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    ALPS volume control replacement on PAS3

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    alyosha

    Posts: 19
    Join date: 2012-04-23

    ALPS volume control replacement on PAS3

    Post by alyosha on Mon Apr 23, 2012 3:34 pm

    Hi,
    I have a question related to the topic title and I hope someone will be able to bring some help.
    I'm trying to change the original PAS3 volume control with an ALPS 'blue' 250k potentiometer while bypassing loudness and can't figure out how to reconnect everything. For info, the ALPS connection tips are numbered 1-2-3.
    Thanks in advance for your replies.

    Best,
    Alyosha

    tubes4hifi
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    Re: ALPS volume control replacement on PAS3

    Post by tubes4hifi on Mon Apr 23, 2012 5:57 pm

    there are 3 connections to each half of a stereo volume control (the old ones had a 4th connection for a loudness filter, which isn't needed).
    1 is input, 2 is output, 3 is ground.
    Looking at the front of the control, the left pin is the input, the center pin the output, and the right pin is ground.
    The input will come either from the output of the selector or the output of the balance control, depending on how those are already wired.
    If you haven't taken the original control out, the new one will connect identical, other than the unused connection to the loudness switch, which is just a capacitor to ground and doesn't need to be connected.
    If that explanation doesn't work, you can download the original PAS3 manual and look at the diagrams.

    alyosha

    Posts: 19
    Join date: 2012-04-23

    Re: ALPS volume control replacement on PAS3

    Post by alyosha on Tue Apr 24, 2012 1:24 am

    Hello and thank you so much for your reply. I will try again based on your comments.
    If I understand correctly, my PAS being a factory wired one, should I exactly follow the original diagram? The reason I'm asking is because I saw on a new volume control modification chart that 2 wires should be connected to PC5 n°1, one from lug 1 and another from lug 4 of the volume pot, hence my confusion.
    Thanks again!

    tubes4hifi
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    Re: ALPS volume control replacement on PAS3

    Post by tubes4hifi on Tue Apr 24, 2012 10:16 am

    without looking at the exact diagram you are talking about, I can't answer that question. But #1 on the PC5 is ground, so it sounds like your diagram has lugs 1 and 4 of the volume control going to ground, and that is likely correct, especially if the lugs are numbered in reverse order of what I put in my last response (so . . . 1 and 4 are ground, 2 and 5 are outputs, 3 and 6 are inputs?)
    It all depends on which way you look at it . . . . that's why I don't like to use written instructions, they are subject to interpretation.
    Anyone have a photo? A photo is good for one thousand useless words . . . .

    alyosha

    Posts: 19
    Join date: 2012-04-23

    Re: ALPS volume control replacement on PAS3

    Post by alyosha on Tue Apr 24, 2012 11:32 am

    Hi, mine follows exactly the one on this forum link:
    http://dynacotubeaudio.forumotion.com/t432-pictorial-diagram-for-dynaco-pas3

    Now, what I've found browsing the web and related to #1 on the PC5 is in a pdf document on a site named curcio audio.
    I've tried to rewire everything today based on the original wiring and it still does not work so... any additional input is welcome.
    Thanks again.

    alyosha

    Posts: 19
    Join date: 2012-04-23

    Re: ALPS volume control replacement on PAS3

    Post by alyosha on Wed Apr 25, 2012 5:02 pm

    can't figure it out, I rewired everything based on the original diagram but there is a lot of 'buzz' in the speakers. I placed the alps potentiometer with the connecting pins on the right side (looking at the preamp from the front panel). Could it be an issue of value, 250k being too much? Thanks.

    tubes4hifi
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    Re: ALPS volume control replacement on PAS3

    Post by tubes4hifi on Wed Apr 25, 2012 6:17 pm

    can you take a good close up photo of the control and how it's connected?

    alyosha

    Posts: 19
    Join date: 2012-04-23

    Re: ALPS volume control replacement on PAS3

    Post by alyosha on Thu Apr 26, 2012 3:48 am

    Here it is, hope this helps.


    And below is a pic of how it was originally.


