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    Please help me finish my PAS-2 upgrade

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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Sun Dec 16, 2018 6:12 am

    None test as fried. They all go well into the "Good" areas on both of my tube testers (an Eico 666



    and a B&K 600)



    But then, where's the guarantee that they are reliable Quis custodiet ipsos custodes?

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    peterh

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    Re: Please help me finish my PAS-2 upgrade

    Post by peterh on Sun Dec 16, 2018 6:52 am

    Forget the tube tester, get a few ecc83 , any brand but new and move them around instead.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Sun Dec 16, 2018 8:25 am

    "Getting" a few means ordering them from the U.S. or from Europe.  So, I've ordered 4 tubes (JJ ECC803S) for $14 each from thetubestore.com, and I'm waiting for
    them to send me an international shipping quote. These tubes cost $31 each if ordered from a Brazilian distributor.
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    peterh

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    Re: Please help me finish my PAS-2 upgrade

    Post by peterh on Sun Dec 16, 2018 10:36 am

    billinrio wrote:"Getting" a few means ordering them from the U.S. or from Europe.  So, I've ordered 4 tubes (JJ ECC803S) for $14 each from thetubestore.com, and I'm waiting for
    them to send me an international shipping quote.  These tubes cost $31 each if ordered from a Brazilian distributor.
    That's very expensive ! I sell them for app. $12
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Sun Dec 16, 2018 3:44 pm

    peterh wrote:
    billinrio wrote:"Getting" a few means ordering them from the U.S. or from Europe.  So, I've ordered 4 tubes (JJ ECC803S) for $14 each from thetubestore.com, and I'm waiting for
    them to send me an international shipping quote.  These tubes cost $31 each if ordered from a Brazilian distributor.
    That's very expensive ! I sell them for app. $12

    Well, perhaps I should buy them from you. I should probably go ahead a get a 12X4 as well, if you have one. Thetubestore wants $21 for shipping to Brazil.
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    peterh

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    Re: Please help me finish my PAS-2 upgrade

    Post by peterh on Sun Dec 16, 2018 4:01 pm

    billinrio wrote:
    peterh wrote:
    billinrio wrote:"Getting" a few means ordering them from the U.S. or from Europe.  So, I've ordered 4 tubes (JJ ECC803S) for $14 each from thetubestore.com, and I'm waiting for
    them to send me an international shipping quote.  These tubes cost $31 each if ordered from a Brazilian distributor.
    That's very expensive ! I sell them for app. $12

    Well, perhaps I should buy them from you.  I should probably go ahead a get a 12X4 as well, if you have one.  Thetubestore wants $21 for shipping to Brazil.
    The $12 to $14 is no big thing, i guess that shipping to brazil plus toll & taxes will be a large amount.
    As for 12x4 : if you think of pas, then 2 1n4007 ( or un4007) is a good alternative. They
    will also save valuable power from the small transformer.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Sun Dec 16, 2018 10:47 pm

    peterh wrote:
    As for 12x4 : if you think of pas, then 2 1n4007 ( or un4007) is a good alternative. They
    will also save valuable power from the small transformer.

    I've read that the easiest way to replace the 12X4 tube is 2 1n4007 diodes soldered on the tube socket. Do you recommend this? If so, where would the diodes be placed on the tube socket?
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    peterh

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    Re: Please help me finish my PAS-2 upgrade

    Post by peterh on Mon Dec 17, 2018 3:52 am

    billinrio wrote:
    peterh wrote:
    As for 12x4 : if you think of pas, then 2 1n4007 ( or un4007) is a good alternative. They
    will also save valuable power from the small transformer.

    I've read that the easiest way to replace the 12X4 tube is 2 1n4007 diodes soldered on the tube socket.  Do you recommend this?  If so, where would the diodes be placed on the tube socket?
    As you power board had place for the diodes there , solder them there and move the
    transformer leads there. ( as i understood some previous comments). UF4007 ( not un4007 as i
    wrongly wrote) has less noice emited and would be better)
    In any case, mounting them on the power board could be neater and cold allocate place
    if snubbers is needed. But keep your 12x4 rectifier until you really need to replace it !
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    Peter W.

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    Re: Please help me finish my PAS-2 upgrade

    Post by Peter W. on Mon Dec 17, 2018 8:59 am

    http://tone-lizard.com/eico-666/

    On the Eico-666. Withal, a decent emissions-tester with a few additional features. However, it gangs dual-triodes, at least per this article.

    Ultimately, the best test for any given tube that has been cleared for shorts and gas is the equipment it serves. But be sure that you have cleared it for shorts and gas. That is something the Eico does fairly well.

    Agreed in making the new cap board serve as the B+ rectifier as well. One less load on the transformer.

