Kolster Brandes EV40L - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

Radio Tech · 16th Apr 2014, 2:43 pm

Hello PJL, I did what Stephen suggested and powered the heater of the U25 from battery source but this did not make any difference, what I did notice though was getting a screwdriver blade about inch and half away from the anode of the U25 and noticed that the healthy spark got very much less healthy as the set warmed, I did try another 6BG6G but that valve just got hot in a few seconds.

Regards

Ken

PJL · 16th Apr 2014, 5:28 pm

OK, so it looks like a damp problem so you will need to take the LOPT out. You say it seems to have a lacquer on the EHT winding? I wonder if this is just a hard wax impregnation. How about a picture?

Freya · 16th Apr 2014, 5:40 pm

A good idea, at least we will be able to see if the transformer construction type

Radio Tech · 16th Apr 2014, 8:51 pm

Hello Stephen

Here is the photo of the LOPT that I have removed from the set.

Regards

Ken

Freya · 16th Apr 2014, 9:10 pm

Maybe a Tripler would be suitable in-place of the EHT winding ? see what John and others suggest.

Does your service info give the winding resistances for the lopt ? how do they compare

Radio Tech · 17th Apr 2014, 12:31 pm

Hi Stephen,

The service data does give resistance figures but the LOPT windings do not match, they are too far out. It gives the readings for Primary, Secondary and EHT winding and Heater winding. Secondary White and Green 6 Ohms, Primary Blue and White 17 Ohms, EHT winding Yellow and Yellow 950 Ohms (Total) and Heater less than 1 Ohm. Firstly, I cant find the colours on the windings and whats given in the service data I cant find any winding that comes near.

If you have a trippler diagram maybe I can make it

Regards

Ken

hans · 17th Apr 2014, 1:01 pm

What do Your Readings look like?

PJL · 17th Apr 2014, 1:11 pm

Looks in good condition and only covered with hard wax over the edge of the EHT winding.

If it were mine I would clean the dust off with GT85 spray oil on a tissue and check for tracking between pins on the plastic mounts.

Then one or more of:
1. Douse with GT85 which is a water repellent shaking it as dry as you can.
2. Shove it in a sealed box with a desiccator (dry rice?) and put it in a warm place for a few weeks.
3. Point a hair dryer or fan heater at it removing the wax from the EHT winding as it melts using a tissue.

Entrapped moisture is not easy to remove. A vacuum desiccator would be the ideal solution.

Radio Tech · 17th Apr 2014, 6:44 pm

Hi Hans, the readings I get are from end of overwind to first tap of where width taping lead goes are all around 21 Ohms, from where the EHT rectifier anode is connected to the first tap (width) is 530 Ohms and EHT to TC is 539 Ohms and the Heater winding is as they state.

Regards

Ken

Radio Tech · 19th Apr 2014, 7:04 pm

Hello PJL

With regard to the LOPT I have done what you suggest and I have left it in the airing cupboard where the boiler is for a few weeks, while its in there I can at least get on with something else, will let you and other folk know what happens, if all else fails then it its a rewind job I reckon

Regards

Ken

PJL · 20th Apr 2014, 8:36 am

Your EHT winding is lower than the service data version but I would not be concerned about winding resistance as the set works when cold.

Heatercathodeshort · 20th Apr 2014, 8:53 am

Resistance readings can be very misleading. Remember 2 types of transformer are fitted in the EV30L and I doubt very much if they have the same readings.
The transformer in your picture 'looks' in good condition. The overwind has not developed any hot spots or dripping wax. I still feel from a distance that this is not your problem but time will tell. Regards, John.

Radio Tech · 28th Apr 2014, 2:54 pm

Hello John,

I took the LOPT out and cleaned it up then sprayed with wd40 and put it in a warm cupboard for about three weeks. I put the transformer back in and now I have what seems like no output from the 6BG6G line output valve, the valve is being driven so is there an alternate to the 6BG6G valve? On saying that I will get the valve tested though then have another go at the set.

Regards

Ken

Freya · 28th Apr 2014, 5:31 pm

Mark has the valves in stock, if that's any help Ken

http://markhindes.easywebstore.co.uk...archterm=6BG6G

Heatercathodeshort · 28th Apr 2014, 11:56 pm

Disturbance! That is probably your fault. First thoughts. Have you connected the wires onto the correct terminals on the transformer? Very carefully check that you have not broken any of the very fine wires from the tag strips to the coil assembly.
I don't like the idea of spraying a LOPT with WD40 or any type of oil. It may not do any harm but I'm just not comfortable with it. If anything it needs drying out and WD40 can soften pitch and wax maybe causing a breakdown of the insulation. If you have an old analogue meter, put it on a high DC range [1000v] and measure the voltage on the top cap of the 6BG6G valve. Under no circumstances do this with a digital meter! If the voltage is present I would suggest it is not being driven. Think, what have I done? It worked to a degree before removing the transformer. Examine it with great care and you might discover the fault. John.

