Ever Ready Sky Prince.

[pepmin 1]

Hi. I have a Sky Prince which i have just restored. It belonged to my sisters ex in laws many moons ago, and was handed down to my sister and husband many years later. ( early seventies im guessing ) At one point someone decided to paint it red, probably to go with the decor knowing them. Something went wrong with it and it was handed to me as a boy to see if i could fix it, as i was always mucking about with old radios. I couldnt fix it then, or couldnt afford a battery to try! Either way i have had it for years in various lofts. A few weeks ago i fell over it in the attic while up there looking for the xmas decorations, and decided i would give it another go. I discovered the valves were missing but managed to get a set on ebay. The variable capacitor was seized , and i freed that off with wd 40. I made up the battery pack with ten pp3 batteries from Poundland, and two 1.5v batteries that i put in a holder i had bought from Maplins. The radio came to life more or less as soon as i switched it on. I then concentrated on the cabinet. I dismantled the radio and then stripped the paint off , then cleaned it up with wire wool. I then sprayed it about eight times with lacquer, cleaned the grill and knobs etc. I think it turned out quite well and my sister has jokingly said that she now wants it back. The only problem that i have with it is the line whistle i think you call it, when tuning into stations, that can be a bit painfull, once tuned in it sounds fine. I think its probably the capacitors that need changing, but my dilemma here is that i dont want to change them, i like the fact that the radio is working with all its fifties electronics, and would probably look at in a different light if i fit 2011 capacitors throughout. I know the reasons why you have to do this sometimes to vintage radios, but my question is, apart from the annoyance, is the line whistle doing the radio any harm? Thanks Colin.

[Heatercathodeshort]

What a nice job Colin. Well worth the effort. You will probably only need to replace one capacitor. It is an electrolytic across the H.T. battery. Usually around 8uf 150v or so. The improvement in performance will be noticeable.
That should clear up the whistles. J.

[pepmin 1]

Hi, Thanks for that. The thing is once i had finished the radio, the next week i think that it was, i turned on the radio, and it wasnt working. I checked the valves in an old sky Queen that i had also restored and they were fine. i decided to change the electrolytic and a couple of other capacitors. It was about ten o clock at night and couldnt really be bothered, but went ahead anyway. I decided to unsolder one leg of the old capacitors and piggy back the new ones on one at a time, then try the radio. Still couldnt get a peep out of the set, and now i am thinking that i have probably introduced a secondary fault into the radio due to me not concentrating 100%. Its now about one in the morning so i decided to put it all back together again and try it another day. Once i had done that i was having a fiddle as you do in the back of the set when i noticed something was not quite right about the variable capacitor. there was a locknut on the rear of it which was slack, which locks in a centre screw that goes through the vanes. I am guessing when trying to free it when it was seized, that i must have slackened this off and altered it. I switched the set back on and re tightened the screw slowly and hey! it burst into life again. I locked the nut up and that solved the problem. The next day i took off the new capacitors and resoldered the old ones back on. I didnt like them anyway as they were radial and not axial, and didnt look the part. I think i may go back in and change out the electrolytic as you suggested, and see if that gets rid of the line whistle. Thanks Colin.

[Radio_Dave]

Originally Posted by pepmin 1

and two 1.5v batteries that i put in a holder i had bought from Maplins.

I presume LT should be 1.5V? Wouldn't one of these battery holders connect the cells in series rather than parallel and give 3V?

[Steve_P]

Yes, but only if they are wired that way. Check this! They still seem to work so they might be OK.

The 'Line Whistle' may be due to the 8uF going funny of course. Does this whistle vary with the station? Have you put anything back in a different place?

Cheers,

Steve P.

[pepmin 1]

Hi, I adapted the holder that i got from Maplins to work in parallel. The line whistle does vary, and sometimes the radio sounds like it working from inside a bell, but a little tweaking and its fine again.The station that im tuned into , usually 5 live does tend to drift slightly then it settles down. I can switch the radio off at night and when i put it on in the morning its whistling quite badly until tweaked again. This is not always the case tho, sometimes i can switch it on and its working fine with no sign of line whistle at all. Also i have just renewed the batteries, and sometimes it does not like full volume, bringing in distortion at that level, next time i try it, it is fine. Colin.