    No where in Brazil for ECC83/12AX7 or any of their clones? That does seem surprising as I have found them reasonably easily from Dammam to Istanbul. But, then, I have not been to Rio, or even south of Costa Rica.

    Best of luck!
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Mon Dec 17, 2018 9:44 am

    So, I'll install the 2 diodes on the cap board, and then move the two red transformer wires from pins 2 & 6 of the 12X4 to the inputs marked "RED" on the cap board.  I assume that since the 12X4 is no longer receiving power, that the wire from pin 7 of the 12X4 to the cap board and the two wires that right now go from pins 3&4 of the 12X4 to the cap board are eliminated.

    Its not that there aren't any 12AX7 available in Brazil.  None from local merchants, of course, but there's the internet. The problem is the cost.  Here's an example from the Brazilian equivalent of eBay:



    That's 38 dollars for a tube that's around $10 in the U.S., plus the guy wants 10 dollars more in order to ship it to me from Rio (about 260 miles).
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    peterh

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    Re: Please help me finish my PAS-2 upgrade

    Post by peterh on Mon Dec 17, 2018 10:15 am

    billinrio wrote:So, I'll install the 2 diodes on the cap board, and then move the two red transformer wires from pins 2 & 6 of the 12X4 to the inputs marked "RED" on the cap board.  I assume that since the 12X4 is no longer receiving power, that the wire from pin 7 of the 12X4 to the cap board and the two wires that right now go from pins 3&4 of the 12X4 to the cap board are eliminated.

    Its not that there aren't any 12AX7 available in Brazil.  None from local merchants, of course, but there's the internet. The problem is the cost.  Here's an example from the Brazilian equivalent of eBay:



    That's 38 dollars for a tube that's around $10 in the U.S., plus the guy wants 10 dollars more in order to ship it to me from Rio (about 260 miles).

    You might do a decent extra cash by importing from JJ and reselling them in brazil.
    Contact them and ask for conditions and a pricelist.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Mon Dec 17, 2018 10:44 am

    peterh wrote:
    billinrio wrote:So, I'll install the 2 diodes on the cap board, and then move the two red transformer wires from pins 2 & 6 of the 12X4 to the inputs marked "RED" on the cap board.  I assume that since the 12X4 is no longer receiving power, that the wire from pin 7 of the 12X4 to the cap board and the two wires that right now go from pins 3&4 of the 12X4 to the cap board are eliminated.

    Its not that there aren't any 12AX7 available in Brazil.  None from local merchants, of course, but there's the internet. The problem is the cost.  Here's an example from the Brazilian equivalent of eBay:



    That's 38 dollars for a tube that's around $10 in the U.S., plus the guy wants 10 dollars more in order to ship it to me from Rio (about 260 miles).

    You might do a decent extra cash by importing from JJ and reselling them in brazil.
    Contact them and ask for conditions and a pricelist.

    The problem is the 100% customs charge that the government collects in order for someone to legally import this kind of merchandise. And then, in order to open any kind of business (even a one-person micro business) there are all kinds of hoops to be jumped through for licenses, including the need to employ a certified accountant. No wonder Brazil ranks very high in terms of difficulties to do business.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Mon Dec 17, 2018 11:47 am

    Bear in mind you previously reported that tekdevice has not "officially" sanctioned connecting diodes to that board to eliminate the 12X4. They referred to it as something like a testing point or something like that. The traces should be checked for continuity to make sure they go where they should.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Mon Dec 17, 2018 3:19 pm

    Thanks for reminding me of that. How does one go about checking the traces for continuity?

    Also in regard to the PC-6 board, there's a comment on this board from Bob that says the following:
    "If you have a PAS-2 or PAS-3 preamp and also use the phono section you may be interested in upgrading the RIAA equalization which (with stock parts) departs from the "ideal" equalization by + or - 2 dB. Also consider that the small value stock picofarad caps have probably drifted from their original values by as much as 50% in the past 40+ years which could now result in as much as a + or -4 dB drift from the ideal equalization curve. The steps are outlined below and the schematic shown at the bottom has red dots where the changes are to be made.

    1. Remove the 750pf caps from the selector switch on both channels. 
    2. Remove the 27K (red/violet/orange) resistors from the selector switch on both channels.
    3. Replace the 68pf caps on the PC-6 pc board with 820pf silver mica caps. 
    4. Parallel the 100K resistor with a 2 Meg metal film resistor
    5. Replace the 2750pf cap with a parallel combination of 2200pf and 470pf. 
    6. Replace the 4.7Meg resistors with 2 Meg metal film resistors
    7. Replace the two .1uF caps connected between terminals 1 & 3 (left channel) and 7 & 9 (right channel) with a larger .33 or .47 cap at 400 volts or higher.

    If you do the changes above your RIAA equalization should now be off no more than .3dB (3/10 of a dB) of the ideal equalization."

