700II resistors/diodes

SG700II

SG700II

New Around These Parts
Joined
May 29, 2024
Messages
29
Want to swap these out. Looks like they warmed up in the past.

From the schematic, seem to be R1 and R101. Not sure which are the diodes, and their value.20240527_115632.jpg
 
Those little things you circled look like diodes to me.
The big ceramics are resistors.
 
J!m said:
Those little things you circled look like diodes to me.
The big ceramics are resistors.
Click to expand...
Correct, im trying to figure out which diodes these are on the schematic, to inturn know their type.
 
I thought it strange that they never drilled holes for the wire connections at the bottom of the boards.
Seems a bit tenuous to me, an opportunity for failure.
 
The components you're looking for are R1, R2 (2.4K, 5W) and D1, D2 (Both 1N4744) as shown in following schematics and diagram from service manual:

Control%20PCB%20Comp%20Placement%20PL700%20S2-L.jpg


Control%20PCB%20PL700%20S2-L.jpg
 
Hexis22 said:
The components you're looking for are R1, R2 (2.4K, 5W) and D1, D2 (Both 1N4744) as shown in following schematics and diagram from service manual:

Control%20PCB%20Comp%20Placement%20PL700%20S2-L.jpg


Control%20PCB%20PL700%20S2-L.jpg
Click to expand...
Thank you very much. This clears up my confusion.
 
Same parts I found "browned" on the PL36 board I just replaced with a WOPL board. I replaced the parts, but they still heated up to an unacceptable level. Keep track of the orientation of the Diodes. I seem to remember having a question about that with the PL schematic vs what I found installed. May have been a mistake of a previous tech, not sure.
 
Sunnbobb said:
Same parts I found "browned" on the PL36 board I just replaced with a WOPL board. I replaced the parts, but they still heated up to an unacceptable level. Keep track of the orientation of the Diodes. I seem to remember having a question about that with the PL schematic vs what I found installed. May have been a mistake of a previous tech, not sure.
Click to expand...
I plan to eventually do a full WOPL conversion. Starting little by little.
 
grapplesaw said:
I’d suggest you upgrade the 2.3k 5 watt resistors to 7.5k 5 watt and change the ic’s to lf351 type

here is the PL docView attachment 81717
Click to expand...
I read about this in another site, but did not have all the info this bulletin gives. Thank you. I will consider it, however I already ordered the 2.4kohm. Perhaps in a few months, but then again, im going to eventually do WOPL.
 
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Attached is the service manual. see the bulletins. It wouldn't hurt to add a small electrolytic cap, say 100uf/25 volt and a 0.1uf film cap in parallel with the zeners.
 

Attachments

Phase Linear chose to reduce the control board voltage from 100V to 15V with large power resistors and Zener diodes. This is not optimal as shown by the "browning" of the circuit board. The White Oak Audio Rev G1 Control Board uses two +15V and -15V precision power supplies (dedicated power transistors with large heat sinks fed by voltage regulators and Zener diodes) for each channel. This ensures the OPAMPs and other related components have constant and reliable DC power available regardless of supply voltage or circuit loading.
 
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