I have a fairly beat PL 4000 here, always thought they were cool but stumbled across this and a 700 and could not pass it up. Both rough condition. I have a bit of vintage repair under my belt, far from an expert. No sound on this one... but surprisingly getting VERY high DC at the outputs, both L and R something like 28VDC... thought my meter was wrong but it was correct. Any ideas on a good place to start to track that down?
Phase Linear 4000 Resurrection
- Thread starter Geezer
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- Victim of the record bug since age five
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- Halfbiass...Electron Herder and Backass Woof
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Yes, I was shocked... I will get the actual exact number when I get home to my meter.
I never even thought to check for high DC on a preamp... then I looked at my oscilloscope and saw the voltages when looking for a clean sine wave I fed into it... I thought "oh, that CANT be right." and checked with my voltmeter...
And, I had I had it connected to my Dynaco ST70, I hope that I did not do any damage....
I never even thought to check for high DC on a preamp... then I looked at my oscilloscope and saw the voltages when looking for a clean sine wave I fed into it... I thought "oh, that CANT be right." and checked with my voltmeter...
And, I had I had it connected to my Dynaco ST70, I hope that I did not do any damage....
Confirmed 29V DC on the RCA out on the 4000 Preamp!
And I just noticed that someone had replaced the RCA inputs on my early 700 power amp with 1/4 inch phono jacks so must have done time as a PA amp! Will get those replaced with RCA and see if things are working... came up fine on dim bulb and does not blow fuses so looking promising.
And I just noticed that someone had replaced the RCA inputs on my early 700 power amp with 1/4 inch phono jacks so must have done time as a PA amp! Will get those replaced with RCA and see if things are working... came up fine on dim bulb and does not blow fuses so looking promising.
The 700 Pro amps came stock with 1/4" phono plugs.
A RCA drops right in, making sure to float it above ground with the inner and outer fiber washers.
Here's mine, fully WOPL'D in the original heavy steel chassis.
Custom made for the sound company Audio Analysts, and likely saw duty at Red Rocks, Colorado.
These are Jensen/Phase Linear and last of the line.
A RCA drops right in, making sure to float it above ground with the inner and outer fiber washers.
Here's mine, fully WOPL'D in the original heavy steel chassis.
Custom made for the sound company Audio Analysts, and likely saw duty at Red Rocks, Colorado.
These are Jensen/Phase Linear and last of the line.
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You can upgrade it with 86 new electrolytic capacitors (those in the audio path should be bipolar types) and replace the RC4136 and RC4739 audio OPAMPs with OPA2134 devices on Brown Dog adapters. Then reflow all the solder connections on the daughter boards and the motherboard.
If it works, put it someplace and never move it again, as soon as you do, the solder traces will crack again.
This is why we don't work on them - they are fine on the bench when we finish with them, but in shipping they become inoperable.
If it works, put it someplace and never move it again, as soon as you do, the solder traces will crack again.
This is why we don't work on them - they are fine on the bench when we finish with them, but in shipping they become inoperable.
Very well put Mark.
The "Joystick" model is pretty to look at, on the shelf, but if you look at them wrong the traces crack.
I think we all have at least one of these pre-amps. I remember when they came out, and 4 channel (Quadraphonic) recordings were the "new" thing. The "Joystick" could really put you in the center of the soundstage. It seemed like the future of things to come. Then they started to "crackle", and fade out, or one channel flat out, didn't work. That "Mudderboard" and daughter boards was a great idea on paper, but such a nightmare to maintain. Good advice to "Never move it again". Mine is in a closet, and that's where it is staying
.
The "Joystick" model is pretty to look at, on the shelf, but if you look at them wrong the traces crack.
I think we all have at least one of these pre-amps. I remember when they came out, and 4 channel (Quadraphonic) recordings were the "new" thing. The "Joystick" could really put you in the center of the soundstage. It seemed like the future of things to come. Then they started to "crackle", and fade out, or one channel flat out, didn't work. That "Mudderboard" and daughter boards was a great idea on paper, but such a nightmare to maintain. Good advice to "Never move it again". Mine is in a closet, and that's where it is staying
.
You would want to open it up and start your own list as many times the book don't match what's actually in the unit. Somebody will chime in on the parts for the amp. It will need more than caps. Gene (gene french ) or Mark (mlucitt) have dealt with the guts of the early 700. If you don't get it right, I hope you have some test equipment or a DBT along with a shitty set of speakers you don't mind losing. I hear that the early 700 control board can be a bear to get right. I guess the 4000 and the early 700 is a great pair to learn on. Start reading, there are a ton of posts on these. Before you buy parts, READ READ READ....... It might be a project you don't want to deal with.
Fix them, you have them, so get them both refreshed with new caps, clean pots and switches, and enjoy them.
There are ways to stabilize those vertical daughter boards in the preamp so the joints don't fail.
I'd desolder and resolder each Molex pin and socket properly with good fresh rosin core solder paying attention to get the Molex connector pin up to proper temperature. The rosin flux will help make a good joint, better than No-Clean flux on those old pins.
Just went through this on the Phase Linear cassette deck I'm rebuilding. Desolder the joint with wick or a vacuum unit, clean with alcohol and a acid brush, resolder with rosin core solder with most of the heat on the pin. Would perhaps be good to even have a tin of extra rosin flux, some pins might need it.
Then clean, clean, clean those boards spotless of all that flux with alcohol.
Use No-Clean elsewhere on the boards, but rosin on those pins, and get them up to temp first. With good technique and equipment, I think the issues can be overcome.
There are ways to stabilize those vertical daughter boards in the preamp so the joints don't fail.
I'd desolder and resolder each Molex pin and socket properly with good fresh rosin core solder paying attention to get the Molex connector pin up to proper temperature. The rosin flux will help make a good joint, better than No-Clean flux on those old pins.
Just went through this on the Phase Linear cassette deck I'm rebuilding. Desolder the joint with wick or a vacuum unit, clean with alcohol and a acid brush, resolder with rosin core solder with most of the heat on the pin. Would perhaps be good to even have a tin of extra rosin flux, some pins might need it.
Then clean, clean, clean those boards spotless of all that flux with alcohol.
Use No-Clean elsewhere on the boards, but rosin on those pins, and get them up to temp first. With good technique and equipment, I think the issues can be overcome.
