve and have it working, but not as well as I would like.
My hopes of using all the original coils did not work out.
The original oscillator and aerial coils that worked well for a convertor stage do not work when hooked to an autodyne arrangement.
Happily, the rest of the set's parts are fine, the problems are centred on the autodyne stage.
The reflex IF audio half works like a charm and the original power tranny, output tranny and speaker work ok.

So, I have a lot of research to do, and this is getting right into the nuts and bolts of how a pentode valve actually works.
I have gone right back to reading the original patents on superhet/autodyne operation and trawling contemporary (1920's 1930's) papers and books on the subject.
Ian Robertson is also doing some research.

It is just a matter of grinding it out and exploring all avenues of previous research.
This is probably just proving why the mixer/oscillator 57 / 6C6 superhet circuit was dropped like a shot as soon as the dual valve mixers were developed like the 2A7 / 6A7 / ect ect triode hexode octode whatever. In those the oscillator is a separate triode function and the mixer 1/2 can get on with it without interference.

Fascinating.

Fred.

Well, it was a long grind and ended in failure!
Failure, in the original intent to use a standard chassis as a "Kit" basis to make a 1 valve Superhet.
Even a failure is not a failure, so long as you understand why the specification has not been met!

I learnt a lot about oscillators and mixers and specifically why the "autodyne" was not a success in the early days of valve radios.
Of course, in the future, the autodyne was the "go to" circuit for early transistor radios.

Once I understood WHY the project was going nowhere, I terminated and will send a PDF of my workshop notes to Brad to add to the sequence at the front of the post. It's a bit of a waffle but stick with it as I wake up to what is going on while battling through trying to subdue a reflex amplifier as well!

That of course leads to a couple of other projects.
one, making a proper Autodyne tuner with valves, using the lessons learnt in this project.
two, putting the Kriesler 11-99 back together, but using 10 pin valves.

Cheers, Fred.

Part 4 uploaded.

Great write-up Fred. You certainly gave it a good shot.

Yes Fred the 11/99 was around when the 6Y9 was too. It was always a design to use up obsolete stock as by this stage the radiograms that had made Kriesler so successful were now solid state.

The 6GV8 is a TV valve that can work as an audio amplifier in lieu of the expensive "audiophool" 6GW8. Not pin compatible I must add.

Dare I suggest adding a FET follower between the aerial coil and the valve?
Or adding a bipolar transistor autodyne converter ahead of it?

But no, that would be cheating!

The 6V9, 6U9, 6Y9 lineup sounds interesting. Since you've got the reflex bit working stably, maybe just add the 6V9?? That'll give you effectively two IF stages and a very hot superhet.

On the subject of single valve solutions, there was a late 50s tiny portable TV in the US that used a 6U8 as the only tube in the audio. Reflexed IF and triode audio output. I always wondered about the FM IF being modulated by the audio. You'd have to not run it as a limiter and rely on just the ratio detector for the AM rejection.

I finally finished this project off by putting the 11-99 back together but with the 10 pin valves.
I have done the usual story, sorry about the bad English and mixture of tenses but it's a story as it happened.
The set is now a pretty two-tone colour scheme.
I just had to paint the cabinet with my "go-go Blue" favourite but left the front panel the original bone colour.
The set works pretty well and tunes in the locals by the internal loop stick. No external wire needed.
There is a lot that could be fixed and made better, like the awful speaker, but you have to stop somewhere and get on with the next project.



I'll send the usual PDF to Brad as a Part 5 to this thread.

Fred.

Document uploaded.

Another interesting story. It seems though that the original design of the 11-99 was quite good, using the 9-pin valves.

Indeed it was quite good, and still is. Mine still operates splendidly, a perfect bedside radio, soft yellow dial lamp as opposed to harsh burn out your retinas blue LED display . Original dial lamp, valves, all caps except one electro. Also a slight mod---fitted an inline mains fuse, precautionary measure only.

Always a pleasure to wake up on a Sunday morning and give it its weekly run for half an hour.

Yes, agreed, the original 11-99 is a master class in getting the most for the least.
A really well worked out commercial design.
There is nothing that you could add to improve it without jacking up the cost.

If you wonder why I went to absurd lengths to cover the 240 mains wiring, I had a version of the project in mind for a SC article.
That won't happen as the "one valve' idea fell apart.
I will do a SC article on the scratch-built version.
I may be able to improve the performance of this as I have learnt some lessons from a project not yet shown which is also an Autodyne that works as well as a convertor set. more on that later.

Fred.

I still have one 11-99 left, after giving the others away. It is a very nice looking bright red and white.

It runs most of the day on Sundays and Mondays. One of the last made, I think.

Certainly the last "toob" radio made in Australia and quite possibly the western world.