    As one of the new vc pins broke, I soldered a different one (green wire on #2 pin). Now, the speaker buzz I mentioned earlier is even more prominent when I touch this very wire while both amp and preamp are on and no source is connected... soldering issue ?
    Thanks again.

    tubes4hifi
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    Re: ALPS volume control replacement on PAS3

    Post by tubes4hifi on Thu Apr 26, 2012 10:47 am

    I couldn't make out all the connections from the photo, so I finally gave up and looked at the PAS3 manual, which I hate looking at,
    one thousand words to describe what a diagram shows. See drawing below.
    Make sure all the grounds are connected together and to eyelet 1 on the PC5 board.


    alyosha

    Posts: 19
    Join date: 2012-04-23

    Re: ALPS volume control replacement on PAS3

    Post by alyosha on Thu Apr 26, 2012 11:20 am

    Thank you so very much for your help and time.

    Just to make sure I do not misread your diagram, based on the alps pin numbers of the first pic I posted (numbers 1-2-3 from bottom to top):

    - all black wires/grounds on 'pin #1 front' including PC5 #1 ?
    - any black wire/ground on 'pin #1 back' of vc pot ?

    Thanks again!

    anbitet66

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    Re: ALPS volume control replacement on PAS3

    Post by anbitet66 on Thu Apr 26, 2012 11:21 am

    Unless my eyes are playing tricks on me, I think the problem is the original wiring was each row had a black wire (ground) then signal wires. Depending on the row, it was blk, grn, grn; then blk, red, red. The wiring now looks like blk, grn, red in each row. try to put the wires as the above diagram shows from tubes4hifi indicates and the color scheme should return to what it formerly was.

    alyosha

    Posts: 19
    Join date: 2012-04-23

    Re: ALPS volume control replacement on PAS3

    Post by alyosha on Thu Apr 26, 2012 11:46 am

    Thanks.
    Actually, current wiring from VC is blk-grn-grn (front) then blk-red-red (back). As it is now, 3 black wires are connected :
    - one going from 'pin 1 front' of VC to 'pin 1 back' of bal,
    - one from 'pin 1 front' of VC to pin 1 front of bal,
    - one from pin 1 back of VC to PC5 #1.
    Now, from my reading of tubes4hifi's diagram, it is unclear to me what exactly is connected to pin 1 of VC, front and back.

    tubes4hifi
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    Re: ALPS volume control replacement on PAS3

    Post by tubes4hifi on Thu Apr 26, 2012 12:07 pm

    I didn't number my diagram because I was running out of space, but on my drawing it would be numbered from top to bottom,
    1 to 3 on the front section and 4 thru 6 on the rear section
    the original Dynaco drawing is numbered the same, except that the loudness taps are numbered 4 and 8,
    which changes the numbering of the volume control rear section to 5 thru 7 instead of 4 thru 6.
    So, on my diagram he balance control top front #1 and bottom rear #6 are ground,
    and volume control bottom front #3 and bottom rear #6 are grounded.
    Balance #2 goes to volume #1, and balance #5 goes to volume #4.
    All balance and volume controls are wired like this.
    One end is ground, center is output (wiper), and other end is input.
    If I had a PAS3 here I could take a photo for you, it's very very simple.
    OH . . now looking at your photo, I see your ALPS pot is actually labeled 1-2-3 in the reverse order of my drawing.
    On the ALPS, pins 1 and 4 are ground, the inputs are on pins 3 and 6.
    I've got some old photos of ALPS volume/balance pots here: http://tubes4hifi.com/SP8-AM3.htm

    tubes4hifi
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    Re: ALPS volume control replacement on PAS3

    Post by tubes4hifi on Thu Apr 26, 2012 12:19 pm

    from your photo and my photo, looks like yours might be wired correctly, but it's hard to see some of your connections.
    I can clearly see that the original pot was wired correctly.

    alyosha

    Posts: 19
    Join date: 2012-04-23

    Re: ALPS volume control replacement on PAS3

    Post by alyosha on Thu Apr 26, 2012 12:40 pm

    which connections can't you see well?
    OK, this is exactly how it is wired now on the alps, using 1-2-3 numbering front and back on the alps and bal from bottom to top (as on posted alps pic):

    2 on PC5 to 2 front on vc (green)
    1 on PC5 to 1 back on vc (black)
    9 on PC5 to 2 back on vc (red)
    3 back of bal to 1 front on vc (black)
    2 back of bal to 3 back on vc (red)
    2 front of bal to 3 front on vc (green)
    3 front of bal to 1 front on vc (black)



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