Sky Queen hums but no sound

[Radioamateur]

Hi everyone,

I have just joined this site, and I am looking for some guidance to help me fix a Sky Queen Radio. The serial number starts with 792 so I think it's an early one.

Apart from the layer of nicotine that was covering it, it's in pretty good condition as it was in my parent's cupboard for many years. I have a stable power supply which isn't drawing excess current, so I have assumed that nothing is short?

The only things I have done to it are: used a soft brush to clean the fascia and tuning mesh, replaced the tuning twine, wire brushed the valve contacts, and cleaned the casing gently with washing liquid (which brought it up a treat).

I have obtained a schematic, but have no way of testing the valves. I can use a multimeter so I am hoping that I can bring this beautiful old radio back to life with some expert guidance that no doubt exists on this site.

Many thanks in advance,

Paul

[TrevorG3VLF]

The first thing to is to get the DC conditions right, particularly the output valve. Measure its grid voltage and if it is positive, turn off quick and change any capacitor connected to the grid.

Check the cathode voltages to calculate the valve currents.

[TonyDuell]

I thought the Sky Queen was an (All Dry) battery set using the Dx96 range of valves. According to Trader Sheet 1098 it is similar to an Ever Ready model T, but using the '96' valves with half the filament current of the older ones.

All filaments are in parellel, running off a 1.5V battery. Chassis is LT-. HT- is connected via a resistor, the voltage drop across this provided bias for the output valve. So the grid of the output valve should be -ve (about -6V according to the trader sheet) with respect to chassis (which is the filament/cathode of the valve).

Be warned there are some high value resistors (1M, 4M7) in the grid circuit of the DL96 output valve and the anode/screen circuits of the DAF96 detector/audio amplifier valve. A typical digital multimeter has a resistance of 10M on all DC volts ranges, and that is low enough to affect voltages in these circuits.

For reference I think the other 2 valves are a DK96 heptode frequecy changer and a DF96 pentode IF amplifier.

Now, you are running this set off a power supply, not batteries, I believe. You must use 2
separate power supplies, one for HT, the other for LT, they must not be interconnected (other than via the set). In particular LT- and HT- are different. If your supply can't do this, then I would use a single D cell for LT for the moment. Make sure the polarity is correct.

Then measure the voltage between HT- and LT-. I think it should be about 6V as I said a little earlier. If it is very low then the set is not passing much HT current, perhaps due to a problem in the output stange. If it is too high (more likely) then the set is drawing too much current, this is often due to leakage in the capacitor (1nF == 0.001uF) between the pentode anode of the DAF96 and the resistor connected to the grid of the DL96 (There is only one capacitor connected to this anode, so it isn't going to be too hard to find).

[Herald1360]

First things- check the filaments with the multimeter on ohms- pins 1&7 either side of the gap for each valve.

Also with meter, check the primary of the output transformer.

If the filaments are OK, power them up from a single 1.5V cell and check for total current of 125mA.

If it's still dead........

Edit: lots of crossing of posts!

[boxdoctor]

As Tony Duell points out, there are several high-value resistors in this receiver. These are probably carbon composition types, but whatever type they are, I would check them anyway, as they have probably drifted well off value considering the age of the set. Tony.

[Radioamateur]

Thank you to those who replied to my post, lots of useful information there and things to check.

The power supply I have does have separate circuits/transformers for HT and LT so that's one thing I can rule out as a potential problem.

I will work through the steps and advice given, and report back.

Thank you all again for taking the time to reply to my post!

[Techman]

It’s a bit of a worry that you’re saying that you’re getting hum. Do you realise that both your supply lines from your power supply have to be smoothed via electrolytic capacitors and preferably regulated, particularly the low voltage for the valve heaters?

I would STRONGLY advise that you use a 1.5 volt AA type cell ONLY for the valve heater supply (LT) until you fully understand how these sets function.

[crackle]

Hi Paul
The filaments in these battery valves are very delicate and easily burned out if anything much higher than 1.6 v is applied.
There are lots of "vintage" battery eliminators around, their use is not recommended for these sets where the valves are in parallel. If one valve heater fails then all the others can fail in a cascade fashion as the voltage rises with the reduced load.

Unless the power supply is a modern one made especially for 1.4v heaters with a DC REGULATED output, dont use it, use a 1.5v battery instead.
I would check all the valve heaters individually as Herald1360 suggested.

Mike

[60 oldjohn]

Which version of the Sky Queen are we talking about? Has it "91" valves or the later "96" ? Most of what has been said applies to both versions, but confusion could occur if we are looking at different circuits.

John.

[60 oldjohn]

Opps, Both Sky Queen models use "96" valves. The newer model has a rectangular cut out at front and rear and makes use of a PCB. I don't have a circuit for either set but presume there will be differences.

John.

['LIVEWIRE?']

Many years ago we owned, at different times, both versions of the Sky Queen. AFAIK the circuits of the two models are similar, though there may be, as John says, some, possibly minor differences. Both SKs are long gone, so I can't check, but the main differences were (a) The first version was 'hard wired' on a metal chassis, also used in the Sky King' (b) the Cabinet was finished in white or pale grey rexine, with a circuluar speaker grille, whereas the second model, was, as John says, built on a PCB.

[Chindit]

And the latter version of the Sky Queen used some potted component blocks as well as being built on a PCB. It was a light tan and cream colour with a cream plastic handle on metal struts that was notorious for cracking.
Colin.

[Radioamateur]

Hi everyone. Just an update to say where I am up to.

The voltage across the -HT/LT was 5.6v, is that within the 6v tolerance?

All of the valves seem ok, none were open circuit, same with the primary o/p transformer.

