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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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1st Oct 2015, 4:08 pm | #21 |
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Re: Telerad radio of 60's
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.
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1st Oct 2015, 4:40 pm | #22 |
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Re: Telerad radio of 60's
Connect at the EL84 end of the coupling capacitor
Have you not already done the treble? |
1st Oct 2015, 5:02 pm | #23 |
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Re: Telerad radio of 60's
Please explain it elaborately how separate bass and treble connection will be?
No treble connection and bass connection. |
14th Oct 2015, 11:20 am | #24 |
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Re: Telerad radio of 60's
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.
Last edited by babuni81; 14th Oct 2015 at 11:23 am. Reason: adding more info |
14th Oct 2015, 1:51 pm | #25 |
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Re: Telerad radio of 60's
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. |
15th Oct 2015, 1:08 pm | #26 |
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Re: Telerad radio of 60's
Thank you for your advice and suggestion
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24th Nov 2015, 7:47 pm | #27 |
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Telerad radio of 1965
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. |
24th Nov 2015, 8:39 pm | #28 |
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Re: Telerad radio of 60's
Are you sure you're not measuring both sections of the cap in parallel?
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24th Nov 2015, 8:45 pm | #29 |
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Re: Telerad radio of 60's
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.
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24th Nov 2015, 9:02 pm | #30 |
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Re: Telerad radio of 60's
If it's the original cap, measuring an increased capacitance is a sign of electrical leakage.
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25th Nov 2015, 5:22 am | #31 |
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Re: Telerad radio of 60's
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.
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25th Nov 2015, 2:04 pm | #32 |
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Re: Telerad radio of 60's
yes you are tru meter has taken around a minuete to read the value which is 100mfd.
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26th Nov 2015, 6:20 am | #33 |
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Re: Telerad radio of 60's
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.
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26th Nov 2015, 9:14 am | #34 |
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Re: Telerad radio of 60's
The resistance of the output transformer's primary winding is immaterial. It's the turns ratio that matters.
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26th Nov 2015, 10:19 am | #35 |
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Re: Telerad radio of 60's
Then what is the reason for sound clipping at half of volume
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26th Nov 2015, 11:00 am | #36 |
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Re: Telerad radio of 60's
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.
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26th Nov 2015, 11:21 am | #37 |
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Re: Telerad radio of 60's
speaker impedence is 4 OHms
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26th Nov 2015, 11:28 am | #38 |
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Re: Telerad radio of 60's
OK.
You do the calculation and we'll tell you if you're right.
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26th Nov 2015, 11:39 am | #39 |
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Re: Telerad radio of 60's
ratio
will be 1300:1 tuns may be 36:1 |
26th Nov 2015, 11:52 am | #40 |
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Re: Telerad radio of 60's
That's correct. All you need now is the specification for the replacement transformer.
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