    In regard to suggestion No.5, my board already has 2700 pf caps, so I'm not sure if doing what he says and thus having 2670 pf would make any difference.
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    peterh

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    Re: Please help me finish my PAS-2 upgrade

    Post by peterh on Mon Dec 17, 2018 4:43 pm

    billinrio wrote:Thanks for reminding me of that.  How does one go about checking the traces for continuity?

    Also in regard to the PC-6 board, there's a comment on this board from Bob that says the following:
    "If you have a PAS-2 or PAS-3 preamp and also use the phono section you may be interested in upgrading the RIAA equalization which (with stock parts) departs from the "ideal" equalization by + or - 2 dB. Also consider that the small value stock picofarad caps have probably drifted from their original values by as much as 50% in the past 40+ years which could now result in as much as a + or -4 dB drift from the ideal equalization curve. The steps are outlined below and the schematic shown at the bottom has red dots where the changes are to be made.

    1. Remove the 750pf caps from the selector switch on both channels. 
    2. Remove the 27K (red/violet/orange) resistors from the selector switch on both channels.
    3. Replace the 68pf caps on the PC-6 pc board with 820pf silver mica caps. 
    4. Parallel the 100K resistor with a 2 Meg metal film resistor
    5. Replace the 2750pf cap with a parallel combination of 2200pf and 470pf. 
    6. Replace the 4.7Meg resistors with 2 Meg metal film resistors
    7. Replace the two .1uF caps connected between terminals 1 & 3 (left channel) and 7 & 9 (right channel) with a larger .33 or .47 cap at 400 volts or higher.

    If you do the changes above your RIAA equalization should now be off no more than .3dB (3/10 of a dB) of the ideal equalization."

    In regard to suggestion No.5, my board already has 2700 pf caps, so I'm not sure if doing what he says and thus having 2670 pf would make any difference.

    There is different opinions regarding this. George rennenkamp made a serious analyze :
    http://www.audioregenesis.com/documents/PAS_Phono.pdf

    According to this analyze there is nothing wring with the PAS RIAA equalization.
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    Peter W.

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    Re: Please help me finish my PAS-2 upgrade

    Post by Peter W. on Mon Dec 17, 2018 5:07 pm

    SNARK WARNING




    billinrio wrote:Thanks for reminding me of that.  How does one go about checking the traces for continuity?

    Also in regard to the PC-6 board, there's a comment on this board from Bob that says the following:
    "If you have a PAS-2 or PAS-3 preamp and also use the phono section you may be interested in upgrading the RIAA equalization which (with stock parts) departs from the "ideal" equalization  >SNIP<.

    One piece of advice:

    DO one (1) thing at a time. Not three-or-more. Such leads to madness. Fix this pre-amp to full working order before haring down dubious rabbit holes.

    And, we have an excellent demonstration of the fallacy of begging the question (to be distinguished from false premises).

    IF.... MAY BE INTERESTED.... DEPARTS FROM.... COULD RESULT.... so do this....

    Classically, Begging the Question draws a conclusion from unproven (not patently false) premises.
    "which departs from". No, OEM and all-parts-to-spec., the PAS phono section is very close to the ideal RIAA curve.
    "may have drifted" - in point-of-fact, the pF caps used were very robust. And if the premise is to be tested in any case, then put OEM values in place, not entirely different values.

    I call BS on this one.

    For checking traces for continuity, just that. I have very 'pointy' probes for my Fluke that I can dig right into the traces.

    https://www.zoro.com/fluke-test-probes-blackred-10a-1000vdc-pr-fluke-tp220/i/G1339003/
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Mon Dec 17, 2018 5:21 pm

    Peter W. wrote:
    SNARK WARNING

    Fix this pre-amp to full working order before  ...

    Ah, that is indeed the consummation devoutly to be wished.  For me, that translates into getting the voltages within 10% of spec .... well, maybe 20%.

    I have a very similar set of very pointy probes, which I will use.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Mon Dec 17, 2018 9:16 pm

    Quoting from the Erhard Audio website http://www.erhard-audio.com/Preamp_Kits.html regarding their PC5/PC6 clones: "The circuit and PCB layout are almost identical to the original Dynaco PC5 and PC6, but we have made some slight changes to the RIAA component values on the PC6 phono preamp to improve its performance."

    So, your Erhard PC6 board has already departed to some extent from the original PC6.  This might require some sort of change or changes to the parts on the selector switch.  If so, specific instructions should have been included with your replacement phono board.  If there are changes that needed to be done and you did not do them, or do them properly, then all bets are off for sonic performance.

