Restoring the Phase Linear 700b

[Slake]

I am in the process of restoring my Phase Linear 700b to the quasi complementary version. Thanks for all the help so far. I have the unit semi-torn apart and have the parts to do the following:

Replace the PC board with the White Oak PL14-20G1-Kit with the Phoenix connector option
Replace the filter caps with the larger versions from White Oak
Replace all the meter lights
Replace the Transistors with the MJ21196G's
Replace the drivers with the RCA 410's
Replace all the resistors
Replace all the diodes
Replace all the capacitors
Replace the RCA inputs

I have the following questions:

1) Is there any good reason to replace the TO3 sockets if they're in good shape. It looks like Keystone has a replacement part, # 4606.

2) I would like to repaint the transformer. I cannot tell if the laminations were originally bare metal and coated with clear or painted black?

3) The resistors I ordered were based on the original values, are their any recommendations I missed regarding values I should have changed?

4) My unit is missing one knob. Is anyone aware of a source that sells a reproduction?

Thanks again for the help

 

[mlucitt]

The issue with the original Sockets is the steel spring clips for the Transistor Pins. They are weakened by insertion and removal as well as heat cycles. You can attempt to squeeze them together with needle nose pliers, but that is a temporary fix. Those sockets were the best solution available in the 1970's. It is a BIG job to replace all those sockets in a PL700B! The ultimate solution is the White Oak Audio Backplane Kit.

The transformers were typically dipped in varnish to seal the windings and as a form of insulation. Most of the transformers I have seen have a thin coat of black paint, maybe lacquer.

The resistors we use are made by KOA Speer, 0.33 Ohm (330 mOhm), Metal Oxide, 3 Watt, 2%. The P/N from Mouser is 660-MOSX3CT631RR33G, they are less than $0.20 in minimum quantities of 25.

Is your knob solid aluminum or thin aluminum over a plastic insert? The solid ones are rare, I have many of the plastic insert knobs. I will send you one. PM Sent.

 

[Slake]

The issue with the original Sockets is the steel spring clips for the Transistor Pins. They are weakened by insertion and removal as well as heat cycles. You can attempt to squeeze them together with needle nose pliers, but that is a temporary fix. Those sockets were the best solution available in the 1970's. It is a BIG job to replace all those sockets in a PL700B! The ultimate solution is the White Oak Audio Backplane Kit.

The transformers were typically dipped in varnish to seal the windings and as a form of insulation. Most of the transformers I have seen have a thin coat of black paint, maybe lacquer.

The resistors we use are made by KOA Speer, 0.33 Ohm (330 mOhm), Metal Oxide, 3 Watt, 2%. The P/N from Mouser is 660-MOSX3CT631RR33G, they are less than $0.20 in minimum quantities of 25.

Is your knob solid aluminum or thin aluminum over a plastic insert? The solid ones are rare, I have many of the plastic insert knobs. I will send you one. PM Sent.

Hello and thanks for the great information. The knobs I have are the solid aluminum knobs. I have a lathe and mill in my shop so I will give making one a try. The knob design is simple except for the subtle concave surface on the front, but I have a second mill head that I think I can replicate it with. I found the 700b back plane kit on the White Oak Audio site but cannot locate any information about it. Is it a PC board that I mount my transistors on?

Thanks

 

[Gepetto]

Hello and thanks for the great information. The knobs I have are the solid aluminum knobs. I have a lathe and mill in my shop so I will give making one a try. The knob design is simple except for the subtle concave surface on the front, but I have a second mill head that I think I can replicate it with. I found the 700b back plane kit on the White Oak Audio site but cannot locate any information about it. Is it a PC board that I mount my transistors on?

Thanks

PM me your email and I will send over details
Joe