I picked up recently an Astor HQ , just like the one that sat on our Kitchen table when I was kid, that my father use to listen to the horses racers on on the weekend.

I know their were some updates and valve changes during the run of og this radio, but can anyone confirm of there was ever a factor variant that included the use of a dual piston Variable Capacitor in place of the standard dual gang type?
Or should I assume this is a modifaction made by the previous owner?

Captgogo,

By "dual piston" could you be possibly identifying a ganged pair of variable coils???

They were quite common in automobile radios.

Any thoughts anyone?

a dual piston Variable Capacitor

What you're describing sounds like permeability tuner -- where the coil is variable rather than the capacitor -- however my schematics for the HQ show variable capacitors. Are you sure about the model number?

GTC,

The most amazing thing about those variable inductor tuners to me was their ability to "preset" a station. I would spend hours
marvelling at the mechanism. Just from memory, it was three steps---tune in station---pull out push-button---push in push-button.

I may have the sequence wrong, nevertheless, the second most amazing thing was accuracy. How did they achieve it? Was AFC involved,
or was it sheer mechanical precision?

Just from memory, it was three steps---tune in station---pull out push-button---push in push-button.

That was about the size of it, and because the controls in older cars were more tactile than the silly touch screens that are employed today, you could do it without taking your eyes off the road.

The version with the permeability tuner is the Mickey HNQ.

The model code should be stamped on the chassis somewhere.

I thought I posted a response last night, but I might have imagined it.

GTC you are right , I meant to say a variable inductance coil replacing the variable capacitor.

I also assumed it was the HQ based just on its physical appearance, but thanks to everyone's input it appears I have a HNQ (thanks MonochromeTV) which did come with the permeability tuner and I now have I believe the correct circuit so I can begin to see if I can get this thing working.
I will come back to the site if I run into any trouble, thanks again for pointing me to the right model.
I will check the Chasis as I missed the stamped letters in my brief look at yesterday.

HNQ is permeability tuned 6BE6, 6AD8, 6AQ5, 6X5. Which means its likely a reflexed set & also at a glance is back biased.

So it's a case of the usual suspects: Replace all electrolytic & paper caps & check resistor's as you go & replace the duds.

In many Astor sets, there is rubber wire and theirs is some of the worst.

Normally to assess viability: I visual check for heater/ filament, tampering & mains shorts (6x5 was notorious for shorting) remove the rectifier & after checking continuity & making it safe: You can power the transformer. I even resort to insulation testing the primary. Some times the secondary but you have to isolate the winding's.

Leaving the rectifier out ensures no "B" Voltage and that is where most damage will emanate from, should one power first & think later.

the controls in older cars were more tactile than the silly touch screens that are employed today

And they didn't rely on a battery for positional memory, either.

I have often found the tuning coils to be open circuit on these.

Thanks Marcc, as always appreciate your advise, insights and experience.
I have the radio running nicely, though occasional after a an hour of operation it begins to get distorted with that motor boating sound, no pattern or any event that I am aware triggers it. It has only happend twice so far, with the radio on and off in about 12 sessions.

I have also notice that compared to my other radios in my man cave it is sensitive to interference from my dual large flouro on the ceiling.
But not from the bench lamps that use smaller flouros and the circular flouro one on my magnifying light.

The major culprit for interference is the switch mode unit, which the modern flouro has & some LED ones are no better. There might be a filter in some of those Flouro's?

Valve equipment is particularly sensitive to lightning & can pick it up from hundreds of miles away.

You could have leaking caps, or thermal issue with a resistor, what I do when "burn testing" is to have an analogue meter monitoring "B" Voltage. It is normal for the oscillator to drift upwards as the set stabilises.

As I change caps I check resistors. That saves re-work. Irrespective of it being a commercial, or other repair, I consider it time wasting to try & fault find a radio with seriously old electrolytic caps & tired wax paper caps, still in it.

Marc.

I have one of those. Horrid things. I've spent hours on mine and it won't work no matter what I do, it's currently in the junk too hard basket.

Hi,

The thing that I would add is that motor-boating is a form of instability. Instability can be caused by lots of things, bad capacitors and poor shielding are prime examples, but one thing that a lot of people overlook is wire routing.

Changing lead length or the position of a wire can cause all sorts of nasty effects. This is especially important on radios that are rather compact underneath. If there were any components that you changed the connection points on, put them back to original, even if the leads end up a bit longer. The actual earth or connection point may have been important for stability. For wiring shorter may not be better. Routing it away from that sensitive part may be more important.

The fact that it is a little more sensitive to interference may be pointing to the fact that it is just about to oscillate all the time. It can be a tough problem to solve, but if your radio was close to original to start with I usually try to keep it that way and most of the time it works out fine.

Regards, Frank.

Hi Frank,
You make some very good points, unfortunately the radio had some work done on it, and I always try to keep the connections points the same, I did not give much thought to the length of interconnecting wire or it's gauge? Also I read somewhere that the wires to the lamps should be twisted ?
I have also checked all the soldering joints looking for poor connections, this is often a cause of intermittent problems.

One of the fun things about this hobby which is also makes it very frustrating, the challenge of problem solving, lots of variables to keep us busy.
Thanks for you input Frank and Marcc.