Hoping someone out there can help me find some of these tubes, asked about a year ago a figured it was time to try again! they are used in some old Collins HF amps looks like a 4CX-250 with a larger dia. heatsink 4CX-600 AKA YC-151, JAN 8809, JAN 8921 HAPPY TO PAY DECENT FOR THEM IF ANYONE CAN HELP THANKS Tony