wattsabundant
Chief Journeyman
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Another Phase Linear 3300 Series 2 Pre Amp
- Thread starter DougD
- Start date
After running without incident for a week at low volume the left channel was dead when I turned the unit on this morning. As I recall the right channel was dead when I first energized the unit after reflowing the solder joints. I left the volume control at a low level and began exercising controls from left to right. The selector switch had no effect, but when I rotated the Bass control the left channel popped in. What I don't understand is that the Tone switch was in the out (open) position - assuming this takes the Bass and Treble controls out of the signal path so not sure why rotating the Bass control had any effect. I should probably stick to wrenching on old English cars.
I've attached a pic of the arsenal I've assembled based upon the input from you folks, and want to make sure I'm using the correct products. I'll flush/clean the 2 gang pots with Deoxit F and finish with a drop of the fader lube. I plan to remove them from the board to facilitate access for cleaning - thinking I might as well open them up for best cleaning and lube, or should I leave them closed? I'm not certain if all of the push button switch internals are all metal or include plastic components, so wondering if it's safe to flush them with the D5 or D100. Appreciate any advice. Will leave the Alps pot alone at this point.
I've attached a pic of the arsenal I've assembled based upon the input from you folks, and want to make sure I'm using the correct products. I'll flush/clean the 2 gang pots with Deoxit F and finish with a drop of the fader lube. I plan to remove them from the board to facilitate access for cleaning - thinking I might as well open them up for best cleaning and lube, or should I leave them closed? I'm not certain if all of the push button switch internals are all metal or include plastic components, so wondering if it's safe to flush them with the D5 or D100. Appreciate any advice. Will leave the Alps pot alone at this point.
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It is most likely that the physical motion of turning the tone pot restored a marginal PCB connection somewhere rather than the pot being involved.
This is fairly classic behavior on some PL preamps, particularly the infamous PL4000 preamp, marginal solder joints.
This is fairly classic behavior on some PL preamps, particularly the infamous PL4000 preamp, marginal solder joints.
Thanks for that - makes sense. Does that suggest it's something immediately adjacent to the pot or could it be anywhere? I'll reflow everything I didn't touch the first time around. In the meantime I've already got the tone pots off the board so might as well clean them. Didn't realize how large the openings are adjacent to the board - thinking a simple flush might be enough.
It could be anywhere on the board that has an intermittent. However, it is not the tone pots if you have the switch in the OUT position. I would recommend a careful look under magnification of all the solder joints. They are approaching 50 years old...
Yes, less likely than at a solder joint connection but yes.
Vynuladikt
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Cracked traces can be extremely difficult to locate, especially if they are under the resist coating. Bright light from behind the board can help.
Only had this a couple times but I won't forget the struggle.
Only had this a couple times but I won't forget the struggle.
For anyone still listening - I cleaned and lubed the tone pots since they were off the board, and did the same to the balance pot in situ. I spent a couple of hours inspecting the board with a magnifying glass for gaps or cracks in solder joints and traces. Remelted a few joints that were a little suspect but to no avail. For the past few days the system has turned on with the left channel dead, which pops in with the touch of any number of the front panel controls or a slight increase of volume. This morning both channels were dead - operating all front panel controls had no effect until I got to the volume control, where a slight increase brought the left channel in and the right channel finally fired at full gain (the household loved that at 6am). Any thoughts on what to do next will be greatly appreciated. Thinking it might be time to take it back to a professional? I've used the ones closest to me for service in the past (Electronics Service Labs in Wethersfield CT and Approved Audio Service in Bantam). Both were able to resolve other issues but neither were able to detect or correct this issue. A friend has offered to give me his old Denon receiver but the thought of giving up the Phase Linear gear doesn't sit well.
mlucitt
Veteran and General Yakker
Bad potentiometer? Replacements are likely available.
Defective muting circuit? Have you tried defeating it to debug your issue?
Assume you're referring to the volume pot? If so is it worth attempting to loosen for access to clean vs replace? Thanks.
Assume you're referring to the mute switch that attenuates the volume? I looked at the schematic to see if I understood how to defeat this function. Way above my pay grade I'm afraid, but thanks for the suggestion - will pass along to whoever ends up working on this. I remember one of the techs previously suspecting the headphone jack/circuit since this cuts out the speaker output - replaced some components but obviously that wasn't the problem.
To defeat the power up muting circuit, pretty straightforward, remove Q103 and Q203 temporarily.
I also think the headphone jack defeat is possibly a culprit, that looks sketchy at best and not clear how it is implemented. Phone jacks are notorious for the nickel plating oxidizing and getting flakey with intermittents.
But the real problem is that the Fudder Mudder circuit board used in the 3300 was approved by Mike F on 10/32/79
I think it was recognition of too much weed smoking on Halloween.
Don't destroy them, you will want to put them back in after debug.
oldphaser
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It has been a while since I last worked on a 3300. However, I seem to recall running into problems with at least one headphone jack before. "The SW outputs are turned off when a headphone is plugged in. This allows headphone listening without speaker background sound. The UNSW outputs are not affected by headphone operation." Both outputs may be used at once, if desired.
By the way, the headphone jack was made in Japan as a Emuden part number P2127.
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oldphaser
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David Willard (the draftsman at Phase Linear) used to like sneaking in things like "Fudder Mudder" on circuit boards. Management wasn't too happy about this.
Mike F. was Mike Frost. Mike worked in the engineering department at Phase Linear. Unfortunately, Mike passed away in 2016.