Sideband · 29th Apr 2014, 3:45 pm

I don't think WD40 should be allowed anywhere near a TV, especially the line transformer!

Radio Tech · 30th Apr 2014, 11:46 am

Thanks Stephen and John for your info, I will check the fine wires John and let you know what the result is.

Regards

Ken

Radio Tech · 30th Apr 2014, 6:48 pm

Hello John, I checked the fine wiring of the transformer and they all seem ok, also I did check with an AVO on the 1000V range the top cap of the LOP valve and when first powered up there was around 450V but this drops down to about 300V as the set warms up but there is no sign of the heater on the eht rectifier, the HT seems ok but I have got a known good LOP valve coming by post, I just wish I could get hold of a known good LOPT to try, apart from having the present on re-wound. any other suggestions please.

Regards

Ken

Radio Tech · 16th Jun 2014, 6:34 pm

Hello everyone again, I got the LOPT back from Mike Barker today 16th June and put the transformer back in the set but still no joy with getting a nice glow from the eht rectifier no not a peep, so I looked at the waveform from the line osc valve with a scope and there appears to be a good strong sawtooth waveform going into the grid of the line output valve, on the anode of the 6bg6 the voltage there measured around 400v I am not sure if this is right and the ht seems to have crept up a bit to almost the same, I have had the original line output valve tested and this is ok and two others I have as spare are ok as well so where do I go from here? And at this point I must thank Mike for doing a good job on the transformer and proving it was ok.

Regards

Ken

PJL · 16th Jun 2014, 11:08 pm

I am no expert, but measuring the line output valve anode does not sound like a good idea as there will be very high voltages from the flyback. It also won't tell you much as you are measuring an average voltage.

If the LOPT is known to be good, I would double check all the work you have done as John suggested above.

16th Apr 2014, 2:43 pm	#41
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Hello PJL, I did what Stephen suggested and powered the heater of the U25 from battery source but this did not make any difference, what I did notice though was getting a screwdriver blade about inch and half away from the anode of the U25 and noticed that the healthy spark got very much less healthy as the set warmed, I did try another 6BG6G but that valve just got hot in a few seconds. Regards Ken

16th Apr 2014, 5:28 pm	#42
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Kolster Brandes EV40L OK, so it looks like a damp problem so you will need to take the LOPT out. You say it seems to have a lacquer on the EHT winding? I wonder if this is just a hard wax impregnation. How about a picture?

16th Apr 2014, 5:40 pm	#43
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,990	Re: Kolster Brandes EV40L A good idea, at least we will be able to see if the transformer construction type __________________ Stephen _________"It`s only an old telly" ___

16th Apr 2014, 8:51 pm	#44
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Hello Stephen Here is the photo of the LOPT that I have removed from the set. Regards Ken Attached Thumbnails

16th Apr 2014, 9:10 pm	#45
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,990	Re: Kolster Brandes EV40L Maybe a Tripler would be suitable in-place of the EHT winding ? see what John and others suggest. Does your service info give the winding resistances for the lopt ? how do they compare __________________ Stephen _________"It`s only an old telly" ___

17th Apr 2014, 12:31 pm	#46
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Hi Stephen, The service data does give resistance figures but the LOPT windings do not match, they are too far out. It gives the readings for Primary, Secondary and EHT winding and Heater winding. Secondary White and Green 6 Ohms, Primary Blue and White 17 Ohms, EHT winding Yellow and Yellow 950 Ohms (Total) and Heater less than 1 Ohm. Firstly, I cant find the colours on the windings and whats given in the service data I cant find any winding that comes near. If you have a trippler diagram maybe I can make it Regards Ken

17th Apr 2014, 1:01 pm	#47
hans Heptode Join Date: Jan 2008 Location: Oslo, Norway. Posts: 632	Re: Kolster Brandes EV40L What do Your Readings look like?

17th Apr 2014, 1:11 pm	#48
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Kolster Brandes EV40L Looks in good condition and only covered with hard wax over the edge of the EHT winding. If it were mine I would clean the dust off with GT85 spray oil on a tissue and check for tracking between pins on the plastic mounts. Then one or more of: 1. Douse with GT85 which is a water repellent shaking it as dry as you can. 2. Shove it in a sealed box with a desiccator (dry rice?) and put it in a warm place for a few weeks. 3. Point a hair dryer or fan heater at it removing the wax from the EHT winding as it melts using a tissue. Entrapped moisture is not easy to remove. A vacuum desiccator would be the ideal solution.

