Marantz 6300 Project

Discussion in 'Marantz Audio' started by Echoplex, May 2, 2014.

  1. Echoplex

    Echoplex Active Member

    Messages:
    173
    Marantz 6300 Project

    Hello my fellow Marantz 6300 owners!

    I have a few questions regarding parts/switches for the 6300.

    Look at the photo of the bottom chassis. Notice the black micro-switches from Omron labeled (LV-3H-1A-S) 3A125.250V.A.C.
    [​IMG]

    In the schematic, the tonearm switches labeled S009 and S010 (ON/OFF switches) are the ones I am needing to replace.
    [​IMG]


    Before calling OMRON, thought I'd ask here on AK first.

    Anyone have any experience replacing these? If so, where did you find them? Thanks!
     

    Attached Files:

    Last edited: Aug 27, 2016

     

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  2. mcsew2k

    mcsew2k Active Member

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    I was curious what are the symptoms leading you to replace these switches. Can they cause quiet but substantial noise or hum if they are bad?

    Edit: S009 and S010 appear to be in the upper-left area of your first photo, where the pivot of the tonearm is.
     
    Last edited: May 2, 2014
  3. Echoplex

    Echoplex Active Member

    Messages:
    173
    Luckily, it isn't having any symptoms, but being that the switches are in the same signal path as the tonearm wire and rca, they're pretty important in the audio food chain of the circuit. I'm assuming that's why they have been tampered with in the past by the previous owner, but of course, that's just a guess at this point.

    The main reason why I want to replace them though is because one of them was damaged and glued back together, and the soldering joints on both switches look horrendous. It's hard to see from the photos, but it looks like a 3rd grader attempted it! lol
     
    Last edited: May 2, 2014
  4. restorer-john

    restorer-john Addicted Member

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    6,075
    Location:
    Australia
    Those microswitches have silver plated internal contacts and the silver tarnishes over time causing them to misbehave.
    The way they've wired it (your schematic) is also strange: the up position shorts the output- and that's normal.
    The down position connects the + from the cartridge to the centre pin of your RCA. It works, but you are relying on the contacts to be absolutely zero resistance with only a few mV- not enough to jump the oxide layer if you ask me. I'd wire it straight through and use the microswitch to short the cart/RCA in the up position like most other turntable cue/mute designs
     
  5. Echoplex

    Echoplex Active Member

    Messages:
    173
    Thanks John!

    I happen to have some spare Cardas Litz tonearm wire laying around, so it will eventually be put to good use. However, I would like to find new replacement switches before I attempt to rewire the tonearm connections as you've suggested.

    Take a look at the photos below. Got any ideas for suitable replacements on these? Thanks!

    Here's what I have:
    [​IMG]
    [​IMG]
    Sorry for the bad photos. My camera doesn't focus all that great up close.

    Switch has this printed on it:
    1615R
    LV-3H-1A-S
    3A125.250V.A.C.
     

    Attached Files:

    Last edited: Aug 27, 2016
  6. restorer-john

    restorer-john Addicted Member

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    6,075
    Location:
    Australia
    They are IIRC, very low actuation pressure microswitches. Are they really soft to press, compared to the others in the tt? They may look exactly the same as normal ones, but they are only a 3A contact rating, probably with the low actuation pressure as it's in the cue mechanism. I don't know Omron's codes, but somebody else might.

    dowload the brochure here:
    http://microsite.omroncomponents.com/microswitch/

    and work out the ones you want- then search the part number locally, they are about $2 each or so.
     

     

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  7. Echoplex

    Echoplex Active Member

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    Yes, mine do have low actuation force, although I wish I knew the exact figure? So far, I've not had much luck getting any detailed info on these rather elusive micro-switches; No data sheet. Nothing. Notta. Zip. All this for a lousy damn micro-switch???:dammit::D:D

    Anyway, I called Omron and talked to a product specialist; they don't have any knowledge and/or info on this part number (LV-3H-1A-S; 3A125.250V.A.C.) Hmmm....:scratch2: You'd certainly think they would being that they designed and manufactured it no? However, the product specialist did take my name/info and said he'd to look into it and get back to me, so perhaps I'll get answer here in the next few days.:music:

    In the meantime, I think I've found a suitable replacement: VX-5-1A2. It's a SPDT 5A 250VAC low actuation switch @ .25 N/25 gf. It's not exact, mind you, but will probably work fine. Heck, with the switches being $2.80 each, what have I got to lose?

