Page 3 of 14 FirstFirst 1234513 ... LastLast
Results 21 to 30 of 140

Thread: PL-700 OTW

  1. #21
    Forum Veteran VSAT88's Avatar
    Join Date
    Sep 2017
    Location
    Phenix City Alabama
    Posts
    426
    Like my BlueTooth ?
    Check that. That is what I did. I read and re read the manual then I adjusted both the pots on both channels for DC offset and re checked it again to make sure I did not miss anything. Everything checks fine as far as DC offset. The Bias is what I am haveing trouble with. The left channel Bias will not adjust any higher than .140 mV. The right channel Bias adjusts easily to the correct adjustment of between .300 -.400.
    Main System: PC-Audioquest Jitterbug / Technics SL-3300-Schitt DAC-Sumo Diana-B&K EX 442-Polk SDA2b's
    Confucius say, panties not best thing on earth, but next to it. Confucius say, man who like stereo love to boom boom.

  2. #22
    Administrator
    laatsch55's Avatar
    Join Date
    Jan 2011
    Location
    Gillette, Wyo.
    Posts
    54,204
    Halfbiass...Electron Herder and Backass Woof
    I was talking about the bias, grab the bias trannt with your fingers and as your fingers warm it up see if bias changes. We are checking to see if the bias tranny has any gain left.. ..
    taking something that's already good, and making it better...........and for the knowing smiles that cross their faces.......Nando-2011...

    "Silence cannot be Misquoted"--Lazarus Short-2012 "

    " I Just Collect Smiles Craig......Cheap Smiles!-----Fishoz-2017

    "anything can be done, it's finding the easiest way that's hard"-----Bobbysdad--2014

    " Synth percussion is deadly to children, house pets and shitty power supplies"---Stephen Evans 2014

    " You have not reached the point of diminishing returns, you've just ran out of money

    " The Pioneer U-24, unfortunately, is just too expensive and rare to find. That's why I have one."--Nando-2014

  3. #23
    Forum Veteran VSAT88's Avatar
    Join Date
    Sep 2017
    Location
    Phenix City Alabama
    Posts
    426
    Like my BlueTooth ?
    Quote Originally Posted by laatsch55 View Post
    I was talking about the bias, grab the bias trannt with your fingers and as your fingers warm it up see if bias changes. We are checking to see if the bias tranny has any gain left.. ..
    You know I should have known to check that. As much trouble as we went thru last time with that bias transistor with the PL 400. Thanks Lee. I will do that 1st thing tomorrow.
    Main System: PC-Audioquest Jitterbug / Technics SL-3300-Schitt DAC-Sumo Diana-B&K EX 442-Polk SDA2b's
    Confucius say, panties not best thing on earth, but next to it. Confucius say, man who like stereo love to boom boom.

  4. #24
    Administrator
    laatsch55's Avatar
    Join Date
    Jan 2011
    Location
    Gillette, Wyo.
    Posts
    54,204
    Halfbiass...Electron Herder and Backass Woof
    Coolness....
    taking something that's already good, and making it better...........and for the knowing smiles that cross their faces.......Nando-2011...

    "Silence cannot be Misquoted"--Lazarus Short-2012 "

    " I Just Collect Smiles Craig......Cheap Smiles!-----Fishoz-2017

    "anything can be done, it's finding the easiest way that's hard"-----Bobbysdad--2014

    " Synth percussion is deadly to children, house pets and shitty power supplies"---Stephen Evans 2014

    " You have not reached the point of diminishing returns, you've just ran out of money

    " The Pioneer U-24, unfortunately, is just too expensive and rare to find. That's why I have one."--Nando-2014

  5. #25
    Forum Veteran VSAT88's Avatar
    Join Date
    Sep 2017
    Location
    Phenix City Alabama
    Posts
    426
    Like my BlueTooth ?
    Did as you said. Finger did nothing so used a hot soldering Iron underneath each transistor at Q6. I looked on the backplane for the bias resistors and saw that they were not mounted there. The heat on the left channel transistor at Q6 made the meter drop but very slowly. Putting heat on the right channel transistor at Q6 dropped the bias quickly. I am guessing I should replace both with the 2N5088 transistors that you sent me for the 400 ?? The transistors that are at Q6 now are marked Motorola MPS 5172. By the way, I am finding that this thing is a bear to work on as opposed to the PL 400....
    Main System: PC-Audioquest Jitterbug / Technics SL-3300-Schitt DAC-Sumo Diana-B&K EX 442-Polk SDA2b's
    Confucius say, panties not best thing on earth, but next to it. Confucius say, man who like stereo love to boom boom.

