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Audio equipment

Philips amplifier Mod. 4202 noise

regomello

hace 5 años

good morning I have left this amplifier to take a look. The problem is that I don't know what it can be. When it has been off for a while and you turn it on, it starts to make noise and oscillates (I think the voltage), since there are some bulbs that illuminate some panels and they flash. Within a few seconds, everything stabilizes. The less time it is off, the faster it corrects the error. I put a video for you to see the problem. First the problem is clearly seen, half of the video is half corrected, and only in the end is when the stabilization is appreciated. https://www.youtube.com/watch?v=QOgnj6p9C6I Thanks in advance for your help

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jomi

38.143

hace 5 años

The model is F4202? I have this circuit of the source where there are two 6.3V bulbs (1010 and 1011) Is it the circuit?

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regomello

hace 5 años

Hi.
That's right

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regomello

hace 5 años

Yes it is. The two bulbs are 6.3v effectively

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regomello

hace 5 años

Hi, I leave you a video so you can see the voltage oscillation from the moment you turn it on until it stabilizes
https://www.youtube.com/watch?v=Y4pFpASYs_0

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jomi

38.143

hace 5 años

Looking at the circuit, you could try measuring the voltage at the output of the bridge diode. And see if it changes its value once it stabilizes. If so, you would change capacitors 2539 and 2540

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jomi

38.143

hace 5 años

At what point of the circuit are you measuring?

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regomello

hace 5 años

Hi.
The measurement of the video is in the alternating input, it is in the input switch.
The measurement at the exit of the diode bridge is 45 to 55 v oscillating all the time until it stabilizes and becomes fixed 68v
Thanks a lot.

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regomello

hace 5 años

Hi.
I have removed the two capacitors from the board and they give me correct values both.
Greetings.

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regomello

hace 5 años

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hace 5 años

Hi. It is fixed!!!!. I had also written in another forum and a user told me to review the welding of the input switch and spray cleaner. I've done it and now it doesn't make that noise anymore. Thank you anyway for your effort to help me. Thank you. Greetings.

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