'Royal Star' brand TV, any info on this make?

[murphyv310]

Hi.
The Wakely & Boynes team yet again, I'll need to stop winding them up on the variac, mind you its usually within 5 minutes!

[mark pirate]

back at Easter I had no vintage TV's, now I have 4!

It is easy to accumulate tv's, while i still love radios, a good old 405 line tv is so much more of a challenge

Mark

[audiomagpie]

So it's now in my posession. Quite clean and all complete, handle, grills, trim all present and correct, tuning knob just missing the disc centre. Cabinet is moulded from what I can only describe as a thick and strong hardboard type material, with a 'grey 'Hammerite' effect finish.
Due to some building and renovation work going on here, my workshop is temporarily crammed full of furniture, domestic appliances, plasterboard and timber. I can't get to my bench and haven't been able to for about a month and probably won't for at least another two weeks, so I am frustrated as I have 'Thermionic Withdrawal Symptoms'.
But I couldn't resist reaching for a screwdriver and having a quick look. This set is amazingly compact. They couldn't have made it any smaller. Although a 17 inch tube, it's probably about the size of a modern 14 inch crt colour portable, but it's heavy. Has a mains transformer and rectifier in lieu of a dropper, lots of sticky looking waxies. It doesn't appear to have had much work done on it in the past, all looks pretty original.
I'm looking forward to this one, but I will have to wait a while until the workshop is clear.

I haven't held a soldering iron in ages now. To help me with my TWS, thought about making a radio restorers equivalent of a nicotine patch to keep me going- maybe some solder, 50 yr old dust, dead spider and some cap wax, all under a band aid plaster stuck to my arm, do you think this would help?

Greg

[chipp1968]

Looks a very nice example. You were lucky to find that especially being the shorter one .Look for ward to it working. The patch would probably be against some health and safety rule

[Heatercathodeshort]

Yes a QVP20. Nice set and wil probably work ok once you have dealt with all those T.C.C. 'Plastiseals'. Much nicer set than the earlier PVP20. J.

[audiomagpie]

Has any one got a circiut diagram or indeed service manual for a QVP20 I could obtain a copy of- or indeed know where I might find one? I have the BVWS Trader CD roms but they only have the PVP20 which is a different kettle of fish!

Thanks

Greg

[mark pirate]

maybe some solder, 50 yr old dust, dead spider and some cap wax, all under a band aid plaster stuck to my arm, do you think this would help?

I know what you mean, i am all packed up & waiting to move house, nothing worse than being away from the workshop
Loooks like a nice tv in unmolested condition, will watch this thread with great interest, good luck with it.

Mark

[Electrical]

Hello Greg
The circuit diagram is in the 60-61 issue, of “Radio and TV Servicing” page 464.
I have scanned the pages and converted them to a PDF file, but the resolution of the drawing is poor. If you find it hard to read let me know and I will enlarge the drawings on a photocopier and rescan at a higher resolution.
Regards Stan.

[audiomagpie]

Many thanks for that Stan, I've printed off copies and can see on the schematic what is a res. and what is a cap. but can't read their circuit designation numbers. I don't (yet) have copies of 'Radio & TV Servicing', if you have the time to enlarge the drawings and scan again I would be much obliged. I will happily refund any costs involved if you PM me.

Greg

[Electrical]

Hello Greg
I have enlarged the drawings to 150% and scanned at 600 dpi, but the files were too large to post so I have converted the files to a PDF. This seems to be the best I can do, as the original drawings are not too clear. If you get stuck for the component values let me know and I will get my old magnifying glass out.
I hope these drawings are of some help.
Regards Stan.

[audiomagpie]

Many thanks Stan! Much clearer, I should be able to manage with this.

Greg

[Peter.N.]

Execellent case condition, I have seen these with the feet pushed through the bottom due to rough handling and not the strongest material in the world, you've got a gooden there.

Peter

[audiomagpie]

So after a bit of a delay I've finally dragged it on to the bench! A few of us are getting together on Sun 27th for a 'Rusty Radio's' repair workshop and I thought I'll take the KB. Not wanting to take something that turns out to have a terminal fault and halt my progress possibly early on in the day, I thought I'd just give it a pre-med to see if it would be a go'er.

This is the first TV I've tinkered with that has a mains transformer rather than a dropper. Wired as an auto transformer though, so chassis still live if L-N reversed. And a Selenium rectifier that has previously been replaced with a 'radiospares' part. Very compact in construction, the steel frame is clamped around the crt perimeter and everything hangs from that. Literally. The paper-mache cabinet offers nothing in the way of chassis support, it's just there to stop your fingers touching the naughty bits!

With the few other sets I've done, I've had at least the luxury of a Trader sheet and sometimes the manufacturers service manual as well. No such luck this time, just a very basic description and schematic in R&TV Servicing, 60/61. So it's been a good exercise in circuit tracing to find where certain components are. First out came the mains filter cap. The smoothing/rect can looked OK with no bulges or crusty bits and gave a good flick on the Avo. No low resistances between the HT rail and ground were measured. Most of the waxies looked very sweaty as one would expect.

