Harman kardon a300 rebuild

I would do a middle of the road approach. If you keep adding uF to power supply filter caps you’ll increase the surge currents and stress the rest of the power supply on turn on.

Assuming you are reading this correctly, and the cap was specified as being at least 60uF and no more than 100uF, somewhere in between is fine.

Yes, thanks for the response. I’ve never seen a power cap with a range specification (I’m sure there are those out there who’ve seen this before). I don’t really understand the ‘hot can’ part of the equation and any time I’ve replaced caps I’ve always tried to find something within 10% of the stated uF value if there wasn’t a direct substitute. Makes me wonder if a so called hot can is meant to supply a variable range of uF’s. 

Please refer to the schematic,

There are total of three filter capacitors in its power supply: one 100µF 200V can, one 50µF 400V + 100µF 200V can and one 3X 40µF can.

Are you talking about the 50µF 400V + 100µF 200V can? It is two capacitors inside a can with 4 taps.

It’s C23 on the schematic. On the schematic it’s rated as 100uF @200v but the can is rated (as per the piece of paper between the metal and the cardboard covering) 60-100uF @ 350 volts. Everything on the unit looks original although I suppose the person who owned it before me could have replaced the cap.
Now after close inspection… I see the resistor between c23 and c24 is 650 ohms instead of the 470 ohms that is shown in the schematic. The soldering looks terrible so it was probably added by someone who couldn’t find the right replacement for the capacitor. Does this seem logical? 
BTW, I’m a beginner with this.

-can’t believe I didn’t notice this earlier…. Beginner mistake 

Well, everyone starts as a beginner. 😊

According to the schematic I would use 100μF for C23 and C24A, higher voltage rating wouldn’t hurt either. I don’t know why 650Ω and not 470Ω, you can try both for best performance.

BTW, since you are rebuilding it, my suggestion is to replace the diodes with UF4007 to reduce noise.

Waste of money for a boutique cap. For the power supply electrolytic caps commercial grade are fine! BTW I have a nicely restored HK A300.

Already replaced the diodes with UF4007’s. 
that whole area I replaced.. the underside of the chassis was black with burn marks… everything is as it should be now (or will be soon).

thanks everyone so much for your responses  -I really appreciate them!

The hot can (cardboard wrapped) is made by GE and its specs are printed on the can as 60-100 micro farads at 350v. I’m concerned about the range of uF as I need to specify a uF rating for them to build a new one. Should I specify 100uF or something in the middle like 80uF?

@ccogopher This kind of power supply is known as a ’voltage doubler’ supply. The cap in the insulated can is floating- its insulated in paper so you don’t get a shock from it. It carries a lot current and so is usually the first part to fail as the filter caps age.

100uF is fine- no worries, especially if you have replaced the original rectifiers, which were pretty sketchy. Obviously a good quality part for that cap is a very good idea- and its mate of the same value. I would find 105C parts for installation if you can find them. 'Snap' caps might be a way that you can find the value and they could be mounted with cap clamps.

This is a very nice sounding amp once properly restored- its worth being careful and as neat as you can with the restoration!!