Solid State Guitar Amp Forum | DIY Guitar Amplifiers

I'm replacing the big filter capacitors (17000uF) on my PS Audio Hifi amp. These are right after the bridge rectifier, one on the + side and one on the - side.

I'm seeing pretty serious ripple coming out the speaker terminals on my scope and when I shake one of the capacitors I can hear it rattle so it's dried out.

There are also two smaller film caps and a resistor in parallel with each of the two larger caps.

Can anyone explain if I am reading these correctly and also what their purpose is?

Pics below:
Yellow cap Westlake 150
.68/5/100
= .68uF, 5% tolerance, 100V


Polystyrene Capacitor
10000J
160
= 10000pF = .01uF, J for 5% tolerance, 160V?

And there's a 6.2 KOhm resistor

Big filter caps are inductive above a certain frequency. It depends on the internal construction of the cap. The smaller caps (which have lower internal inductance) are added in parallel to insure that the impedance across the big filter caps remains low across the audio band up to some upper limit probably to a couple of hundred Kilohertz.

This is mostly an audiophile thing that may or may not be measurable.

Quote from: jpcar on April 14, 2020, 04:23:51 PM
I'm replacing the big filter capacitors (17000uF) on my PS Audio Hifi amp. These are right after the bridge rectifier, one on the + side and one on the - side.

I'm seeing pretty serious ripple coming out the speaker terminals on my scope and when I shake one of the capacitors I can hear it rattle so it's dried out.

There are also two smaller film caps and a resistor in parallel with each of the two larger caps.

Can anyone explain if I am reading these correctly and also what their purpose is?

Pics below:
Yellow cap Westlake 150
.68/5/100
= .68uF, 5% tolerance, 100V


Polystyrene Capacitor
10000J
160
= 10000pF = .01uF, J for 5% tolerance, 160V?

And there's a 6.2 KOhm resistor

Looks to me like you read the values correctly and Loudthud's explanation is exactly what I would have said.