Sony c800(non G) noise issue help!

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ktziavos

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Dec 2, 2020
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Hello to everyone! Update! I' ve changed the supercaps and the noise is much lower... There is still some noise but this made big difference!! I am going to change more old caps and i will come back with the results! Take care
 

ktziavos

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Dec 2, 2020
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I was reading up about supercaps like used in the Sony , seemed to suggest the usefull life of these components is only a few years .
This was really an improvement to the issue. Just changed both supercaps and some of the ocean noise now is gone. I will change some more caps from the ps and I will let you know! Really appreciate the help!!
 

rock soderstrom

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This was really an improvement to the issue. Just changed both supercaps and some of the ocean noise now is gone. I will change some more caps from the ps and I will let you know! Really appreciate the help!!
That's a good thing , but I'm surprised that replacing the fat electrolytic capacitors reduced your ocean noise problem!
 

ktziavos

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Dec 2, 2020
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That's a good thing , but I'm surprised that replacing the fat electrolytic capacitors reduced your ocean noise problem!
not the fat... the small in shape but big in capacity 1F supercapacitors! the fat 10000mF i am going to change them in a couple of days!
 

ktziavos

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Hello there, Unfortunately changed all the caps in the ps and the basic ocean noise is there. Here some photos from the resistors with thermal camera. It seems that are real hot! Is that normal l?
 

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Matt Nolan

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Is there any chance that the problem is the resistor itself?
Unlikely. The problem is elsewhere I would say, but near to the resistor. Something that is causing a short-circuit or much lower resistance than designed such that there is an excess of current flowing in the resistor.

You are, at least, homing in on it having found that hot spot.
 

Gus

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Are you measuring the heat with microphone tube installed? If not the resistor and zeners will get hot.
You could calculate the wattage knowing the fil current and pin 7 should be about 5.7VDC.
Go to the tech section and look at the G PS schematic that part of the supplies look to be the same
The schematic has that resistor voltages
10.2VDC - 5.7VDC = 4.5VDC
P = voltage x current
What is the voltage do you measure across that resistor? Use that and the resistor value and calculate the power being dissipated is it lower than the resistor rating?

The noise can still be the tube, how many have you tried?
 

ktziavos

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Dec 2, 2020
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Are you measuring the heat with microphone tube installed? If not the resistor and zeners will get hot.
You could calculate the wattage knowing the fil current and pin 7 should be about 5.7VDC.
Go to the tech section and look at the G PS schematic that part of the supplies look to be the same
The schematic has that resistor voltages
10.2VDC - 5.7VDC = 4.5VDC
P = voltage x current
What is the voltage do you measure across that resistor? Use that and the resistor value and calculate the power being dissipated is it lower than the resistor rating?

The noise can still be the tube, how many have you tried?
Hello Gus, i am measuring with the tube mic on! I will measure the voltage and i will come back!
Ps is not the G version. So i think that the volts are 11v.
 

Matt Nolan

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Did you replace the Zeners? Did you put them in the right way around?

With the caps that you replaced, were they the correct voltage rating, and did you put them in the right way around? The heater voltage is elevated (not referenced to ground, but referenced to 140 or so volts I think). This is why some of those caps in the heater circuit are 220V.
 

ktziavos

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Dec 2, 2020
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Did you replace the Zeners? Did you put them in the right way around?

With the caps that you replaced, were they the correct voltage rating, and did you put them in the right way around? The heater voltage is elevated (not referenced to ground, but referenced to 140 or so volts I think). This is why some of those caps in the heater circuit are 220V.
No i didn't replace the zeners. The heating problem was before the caps change but i didn't have the thermal camera to measure. But the same feeling of heat was there.
 

ktziavos

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Dec 2, 2020
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Did you replace the Zeners? Did you put them in the right way around?

With the caps that you replaced, were they the correct voltage rating, and did you put them in the right way around? The heater voltage is elevated (not referenced to ground, but referenced to 140 or so volts I think). This is why some of those caps in the heater circuit are 220V.
Maybe it has faulty zeners? Is there any chance?
 
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