Where can i buy D1510 and B2510 transistor for my RD-6503 Sherwood audio/video receiver? or its equivalent? thanks

SOURCE: sherwood rx-4105 output transistors

You can also use 2SD2560 and 2SB1647 130watt 150volt 15amp transistor, but it may require some rebiasing the on output transistors. Sherwood have used these transistors in their older model receivers. I just replaced those transistors in my Sherwood RX-4105 Receiver, and they work good as well.

Before I install those transistor. I did a out of circuit 20volt 4amp DC current test to a 4ohm resistor @ 200watt load to compare 2SD2560 / 2SB1647 to the B2510/B1510 mounting them on 5 square inch, 1/8" thick piece of Aluminum, and the results of the test, the 2SD2560 / 2SB1647 heats up in 60 seconds to around 120 degrees F, and the B2510 and D1510 heats up in 30 seconds to around 120 degrees F.

SOURCE: sherwood rx-4105 output transistors

The actual part numbers are: 2SD1510 and 2SB2510. Perhaps the easiest for you would be to use NTE substitutes as follows:

2SD1510 ==> NTE261

While I don't have a direct cross for 2SB2510, the compliment to the NTE261 is an NTE262. These are complimentary darlington transistors and should be the correct ones for you. Please re-check the markings on the transistors to verify them.

Let me know if you need anything else.

Dan