Hum in a transistor radio

Hi, I am working in a 1967 Philips transistor radio AC powered only.

I did change the electrolitic capacitor of 1000mF for a new one of the same capacity.

The radio is still with a 60Hz hum.

With another 1000mF capacitor in parallel, the hum almost disapears.

The radio is drawing 210mA with one and with the two capacitors.

The transformer is not getting hot.

Can I use 2000mF in definitive for this radio without harm to the power transformer?

Thanks,

Alvaro

Rio de Janeiro

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Hello

do you have the exact type designation? Is it perhaps already created here in Radiomuseum?, if so then post your question from the model, so more help is possible.
What mains voltages do you use? 110, 220V? Brazil use both voltages.
What does the nameplate say for power consumption?   This can answer the question about the correct current consumption.  Assuming 220V and 210mA are 46W, this is ok for a valve radio, not for a transistor radio. Excat type of your radio would be helpfull.

best regards

Heinrich

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Hi Heinrich,

I did not find the radio on Radiomuseum.

I am using 130/131V (it was supposed to be 127V...).

I did find the schematics in a 1969 Brazilian magazine, there is not much explanations on it.

Output power: 300mW

Speaker: ND 2400Hz 25ohms

5 transistors: AF114(2), AC126 and OC74(2)

Diode: BY127

I was  trying to attach the link for the schematics but the system here is not allowing, even following the instructions for the attachment of links.

My mistake: the radio is drawing 21mA.

Thanks,

Alvaro.

P.S.: I am still making tests with the radio and the transformer and diode are not getting hot, even with the radio 2 hours on and with 2000mF. 

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Hello,

if you double the loading capacitor the inrush current will be higher so the rectifier has to deliver more current but only for some milliseconds so may be a stronger type is neccessary.

After loading the capacitor the current through the rectifier and therefore the power consumption of the radio will be just the same like before because the load hasn't change - you can check that with any simulation software of your choice ;-)

Regards,

D. Consales

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Thanks Daniel.

Alvaro.

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