The QX-949 lists 2 different switches for the power switch. ASG-070 (4 prong O/S use) and the ASG-043 (2 prong U.S. use)
I'm presuming that the QX-949A that you have is a non US version (multi-voltage)as the US version shows the ASG-043-0 as the power switch.
The ASG-070 is used in the (Multi-voltage switch)
QX-747
QX949A
The "ASG-043-0". is also used in the following gear; (U.S. single voltage switch)
QX-747
QX949 &949A
SA-9500
SA-9900
SX-535
SX-636
Physically they are probably interchangeable. Electrically they are not. So make sure you get the correct one.
On the back of your unit should be a sticker with a 3 letter designation like FUW on it. You need that designation when you ask about the donor unit.
Couple of things to do.
1.) on POWER SWITCHES, use ONLY a NON Residue Contact cleaner, like CRC QD Contact cleaner. All it's going to do is remove the loose carbon and sludge from the inside, leaving clean "BURNT" contacts. DeOxit has lubricants that gum up the inside of power switches of this type especially if it's been arcing . You still either have to tear it down and burnish the contacts or replace the switch, usually from another unit. There are NO NEW SWITCHES to be had. With this being a push- push switch it's possible the latch is broken inside and it's not latching in the on position.(This is the more probable scenario).
2.) Find a parts donor unit from the above list(s) and use it's (correct) switch.
3.) Contact AK sponsor "YESTERDAYS AUDIO". They deal strictly in 70's era PIONEER PARTS. Email with the part number to see if they have it if it's not in the parts catalog online. (ON AK HOME PAGE is a SPONSOR LIST, click on y'days audio, and you'll be sent there).