Hi All

I recently found this Kingsley RKR model portable radio/record player in the local Op Shop. It didn’t power up in the shop when briefly plugged in. I think its from around 1955-1963 roughly. I cant find very much info on it online just a pic or two.

I have done some initial inspection of it and traced the circuit. It appears to have all original components, and is in reasonable nick. Cosmetically the cabinet is good, with just a minor ding on the top, and a 10cm shallow scratch down the left side. The controls knobs aren’t good, one missing, and two broken.

It has a garrard turntable in it with 78, 45, 33 and 16 speeds which is good (not that I have anything other than a box of 33 I haven’t played for 20 years ).

The 4 valves are 6AN7A,6N8,6GW8,6GW8


Image Link

Image Link

Image Link

Image Link


The power transformer is not labelled that I can find, has a 220,240V selector switch. It also has a dark baked slightly rusty look to it which is out of character with the rest of the set, so I don’t know if it has baked. I have tested it with ohms meter ( I don’t have a proper megger), the primary side measures 36Ohms on the 220 and 40 ohms on 240V tap. The primary to ground/chassis measures around 5-10 Meg ohms, so not shorted. The secondary measures around 68 ohms, its a single winding with no taps. It measures around 1.5 -2,0 Meg to chassis ground, and around 2-3 Meg to the primary winding, depending on which end. The heater winding measures around 0.5 Ohms which seems reasonable as its probably around 6.3V 2.5Amps. its not shorted to the chassis or other windings

The rectifier is selenium, I am assuming it is a bridge rectifier giver the circuit layout, and the output winding of the PT. Ant tips on this would be great, I have read they are nasty if they burn out or fail.

The two output transformers are Rola E47-1 6500/15 ohm. They measure around 330ohms on the primary, and 3.5 ohms on the secondary on both Tx. They are not shorted to ground/chassis. They are supposed to be 15Ohm output, so 3.5 Ohms seems a bit low?

Image Link

The radio section has a ferrite tuner rather that a Variable cap one, and a couple of IF transformers. I don’t know much about what is inside these except a pair of coupled coils with tuning slugs for alignment. I have drawn these three as”black Boxes” on the schematic above.

Image Link

I haven’t has much of a look at the turntable yet, but it looks undamaged, and very claen on the underside. Topside just has some dust on it.

My initial guess is the Selenium rectifier is open circuit or not working. I haven’t powered it up at all so haven’t measured the mains PT. I might connect a small supply to it (6-12Vac plug pack and do some measurements. I have unsoldered and resoldered the PT wires from the rectifier to test the PT.

My plans at this stage are to get the power supply side sorted out.
-rewire mains wiring with new lead mounted securely to chassis not just with a big Knot in it. Suggestions?
-Fit a mains fuse in mounting on chassis(no back plate to mount in)
-Remove 220V240V switch and hard wire to 240 only
-Insulate all HV terminals though mains and B+
-Replace the selenium rectifier with Diode bridge.
-replace the three filter caps with new.
-Replace coupling caps in audio section with new
-Fit grommets for all through chassis wiring or reroute
-replace front knobs ( will need to find these, 3/16 shafts with grub scews?)
-Test Heater circuits
-Test B+
-any other suggestions?

Thanks

According to information on the Radiomuseum site, some models of Kingsley (Kingsley Radio Pty. Ltd. 380 St. Kilda Rd., Melbourne) sets were sold as kits, and it seems Kingsley was fond of inductive permeability tuners.

Some other members of this site have mentioned interest in the RKR model:

http://vintage-radio.com.au/default.asp?f=3&th=476.

Powering up any of these old sets before a thorough inspection is fraught with danger. It's lucky that it didn't go "bang" in the Op Shop -- but then if it did I guess you would not have bought it.

I've not yet had to deal with/replace a selenium rectifier, but there's plenty of material on the Web on that subject. I'd be inclined to replace it on principle.

The under-chassis photo shows some modern capacitors, but some old ones too. That grey Elna electrolytic should be replaced and any other old electros as a matter of course.

The power transformer looks to have had a hard life, but looks can be deceiving. I'd be giving that the sniff test. A megger test is best.

The DC resistance of speaker coils tends to be about 80% of the nominal impedance, so I'd expect to be seeing around 12 ohms for 15 ohm speakers. You need to disconnect the coil from the output transformer for that measurement.

Procedure-wise, you should concentrate on getting the power supply working first, then work progressively from the audio stage through to the RF stage.

As to your other questions:

Yes, replace the power cord with a modern one, properly anchored, and earth the chassis.

Fuse is optional.

I don't know why you want to remove the power switch. I wouldn't.

Use new grommets when taking wires through the chassis.

The hookup wire looks to be in good condition, so not sure what you mean by insulate HT terminals.

Finding replacement knobs can be a problem, although assortments of knobs do appear on eBay with some regularity.