    I agree that you should only do one thing at a time.  You have bigger fish to fry.
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    erhard-audio

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    Re: Please help me finish my PAS-2 upgrade

    Post by erhard-audio on Mon Dec 17, 2018 9:55 pm

    PeterCapo wrote:Quoting from the Erhard Audio website http://www.erhard-audio.com/Preamp_Kits.html regarding their PC5/PC6 clones: "The circuit and PCB layout are almost identical to the original Dynaco PC5 and PC6, but we have made some slight changes to the RIAA component values on the PC6 phono preamp to improve its performance."

    So, your Erhard PC6 board has already departed to some extent from the original PC6.  This might require some sort of change or changes to the parts on the selector switch.  If so, specific instructions should have been included with your replacement phono board.  If there are changes that needed to be done and you did not do them, or do them properly, then all bets are off for sonic performance.

    I agree that you should only do one thing at a time.  You have bigger fish to fry.

    nope, no other changes need to be done to any other parts of an original PAS, otherwise we would have added that to our instructions :-)
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Mon Dec 17, 2018 10:01 pm

    Well, that's good to know.  However, looking at the image in Post n°4, I believe I do see at least two non-original parts installed on the selector switch.  A subject for Bill to expound upon, later.
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Mon Dec 17, 2018 10:05 pm

    billinrio wrote:Thanks for reminding me of that.  How does one go about checking the traces for continuity?

    Of course, you need to know how to interpret the continuity.  You have to be able to tell if the continuity you are measuring matches the schematic, in this case, for the portion of the circuit containing the two diodes replacing the 12X4. It's actually pretty simple.
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    billinrio

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    Re: Please help me finish my PAS-2 upgrade

    Post by billinrio on Tue Dec 18, 2018 7:43 am

    PeterCapo wrote:
    billinrio wrote:Thanks for reminding me of that.  How does one go about checking the traces for continuity?

     It's actually pretty simple.

    "Simple" is relative, or course.  A matter of experience and study. I think that speaking, reading, and writing Portuguese is really easy.  Most people, who either haven't resided in one of the ten countries where it's spoken or haven't studied it extensively, can't make heads or tails of it. scratch  You can glance at a circuit diagram and immediately know what's going on in it, while for me it looks like something carved on the wall of an Egyptian tomb.
    For continuity I can, however follow the instructions provided by Fluke https://www.fluke.com/en/learn/best-practices/test-tools-basics/digital-multimeters/how-to-test-for-continuity-with-a-digital-multimeter
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    PeterCapo

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    Re: Please help me finish my PAS-2 upgrade

    Post by PeterCapo on Tue Dec 18, 2018 12:23 pm



    billinrio wrote:... for me it looks like something carved on the wall of an Egyptian tomb.
    Here's a lesson in hieroglyphics, then.  This procedure assumes there are no diodes yet installed in the D1 and D2 locations.  CN1-2 and CN1-3 are terminals on the cap board - the little circles are the terminals.  The horizontal lines proceeding to the right represent circuit traces.  The traces from CN1-2 and CN1-3 arrive at diodes D1 and D2, respectively.   Diodes D1 and D2 appear to be what could replace your 12X4.  Note the diodes look like arrowheads with a vertical line at the point of the arrow.  The left ends of the diodes (connected to CN1-2 and CN1-3) are referred to as their anodes.  The right end of the arrowheads with their respective vertical lines are their cathodes.  The cathodes of D1 and D2 are connected by circuit traces to fuse F1, which in-turn connects to the + side of C1 as well as to the one end of R1.

    What you need to do is to verify the indicated traces are intact (continuity test) from CN1-2 and CN1-3 terminals respectively to the pads [apparently intended] for the anodes of the respective diodes D1 and D2.  Then, make sure the pads [apparently intended] for the cathodes of both diodes are both connected to the fuse, which might be easier to check at the + end of C1 or the one end of R1.  Also, again without having D1 and D2 actually installed, make sure the pads for the anodes of D1 and D2 respectively are at open circuit to the pads for the cathodes as far as the board is concerned.  Should you install the diodes at some point, they will make a circuit between these respective pads.  But, while they are not installed, there should be no connection from the pads for their respective anodes to the pads for their cathodes.  

    Yes, your wire to CN1-1 should be disconnected if D1 and D2 are installed into the board.

    A caveat... IMO, given the difficulties you have had, the circuit arrangement of your tekdevice cap board is not cleared of suspicion.  The procedure above, along with any attempt to use D1 and D2 as replacement for the 12X4, relies upon the board actually matching the schematic.  You had previously reported that the sellers of this tekdevice board referred to CN1-2 and CN1-3 as "test points," or something like that.  Who knows what that might mean in terms of how the traces are actually arranged on the board.  Even if the continuity checks described above are okay, traces from these "test points" might possibly run off to other places not indicated on the schematic, depending on what tekdevice had in mind.  Everything taken together, proceeding with D1 and D2 could be risky.  Of course, it's your call.

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