    The funny thing is, I posted this thread on AK thinking, of all of the fine folks here @ AK that own the 6300, surely ONE of them will have a replacement part number and info right? ;) Nope. Guess I'm the guinea pig here. :D
     
    Last edited: May 6, 2014
  8. mcsew2k

    mcsew2k Active Member

    Messages:
    474
    Location:
    California
    :lurk:
     
  9. Echoplex

    Echoplex Active Member

    Messages:
    173
    Marantz 6300 upgrades/modifications

    FWIW, to those who are tuning into this thread, I am going to be undertaking and documenting a Marantz 6300 project in finite detail within the next few weeks. I'm waiting on new parts and shipments to arrive, hence the delay.

    My overall plan with the project is to post detailed photos, procedures I used, list the parts and provide an updated wiring schematic for the US/Canada models. My apologies to the international folks. To my knowledge, there are currently three different schematics that are in regular circulation on the web. Problem is, all three of them have minor mistakes on them, and the two US versions have different tonearm wiring diagrams, making it even more confusing for the newbies like me. HA!

    I will also be including detailed photos of the Auto Mode/Photo Unit (H002) circuit and where to find replacement parts for it etc. FYI - the service manual has a pretty thorough explanation into the circuits operation and provides part numbers, although they're old and outdated, so new component replacements will be helpful for those looking for answers. I've seen many threads on the web asking how to fix and/or adjust this, so thought I'd include it as well.

    This is going to be a lengthy project, but hopefully, will benefit those wanting to learn more about the 6300's internals and perhaps give them some ideas on how to approach it and in the end, make it sing! I do hope that lots of folks here will contribute to this project and share their insight as well, with the end-goal of the thread becoming a sticky, so everyone can get the answers they need.

    6300 Project Detail:
    • Rewire tonearm using Cardas/Litz OFC .33 awg
    • Dampen the tonearm internally using cotton sleeve
    • Install new custom RCA jack plate on back for removeable IC's
    • Install new Sumiko HS-12 Headshell w/litz leads (**)
    • Install new strobe light and resistor
    • Provide new wiring schematic (USA/Canada model)
    • Provide auto mode operation (possibly via video), adjustment and fixes etc.
    • Document & photograph all procedures used

      (**) HS-12 has adjustable azimuth, is slightly lighter than original headshell, and is also non-resonant. The result: better soundstage, less weight, less wear and tear on your records and more adjustment features = happy record owner and longer lasting records.

    By the way...

    I'm doing this project because I have micro-switches and tonearm wire that need serious attention due to the previous owner taking liberties where they probably shouldn't of, so that said, a modification is in order.

    Also, I'm not suggesting for a nanosecond that current 6300 owners should try or attempt to mod/tweak their equipment in any way. Like most of you, I'm here to learn and understand the science behind the circuits operating parameters and share with you what I find, as well as, learn from all of you too! However, if you're happy with your equipment the way it is, then by all means keep it that way.;)

    Lastly, I'd like to say that the community here @ AK is truly an awesome place to come and hang out and learn about audio. There are a ton of talented folks here lurking and posting all of the time. No joke. I'm amazed by their knowledge and know-how of electronics. I've learned way more here than I have studying circuits in school, so thankyou for that! :thmbsp:

    OK, I've written a novel. Sorry bout that...:D

    Stay tuned...
     
    Last edited: Jun 12, 2014
  10. Echoplex

    Echoplex Active Member

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    173
    Last edited: Aug 27, 2016
  11. mcsew2k

    mcsew2k Active Member

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  12. Echoplex

    Echoplex Active Member

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    Yes. I double-checked and they are for the whole unit.:yes:
     
    Last edited: May 7, 2014
  13. mcsew2k

    mcsew2k Active Member

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    474
    Location:
    California
    I see that the motor has e-caps inside. My first thought is don't touch the motor!
     
