alp10a 40vdc 6800uf

[rooprob]

Hi,
I’m debugging my 1980 Ariston amplifier. I have distortion at medium volume, +2v dc offset on the right channel, 500mV on the left. The left shows distortion on a sine wave from the preamp/feedback stage, the right is good.

But this post is not about that, this post is about these two big blue ALP caps.

Can’t seem to find any specs on them - still looking.

There are two, looks like one per channel.
They have 4 pins.

6800uF +/- 20%
40VDC -NEG 1 POS
ALP10A 1014 BB
UK MADE 8836


Pins 1 & 2 seem to be the capacitor.
Sending 300KHz 1v square wave into both of them, pins 1 (+ve) and 2 (-ve) shows a little spiky on the oscilloscope initially, then settle down to look like good caps with low ESR.

I couldn’t interpret the other two pins.

My questions
What purpose do these caps serve? They are next to the AC power supply and go directly to the output stage. They are smoothing the rectified output, but what are the other two pins, and how to test them?
What’s an alternative replacement?
The DC part of this confuses me, as I understand things, regular two pin caps filter out DC, but I don’t fully understand all the use cases of capacitors.

Thanks for reading!
Rob

[rooprob]

Re: alp10a 40vdc 6800uf

https://cdn.badcaps-static.com/pdfs/...863832e1cf.pdf

I think I found a spec sheet.
Extra pins should be mechanical.

[stj]

Re: alp10a 40vdc 6800uf

caps with 3 or more pins use the extra pins for mounting strength.
it was done before they invented the 10mm snap-in standard.