  6. #26
    Administrator
    laatsch55's Avatar
    Join Date
    Jan 2011
    Location
    Gillette, Wyo.
    Posts
    54,204
    Halfbiass...Electron Herder and Backass Woof
    You did notice the bias trannies are on the board and not the backplane..
    taking something that's already good, and making it better...........and for the knowing smiles that cross their faces.......Nando-2011...

    "Silence cannot be Misquoted"--Lazarus Short-2012 "

    " I Just Collect Smiles Craig......Cheap Smiles!-----Fishoz-2017

    "anything can be done, it's finding the easiest way that's hard"-----Bobbysdad--2014

    " Synth percussion is deadly to children, house pets and shitty power supplies"---Stephen Evans 2014

    " You have not reached the point of diminishing returns, you've just ran out of money

    " The Pioneer U-24, unfortunately, is just too expensive and rare to find. That's why I have one."--Nando-2014

  7. #27
    Forum Veteran VSAT88's Avatar
    Join Date
    Sep 2017
    Location
    Phenix City Alabama
    Posts
    426
    Like my BlueTooth ?
    Our posts must have crossed/posted at the same time. I found them on the mainboard at Q6, at least I think those are the bias transistors.

    Quote Originally Posted by VSAT88 View Post
    Did as you said. Finger did nothing so used a hot soldering Iron underneath each transistor at Q6. I looked on the backplane for the bias resistors and saw that they were not mounted there. The heat on the left channel transistor at Q6 made the meter drop but very slowly. Putting heat on the right channel transistor at Q6 dropped the bias quickly. I am guessing I should replace both with the 2N5088 transistors that you sent me for the 400 ?? The transistors that are at Q6 now are marked Motorola MPS 5172. By the way, I am finding that this thing is a bear to work on as opposed to the PL 400....
    Last edited by VSAT88; 02-20-2018 at 01:09 PM.
    Main System: PC-Audioquest Jitterbug / Technics SL-3300-Schitt DAC-Sumo Diana-B&K EX 442-Polk SDA2b's
    Confucius say, panties not best thing on earth, but next to it. Confucius say, man who like stereo love to boom boom.

  8. #28

    Phase Linear 700 (PL0171 PC Board Comments)

    The original Phase Linear 700's are a pain in the ass to work on. I am afraid you will be chasing your tail working on an original 700.

    The carbon composition resistors are all going up in value with age and will not provide you with some sort of visual cue as to the fact they are going bad. (NOTE: Phase Linear eventually went to using carbon film resistors (which have better reliability) in place of the carbon composition resistors in later 400's and 700B's.)

    The brands of electrolytic capacitors Phase Linear used in the early 1970's on the PL0171 and PL400C pc boards are going bad. (NOTE: Phase Linear eventually went to using different brands of electrolytic's which didn't nearly have as many problems as the early ones did.)

    The ceramic disc capacitors in all Phase Linear amps are going down in value with age as well. Albeit, the tolerances on the ceramic disc capacitors were pretty loose and I haven't seen a low value ceramic disc capacitor effect the performance so much as I do the carbon composition resistors going up in value.

    By the way, all of the PL0171 pc boards I work on these days, I remove all parts and start anew measuring all parts before they are installed.

    With all that being said, the 700 series 1 amp and 400 series 1 amps had the lowest (best) signal-to-noise ratio of all the amps that Phase Linear made. The original signal-to-noise ratio spec was also "unweighted". Later series 2 amps were all "A weighted". Even after the 700B's were produced most recording studio owner's who were in-the-know preferred the 700's over the 700B's.

    Lastly, measuring and adjusting DC offset on a PL0171 pc board begs the question.... do you adjust the DC offset when the amp is cold (running at idle after 5 minutes) or after the amp has heated up? The service manual doesn't give any guidance. The DC offset also drifts on PL0171 pc boards.

