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Old 04-16-2020, 09:40 AM   #1
golfather
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Default Fuhjyyu 3300uF 35V TNR Replacement

Hi all

Currently have a slight hum coming from my PC speakers when power is connected. Not audible when music is high volume but only on low volumes you can hear it in the background. Have a ferrite core on power lead but no difference.

System is a TEAC Powermax 1300 - same as Hercules XPS2.100 system

Checked the caps visually but none are bulging

Have been advised to change the main rectifier cap which is currently a Fuhjyyu 3300uF 35V 18x32mm (not sure what pitch, probably 7.5mm)

Is there a decent replacement anyone can recommend please? Or anything else I should be checking?

Rest of the board seems ok

Cheers!
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Last edited by golfather; 04-16-2020 at 09:42 AM..
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Old 04-16-2020, 10:34 AM   #2
R_J
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Default Re: Fuhjyyu 3300uF 35V TNR Replacement

I would check that cooked resistor (R48?) in fornt of that to220. I would also check the zener diode next to it, If that to220 transistor is a reguator or just a normal transistor acting as a voltage regulator, one of the small caps in that location might be the cause of the hum, I doubt the large cap is the issue, but if you have a 1000f/35v just solder it acrcoss the 3300f, if that eliminates the hum then I would replace the 3300.

What is the number on that to220 transistor?
The 3300 is not that special, any 3300/35v or 50v, 105 degree cap would work.

Last edited by R_J; 04-16-2020 at 10:46 AM..
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Old 04-16-2020, 02:29 PM   #3
stj
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Default Re: Fuhjyyu 3300uF 35V TNR Replacement

thats a nice looking oldschool linear amp there!
shame about the cap brand!
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Old 04-17-2020, 04:04 PM   #4
momaka
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Default Re: Fuhjyyu 3300uF 35V TNR Replacement

Quote:
Originally Posted by R_J View Post
but if you have a 1000f/35v just solder it acrcoss the 3300f, if that eliminates the hum then I would replace the 3300.
+1
This is probably the easiest way to determine if the big cap is the issue or not.

Quote:
Originally Posted by R_J View Post
I would check that cooked resistor (R48?) in fornt of that to220. I would also check the zener diode next to it, If that to220 transistor is a reguator or just a normal transistor acting as a voltage regulator, one of the small caps in that location might be the cause of the hum
+1 again
More than likely you will find some of the small caps in there are high in ESR.

In general, if you care about keeping this amp, I would suggest to do a full recap and not just change the big cap. Also check the cooked resistor, as R_J suggested. If it's in spec but still runs hot even after recapping the amp, consider replacing it with a bigger (higher power) resistor (of the same type and resistance.)
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Old 04-17-2020, 04:08 PM   #5
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Default Re: Fuhjyyu 3300uF 35V TNR Replacement

I would replace that resistor with MOX type and leave the legs long so the body will be 1/4 inch. or more above the board.
Agree on recapping for the unit this old.
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Last edited by budm; 04-17-2020 at 04:09 PM..
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