korting nobilis 40wk....help please

hi everyone
* *i got korting nobilis 40wk radio....it was in a mess,so gradually i replaced the caps. , resistors that were out of tolerance and the old cracked wires
but when i came to the wiring of the speaker to the main circuit i got stuck,,so with the help of few gentlemen in other forums i could solve some of but not all the connections and here is what i'v been told about the speaker connections

1- pentode section's plate of ecl11
2-low side of the volume control pot
3-anode side of 2nd 8 micro f. cap.
4-heater pin of AZ11 and anode of first 8 micro f.cap
5-no connection
the problem is:
1-i'm certain that No.5 is connected some where and confirmed it by looking in to some photos of the radio in the web
2- with the use of a variac ,i pluged the radio to the power and i made some voltage measurement which was as follows
pin 1 of ech11 137 volts,pin 4- 246 volts and pin 8 -118 volts
pin 1 of ebf11 135 volts and pin 4- 227 volts
pin 1 of ecl11 0 volts(zero) :!: *:?: *and pin 4- 227 volts

the radio does not make any sounds except for a low crackling sound when the meter probe touches pin 1 of ecl11 tube
i appreciate any kind of hints or help :confused: 
i attached a diagram of the speaker connections and the radio schematic

*much obliged
* * Aras

Attachments:

• speaker 3 (27 KB)
• Korting_40W (43 KB)

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Hi Aras Mahmood,
I wonder, why you attach a schema of Novum 40W and not of  Nobilis 40WK.

Which model you have? The schemas and also the number of tubes are different. I assume, when you use the correct schema, you will fix the problem. You find the schema at the model page.

Kind regards,
Heribert Jung

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I'm really sorry for the mistake i made

this is te schematic of the korting nobilis 4owk

thank you very much

Attachments:

• Korting_40WKNobilis (69 KB)

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Hello Aras

Connection 5 on the speaker socket has to go to the other side of the speaker voice coil.  See how they both have the little square U.  This is most likely a symbol for the chassis metalwork and is easily checked.  There is no reason to have a speparate bus for HT -ve  as this is not an AC/DC radio.

The secondary of the speaker transformer always has to feed the speaker voice coil so you need a complete circuit.  Here because it is a field coil type speaker so the hum bucking coil is also in circuit.

The radio probably consumes about 50 mA so a quick check is to measure the voltage across the field (3 to 4).  By Ohms law this gives around 80V if your quoted value for the field is correct.  The circuit number for the field is also 164 ...

Another easy check and one I always do is to measure the voltage across the primary of the speaker transformer 156.  If you have a meter measure the Ohms of this, say it gives  500.  Then the ECL11 should be passing for a good valve (tube) about 35 mA and so the voltage will be about 17 to 18V.

Hope this helps  Gary

Attachments:

• Kort (63 KB)
• Kort 2 (42 KB)

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Hello Aras,
why do you use the "Lange" schema? They have often errors. You find 10 files at the model page Körting Nobilis 40 WK 40WK.  5 of them are schematics from differen sources. One is the original from Körting.

Looking to differnt kind of drawings helps to get a better understanding and to identify drawing erros.

Kind regards,
Heribert Jung

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I am using the Korting schematic or circuit diagram S6004 b.  It has the Korting symbol at the lower left side and is the one recommended by Heribert.

By the way you of course measure the Ohms of the output transformer primary with the power off.

You dont say what items you have changed already and some need to be before making voltage measurements. The electrolytics 144 & 145 are suspect and also many of the wax paper capacitors.  At least 20 from the volume control, 26, 29 & 30.

Other important and easy voltage measurements are the grid bias voltages for the ECL11.  The triode section (Pin 8) should have -2V on it relative to the cathode which is at earth.  The tetrode grid (Pin 2) should have -6V.  This is with a digital meter and an AVO due to loading may make it read lower.

Really you should get the audio section working first before thinking about the EBF11 and the ECH11.  The voltages you have given for the EBF look OK but those for the ECH not right.

If the audio is working correctlly you should hear hum and it gets louder with turning up the volume.

Gary 

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well..that was really helpful

i'm gonna check the schematic you mentioned,,,check every thing again and see what happens

thank you very much for your help

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thank you very much for your help

i will review the schematic you mentioned check every thing again

thanks again

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gentleman have we sound from the radio ..

the radio is making a squealing(whistling) sound...not the sound that i expected but it's a progress.

i checked the voltages and all seems to be ok except on pin 1 of ECH11 and EBF11 which reads about 180 volts instesd of 100-120 volts???? 

what could be the reason of this sqealing sound and the high voltage on pin 1 of ech11 and ebf11

(please forgive my dumb questions as i'm just a hobbyist)

thanks a lot

Aras

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You dont provide enough information.  What have you replaced so far?  Is the squeal controlled by the volume control?

The 180V on those two valves is high, what is the voltage of the HT (the second 8mF or the field coil and output transformer primary).

What is the drop across the field coil?

Gary

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first....thanks for your help

i did change the electrolytic and the old paper caps and most of the old resistors that were out of specs.

and there was two wrong connections that i fixed

the sqealling occur only in the upper end of the volume pot

the voltage on the 1st 8 mf is 380 volts ,,on the 2nd it's 260 volts

the field coil voltage 380 volts and 258 volts on it's end

the voltage of the primary of the output transformer are 380 volts and 258 volts on it's end

the tubes voltages

ECL11

pin 1 150 volts

pin 2  -1.3 volts

pin 4 240 volts

pin 7 254 volts

pin 8  -6 volts

ECH 11

pin 1 180 volts

pin 2 - 5.7  volts

pin 4 230 volts

pin 7 254 volts

pin 8 - 6 volts

EBF11

pin 1 same as pin 1 of ECH11

pin 4 254 volts

pin 7 - 1.47 volts

pin 8 -1.78 volts

thanks again 

 Aras

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I have marked up part of the circuit around the ECL11 and put the voltages as given by you.  The valve should take about 35mA, according to tube data and that makes the output transformer (with 20V across it) have resistance of about 570 Ohm. 

The field coil is dropping about 120V and so guessing the whole radio will take about 50mA then the resistance should be about 2400 Ohms.

With the power off you can measure these resitances to confirm.

I would attempt to get this stage working correctly before worrying about the other valves although the voltages look about right and the 180V on the screens wouldnt stop it working.

If the output stage is correct you should be able to turn the volume up and hear increasing HUM without squeals.  Did you possibly reverse the connections (2 and 5) of the volume control feedback?  This would turn the feedback into positve and it would squeal.

Please work safely but with one hand in your pocket you can safely touch Pin 2 of the ECL11, with the volume control advanced, and you should hear hum.  It should be controllable with the control.

I would suggest you join: the Antique Radio Forum, in the US, or the UK Vintgage Radio Repair Forum and then ask there as someone my have other ideas and possibly know the radio.

I'm away for a week or so and cannot help you tell I get back.

Good luck   Gary

Attachments:

• Capture (156 KB)
• KORT 3 (260 KB)

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thanks a lot 

you helped me so much...i really appreciate it

thanks again

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