This excellent transceiver, some time, present a series of different defects when he have more than 15 years old.. In mi case, a series of 17 defects, like intermittent display, send, power, receive, 21 volts DC supply disappeared, etc… was presented.
I’m not require to change any parts. Each defect funded, was finished by a bad soldering in any part of one PCB´s involved.
Latter I solder the first 4 PCB´s, I take the decision to revise and solder “all” the 12 PCB´s of this transceiver. Big solution, because I encountered more than 100 bad solders.
When You have a bad solder in any circuits, cut the futures problems revising and solder all other Printed Circuits Boards, specially if the defects appear and disappear when you move or chock the equipment.
Yes, I know that is a long and difficult job, specially taking care to not make solder jumpers, but is the only way to solve definitely the future defects.
Please, clean each PCB´s after solder with a tooth brush and Thinner, only to the soldered side, making care that plastic parts was not affected. This attention will clean all interfering scratch metals and give you the facility to recognize any undesired jumpers.