First off no expert on any of this and I may get it wrong with regard to Valve Tech

one document I read from I believe a reputable source said Selenium rectifiers Fail (deteriorate) over time regardless of use...I cant conclusively say one way or the other but yeah ideally get rid of it

The catch is they do from what I understand have a finite effective resistance like a tube
so you may want to check the B+ or research the characteristics of that rectifier to make sure you dont boost the B+ too much for the circuit when replacing with silicon diodes ...just a point to be wary of that all

I think if it it isn't stuffed better it be gone anyway So yes silicon diodes or a bridge rectifier

From reading and not the voice of experience on this at all... but fuses at times dont protect as much as you can hope with tube circuits

Still any mains side fuse is a good Idea I think personally ...transformers in those days didn't come with thermal fuses as is a must now...but I was a little surprised really mains fuses were not used at all for the most part that I know of in early radio gear

Thought I believe getting the type (slow fast) and Value right can be a bit tricky
Slow blow I think for tube circuits and there is some rule of thumb for valves but I cant recall it
I'll let others with more knowledge here answer that one

As to your measured transformer specs, well seems high but a true insulation tester is the best way to go
I dont have definitive yes or no on that, Marc or one of the others may chime in
other wise some research might better answer that one
(BTW Altronics sell one for $ 99 that should do the job for you if you want to get one, probably a worth while investment for old gear)

looking at the pictures it doesn't look in bad shape just the victim of time and heat
(if you want a worry look at my bee transformer and my other one is worse...the first one seems OK thought and does work..the other I haven't checked yet and I am going to get that $99 unit)

yeah you could use a lower voltage on the mains side to get the turns ratio of the transformer and calculate out what it should be for the secondary

Theres a few ways I think it can be done to work out what the voltage should be on the secondary

The 6v3 sounds about right to me at half an ohm

The output Transformers I think thats probably "impedance value".... not DC resistance?

Again no expert here but if you got continuity they are probably fine

on a soldered Earth wire..I am not sure if these days thats considered acceptable?.. I have a feeling not ...so you may have to secure with a bolt locking washer etc... seems to be the done thing
maybe one of the Sparks here can answer that one

Your game plan sounds like the go and yes power supply first but as I said just make sure your B+ is not going to cause a problem...it probably wont but just a point to note
(I haven't looked at the other thread but maybe its a mute point anyway)

Insulating High Voltage points, well if your hands liable to brush them then a good idea

Defiantly all mains exposed points, cover!...which kinda seems a bit strange when you got like 300 Volts DC that could be anywhere inside that could kill you ...still thats after a transformer were as the mains side is part of the electrical system...so even thought its on a plug it would still have to meet todays safely criteria for termination I'd expect

Anyway hope this helps but remember I am a Noob here..lest with Valve Tech.

Thanks for the replies

Yes getting the power supply sorted out and safe is the first step.

The selenium rectifier is going to go, I'm just not sure if its a bridge arrangement, but I'm going to replace it with a diode bridge anyway. Just hope the B+ voltage will be the same.

The 220/240 switch is mounted in a small socket on the chassis, like a 9 pin valve socket, but with only 4 holes. The main power switch is the left hand on on the front panel. I was going to leave the front on/off switch, but get rid of the voltage selector one. Or at least not wire it in but leave it there for posterity.

I will insulate all the HV and Mains terminals, if only just to help prevent me zapping myself.

The three grey power supply electrolytic will go, just got to get some axial replacements.

There are two Rola 15ohm speakers in there with a plug on the cable. I unplugged them to get the chassis out. The output side of the speaker tx were measured without them plugged in, and 3.5ohms does seem a bit low, as you said GTC it should be around 12 or so DC resistance

As for plugging it in in the shop, the op shop guy didn't want to sell it to me without knowing if it worked as it would be more money for them if it did. Fair enough. I did explain it may cause damage. So he plugged it in before I bought it. There was no smoke, flash or bang, just no life at all. So I got it for not much in the end.

.. and thanks for that nicely drawn schematic, clearly laid out and labelled so an amateur like me can follow it. It's too late for me to start accumulating a lifetime of experience.

The B+/C+ circuit is unfamiliar to me, so I assume you know how to calculate what voltage and load you will need to produce when you replace the selenium recitifier with a silicon bridge. I nearly cooked a centre-tapped transformer recently when I put a bridge recitifier across the two active taps - saved by an active sense of smell.

Maven

Thanks Maven

The B+/C+ is drawn just to separate the two sections of the power filter. The Audio plate supply (~60mA) section comes off the middle tap of the filter between R6 and R2, and the low power/screens (~10mA)comes off the other end of R2- this is for power valve screen grids, and signal valve plate supplies. Normally the whole high voltage supply is called B+, but I labelled it B+ and C+ just to aid my drawing.

It occurs to me that I posted this in the wrong forum section, as there is a Vintage Gramophone and Phonograph section...