17th Apr 2014, 6:44 pm	#49
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Hi Hans, the readings I get are from end of overwind to first tap of where width taping lead goes are all around 21 Ohms, from where the EHT rectifier anode is connected to the first tap (width) is 530 Ohms and EHT to TC is 539 Ohms and the Heater winding is as they state. Regards Ken

19th Apr 2014, 7:04 pm	#50
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Hello PJL With regard to the LOPT I have done what you suggest and I have left it in the airing cupboard where the boiler is for a few weeks, while its in there I can at least get on with something else, will let you and other folk know what happens, if all else fails then it its a rewind job I reckon Regards Ken

20th Apr 2014, 8:36 am	#51
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Kolster Brandes EV40L Your EHT winding is lower than the service data version but I would not be concerned about winding resistance as the set works when cold.

20th Apr 2014, 8:53 am	#52
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Kolster Brandes EV40L Resistance readings can be very misleading. Remember 2 types of transformer are fitted in the EV30L and I doubt very much if they have the same readings. The transformer in your picture 'looks' in good condition. The overwind has not developed any hot spots or dripping wax. I still feel from a distance that this is not your problem but time will tell. Regards, John.

28th Apr 2014, 2:54 pm	#53
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Hello John, I took the LOPT out and cleaned it up then sprayed with wd40 and put it in a warm cupboard for about three weeks. I put the transformer back in and now I have what seems like no output from the 6BG6G line output valve, the valve is being driven so is there an alternate to the 6BG6G valve? On saying that I will get the valve tested though then have another go at the set. Regards Ken

28th Apr 2014, 5:31 pm	#54
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,990	Re: Kolster Brandes EV40L Mark has the valves in stock, if that's any help Ken http://markhindes.easywebstore.co.uk...archterm=6BG6G __________________ Stephen _________"It`s only an old telly" ___

28th Apr 2014, 11:56 pm	#55
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Kolster Brandes EV40L Disturbance! That is probably your fault. First thoughts. Have you connected the wires onto the correct terminals on the transformer? Very carefully check that you have not broken any of the very fine wires from the tag strips to the coil assembly. I don't like the idea of spraying a LOPT with WD40 or any type of oil. It may not do any harm but I'm just not comfortable with it. If anything it needs drying out and WD40 can soften pitch and wax maybe causing a breakdown of the insulation. If you have an old analogue meter, put it on a high DC range [1000v] and measure the voltage on the top cap of the 6BG6G valve. Under no circumstances do this with a digital meter! If the voltage is present I would suggest it is not being driven. Think, what have I done? It worked to a degree before removing the transformer. Examine it with great care and you might discover the fault. John.

29th Apr 2014, 3:45 pm	#56
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,577	Re: Kolster Brandes EV40L I don't think WD40 should be allowed anywhere near a TV, especially the line transformer! __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

30th Apr 2014, 11:46 am	#57
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Thanks Stephen and John for your info, I will check the fine wires John and let you know what the result is. Regards Ken

30th Apr 2014, 6:48 pm	#58
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Hello John, I checked the fine wiring of the transformer and they all seem ok, also I did check with an AVO on the 1000V range the top cap of the LOP valve and when first powered up there was around 450V but this drops down to about 300V as the set warms up but there is no sign of the heater on the eht rectifier, the HT seems ok but I have got a known good LOP valve coming by post, I just wish I could get hold of a known good LOPT to try, apart from having the present on re-wound. any other suggestions please. Regards Ken

16th Jun 2014, 6:34 pm	#59
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: Kolster Brandes EV40L Hello everyone again, I got the LOPT back from Mike Barker today 16th June and put the transformer back in the set but still no joy with getting a nice glow from the eht rectifier no not a peep, so I looked at the waveform from the line osc valve with a scope and there appears to be a good strong sawtooth waveform going into the grid of the line output valve, on the anode of the 6bg6 the voltage there measured around 400v I am not sure if this is right and the ht seems to have crept up a bit to almost the same, I have had the original line output valve tested and this is ok and two others I have as spare are ok as well so where do I go from here? And at this point I must thank Mike for doing a good job on the transformer and proving it was ok. Regards Ken

16th Jun 2014, 11:08 pm	#60
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Kolster Brandes EV40L I am no expert, but measuring the line output valve anode does not sound like a good idea as there will be very high voltages from the flyback. It also won't tell you much as you are measuring an average voltage. If the LOPT is known to be good, I would double check all the work you have done as John suggested above.