Decided to go for it, but having a big yellow streak down my back, I did it slowly with the variac. At around 180 volts (mains in) the speaker started to rustle and responded to the volume control. At 200 volts, Cassie, my labrador, who was lying on a smelly blanket in the corner of the workshop, lifted up her head and tilted it to one side. She always hears the line output stage start to oscillate way before I do. Nothing on the screen yet. All heaters lit. Pulled off the EHT rect (U26) anode cap and stuck a well insulated screwdriver into the cap connector. Not very exciting. Decided output from LOPT was not giving as good a spark as I'd have expected (compared with 12" roundies with lower EHT that gave some cracking firework displays). HT was only 167 volts, should be 230. Virtually no first anode voltage on tube base. Changed the tired waxies around the line output stage. One or two of these were quite tricky to get at, ideally easier if chassis was removed from tube (any other set you'd remove the tube from the chassis!) but I didn't want to disturb too much at this stage. Tried set again and a blue flash caught the corner of my eye, from within either the PL81 horizontal output drive or the PY83 boost diode who reside next to each other. This happend again and I couldn't decide which it was coming from. Changed both valves as I had spares. Switched on again and frame collapse! Great result! So tube and LOPT look promising. Connected the Aurora and the audible test tone came through well. So decided to stop now, if I do any more I'd probably have it more or less sorted, so I'll save the rest for the workshop. HT still on the low side (197 volts) so hopefully down to the remaining leaky waxies pulling on it

Greg

[oldticktock]

Hi Greg,

nice set I've often seen these come up and have been tempted, first one I saw in the flesh was at David Boynes shop. I suspect the low HT might be the metal fin rectifier, the last two sets I've done this has been the cause. Might be worth taking a BY127 or IN4007 and a high watt (5) low value (22) series resistor just in case.

Sounds like you will have fun, have a great day
Chris

[flyingtech55]

I used to have two of the PVP20 type when I were a lad. These were pretty hard to work on because the boards were screwed into the chassis and coudn't be hinged open. This made access to the print side very difficult. Unfortunately they eventually got thrown away.

The PVP20s had a sheet of glass over the front of the tube. Did the QVP20 not have the glass because I don't see it in Greg's one.

TimR

[audiomagpie]

Originally Posted by oldticktock

I suspect the low HT might be the metal fin rectifier, the last two sets I've done this has been the cause. Might be worth taking a BY127 or IN4007 and a high watt (5) low value (22) series resistor just in case.

Good point Chris, as the rectifier is a more recent replacement and was dust free compared with the rest of the innards, I was assuming that this was probably OK. But assumption being the mother of all mess ups (or words to that effect) I will indeed take heed of your comments!

Tim, the set does indeed have a piece of glass in front of the tube, held in place by the gold rim, just doesn't show in the photo. The printed circuit boards do easily hinge out on this model. It is just the components hard wired on the back of the chassis frame and aginst the tube that are more tricky to get at.

Greg

[audiomagpie]

Since the last posting, this set was one of my subjects at the workshop at Cottered in February. There waxies were all very sticky and getting stickier(?) as I had the set powered on. I changed all of them and was rewarded with a good but undersized picture.
The set has since remained untouched until this evening.

Full picture width cannot be achieved and height can only be gained at the cost of linearity. Although brightness level seems good. Before I attempted to do any more, I measured some voltages to compare with the R&TV servicing book. I chose the tube base, as to get to the underside of the valve holders, the pcb's fold out but only after leads have been disconnected! The recommended values in brackets:

Smoothed HT 208v (230)
Tube 1st anode 245v (400)
Tube cathode 64v max (120-140)
Tube grid 36v max (14-130)
LOP boost cap 537v (680)

So a bit low all round. I replaced the selenium rect with a 1n4007 diode with a couple of 8.2ohm resistors in series with it. HT now 216 volts but things still pretty much the same around the tube base. There are still some original 'plastic' caps and some small electrolytics so these will be next to be checked.

I'm not starting another set until I've got this one sorted!

Greg

[audiomagpie]

I'd halted work on this set, I was struggling due to lack of info. But following my request for a manufacturers service manual, a member of the forum came up trumps! (Thanks Mike T ) So with a clear crisp copy, back to work:

Although the set has two easily accessable PCB's (I.F. and timebase), there are some components on tag strips sandwiched in the tight gap between the front of the chassis and the back of the tube. Much of the higher voltage stuff and HT reducing resistors are here. The fault with the set is slightly low HT, low tube A1 volts, symptoms being a picture reduced in both width and height. I'd previously replaced the selenium rectifier with diode and resistors, to little avail.

I removed the chassis from the tube, then scan coils being loose on the tube neck came away also which saved desoldering them. I've now got good access. The 1M resistor in series from the LOPT to the 1st anode was high at 1.5M, so that won't help. There are a 3 resistors in the frame/height section that are certainly not original, one of which is o/c. Neither do they relate to the circuit diagram, in position or value, or to later mods as listed. Thre are also two varistors in series with the height pot. One of these is open circuit (broken in half) but these were fitted remotely in a sleeve, well hidden at a cool part of the chassis. I've drawn sketches and taken photos and I'm going to try and re string it as per manual. But if there's a good reason for how it is, I can always put it back.

So these varistors- the manual doesn't give any value or specs, just 'type VA 1008'
Does that mean anything to anyone? There are two in series, one is still OK. At room temp it measures about 160k, if I heat it with the iron drops to about 20k. But I appreciate varistors are voltage dependant rather than heat. What could I replace the faulty one (or both) with ? Any suggestions? There's a pic of them below, sorry about quality.

Thanks, Greg