I have done some testing.

I removed the Selenium rectifier and desoldered the PT primary side wires from the power switch. I found a 9vac 800mA plug pack in the parts box, and replaced the plug with two alligator clips. Connecting through the power switch didn't work until I re-soldered the terminals- maybe they were dry joints? Once connected to the primary of the PT I got-

9vac plug pack = 10.61vac unloaded
Secondary PT = 10.55Vac
Heater winding 0.295Vac

This becomes 238.6Vac secondary and 6.8vac heater- near enough. Seems like the PT is working OK

The B+ would be 238.6*1.41=336.5V. Under load it might drop to 300V.

Finally I find the post and sorry late correction

I should have said with regard to the output transformers "if they measure close to the same" chances are then they are probably ok

Anyway sounds like you on the right track

I may be accused of being pedantic here, but do be careful when labelling circuits if you are drawing them.

A,B &C, still have relevance in Vintage Radio and whilst you may think "C" is uncommon I have a line amp, there is one current on the American Forum and I have serviced a Lyric 70 series (1929) where a separate "C" power supply is used to supply the grid voltage to valves. In the case of the Lyric with nearly 400V on the plate around neg 60 or more to the 50 Grid.

"A" was the filament battery; "B" The plate supply; "C" the grids. I have seen circuits with that sort of lettering, so it is a case of be careful & try and avoid doing it.

Marc

DJ Oz

Yep I think the output transformers should be ok too

Marcc

I have read somewhere that the old battery radios used three batteries, a large (A) battery for the filaments, a high voltage B battery (or sometimes via a vibrator supply) and sometimes a C battery if the output tubes used fixed bias. Point taken the way I have drawn the circuit could seem like there may be another negative supply for the bias.


I have done some testing with the power supply connected via a 40W lamp load- the lamp turns on almost full . The PT was drawing a heavy current, not sure why as it didn’t seem to have any major faults.

I connected it up enough to run the turntable motor briefly- it didn’t turn. Once I sprayed liberal amounts of contact cleaner on it it ran fine. The speed selector wheel ( I think this is what it is), and drive belt aren’t contacting very well. After about 5 minutes of running, there was a small amount of smoke from the PT secondary.

I have disassembled the power transformer- it has a single bobbin with the windings next to each other. I have stripped off the heater winding(1.08mm,31 turns), and some (10%?) of the secondary winding so far (310turns,0.25mm). I guess there will be around 3000 turns? I plan to rewind the secondary with new wire, and test again. Should cost about $20 from a quick check online for wire prices. I’ll check valves etc work OK before going further than this


If this doesn’t work there is another option to rebuild the power supply. Evatco have a replacement PT that sould suit. My main aim is to get it working again, not so much to keep it really original, so new parts are fine.

I need to check the phono cartridge is OK, this might be an issue if its dead. How do I test this easily if the rest of the CCt isn’t working?

One of the best ways to fry a transformer is to fire up the apparatus after is has been left sitting for a long long time. The electrolytics can lose polarity & short. I see a lot of yanks cooking transformers this way as they are, perhaps, used to sets without one.

That looks a bit like a Selenium rectifier & they have an attrition rate & are notorious for sending toxic smoke signals, to tell you that they have failed.

Secondly, note the voltages on the Ecaps that look like ELNA. Many modern caps do not list "surge volts" If those caps have surge volts on them, filament (with no cathode sleeve) & diode rectifiers surge to near twice EMF before the heaters cause the valve to conduct. Under rated caps will fail.

Check those green caps if they are polyester they are probably OK, some were paper. there should have been alarm bells when it did not work in the shop. People often flip these things, if they do not work & that could have also been cleaned out of Granny's garage after Pa put it there when it died, then he died & she died, or they moved into a home for the terminally confused?

I have had several turntables & 3 1983 fans so far this year with lubrication issues, mainly from hardening soaps: Clean all of the old stuff off before renewing.

You have painted yourself into the corner. You will now have to fix the PSU section before moving on. Do be aware that some turntables are 110V (recent Grundig here) and that runs from a tapping in the transformer. If this is one of them and the turntable ceased, that has the potential to cook a section of the primary.

A Diode bridge rectifier is not a direct replacement for a Selenium & will produce more volts: That has to be compensated for.

Marc

Hi Matt, just letting you know I have some spares for this model, having repaired mine using another with a bad cabinet. Yours, judging from the turntable, is from the late Sixties. Mine, which is from 1966, is running on the original power supply with no problems. I'm a "test it carefully, but don't fix it if it ain't broke" type, which is a different approach from those of us who repair vintage machines for paying customers and must avoid potential breakdowns.

I don't think anyone's managed to find the official circuit diagram or repair data for the RKR yet, though it may be based on a Philips design. The RF and IF coils are Philips types.

Anyway, I'm sure I have a couple of those knobs spare.