  14. Echoplex

    Echoplex Active Member

    Messages:
    173
    Yup, unless you really know what you're doing, I wouldn't advise it.
    Of course, there are those who may want a glorified doorstop. :D
     
  15. restorer-john

    restorer-john Addicted Member

    Messages:
    6,075
    Location:
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    That motor was used by a bunch of TT manufacturers in the 1970s. Hitachi had them in some of their TTs. Marantz did not manufacture the motor.
     
  16. restorer-john

    restorer-john Addicted Member

    Messages:
    6,075
    Location:
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    The same motor was also used on the Pioneer PL-71 and it is notorious (as in the hitachis too) for speed wandering.
    Firstly, you should lube the 33 and 45rpm speed trim pots under the motor cover and replace the electros, especially the three alongside the flag heatsinks for the coil driver transistors as they do dry out and get flaky. I'm not a wholesale recapper, but in these motors case, it is a good idea for speed stability.
     

     

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  17. Echoplex

    Echoplex Active Member

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    Good to know John. Thanks for the heads-up!

    Here's some photos I took of my Marantz 6300 motor. It has a date of Aug 1975 on the outer case, so it appears to be an early 1st gen model. Later on, Marantz updated these motors to IC types, though as usual, they left everything vague and didn't include any info in the schematics. Looks like I'm going to need to go cap shopping again.

    Version 1 motor: Transistor based design
    [​IMG]

    [​IMG]

    Version 2 motor: IC based design (AN620 Matsushita IC)
    [​IMG]
     

    Attached Files:

    Last edited: Aug 27, 2016
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  18. Echoplex

    Echoplex Active Member

    Messages:
    173
    Marantz 6300 Project: Part 1

    After spending two weeks on researching and locating replacement parts, I finally got started on my 6300 project.

    First, I went through and replaced all ten of the micro-switches with new equivalents from Omron. The old ones were fairly worn out and a few barely had any spring actuation left in them. As you can see, the new ones have a slightly longer lead and the common contact is located on the bottom side instead of being off to one side.

    Original switch: Omron LV-3H-1A-S (3A125.250VAC)
    [​IMG]

    Replacement switch: Omron VX-5-1A3 (5A125.250VAC)
    [​IMG]

    Next, I replaced the SCR (thyristor). I've been having trouble with my photo unit circuit due to the Automatic Shut-Off not triggering properly, so I went ahead and found this equivalent from ON semiconductor.
    Long story short; the collector on the phototransistor is coupled to the gate of the SCR, so as the collector voltage rises the gate voltage on the SCR also rises, thereby triggering the circuit to turn on.

    Original SCR (thyristor): NEC 2P1M
    [​IMG]

    Replacement SCR: ON Semi MCR72-3G
    [​IMG]
     

    Attached Files:

    Last edited: Aug 27, 2016
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  19. karltonkrill

    karltonkrill New Member

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    Iowa City, IA
  20. Echoplex

    Echoplex Active Member

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    173
    Marantz 6300 tonearm disassembly

    Finally, disassembled the tonearm tonight. I was initially having trouble getting the bayonet to come loose, so I reattached the headshell (unfastened) and gently twisted left to right, and out she came! There was a little glue around the outer perimeter of the bayonet joint as well, which is what made it so difficult to remove, but once I reattached the headshell it gave me just the right leverage to break the bayonet joint loose. Remember to be very careful here! DO NOT force it to come out or you'll be doing much more than replacing tonearm wire. Also, be very careful not to strip the setscrew here. Chances are high that it hasn't been touched since it left the factory, so make sure you use a tight fitting screwdriver and a firm amount of pressure so it doesn't slip on you.

    6300 tonearm assembly and associated parts.
    [​IMG]

    Close-up of the headshell bayonet and set screw. As you can see, there are four tiny little solder lugs for the tonearm wire. I'll be adding some small heat sink shields around each of the connectors like the Technics 1200 arm just for added protection and to minimize interference just in case. Also, I'll be adding a small cotton sleeve to dampen the tonearm internally.
    [​IMG]

    Close-up of the rear inner tonearm ground plate and set screw. You don't need to desolder this, so leave it as-is. As I said in an earlier post, the ground plate is very difficult to get back into place because it doesn't have a plug-style connector that positions it perfectly into place.
    [​IMG]
     

    Attached Files:

    Last edited: Aug 27, 2016
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