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Thread: PL-700 OTW

  1. #131
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    Halfbiass...Electron Herder and Backass Woof
    The Qua-co kit ain't bad. I would assume they are using the 2N 3439 in place of the 40412V's.,.. The 1304's/1305's are no longer made but can still be had on e-bay...matching q1/q2 can cut down on DC offset, but on your board it's a adjustable...

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  2. #132
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    Halfbiass...Electron Herder and Backass Woof
    Looks like the 40412V's they supply come without the factory heatsink...
    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. #133
    Quote Originally Posted by VSAT88 View Post
    Lee, is this still so ? http://forums.phxaudiotape.com/showt...Transistor-Set Can these be bought for my board ? Do I need replace them, or not put them in at all ?? Possibility get some to keep in stock ? I would like to replace all the transistors on the board as well as the diodes and caps but when it comes to this beta testing / matching I have no real clue what to do. There is this guy on e bay that has all of them and says that they are already matched... https://www.ebay.com/itm/PHASE-LINEA...sAAOxyaTxRQnHl Should I just buy these ?
    I downloaded a copy of the picture from ebay and rotated it 180 degrees and took a closer look at the transistor part numbers:

    It appears Qua-co is selling:
    (4) TIS97's
    (4) MPSA93's
    (2) 2N3417's (NOTE: Phase Linear never used these)

    and
    (2) 036MAL's
    (2) 201MAL's
    (2) 116MAL's
    These are date codes and not the model numbers and more than likely made by STMicroelectronics. Qua-co edited the photos to hide the part numbers. My best guess is that Qua-co is using 2N3439, 2N3440 and either 2N5415's or 2N5416's.

    Anytime I see anyone on ebay selling matched transistors, I always want to know more about what means or methods they used. What voltage and current they used and the manufacturer and the model numbers of the test equipment they are using.

    In the case of gain/beta matching of the pre-drivers (i.e. 2N3440 and 2N5415/6's), I am not sure that you will find any measurable improvements if you tested the amplifier to its manufacturer's claims.

    In the case of the first and second differential pair transistors (i.e. TIS97 and MPSA93's), if you match the transistors, you will see a difference in: 1.) dc offset (albeit, as Lee has already mentioned the PL0171 pc board has adjustable dc offset trimpots) and 2.) turn-off thump. Lee has shared on the Phoenix forum a simple technique (I have seen best used for low power transistors) using a digital multimeter; measuring the transistor junction resistances and closely matching the results (between any two transistors) that works quite well. Perhaps Lee can provide a link to this technique.

    Ed
    Last edited by oldphaser; 03-26-2018 at 09:17 AM.

  4. #134
    Forum Veteran VSAT88's Avatar
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    Like my BlueTooth ?
    Makes me wonder if I should change the transistors at all. Especially with unknown parts or parts PL never used. I have high bias on one channel, the left. The DC offset has never been a problem it zeros out. I have already replaced the bias transistors and now I have replaced all of the pots on both channels (with new CTS pots) as well as all the capacitors on both channels of the board. I have also replaced the zener that was in place at R 19 with new 1N4752 A 33V. I have all of the rest of the resistors as well as the diodes to complete the job but I have really been taking my time as I have lifted one trace already. Nothing I cannot fix but I would just as soon not have that happen again. You guys know by now that I am nothing more than a beginner but I am starting to pick some knowledge by working with you and I damn sure appreciate it. I do believe the next thing I am going to do in the shop is build that Octopus tester. Everything I needed to build it has come in now and I will take that to task next....I want to learn more ! Thanks again .
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  5. #135
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    Quote Originally Posted by oldphaser View Post
    700HF (High Frequency) amps built for Bell Labs.
    Hey Ed,
    What is the story behind the 700HF for Bell Labs? What makes the 700HF different / better / unique?

    Nick

  6. #136
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    Screw it
    Quote Originally Posted by laatsch55 View Post
    Backlanes won't fit, the Series 1's have a different bolt pattern for the outputs. You have to drill two holes to mount the driver board. You can, however, buy a new chassis and heatsink. The faceplate will fit...
    Lee, I was just refreshing my old brain and If I remember right, the reason I didn't buy an original 700 was the transformers had a different bolt pattern and would not fit the new chassis??? I recall something about the transformers. Hell, if the transformers fit the new chassis, that's half the battle (And all the money)..... But I think I remember that we figured out the transformer will not fit. Thanks

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  7. #137
    Quote Originally Posted by THD+N View Post
    Hey Ed,
    What is the story behind the 700HF for Bell Labs? What makes the 700HF different / better / unique?