[pepmin 1]

I should clarify that when i say distortion, i dont mean that it is just too loud!! I mean that a loud sort of hum is introduced, but not always. My limited knowledge is pointing to the capacitor and i may change that before my ears start to bleed.

[kalee20]

Originally Posted by pepmin 1

... I think its probably the capacitors that need changing, but my dilemma here is that i dont want to change them, i like the fact that the radio is working with all its fifties electronics, and would probably look at in a different light if i fit 2011 capacitors throughout...

Well, the big electrolytic may benefit from changing.

C16 (trader sheet) - which is connected to pin 3 of the DL96 - should be changed. If faulty, you'll have slight distortion, a short battery life, and the DL96 will also have a caning.

Adjusting the screw at the back of the variable capacitor can push the vanes so they are touching - that's why it suddenly stopped and started again.

The whistles shouldn't be there. It sounds like instability to me. As Steve P says, changing the electrolytic may help. Other capacitors which could account for this are C2 (on the DK96 screen grid) and C8 (on the DF96 screen grid), and barely possibly C15 (on the DAF96 anode).

Nice job with the cabinet by the way!

[pepmin 1]

Hi, Thanks for that information. I am listening to the radio now and it is performing fine, there is no rhyme or reason to it. It may be purely coincidence , but the line whistle is not that much of an issue at night?? I have a Sky Queen 2, and dont have that problem at all on that.

[pepmin 1]

Just a quick update on the radio. I changed the 8uf electrlytic capacitor and the line whistle has now gone. Thanks for all your help. Colin.

[Station X]

I have known "Line Whistle" to be caused by dirty wavechange switch contacts. This was the case with my Pye New Baby Q, where the wavechange and off on switches are combined.

[geoff999]

I hate to be pedantic and am open to contradiction, but is not "Line Whistle" the whistle of fixed pitch emanating from the line oscillator of a TV: about 16 kHz for 625 lines and 10kHz for 405 lines.

The whistle from a radio is the heterodyne frequency resulting from the interaction of an oscillation in a tuned circuit of the radio with the incoming signal. This drops in pitch as the set is tuned nearer the transmitter frequency and disappears when the two frequencies coincide.

I suggest it is inaccurate and confusing to use the term "Line Whistle" to refer to the latter.

[pepmin 1]

Hi. You may be right. I am a newbie to this hobby and only picking up terminology from various sites that i visited when trying to rectify the fault. Colin.

[Heatercathodeshort]

Don't worry Colin, we will soon be having you use the right terms. J.

[pepmin 1]

Thanks John.

[pepmin 1]

Hi John. I was having a bash at measuring the current today. I havent changed anymore capacitors yet as the radio is now working great. I am getting a reading of 06.3 on the meter. I have the meter set at 200m. Does this sound good to you? Thanks Colin.

[Heatercathodeshort]

Yes Colin, that does sound O.K. if not a little low. The original data shows around 9-10m/a at 90v H.T. Better to be lower than higher. Please check the coupling capacitor for a leak with your meter on the high resistance range. It should read at least 5 meg to guarantee reliability. The delicate battery valves used with these receivers are very susceptible to incorrect grid bias and can seriously loose efficiency if upset by capacitor faults. If your happy with it and at 6.3m/a, it's probably working O.K. J.

[pepmin 1]

Hi John. I have two coupling capacitors listed on the service sheet, could you tell me which one i should check/change? I can see two AF coupling capacitors C13 and C16, both 0.001 uf. I do not have a multimeter with capacitance measurement, is there any other way to check it ? Colin.

[Heatercathodeshort]

Hello Colin, As Kalee has suggested in post 8 C16 is the coupling capacitor that will cause the difficulties. You do not need to know it's value as being slightly faulty [probably] it will have a very high resistance. Put your meter on the highest resisitance range [as if you were measuring say a 2m resistor] across the capacitor after unsoldering one end. The meter should show infinity. [open circuit] Don't worry about the others as your H.T. consumption is under 7m/a. To be honest, it's a tiny capacitor and I would just change it for good measure, It's just good servicing procedure. John.

[pepmin 1]

Thanks for that John. I will do that. Aplogies to Kalee if he reads this, for suggesting that, then me asking someone else. I need to read and reread all the replies. Colin.