    Ed
    Last edited by oldphaser; 02-20-2018 at 02:45 PM.

  9. #29
    Administrator
    laatsch55's Avatar
    Join Date
    Jan 2011
    Location
    Gillette, Wyo.
    Posts
    54,204
    Halfbiass...Electron Herder and Backass Woof
    Quote Originally Posted by VSAT88 View Post
    Our posts must have crossed/posted at the same time. I found them on the mainboard at Q6, at least I think those are the bias transistors.

    Yep, those are theones...
    taking something that's already good, and making it better...........and for the knowing smiles that cross their faces.......Nando-2011...

    "Silence cannot be Misquoted"--Lazarus Short-2012 "

    " I Just Collect Smiles Craig......Cheap Smiles!-----Fishoz-2017

    "anything can be done, it's finding the easiest way that's hard"-----Bobbysdad--2014

    " Synth percussion is deadly to children, house pets and shitty power supplies"---Stephen Evans 2014

    " You have not reached the point of diminishing returns, you've just ran out of money

    " The Pioneer U-24, unfortunately, is just too expensive and rare to find. That's why I have one."--Nando-2014

  10. #30
    Forum Veteran VSAT88's Avatar
    Join Date
    Sep 2017
    Location
    Phenix City Alabama
    Posts
    426
    Like my BlueTooth ?
    Quote Originally Posted by oldphaser View Post
    The original Phase Linear 700's are a pain in the ass to work on. I am afraid you will be chasing your tail working on an original 700.

    The carbon composition resistors are all going up in value with age and will not provide you with some sort of visual cue as to the fact they are going bad. (NOTE: Phase Linear eventually went to using carbon film resistors (which have better reliability) in place of the carbon composition resistors in later 400's and 700B's.)

    The brands of electrolytic capacitors Phase Linear used in the early 1970's on the PL0171 and PL400C pc boards are going bad. (NOTE: Phase Linear eventually went to using different brands of electrolytic's which didn't nearly have as many problems as the early ones did.)

    The ceramic disc capacitors in all Phase Linear amps are going down in value with age as well. Albeit, the tolerances on the ceramic disc capacitors were pretty loose and I haven't seen a low value ceramic disc capacitor effect the performance so much as I do the carbon composition resistors going up in value.

    By the way, all of the PL0171 pc boards I work on these days, I remove all parts and start anew measuring all parts before they are installed.

    With all that being said, the 700 series 1 amp and 400 series 1 amps had the lowest (best) signal-to-noise ratio of all the amps that Phase Linear made. The original signal-to-noise ratio spec was also "unweighted". Later series 2 amps were all "A weighted". Even after the 700B's were produced most recording studio owner's who were in-the-know preferred the 700's over the 700B's.

    Lastly, measuring and adjusting DC offset on a PL0171 pc board begs the question.... do you adjust the DC offset when the amp is cold (running at idle after 5 minutes) or after the amp has heated up? The service manual doesn't give any guidance. The DC offset also drifts on PL0171 pc boards.

    Ed
    Mr. Ed. I agree 100% with what you said. I know that everything will need be replaced in this amp. In fact the only two things that I will not wind up replacing would be the face plate/meters and the transformer. I will WOPL with this one however (that means but, but , but. LOL) my intention for now is to get her up and running with a minimum of parts time and effort if I can. I want to listen to it and I have some old speakers that I care not for to do so (if possible). I will order a bit at a time the parts from White Oak to WOPL and Watts Abundant to put the relay in then put them aside building those parts as I go. If this thing goes nuclear in between I do not think I have really lost anything as all the internals will be replaced by WO parts in time anyhow. What do you guys think about that. As it stands right now all I think I need for it to just work are two : 2N5172 transistors to sub for the stock Motorola MPS5172 's at Q6. It will be doubtful that if this does not work that I would go any farther as far as trying to "fix" this amp.
    Main System: PC-Audioquest Jitterbug / Technics SL-3300-Schitt DAC-Sumo Diana-B&K EX 442-Polk SDA2b's
    Confucius say, panties not best thing on earth, but next to it. Confucius say, man who like stereo love to boom boom.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •