Phase Linear 700 resistors

smallies · 28th January 2011, 04:48 AM

The right channel of my 700 is going gangbusters but the left is a tad lower. After recap I ordered a driver board transistor kit but perhaps the solid appearance of my carbon comp resistors is deceiving me. The 7.5k's on the left are baking hot. My problem is wattage of all resistors. Schematic says marked resistor is one watt and who knows about the small ones.

stratus46 · 28th January 2011, 05:46 AM

Typical schematics may say something like 'All resistors 1/2 Watt unless noted' or 'All capacitors 0.1uF unless noted'. Be very suspicious of carbon resistors running 'baking hot'. Very often they change values downward until something fails.

G²

wg_ski · 28th January 2011, 05:49 PM

The small ones are 1/2 watt - you can tell by the size. All 1/2 watt from that vintage are that size - modern ones are a lot smaller.

The 1 watters on those boards do get baking hot in normal operation. The PCB cooks over time, the traces can peel up form the board, and the solder joints can fail. Replace with a *2 watt* metal oxide type and space it up from the board so it can cool. And beef up the PCB traces with a piece of a resistor lead and fresh solder.

smallies · 29th January 2011, 12:23 AM

Oh Hell yes! thanks!

smallies · 29th January 2011, 10:53 AM

So the choice for the 1/2 watters was 9 cents for xicon and 32 cents each for koa. Carbon film through hole. Am I done yet? I got the koa

smallies · 16th February 2011, 03:21 AM

These 100k and 50k trim pots are confusing to replace. Can anyone point me in even an aproximate right direction?

29th January 2011, 10:53 AM	#5
smallies diyAudio Member Join Date: Jan 2011	Is this right? So the choice for the 1/2 watters was 9 cents for xicon and 32 cents each for koa. Carbon film through hole. Am I done yet? I got the koa

16th February 2011, 03:21 AM	#6
smallies diyAudio Member Join Date: Jan 2011	offset trim pots These 100k and 50k trim pots are confusing to replace. Can anyone point me in even an aproximate right direction?

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28th January 2011, 05:46 AM	#2
stratus46 diyAudio Member Join Date: Nov 2009 Location: Los Angeles	Typical schematics may say something like 'All resistors 1/2 Watt unless noted' or 'All capacitors 0.1uF unless noted'. Be very suspicious of carbon resistors running 'baking hot'. Very often they change values downward until something fails. G²

28th January 2011, 05:49 PM	#3
wg_ski diyAudio Member Join Date: Oct 2007	The small ones are 1/2 watt - you can tell by the size. All 1/2 watt from that vintage are that size - modern ones are a lot smaller. The 1 watters on those boards do get baking hot in normal operation. The PCB cooks over time, the traces can peel up form the board, and the solder joints can fail. Replace with a 2 watt metal oxide type and space it up from the board so it can cool. And beef up the PCB traces with a piece of a resistor lead and fresh solder.

29th January 2011, 12:23 AM	#4
smallies diyAudio Member Join Date: Jan 2011	Oh Hell yes! thanks!

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