Philips B3LN66U /35 - capacitor replacement advice please

[Diniz Diniz]

Originally Posted by Maarten

Edit: I see now that the usage of X- and Y-rated capacitors was already explained by others. Better 1 time too many than not at all.

Thank you Maarten. I am very grateful to have several opinion.
I would like to ask you, and all of the forum members to classify the capacitor in the images attached. Could it replace a 33nF /600V (C32 in 3rd image)?

Thanks in advance and congratulations for this magnific forum!

Diniz, Portugal

[Freya]

Normally it would be clearly marked if X2, yours is AC and Pulse Metalized Polypropylene normally used in switch mode power supplies so not sure, will wait for other to confirm suitability.
Example picture of marked X2

[Diniz Diniz]

If it helps the identification...
https://www.westfloridacomponents.co...376-56-250.pdf

['LIVEWIRE?']

C3 goes from the aerial socket to SK2, and C34 from the earth socket to chassis. Apologies if I inadvertently misidentified them. C34 should be a class Y type.

[Freya]

No, you already got it right in post #4.
We already have a sticky on this from 2010 https://www.vintage-radio.net/forum/...ad.php?t=62984

[Diniz Diniz]

Thanks for your comments.

I understood that Y type capacitors must be used between live and chassis and between aerial sockets and the chassis.
I still have one question regarding this issue... Despite of safety questions, does the use of, for instance a polypropilene capacitor or a polyester capacitor, in the place where it should be a Y type capacitor affect the functionating of the set? i.e., does it affect the quality of the signal?

Today I received the valves for this set and I was able to test it. It seems to run well. The big ceramic resistor (R4 + R3 +R2) run very hot, but I believe it is normal. Also, it has (the resistor) a strange 'sweet' smell...

I was able to listen the portuguese AM station (Antena 1) with some interferance (no proper antena) and a very discrete 'hum' was present. Tomorrow I will check the electrolitics.

Regards,

Diniz, Portugal.

[Maarten]

A 2kV MKP capacitor may last forever across the mains, but it not being an X-class capacitor means that if it ever fails it might not fail in just the right way. It will probably make the radio as good as original or better, but not up to modern standards. This could cause trouble when selling it or with fire insurance claims etc.

[Diniz Diniz]

Thank you Maarten.

Would you please comment on the fact that the resistor (see post #26) run very hot and it smeels strange (but nor a burn smell)?

Regards from Portugal

[Maarten]

When using the set on 230V mains, the resistor will probably dissipate at least 12 watt so it will indeed get quite hot. If, however, it dissipates significantly more, there might still be some defect.

I'm using the B2X60U schematic, I think that should be about correct.

Most important would be to measure the current draw of the +++ supply line. If C29, C30 or the UL84 are faulty, current draw will be too high. Instead of the current you could measure the anode voltage of the UL84. This should be around 169V, not significantly lower, maybe a bit higher.

[Freya]

It could be residue on the resistor burning, but if you are concerned measure the current being drawn. If it exceeds the tolerance then you will have to look for the cause.

Crossed posts at exactly the same time

[Diniz Diniz]

Thanks, I will perform those measurements when I arrive home, and I'll let you know the results.

Maarten, I am using the B3X66U schematic, but I believe there are no differences at this level.
Can anyone of you explain me why in the schematics (see image attached) there are 3 series resistors (R5 + R4 + R3) and in the set there are only this big green resister which I assume are the sum of the 3 mentioned, plus R2, I mean:

wire --> R5+R4+R3 (all in the same resistor) + R2 --> wire
|
|
V
wire
I just want to understand Why they distinguished it in the schematic....?

Regards

[Diniz Diniz]

In post #31: The down arrow pointing to the word wire must be placed above the 3rd "+" signal, sorry...I'll attach a drawing....

[Diniz Diniz]

ok, see attached...

[Freya]

R2 R3 R4 are a combined mains dropper resistor used in different combinations of resistance to achieve the correct voltage on the rectifier and heater circuits depending on the input voltage selected.
Your mains 220~240 volts would be selected as in the picture.
Or am I misunderstanding your question.

[Diniz Diniz]

I believe you misunderstanded me. Since R5, R4 and R3 are in series in the same branch I believe they are a single resistor, therefore I dont understant why separate them in the schematics. I was not talking about R2 (which also integrate the big ceramic resistor but with two wire ends). Feel free to comment if I am analysing the schematics incorrectly.

I performed some measurements and I hope you can spend some time looking at them. Please see the images attached.

Thanks in advance,
Diniz, Portugal

[Diniz Diniz]

Please ignore the 1st paragraph of my last comment: "I believe you misunderstanded me. Since R5, R4 and R3 are in series in the same branch I believe they are a single resistor, therefore I dont understant why separate them in the schematics. I was not talking about R2 (which also integrate the big ceramic resistor but with two wire ends)." I misinterpreted the schematics. My apologies.

[julie_m]

It's not beyond the bounds of probability for there to have been versions of the same set, optimised for particular, fixed voltages, delivered to certain territories.

[Diniz Diniz]

I think I now got it right (please see image). Since one of the ends of the big ceramic resistor (the one on the left side of the drawing) connects directely to R5 (grey resistor not rated) I believe that R3+R4 are integrated in the same parte of the ceramic resistor (see image). Otherwise R4 should be missing.
I measured: R3+R4 = 930 ohm; R2 = 194 ohm
According to the schematics should be: R3+R4 = 580 ohm; R2 = 180 ohm.

If I am correct the power dissipated by R3+R4 = 930*0.0897*0.0897 = 7.48 W
Being the voltage drop 7.48/0.0897 = 83V. I measured 84V.
Feel free to correct me if I am wrong.

What to do with this differences of resistance value? 580 ohm vs. 930 ohm?
Should the resistor be replaced?

I invite you to comment and, once more, I apologize for the misunderstanding in previous comments.

Regards from Portugal,
Diniz

['LIVEWIRE?']

IF R3 + R4 have almost doubled in value, then they need to be replaced. Whether it is still possible to obtain mains dropper resistors of the type used in valve radios I do not know, although it's unlikely. If you put a request in the 'Sets, Parts, & Service information wanted' section, someone may have someting suitable, otherwise, if suitable values are available, the modern 25 watt resistors sold by RS and others would be suitable replacements.

[Diniz Diniz]

Hi,
The resistors R2 and R3+R4 have been replaced by others with the same rated value (180ohm and 200ohm+380ohm).

The set is working. Although a loud 'hum' is noticeable. I would like some advice on that.
The electrolytics seem to have normal values (53 uF + 53 uF) but I have replaced them by two 50 uF electrolytic capacitors, with no effect on the 'hum'.
The 'hum' increases when the volume control goes from its minimum to its maximun.
With SK3 closed, it almost disapear (note: with sk3 closed, it is still possible to ear a tuned station, though very low sound).

I would like to invite you to take a look on the attached images, with some voltage measurements, because I believe some values are not in accordance to the specified in the circuit diagram.

Notes:
- voltage between pin 2 and pin 3 of UL84 --> -7.25V=
- continuity between point 4 and point 5 of output transformer.

See images please,
Thanks in advance.