Marantz 7T Restoration

Discussion in 'Marantz Audio' started by CohibaJoe, Oct 13, 2017.

  1. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    Never saw an original.
    My guess would be the 3 Brown elna e caps and the 2 IC yellows?
     

     

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  2. jstang

    jstang Honey,I can't hear you... Subscriber

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    Have two 100% stock 7ts right now... 0ne is a very early one and one is a very late. There are 3 different versions. Each have a slight different sound. I have heard early, mid and late versions.... The later SM show the three different schematics. And there are slightly different shielding designs inside. Plus the earlier ones have a clear coat on the face plate and the later ones are bare anodized.

    I have a 3rd very early one that I use every day. It is highly modified in terms of caps but no changes to circuit or otherwise.

    The modified one is my favorite. They each have a different combination of transistors too. The late version is brighter compared to the early one, the early sounds more tube warm.... The mid version sounds more like the early one if I remember.

    Early, mid or late version ... They are great sounding in my opinion, provided they are in good shape...

    Johnk
     
  3. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Makes it easy to replace.

    Marantz7Tf.png
     

    Attached Files:

  4. jstang

    jstang Honey,I can't hear you... Subscriber

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    Maybe we Jersey boys should get a AudionKarma get together going..... This is a bunch of us.... After all, we are all "GoodFellas..."

    [​IMG]
     
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  5. nj pheonix

    nj pheonix AK Subscriber Subscriber

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  6. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Local get together would be good. I'm in on this....
     

     

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  7. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    You should ping in on the other thread.
    I'm not sure they know how much interest there is.
    Could be the difference between it happening and not happening
     
  8. nj pheonix

    nj pheonix AK Subscriber Subscriber

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  9. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Recording Output RAEF Board: 11-1028

    Resistors: TAKMAN REX Carbon
    Films: ClarityCap ESA 0.047uf/630V
    Caps: ELNA Silmic II

    Marantz7Tg.png

    Marantz7Th.png
     
  10. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    While I was removing the Resistors I noticed this with a few....

    Looking at some of the other Resistors I do noticed that Crack...:idea:....I never seem this before????

    Marantz7Tf.png Marantz7Ti.png
     
  11. jstang

    jstang Honey,I can't hear you... Subscriber

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    Yuck.... Where were those?

    Johnk
     

     

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  12. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    On the Recording Output RAEF Board. It is also thru out the unit. Strange...Working on the Main Output board and finding the same.

    I was going to leave the Switch Resistors alone. Maybe will need to replace these to.
     
  13. jstang

    jstang Honey,I can't hear you... Subscriber

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    Were there any symptoms ? I would think so... But sometimes not....

    I have not been in my main 7t for a long time, guess I will need to perform a detailed inspection. Been listening a lot lately, system sounds fine...but might be time for a cleaning and inspection.

    Johnk
     
  14. twiiii

    twiiii Addicted Member

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    A 7T was quite a piece. It really out surpassed a C-26 and C-24 from Mac, but couldn't quite keep up with a C-28. But that said I much preferred the controls on the 7T and 7C over the Mac pre-amps of the time. I hope once you get it restored its even better than new. Its a real classic . Its a shame Marantz has strayed away from its original path over the years. I would be fun to see some updated classic Marantz that still has the classic look, feel and sound.
     
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  15. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Main Output RAEF board 11-1029:

    Resistors: TAKMAN REX Carbon
    Films: ClarityCap ESA 0.047uf/630V
    Caps: ELNA Silmic II

    1 side done....waiting on the Films(0.22uf, 0.47uf and 0.33uf) from Parts Connexion (January). Going to
    start the Luxman C-1010.

    Marantz7Tj.png
     
  16. jstang

    jstang Honey,I can't hear you... Subscriber

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    What serial number is that? I see a grounding pressure strap on the board that I have never seen before.... or never noticed... The one at the view bottom middle of the pic... It seems to ground the cover....

    By the way I use all films in the signal path as well on my modded 7T including the feedback caps that were once tantalums.... Large in size, but the 7T is not lacking for interior space....

    I never get tired of looking at the interior of a 7T.... I always marvel at the craftsmanship....


    johnk
     

     

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  17. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    S/N: 17802

    Yes....Lot's of space
     
  18. USMC Spike

    USMC Spike Active Member

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    CohibaJoe, and others following along...

    I'd like to see a top side view of the 332 resistor that showed a crack.
    If that is original from the factory, it looks like the factory got lazy
    or missed some process indicators at the time.

    From your picture in post #30
    It appears that the resistor was installed
    to the left side of the image first.
    It was hanging towards us (the camera).

