Kolster Brandes RV 10 (Crown)

[sexton_mallard]

Hi All,

I have treated myself to the world of 405 line TV by picking up a Kolster Brandes RV 10 (Crown) at a car boot sale Being 45 years old I apparently last watched a 405 line TV on a rented Rediffusion set in the early 1970s. I'm also new to this forum so go easy on me . An image of my find is attached here.

Initial checks show a complete set. The EHT cage shows signs of being opened in the past and the CRT looks to be the original C17SM. One valve (PCC89) has gone gassy and a host of melty looking 'waxies' greet me. The tube appears to be stuck to the bezel on one side when attempting to pull the chassis.

I ask if I could be directed to a service sheet/schematic to purchase for this telly please - and if anyone can tell me their experiences of repairing these sets. They are generally good from what I have seen so far on the interweb.

[FERNSEH]

The RV10 was a popular rental set, it was in fact made for that purpose. I remember the set well, very reliable and easy to service. Before you fire the set up I'd replace all those waxies in the frame timebase. Clip out the mains filter capacitor, it can be replaced later. Also replace the boost capacitor C63 (0.1mfd 500V) and C65 the A1 supply capacitor.(0.05mfd 1000V). These capacitors are easy to find, they are on a tag strips near the aerial socket.
I serviced a KB QF80 way back in 2011, this 21" set is similar in many respects to the RV10. I might be possible to search the forum for the restoration of this set.
Information for the RV10 can be found in the 1960/61 Radio and Television servicing book.

DFWB.

[FERNSEH]

And here it is: https://www.vintage-radio.net/forum/...hlight=KB+QF80
The KB QF80 Majestic. The RV10 has a fireball tuner.

DFWB.

[sexton_mallard]

Thanks FERNSEH. Did you retain the selenium rectifier in your set?

[FERNSEH]

The QF80. The original FC31 selenium rectifier had been replaced by a silicon diode of the BY127 type. The replacement diode along with an additional series resistor were fitted on to a piece of tag strip. The resistor can be 21 to 25 ohms 7watt. A 0.001 mfd capacitor was connected across the diode to protect it from mains borne spikes.
The FC31 is a contact cooled rectifier. Best replaced. The RV10 uses an RM5 finned rectifier, it could well be OK. If the smoothed HT is 228 volts and the unsmoothed HT is 235V I'd leave the old style rectifier in place. Boost voltage measured at C63 is according to the R & T book is 590 volts.

DFWB.

[sexton_mallard]

Thanks again I have just ordered a copy of J.P Hawker's 1960/61 Radio and Television servicing manual. I will provide regular updates on my progress. Tomorrow (hopefully) I intend to work on the cabinet, starting with a dose of woodworm killer and provide some 'before' pictures of the chassis.

[Heatercathodeshort]

I sorted a RV10 in 2005 and an RV30 which is very similar a while later.
https://www.vintage-radio.net/forum/...ad.php?t=61588.
https://www.vintage-radio.net/forum/...ead.php?t=6316
Both are still working very well. Hope you sort it out. Regards, John.

[sexton_mallard]

Here's an update on progress. I managed to pull the chassis/tube from the cabinet, (see pics). the gasket around the tube surround is still soft and in good condition. The chassis components look OK with no major heat damage or other mishaps. I now realise the valve that has gone to air with a crack in the base is a PCC89 in the socket for V4 (6BW7). A replacement 6BW7 will be ordered. I will check all the other valves shortly for the correct types. I have dismantled the cabinet, removing the front glass, bezel and liberally treated the woodworm infestation in the front baffle. The woodgrain effect appears to be a painted/printed effect in a dark brown. There are some deep scoring that's removed the grain effect. I was going to paint in the 'grain'. The varnish appears to be a cellulose lacquer - is this correct? Work on cleaning and recapping the chassis will start once the cabinet is sorted.

[mark pirate]

I think you have picked a good set for your first TV restoration, access to the bottom of the chassis is good and should be fairly straightforward to replace the capacitors and out of spec resistors.

KB build quality is high, and this set uses the excellent 'Fireball' tuner.
If the CRT is good, it should produce a cracking picture once restored.

Mark

[FERNSEH]

The more common EF80 can be used as a temporary substitute for the 6BW7 until the correct valve can be found. But it must be remembered that the IF alignment will be impaired when using the EF80. The interelectrode capacities differ.

DFWB.

[sexton_mallard]

Thanks Mark .

[sexton_mallard]

After a 3 year gap I am resuming action on this TV. As I don't have a 0.5mfd 200v capacitor (C60 in JP Hawker, p451) to hand. Can I get away with lashing 5 0.1mfd X2 caps in parallel instead?

[sexton_mallard]

I should have mentioned that the lashup I proposed in my post is just to get the set working as i still don't know if the tube is a runner. if the tube is good I will replace the lashup with a proper replacement. I have lots of these X2 caps to hand.

[AC/HL]

Well, unless anyone knows to the contrary, I'd say yes. The value should be the same, barring any weird stray effects. X2 is just a self healing ordinary capacitor.

[jay_oldstuff]

I've done similar in the past as a test lash up, should be fine for a quick test. 3 year pause in a restoration and I thought I was the only one to do that! Now that reminds me must get on with recapping the IF section of that bush TV42 I started about 7 years ago.

Jay

[AidanLunn]

Or you could just use a 0.47uF capacitor, as these are far more common.

[Graham G3ZVT]

sexton_mallard,

Have you given any thought as to how you will get a picture one that set once you have repaired it?

The Aurora standards converter is excellent, and works out of the box, but it is also many times the cost of your TV, and you have to make all your material available as a 625 line signal.

However, a Windows PC with the right graphics card is able to generate a 405 line output directly, and this is what I am doing here
https://www.youtube.com/watch?v=Q9b7_x0g0uM

All you need is a dual-head ATI Radeon HD 2400 Pro, and a VHF modulator, I built this
http://www.earlytelevision.org/405_modulator.html

Have a look at the posts by Peter Scott and myself in the "System converters" area of the forum, so far we seem to be the only two using this route.

Graham.
G3ZVT

[Heatercathodeshort]

It's hard to believe but I overhauled an RV10 back in 2005.

https://www.vintage-radio.net/forum/...ead.php?t=6316

That was twelve years ago, probably longer than it was used by it's original owner from new!

It still works very well on it's original tube. Took this picture a few moments ago. This particular section of my 'museum' has become somewhat cramped.
Oh dear..

Regards, John.

[sexton_mallard]

Thanks for the encouragement guys. I have now installed my novelty 0.5mfd cap, the next task is to replace the mains electrolytic with 100 and 470 mfd caps which is bulged and appears to have burst a small hole. I think this failure or the valve gone to air consigned the set to retirement and hopefully prevented many more hours on the tube. I have a working Sony 9-90UB (dual standard) running in 405 mode and produced some crude patterns and sound with a AF signal generator. At least this will give me some insight on the health of the set.

Hi Graham, your PC video + VHF modulator system is the route I may take. i wonder if a raspberry Pi could emulate something in place of the PC...

[Graham G3ZVT]

Hi Graham, your PC video + VHF modulator system is the route I may take. i wonder if a raspberry Pi could emulate something in place of the PC...

Nice thought, and I have three Pis here performing various tasks, but sadly the only people who really know what the Pi GPU can do will have signed a non disclosure agreement with Broadcom.
I know it don't sit well with the Open Source paradigm, but there it is.

Graham.
G3ZVT