Techman - I am using a modern, smoothed and regulated supply. I understand this is critical with respect to the LT side, and if I bought an old supply I would test it before connecting it to anything.

Strangely while moving the tuner I did hear a station faintly when the volume was at maximum (on LW, nothing on MW).

The model I have is hard-wired onto a metal chassis (lovely rats nest). The case is cream, and the handle is clear plastic, both in good condition

My next course of action was going to be: changing the decoupling capacitors (are modern equivalents available from RS, Maplin, etc?), and testing all the resistors (out of circuit) to see whether their values are still close the original spec.

Any further ideas, suggestions or help would be greatly appreciated!

[Herald1360]

Try poking a screwdriver at the slider of the volume control- you should get a good crackle if the audio end is working.

What sort of multimeter do you have? Any idea of its ohms per volt (moving coil) or input resistance (DMM)? It's worth a check on each valve to see if there's volts at the anodes and screens, though with a moving coil or cheapo DMM the indicated voltages will be rather lower than actual unloaded ones.

With a tranny next to the set tuned to something weak at the top (HF) end of MW, try tuning the SQ over the medium wave band to see if you can hear its local oscillator. Worn out DK96s are not unknown.

With the set off, use the meter to check that aerial coils etc are connected where they should be and not open circuit.

[Techman]

The power supply arrangements sound good to me.

That model of the Sky Queen radio was the first proper working radio that I had when I was a child, I seem to remember that it cost 30/- and I struggled to save my (probably) half a crown weekly pocket money to buy those wretched 90+1.5 volt batteries that lasted no time at all. I well remember as a young child one day finding that row of screw heads that are down one side of the chassis were all loose, so thinking that this can’t be a good thing, I tightened them all up – then I wondered why the radio would no longer receive any stations. This was my first introduction to trimmers and one of my first lessons in radio, having realised that it worked before I had tightened all those screws, I soon had them re-adjusted and the radio working fine again.

I painted the case of my radio with cream paint, painting the speaker surround in another colour, the grill in another colour and polishing the bit of brass trim at the top of the grill surround with Brasso. A while ago I found an old picture of me at a sea side resort standing with my Ever Ready Sky Queen radio at my feet. I later got a Sky King, this had the same innards but the cabinet was wider at the bottom than the top and it had a cloth front. I can’t remember where this radio came from, but it was either free or from a jumble sale for 6d or something like that. Sadly, these radios were both dumped when we all moved house back in 1967 and I had by then moved onto ‘better’ radios with short wave!

['LIVEWIRE?']

Several of the coupling & decoupling caps. will be waxd paper types and should be changed. Values such as 0.01uf, 0.047uf (originally 0.05uf) will be used, and firms such as those you mention stock suitable replacements. THey are yellow axial typles usually rated at 400v or higher.

[Radioamateur]

Hi again everyone. Thanks to those who've recently added suggestions.

I had a bit of luck regarding the Sky Queen. It was powered up earlier and I was taking readings from various things, and moving it around where necessary.

Suddenly it sprang into life, but just as quickly went off again! So now I'm thinking definite dry joint somewhere (even though I'd done the classic tap-tap everywhere previously).

I inspected the cores L4/5 and L10/11. I removed the covers and had a mess around, nothing much happened, although when screwing L4/5 cap on and off occasionally some minor changes. I then turned my attention to the screws which hold the cap bases in place (and provide the ground?). I removed the screws and scratched the bases where they were, screwed them back in, and hey presto!

Not sure how common this might be, but very pleased to hear that radio after decades of silence. The last time it would have been heard is probably when my grandmother sat listening to it many years ago.

One more issue now. At the low end of the scale, up to about 350 I can get stations clearly, after that lots of crackling, and nothing else. I have cleaned the tuner mesh with a brush and contact cleaner, but that has made no difference.

Any suggestions how I might fix this please, or do I need to replace the tuner unit itself?

Techman - Love the narrative about your Sky Queen! I read somewhere they were about £9 10s in 1953.

Livewire - Should I replace the decoupling caps even though it's working now?

Herald1360 - My DMM is nothing special (impedance of 10M).

Many thanks again for taking the time to respond

[crackle]

The crackling on the tuning capacitor could be bent vanes, the best way to check is switch your multimeter to continuity, if it has a buzzer it helps. Disconnect the power to the radio and unsolder the wires to the fixed vanes of the capacitor (on both sides) and connect the multimeter using some croc clips to the body and each fixed vane tag in turn.
You should have a reading of infinity on the multimeter as you turn the dial through its whole range. If there is a short on either of the vanes then the continuity buzzer will alert you.
It is often possible to move the vanes slightly if there is a short, sometimes the whole of the fixed vane part is dislodged and this can also normally be carefully levered back into alignment. If all the vanes look off alignment, one way, with a close gap one side and a wide gap the other when the capacitors moving vanes can be adjusted with the screw at the end of the capacitor, by first undoing the lock nut.

Failing all the above it could also be a dirty contact on the moving vanes, constant use may help, rocking to and fro, and a little switch cleaner on the wipers.

Mike

[Techman]

Originally Posted by Radioamateur

I read somewhere they were about £9 10s in 1953.

Ah yes, it's interesting to know what the new price was - 30 shillings was the second hand price paid from a junk shop during the 60s.

[Radioamateur]

Thanks for the help with the tuning mesh Mike. It was an outer vane that was bent in slightly. It works perfectly now, no crackling! I have reassembled it and will use it daily. It has a lovely warm sound, and a pretty powerful amp.

Techman - I found the prices for other models:
Sky Prince (June 1954) £10 12s 6d.
Sky King (June 1956) £10. All plus tax. Batteries were not included...
Source: British Radio and Television Retailing, September 1957