Start by removing the heatsink that covers the side of the amp with the attenuator pot. This is the side with the label. There are 24 small allen head bolts holding this heatsink in place. Also remove the shaft nut on the attenuator pot. The pot is mounted to the bias board inside and will stay behind when the heatsink is lifted off. You should now be able to see 3 feedthrough capacitors which bring in the original -24 volts and bring out the + 10.5 and -12 to the bias board. Mark the leads going to the bias board or simply cut them in the middle . You will need to connect the new supply to these original connection points. Most of these amps have a toroid inductor and large diode in series with the input power. These may be saved and put inside if you wish, but they take up space where we need to mount the +10.5keying relay.
You will see a switching power supply surrounded by a fence that is separate from the RF section and bias board assembly. This is held in place by 6 more allen bolts through the remaining heatsink. There are bolts (6)through the power supply board and more bolts through the TO220 parts (3) that need to be removed. Once all these bolts are removed you should be able to lift the entire power supply assembly from the heatsink.Once these are lifted off you can separate the leads from the feedthrough capacitors.
I chose to use a 317 adjustable regulator driving a pair of 3055 pass transistors. You might get by with paralleling a bunch of 7810 three terminal regulators. I'm not sure how much gain would be lost by being 1/2 volt low, although it is possible to raise the output of the 7810 by using a diode in series in the ground reference terminal.. Plan on having enough current capacity for 8 amps at 12 volts. This is a lot of heat ! Make sure the board traces are plenty wide to accomadate the required current. I ran the +10.5 through an automotive syle relay from Radio Shack. This relay is rated at 30 amps and has both coil terminals available for use. If you connect the +12 volts to one side of the coil, you only need to ground the other side of the coil to complete the circuit and send the +10.5 to the bias board.The high current path comes from the 12 volt input, through the pass transistors, through the relay and right to the bias board. I did not include the relay in my original incarnation of this thing, but after seeing how much heat was generated by leaving the load connected, I decided to only turn it on during transmit. I mounted an RCA phono jack through the perforated end to connect to the transverter keying.
The -12 volts is generated from a pair of 7660 or 7661 charge pumps. I did not feel comfortable with the amount of current available from just one device, so I chose to use 2 of them in parallel. I used a 7812 12 volt posite 3 terminal regulator on the input of the pair and get -12 on the output. This is applied to the bias board through a series diode.
(SCHEMATIC OF CIRCUIT)
I made my own circuit board from a piece of double sided .031 material. Single sided would work just as well, but I only seem to have double in my stock pile. I used a "DREMEL" motor tool with a burring style tool to separate paths in the copper. This is handy for me, as I just add more traces as I think of them. You will need to look at where all the parts will mount and mark some locations on the copper where the regulator leads will line up when the fence is remounted. Then you can etch or grind out your board. I suppose this could all be wired without the circuit board by going point to point and putting in a few insulated tie points, but the board is really easy to make and use. None of this stuff is too critical, although I highly recommend using a diode in series with the 12 volt supply to prevent accidental application of reversed voltage.
If you need help with schematics for pass transistors or whatever, let me know and I'll link more pictures and arrows..