Kolster Brandes EV40L

[Radio Tech]

Hello PJL, This is what I have done but the odd thing is what I do not understand is that although the Brilliance / EHT died after a little while before, the set should now work as the transformer has been proved to be ok. But it does make me wonder if these 6BG6 valves I have are really ok, I bought one that was tested and supposed to be new, the other two I got a colleague of mine to test them on his Mullard HS tester and he said that they where ok, surely one of the three should be ok. I have even changed suspect resistors but still no joy. It's a bit of a mystery this set.

regards

Ken

[Freya]

I know you renewed the wiring to C72 the EHT capacitor, you had it disconnected for a while. I suggest you keep it disconnected until this fault has been remedied.
Looking back through the posts it seemed like you had a decent raster about post #22 which faded after a period of time. You need to have a think about what has changed in the meantime to cause the U22 not to light at all. Does altering the line hold produce a glow in the rectifier ?

It all seems very odd

[murphymad]

Ken, Freya,

The EHT capacitor is NEW as is the wiring from the LOPT to the capacitor and to the tube.

There is no gain from leaving it disconnected. Freya probably thinks it is the original visconol, but it is not.

Your LOPT worked perfectly on my dummy line stage for many hours and if anything it lit the U25 valve rather more brightly than I would have expected.

Having looked at the circuit, I suspect that the line stage is being dragged down by something external from the LOPT and line output valve. A heavy damping load.

I have the Line output valves in stock (new) if you want to try that, but I suspect that will not cure the fault.

I am wondering about the scan coils and associated circuitry and the tube itself.

I think you would be wise to take a trip over to John's (heatercathodeshort) for a few hours as he is in your area and has many spares and knows every trick in the book!
He won't just fix it for you, he will guide you in fault finding the problem yourself, but have all the required test equipment and substitute spares to hand.

Mike...

[Freya]

Good advice Mike, John is sure to spot the issue and its got me interested as to the problem. I had only been going on the info Ken had posted about the Visconal which got a mention about being disconnected but not about being replaced.

[Radio Tech]

Hello Stephen, Yes, I did try varying the line hold but this made no difference, and thank Mike about mentioning the coils, it does look like as if something external to the lopt is dragging something down, and I might take your offer up on the lop valve. I did change all resistors around the lop stage but this made no difference and thanks Mike for the suggestion of taking the set over to John but its a long way to haul something of this size by train. but I will ring him and see what else he can suggest, I am hoping it is not the tube as chances of getting a replacement are very very slim if not at all but I cant give up as I have spent a lot of time on it.

Regards

Ken

[Heatercathodeshort]

Hello Ken,
Your more than welcome to bring it over but as you say it's only the heavy chassis that is needed but difficult [impossible] by train.
It really needs a fresh approach by another guy as you can get locked into a situation rather like a computer and the brain refuses to accept the real cause. Did it hundreds of times and learned to put it down for a day and with a fresh start, all was revealed. I think you have done just about everything possible within your knowledge and need some hands on help. 6BG6G valves are very reliable and I very much doubt if you have a faulty one. I have a couple of receivers including an EV30 that use them and have never had a problem.
Going back to my original restoration notes you will see that I did indeed have an odd vacuum problem with the Cintel C12B tube. I think you would see a blue glow within the tube if it was drawing a heavy current from the EHT supply.
I don't know your situation but if you have a friend with a car you are welcome to drive down and spend a few hours. No promises as it might be a stinker but I can't see any other way to go. Regards, John.

[Radio Tech]

Hello John

Thanks for your thoughts, its difficult for me to get the chassis down to you, so I will leave it for a day or so and think about what you have said in past posts

Regards

Ken

[Radio Tech]

Hello John and everyone

I had another deep think about what is happening with regard to this problem with the line output, there appears to be an input to the line output valve from the line oscillator valve and there appears to be waveforms on the line scan coils and the vertical coils but no eht, although there appears to be a waveform on the horizontal scan coils the line output valve seems to be a little hotter than what I think is normal, I have checked various components around the line output stage and the frame stage so what do I suspect at this stage?

Regards

Ken

[Radio Tech]

Hi Every one and that includes John W, I spoke to John on landline yesterday 4/8/14 and something he mentioned about the reclaim diode, originally I had replaced the metal one with a silicon 1N4007 and thought no more about it until John happened to mention this might be not fast enough in its switching speed so I had a rummage in my bits and pieces and found a diode that had come from a mains power pack, marked RS 51A something , it looked a bit meaty so thought I wonder. After putting it in powered the set up and now I have a picture that 3/4 fills the screen, not quite there but at least the picture stays, there is a white thin bar down the left from top to bottom so maybe I may be able to find an even more efficient diode that can handle this. But the more inpotant thing I must mention at this time is Thank you John for giving away that little prompt about diodes and of course the help you have been so for and that thatnks must go to all of the other folks who have given their help, not forgetting of course Mike Barker for his assistants in the matter.

I am looking two replacement knobs that go through the front, they are long shafted ones 1/4 inch shaft I guess

Kindest regards

Ken

[Radio Tech]

Hi everyone who has been following this enormous thread on my KB EV40 but I thought it would be nice for all of you to see a picture of the test card after I changed the reclaim (boost) diode from one I found in my junk box to a UF5408 (ultra fast) diode I obtained from Rapid Electronics. I cant at the moment quite work out what is causing the white streak down the left side of the picture running from top to bottom.

But here is the picture


Regards

Ken

[nigelr2000]

looks like the pictures folded over to me can't remember why it happened though been too long since I did telly's

[Mikey405]

Hi Ken.

It may be a little bit late now (as you've already done most the hard work) but I've just finished scanning-in and tarting-up the KB service manual for this set so if you'd like an electronic copy or a version you can print then please feel free to download it and use away.

http://www.oldtechnology.net/documen...0_and_EV40.zip

Thanks Ken.

Kind regards.

From Mike.

[Radio Tech]

Thanks Mike

Its always handy to have a spare copy from else where. Yes, it has taken a lot of hard work to get it this far and looks even better when the chassis is slid in to the cabnet.

Best wishes

Ken