What wattage rating for a 700B dim bulb test?

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DSMtech

New Around These Parts
#21
Joined
May 27, 2023
Messages
42
#21
mlucitt said:
Naturally, the Power Supply is common to both channels. However, if the amplifier is quiet with no input signal (idle) then the problem is not with the Power Supply. The Power Supply provides the Control Board and the Output Transistors with full rail voltage whether there is an input or not.
On the original Phase Linear Control Board there are many shared power connections common between the Right and Left channels. On the other hand, the White Oak Audio Rev G1 Control Board is a true Dual Mono circuit board. You could break it in half and it would work just fine.

Save yourself some time and just order a new WOA Control Board.
Click to expand...
Thanks for the info. I'll talk with the customer. He said he didn't pay much for the unit.
 
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DSMtech

New Around These Parts
#23
Joined
May 27, 2023
Messages
42
#23
WOOHOO!!! New control board, rectifier and sil-pads. Sound is way beyond excellent. The pre-constructed control board is phenomenal. Looks very professional. I am super impressed by the quality parts from WO and the crystal clear instructions. Bias was very easy to set. I lost sleep hoping once I installed everything the screechy noise would be gone and it is! I went ahead and checked the outputs and drivers as I was installing the new sil-pads. All good readings. I did notice that two of the original pinkish sil-pads had cuts near the mounting holes. Some looked like PL had tighted them too tight and they might have used ones that were too thin. Thanks PHX and all who had good suggestions.
 
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mlucitt

mlucitt

Veteran and General Yakker
#24
Joined
Jun 24, 2011
Messages
3,464
Location
Jacksonville, FL
#24
DSMtech said:
PL had tightened them too tight
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You mean the folks at Phase Linear might have made a mistake??? I trust my torque screwdriver set to click at 7 inch-pounds.
Actually, I don't think Phase Linear ever used the pink Sil-Pads.
Here is a fun fact - I recently acquired an early 4-fin PL400 that was originally bought for background music in a restaurant in Boston. The Serial number is 452-115. Many folks on the forum know that the second digit in the S/N is the model designation: 7 for a PL700 or 4 for a PL400. There is no model 5-anything, except for the PL5000 tuner, which is not an amplifier. The XPL909 Output Transistors are date coded 218 or the 18th week (April) of 1972.
So I believe the amplifier was assembled in May 1972, which would have made the first part of the S/N 542. Was somebody at Phase Linear dyslexic?
 
wattsabundant

wattsabundant

Chief Journeyman
#30
Joined
Apr 26, 2011
Messages
925
Location
Central Ohio
#30
DSMtech said:
See the tear. Found two just like it.
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Yes that one was over tightened. It's also possible that the original transistor was replaced and the silpad reused. Never reuse them. When I install transistors I use thumb and index finger on a nut driver. When the nut driver slips in my hand it's tight. During testing I use a thermocouple or infrared gun/camera on each output to confirm all transistors are about the same temp. I typically run them up to about 90 degrees C. On a 400 I do the test at about 25 volts on the output. That is worst case conditions.
 
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