Pioneer SX-990 need help with C15 & C16 caps + connection location

[Don_M]

Hi first time posting. Been doing some reading and great forum. I'm working on a Pioneer SX-990 receiver. It was given to me to work on in a disassembled state. The amplifier board had been removed because it did not work (blew fuses). I completed the repairs and got the amplifier board working again but I'm left with 2 electrolytic caps that are tied to the output and I don't know where the + lead is supposed to be connected. I have included a snippet of the schematic and placed 2 red arrows indicating the connection I'm trying to make.

All the connections on the board- IN1, IN2, E1, E2, E3, E4, +B, OUT1 & OUT2 are all connected as per the schematic and the amplifier works in the receiver. However the + lead on C15 & C16 show going to the board but there is no designation as to what they connect to.

Can someone here tell me where they need to be connected? Thanks for your help.

Don

 

[Don_M]

Looks like maybe they are just in parallel with C13 & C14 that are on the amplifier board but just located external to the amp pcb.

 

[elnaldo]

Welcome to AK.

A complete schematic of that board should give you that information.

Please check if this picts can help
http://www.cdkands.com/sx990/sx990.html

 

[Tom B]

As stated by Don above, those external caps are in parallel with C13 and C14. The - connection goes to the "out 1" and "out 2" connections, and the corresponding + connection goes to the plus connection of C13 and C14. If you can't easily see the + connection, it is the one that goes to the collector of the Q11 and Q12 output transistors. Be careful as those 1000uf caps mounted on the board have the single + connection going to the collector, and the 2 adjacent connections are - connections. The pin opposite of the positive connection is no connection..
These parallel external caps may have been a factory mod to boost the series capacitance to 2000ufd instead of 1000ufd.

 

[Stillhouse]

When I recapped my 990 I used the service manual from here:

https://www.hifiengine.com/manual_library/pioneer/sx-990.shtml

Much easier to identify layout and location for me.