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Head adjustment; do I need to?

Discussion in 'Tech talk' started by 16s, Dec 3, 2017.

  1. 16s

    16s Member

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    hi, I think I am missing some treble response on my DD30. Also there seems to be a channel imbalance, (more in the left channel). Can I change this by using the screws on the head assembly? Does the head look wrong in the pic here?
    7506ED43-4655-4790-B8EB-06B5BFD4E0BF.jpeg
    The head on my DD33 isn’t tilted on right side with the adjustment screw like my DD30. Please can you give me some advice?
    Thanks a lot.
    Rich
     
  2. enryfox

    enryfox Active Member

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    In the DD walkman's there are just two adjustments for the tape path (actually three, but head height is complex to adjust): the black plastic tape guide and head azimuth. The tape guide is typically correct and if there is still lock paint on the screw I would not touch it; head azimuth can be adjusted to increase treble response. The screw is located opposite to the tape guide soldered on the head (referring to your picture, on the right on the head); remove the cassette door from the walkman and use a non-magnetised philips screw-driver. To align azimuth a reference tape with a 10 kHz tone recorded full track would be required, but for a playback only machine you can use some pre-recorded cassettes; adjust the screw to find a position where treble response is max. Use good quality pre-recoded cassette and test the adjustment using 3~4 tapes.

    Channel unbalance is hardly caused by tape path misalignment, unless the tape path is so off as to damage the tape itself. The DD30/33 do not have internal levels adjustment and in case of unbalance the problem is likely in the head. A full track tape with a 1 kHz tone and an oscilloscope would be required to correctly diagnose the problem.
     
  3. bub

    bub Active Member

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    Could you get a better picture of the head? Something looks off about the surface from that photo.
     
  4. 16s

    16s Member

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    Here are a couple more pics
    58278922-7B85-41C3-8302-65A9F3F3FD2D.jpeg
    746376A8-5E9D-4732-B9DB-6149ED15654A.jpeg
    12399A79-336A-4930-9ECA-2A18B43BC4D5.jpeg
     
  5. bub

    bub Active Member

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    I think I see a tiny amount of pitting on your DD head, and if any of those tiny pits are on the head gap you might get a loss in high frequencies on the channel the pit is over. Let's try an experiment. Can you record the following tones on a known good deck: 440hz, 1000hz, 10,000hz.
    Connect your Walkman to a PC line in and download a digital level meter app. Verify the tones you recorded are level between the left and right channels on the original deck and then play it back on your DD, and see if the level imbalance is across all the tones or only the highs.

    If your highs are lost due to pitting, you have 2 options: replace the head or Lap it with Lapping film. I recently had to do that to some of my machines as some defective Sony CDIT damaged my heads and caused pitting. Lapping will even out the pitted head surface (especially at the head gap) and restore performance.
     
  6. enryfox

    enryfox Active Member

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    Can a tape damage the head ? I mean, over time the repeated listening of tapes wears the head like a very fine sandpaper, but how can a single batch of tapes cause dip and pit on a head ?
    I have a DDIII with a damaged head, but it is mostly due to use and ageing in a head with metallurgic imperfections prone to wear.

    On the DD there is no specification for the equalisation , so I guess that if the 10kHz tone is within +/- 3 dB of the low frequency tones it will be more than fine.
    Anyway the head appears to be too tilted, I would check the azimuth first and see how much that improves.
     
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  7. bub

    bub Active Member

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    I believe it is chemical erosion! Look up my thread "CDITs destroyed my heads" on tapeheads. It's the only case I've ever seen.
     
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  8. 16s

    16s Member

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    Thank you both @bub and @enryfox . I will perform a tone test and also attempt to adjust the azimuth. The other thing I have to do is open up the DD30 (again!!) and apply some contact cleaner to the volume potentiometer because when I adjust the volume it crackles and sometimes a channel disappears.
     
  9. enryfox

    enryfox Active Member

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    I would first adjust azimuth and then do the tones test; adjusting the azimuth is much easier than what it seems, also you do not have to be too precise as anyway the head mount assembly does not ensure a too stable azimuth. Just look for the strongest and most balanced high frequency and you will surely have adjusted the azimuth within +/- 60 degrees.
     
  10. Strangelove

    Strangelove Member

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    If you don't mind dropping some IPA in there that's a possibility. Turn the volume pot as you do.
    I was too lazy to open up the 701C a sixth time so that's how I fixed that horrible crackling noise those Walkman with an overly exposed volume pot tend to have.
     
  11. 16s

    16s Member

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    I think i have to drop the IPA into the volume pot side with the small gap on the DD30. Not that easy, but i will try it. Thanks
     
  12. Strangelove

    Strangelove Member

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    That's what I meant. I used a Q-tip imbued with IPA and pressed it a bit against the casing. There is a slight gap between the case and the volume knob, where you can clearly see the actual potentiometer (being exposed that much probably amplifies the need for proper cleaning).

    If your pot is really dirty or oxidised , proper disassembly will still be required of course.
     
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  13. 16s

    16s Member

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    I assembled the DD30 again to get access to the volume pot module. I took the volume wheel off and sprayed electrical contact cleaner into the 3 little"holes" on the board mounted volume module, reattached the wheel and moved it around to get the cleaner working. I reassembled, played a known tape and adjusted the azimuth to where my ears could tell the treble was at its full extent. All good.
    The walkman defintely sounds better except that the i still have a channel problem and i think its related to the volume adjust. Sometime if i nudge the vol wheel i loose a channel, sometimes it crackles, sometimes at volume i actually get both channels properly... :hmmm
    So what do i do? Can the volume module be unsoldered from the board and replaced? I have a donor DD30 and DD33 so i have spare volume modules but I'm not confident in my poor soldering skills......:nonoplease

    What should i do????? Please advise.

    Thanks, Rich
     
  14. bub

    bub Active Member

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    Alcohol won't fix this. Try Deoxit D5 (from a syringe) or Deoxit Faderlube (tube). It will change the feel of the pot but it is usually a 100% fix for me if it's not a bad solder connection. Check the legs of the pot, head connection wires.

    Edit: If it is the pot tracking badly, my DDs do not track 100% linearly below volume 4. What volume are you listening at? Can you record a 315hz tone on a good deck and check the tracking of the pot by hooking it up to your computer and using a level meter? Check your soundcard's balance with a good source to make sure it's accurate.
     
    Last edited: Dec 10, 2017
  15. 16s

    16s Member

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    @bub i didnt use alcohol i used Servisol Switch Cleaner but still the pot is not working properly. I hate to say it but i think the volume pot will have to be replaced. Is that a job for a soldering expert?...which i am not!!!!
     

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