    Nick
    Nick,

    The Bell Labs 700HF's will meet spec (.25% THD) all the way to 100KHz at rated output. Albeit when you test them you can't hold them there for very long (just a few seconds or so/just long enough to verify that it meets spec) or you will start blowing the Zobel network and potentially the output transistors as well.

    I have purchased (3) 700HF's over the years. The first one I acquired I either sold or gave to Dean. The second and third (which I purchased from someone who bought them at an estate sale in New Jersey) were sold to the same collector in Massachusetts.

    I have a copy of the schematic. I am not sure if I have posted it on the Phoenix forum. I did provide copies to Lee and Joe. Would you like a copy? A number of parts were actually removed as well as some changes in the transistors.

    According to Dean about a dozen or so were built. I have heard (3) variations to the story as to why they were built; 1.) Magnetic bubbles on tape. 2.) Underwater experiments with dolphins. 3.) Use at trade shows.

    Ed

  8. #138
    Quote Originally Posted by WOPL Sniffer View Post
    Lee, I was just refreshing my old brain and If I remember right, the reason I didn't buy an original 700 was the transformers had a different bolt pattern and would not fit the new chassis??? I recall something about the transformers. Hell, if the transformers fit the new chassis, that's half the battle (And all the money)..... But I think I remember that we figured out the transformer will not fit. Thanks

    P
    Perry,

    I haven't heard from Lee on the forum for a while. My guess is that he must be fishing?

    I just went downstairs and took a 700B transformer and placed it into a carcass 700 chassis. It appears that the holes line up. The center distances are approximately 4-1/4" x 5-5/16" (as eye-balled with my ruler).


    Ed

  9. #139
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    Quote Originally Posted by oldphaser View Post
    Nick,

    The Bell Labs 700HF's will meet spec (.25% THD) all the way to 100KHz at rated output. Albeit when you test them you can't hold them there for very long (just a few seconds or so/just long enough to verify that it meets spec) or you will start blowing the Zobel network and potentially the output transistors as well.

    I have purchased (3) 700HF's over the years. The first one I acquired I either sold or gave to Dean. The second and third (which I purchased from someone who bought them at an estate sale in New Jersey) were sold to the same collector in Massachusetts.

    I have a copy of the schematic. I am not sure if I have posted it on the Phoenix forum. I did provide copies to Lee and Joe. Would you like a copy? A number of parts were actually removed as well as some changes in the transistors.

    According to Dean about a dozen or so were built. I have heard (3) variations to the story as to why they were built; 1.) Magnetic bubbles on tape. 2.) Underwater experiments with dolphins. 3.) Use at trade shows.

    Ed
    Hi Ed,
    Please email the 700HF schematic.

    Thx

  10. #140
    Forum Veteran NavLinear's Avatar
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    Quote Originally Posted by oldphaser View Post

    Anytime I see anyone on ebay selling matched transistors, I always want to know more about what means or methods they used. What voltage and current they used and the manufacturer and the model numbers of the test equipment they are using.

    In the case of gain/beta matching of the pre-drivers (i.e. 2N3440 and 2N5415/6's), I am not sure that you will find any measurable improvements if you tested the amplifier to its manufacturer's claims.

    In the case of the first and second differential pair transistors (i.e. TIS97 and MPSA93's), if you match the transistors, you will see a difference in: 1.) dc offset (albeit, as Lee has already mentioned the PL0171 pc board has adjustable dc offset trimpots) and 2.) turn-off thump. Lee has shared on the Phoenix forum a simple technique (I have seen best used for low power transistors) using a digital multimeter; measuring the transistor junction resistances and closely matching the results (between any two transistors) that works quite well. Perhaps Lee can provide a link to this technique.

    Ed
    Ed - here's a link to Joe's bipolar transistor grading thread:

    http://forums.phxaudiotape.com/showt...sistor+grading
    If you get offended by the jokes and comments on here, go ahead and blame your parents... for raising a pussy.

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