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PL-700 OTW
- Thread starter VSAT88
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- Joined
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Thanks Lee. Testing and organizing the parts shipments today. Going to take value for value on that main board and jot them all down. Trying to plot every part on an image using Microsoft paint with the values printed on the image. I am also going to do my best to take the best schematic I have and print the values on it legibly. It will take a while but it will be worth it for someone down the line.
Here is a preview of what I am trying to do. On this board only diodes are marked. I will probably do one board with diodes, one with resistor values and another board with capacitor values and another with transistors.
Eeek, looks like I have more work to do. When I uploaded it and I view it afterwards I cannot see the numbers I marked on the board...
Eeek, looks like I have more work to do. When I uploaded it and I view it afterwards I cannot see the numbers I marked on the board...
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Am I going to have to go to Fastenal and get SS cap screws with the marks on them to fasten my faceplate on or do you guys know a source for original ones. The guy I bought it from thought it would be a good idea to put zinc plated phillips head screws on it...Arrrgggg. I don't even know where you could get a philips head screw that big !
Lee, is this still so ? http://forums.phxaudiotape.com/showthread.php/2280-2N1304-2N1305-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-LINE...490699?hash=item41dc55e40b:g:gesAAOxyaTxRQnHl Should I just buy these ? 
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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...
Your call bud....you can rebuild him, you can make him better...........
Your call bud....you can rebuild him, you can make him better...........
- Joined
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Lee, is this still so ? http://forums.phxaudiotape.com/showthread.php/2280-2N1304-2N1305-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-LINE...490699?hash=item41dc55e40b:g:gesAAOxyaTxRQnHl Should I just buy these ?
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
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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 .
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
P
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
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
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
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
Ed - here's a link to Joe's bipolar transistor grading thread:
http://forums.phxaudiotape.com/show...-grading?highlight=bipolar+transistor+grading
http://forums.phxaudiotape.com/show...-grading?highlight=bipolar+transistor+grading