Telerad D 2642 WK Radio of 1960's. India.

[babuni81]

Do you mean to say EL84 Power output pentode or EBC81 anode. If you just elaborate about connections of bass and treble it will be easy to understand.

[peter_sol]

Connect at the EL84 end of the coupling capacitor
Have you not already done the treble?

[babuni81]

Please explain it elaborately how separate bass and treble connection will be?

No treble connection and bass connection.

[babuni81]

Thanks to all of you. I got the schematic of my radio set it matches with H.M.V. 5175 model. I have another question also about ebc 81 biasing if i put a 20 meg resistor in Rg and 680k or 330 k in Rg' and grounding cathode will it improve performance. of the audio pre- amplifier. Please if you people help me here. I saw in my set that a 2.2m rsistor is conected between el84 plate and ebc81 plate why is this so what does it function.

[peter_sol]

The 2.2 m resistor is for negative feedback to improve the quality
No don't alter anything else, you won't improve on your own sets original circuit .
It is just different ways of doing things.

[babuni81]

Thank you for your advice and suggestion

[babuni81]

Dear Friends,

Thanks for all your suggestions most of the problem sorted out But I found filter capacitor value is doubled what is printed in it. it is printed as 50MFD X2 but actually it is 100 mfd. Does it make any harm. another problem I am facing sound getting distorted and clipped after 50% of the volume. Does it has any relation with filter capacitor? Should I change it.

[Station X]

Are you sure you're not measuring both sections of the cap in parallel?

[babuni81]

Yes I have measured it with my digital capacitor meter from ground to cap leads. Volume also getting clipped and distorted after 50% wipping. Is it a problem with el84 power consumption of filter cap or OT. I am confused.

[Station X]

If it's the original cap, measuring an increased capacitance is a sign of electrical leakage.

[julie_m]

Agreed. A digital capacitance meter works by timing how long the capacitor under test takes to charge by a set amount, which will take longer if the capacitor has developed an electrical leak. This will cause the meter to read falsely high.

[babuni81]

yes you are tru meter has taken around a minuete to read the value which is 100mfd.

[babuni81]

My radio has EBC81 and El84 in Audio what should be the resistance of the output transformers primary winding. I am asking this as it has been changed earlier by local technician.

[Station X]

The resistance of the output transformer's primary winding is immaterial. It's the turns ratio that matters.

[babuni81]

Then what is the reason for sound clipping at half of volume

[Station X]

I don't know the answer to that one.

As far as the output transformer goes, an EL84 requires an anode load impedance of 5200 ohms. If the speaker's impedance is 8 ohms, then the impedance ratio is 5200/8 or 650:1. The turns ratio will be the square root of this or 25:1 (25 to 1). It isn't very critical. You'll need to redo the calculation if the speaker's impedance is different.

You'll need to check the specification of the replacement transformer.

[babuni81]

speaker impedence is 4 OHms

[Station X]

OK.

You do the calculation and we'll tell you if you're right.

[babuni81]

ratio
will be 1300:1 tuns may be 36:1

[Station X]

That's correct. All you need now is the specification for the replacement transformer.