WOPL 700B Has more output on the left channel.
- Thread starter Mohawk
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- Jan 14, 2011
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- Halfbiass...Electron Herder and Backass Woof
Originally the stickers represented who was responsible for the work. Now we (at least I) use them as a way to honor (some might disagree it's any honor given I assembled the amp) the people who built Phase Linear amps back in the day. Even named a few amps for the original builders on the stickers. Think I'll name one Ed 
To add to what Joe said earlier. There's a lot of evidence of insufficient heat when soldering. Zoom in and look at all of the rough B+/B-/ground connections along the edge of the backplane board. Also zoom in and look at the Q7L/Q8L pin solder joints. Even the joints at the copper ground strap between the main caps don't appear to have flowed much solder at all onto the copper strap. I like to see the solder wick up the wire and out onto the surface/plane I'm connecting it to. I'd say a full reflow of all the solder joints is in order.
I just finished putting a WO control pcb into a local friends 700 and I had a few joints that had to be touched up. I always inspect any boards I'm building under a magnifying lamp (old eyes) on both sides. I think some folks solder from one side and are in such a hurry so they don't check the joints on the opposite side of the board. Checking and reflowing dodgy solder joints should be standard practice but it appears whoever built this one didn't do that last bit of work. If you flip that control pcb down and inspect the back of it you may find some more solder joints that are questionable.
I just finished putting a WO control pcb into a local friends 700 and I had a few joints that had to be touched up. I always inspect any boards I'm building under a magnifying lamp (old eyes) on both sides. I think some folks solder from one side and are in such a hurry so they don't check the joints on the opposite side of the board. Checking and reflowing dodgy solder joints should be standard practice but it appears whoever built this one didn't do that last bit of work. If you flip that control pcb down and inspect the back of it you may find some more solder joints that are questionable.
Looks like kind of dendritic growth on the board around the D7L, D8L area. Also some strange stuff on the left channel around R12L and R13L that I cannot tell what it is from the photo. Almost looks like there is a solder ball between the top side of these 2 resistors. Worth checking out. This is the feedback resistor for the left channel.
Pls ask what type of flux was in the solder used to build this board.
Pls ask what type of flux was in the solder used to build this board.
Well the back side of the board looks pretty good. The fact that you've cleaned it up and it's shiny helps. Due to the type of issue you're seeing I'd still reflow all of the solder joints on this board. It'll take all of 10 min to do so but should give you peace of mind that the joints are all solid.
Did you happen to measure the input signal level at the board? This will verify that something is not screwed up with the volume pot's thats causing a loss of input signal on the right channel. I'd leave the amp off and feed it a 1V rms signal and measure that signal level at the control board. If the amp is together its easiest to get to this input signal at the top of the board on the right side of R1L/R1R.
Hi
Just reading this thread now
It may have been suggested to bypass the volume pots. If you can input direct to the control board from your source. You can take a old set of rca interconnects and cut off the plugs at one end and pre that to go in the control board. Make sure you get ground into the right hole on the board. Connect these cable to you sound source direct bypassing the volume pots and input connections.
You could also just flip the two input cables from one channel to the other and se if you problem moves to the opposite channel.
I feel this may be a bad volume pot.
If you have already done this pardon me for not reading the complete thread.
Just reading this thread now
It may have been suggested to bypass the volume pots. If you can input direct to the control board from your source. You can take a old set of rca interconnects and cut off the plugs at one end and pre that to go in the control board. Make sure you get ground into the right hole on the board. Connect these cable to you sound source direct bypassing the volume pots and input connections.
You could also just flip the two input cables from one channel to the other and se if you problem moves to the opposite channel.
I feel this may be a bad volume pot.
If you have already done this pardon me for not reading the complete thread.