700II resistors/diodes

SG700II

New Around These Parts
Joined
May 29, 2024
Messages
26
#1
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
 

SG700II

New Around These Parts
Joined
May 29, 2024
Messages
26
#3
Those little things you circled look like diodes to me.
The big ceramics are resistors.
Correct, im trying to figure out which diodes these are on the schematic, to inturn know their type.
 

MarkWComer

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,481
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#8
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.
 

Sunnbobb

Journeyman
Joined
May 25, 2023
Messages
197
Location
Mount Vernon, WA
Tagline
Bikes, baseball and big amps.
#12
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.
 

SG700II

New Around These Parts
Joined
May 29, 2024
Messages
26
#13
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.
I plan to eventually do a full WOPL conversion. Starting little by little.
 

SG700II

New Around These Parts
Joined
May 29, 2024
Messages
26
#15
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 doc View attachment 81717
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.
 
Last edited:

SG700II

New Around These Parts
Joined
May 29, 2024
Messages
26
#17

mlucitt

Veteran and General Yakker
Joined
Jun 24, 2011
Messages
3,466
Location
Jacksonville, FL
#18
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.
 
Last edited:
Top