    Or with study, with the radius bend on the
    right side of the resistor, soldered to the
    terminal and and then the left side
    just pulled against the insulator and
    eventually soldered like that.

    Either method was incorrect and resulted
    in cracking at the stress point.

    You want to be very careful with your new
    resistors too. You want to hold the wire lead
    right next to the resistor body (or cap body also)
    and only bend the lead on the side away from
    the resistor. That way, the end cap should
    never be under stress and the outer coating
    remains intact (so moisture and contaminants
    can't enter the resistor body).

    I have two special tools just for bending
    the wires so this won't happen. They are
    cone shaped wire bending pliers. Dentists
    use them. Orthodontists also have all kinds of
    useful tools for us.

    Additionally resistors should never be mounted
    straight ahead or axially. A radius of at least
    1/2 diameter of the resistor body should be
    employed. So with staked terminals the
    resistors should be mounted with their
    leads bent in a gentle S shape.

    Like this:
    . . . . . .
    SSSSS
    . . . . . .

    Not like this:
    . . . . . .
    | | | | | |
    . . . . . .

    Those are from the IPC or J-STDs.

    You will rarely see anything built to
    that standard.

    Two key thoughts about this and assembly.

    Stress relief. the s shape above, a loop also works.
    Service loop.
    Wire it longer than you need because if it needs servicing,
    and it will, ensure it long enough to clip off some of the
    wire, re-strip and re-solder with out having to pull and
    replace the whole wire.

    Much of this old gear we like was assembled in this
    manner. Much new gear is not and look at some
    of the boutique stuff out there.

    I hope this helps you go forward.
    I'm just trying to make you and others
    aware of this and other assembly errors
    commonly made. We spend a lot for this
    gear and we invest our time repairing and
    making it sound good, these procedures
    will help our gear last a longer functional
    time and when ready for the next go round
    we want to ensure longevity.

    Thanks,

    USMC Spike
     
  19. jstang

    jstang Honey,I can't hear you... Subscriber

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    Agreed the 7t component mounting and lead forming is some what counter to standard practice.

    But you should keep in mind that the whole unit uses only a rated 9 watts of power including the pilot lamp..... think 1 watt is the pilot lamp, maybe 3 are wasted in the transformer, maybe a 1 watt ( or less ) goes to driving the amp on the other side of the RCAs. The rest, 5 watts, is in the unit itself......

    Just measured the current draw on the AC side of a properly functioning 7t .... .035A ..... hmmmm PIE = 4.2 watts..... So Marantz was very conservative with the 9 watts.... Think the rated 9 watts maybe if you are driving headphones to the absolute max.

    That would leave ~2.5 ( more or less, likely less ) watts for component heating inside the 7t if you use my estimate above but starting with the actual 4.2 watts as the starting point.

    There is not a lot of expansion from waste heat going on in there..... Maybe none.....

    So maybe they were justified with the non standard lead forming.... Clearly after years of building high end heat producing tube amps, they knew about lead forming for tube units.

    Seems they were trying to keep leads as short as possible for less self inductance vs worrying about expansion from heat.... If you don't have to worry about heat expansion --- In an ideal electrical world...leads & wire runs should be as short as possible to reduce self-inductance and capacitive loses .

    Remember that Sid Smith was very accomplished and highly trained Engineer by the time he designed the 7t. I have often looked at the component placement and forming in the 7t... then scratched my head.... then said to myself... "Wait ! This was Sid Smith's design.... He did this on purpose....brilliant !"

    I have seen/serviced 10 or more 7ts ( own 3 right now ) all of which are 50 years old.... fist time I have seen resistors that appeared to have been stress cracked on a 7t. After 50 years ( the units that is, I am just a little older :) ) ..... hmmmm, some stuff will happen.

    Component layout can have a substantial affect on sonics..... I would avoid straying from what Sid Smith did in the 7t by too much.

    My 2 cents....

    johnk
     
    Last edited: Dec 31, 2017
  20. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    WOW...Thanks for the information ...Need to re-read this a few X's. The Resistors are Original. There are a number of these that have that Bump
    in the Case. Once this is removed is falls apart or a twist at the end. I never have seen this and the other 60's piece I have worked on is Scott LK-72B which the caps
    were OK. I believe this is a Factory woops. The Bends are being made as you said and I am following what I remove.

    As for the Films...I picked out what I believe will not stray for Sid Smith's vison of the Sound Signature. These Film should Open this up without going to extreme changes. The ClarityCap ESA/CSA is a well balanced, neutral capacitor highlighting clarity and smoothness.
     

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