Technics ST-7300 meter lamps

Discussion in 'Tuners' started by hotdogst, Jan 1, 2017.

  1. hotdogst

    hotdogst Active Member

    Messages:
    101
    Hi all,

    I recently picked up a Technics ST-7300 to go with an HK 505 I also got recently. I'm having trouble actually getting to the meters, which appear to have burnt out lamps.

    There aren't any fasteners accessible from the backs of the meters, so the faceplate probably needs to come off. The bottom of the faceplate is held on by three screws that come down from above, the pic isn't great but there's one under the three green buttons, one to the right above the foot, and then another to the left out of the shot:
    IMG_3905.JPG

    The trouble is, you can't access the tops of these screws from the top of the unit. The left screw is under one of the meter assemblies and the middle screw is directly under the middle button. Tough to see, but you can see the screwhead right by the middle switch here:
    IMG_3898.JPG

    The one over by the tuning knob you can actually get to:
    IMG_3899.JPG

    And here's a shot of the area I'm talking about:
    IMG_3900.JPG

    Here's the back of the faceplate:
    IMG_3903.JPG

    The tracks along the top and bottom of the faceplate make it seem like it wants to just slide off, but the power switch and buttons all stick out too far for it to slide past them:
    IMG_3904.JPG

    Here's the front:
    IMG_3902.JPG

    Feel free to ask for more pictures or descriptions and thanks a lot!
     
  2. 39cross

    39cross AK Subscriber Subscriber

    Messages:
    908
    Location:
    Beverly, MA
    Perhaps the service manual has the answer. Have you tried removing the face plate, the tuning knob may be attached by an inset hex screw.

    When you reassemble be careful not to misalign the dial pointer. Once the dial string is loose it can be an interesting time getting it all back the way it was.
     
  3. hotdogst

    hotdogst Active Member

    Messages:
    101
    I haven't been able to find a service manual with a blow-apart diagram of the chassis. Is that pretty standard? Maybe I just need to keep looking?

    Oh good call with the inset hex screw. I couldn't figure out how to get the tuning knob off.
     
  4. hotdogst

    hotdogst Active Member

    Messages:
    101
    So, those three screws I was talking about at first don't actually hold the faceplate on, I was wrong about that.

    It seems most likely to me that the faceplate wants to slide off the chassis to either the left or right. But, the switches all stick out a tiny bit past the faceplate so there's no way to actually slide it. There's no way I need to remove all the switches from the circuit board just to take the faceplate off...right?

    I couldn't get a good picture of it, but the track along the bottom of the faceplate slides along a ridge on the bottom panel of the chassis.
    IMG_3920.JPG

    But, the switches all poke out beyond the faceplate, so there's no way to slide the faceplate off.
    IMG_3924.JPG

    I really don't know how I can get the faceplate off without unscrewing literally everything holding this thing together. Does anyone have any idea where I could find a more complete service manual that has a blow apart diagram of the unit?
     
  5. 39cross

    39cross AK Subscriber Subscriber

    Messages:
    908
    Location:
    Beverly, MA
    The faceplate does not slide out. You need to remove the tuning knob (2.5mm hex wrench is probably the size, I'm not 100% sure). Then remove the face plate from the front. That looks like the way get to the lamps. Yes, some disassembly is required.
     
    Last edited: Jan 6, 2017
  6. jlovda

    jlovda Things I loved from the 60's and 70's

    Messages:
    3,125
    Location:
    NE Ohio
    Thanks for cluing me to keep moving down the page if I see an ST-7300 on CL. :crazy:
     
  7. hotdogst

    hotdogst Active Member

    Messages:
    101
    Success! The faceplate just drops straight down once you get the knob off and a nut behind it.

    It's a nice looking tuner but I'm not sure I'll ever get new lights into it haha.
     
  8. hotdogst

    hotdogst Active Member

    Messages:
    101
    So I got the faceplate off, but the meters are still inaccessible. They appear to be either glued onto the faceplate or bolted on somehow from the front, maybe there's a hole threaded partway through the faceplate or something? The pink things are nuts, set into little hex holes on the back of the meter so you can't get the nuts off.
    IMG_3925.JPG

    On the bottoms of the meters there is something that looks like a clear plastic insert. It sorta looks like it could slide out somehow but does not seem to want to. The hash marks in the clear plastic that look like they should be grippy so your fingers could slide them out are not actually rough, the hash marks must be on the inside of the plastic.
    IMG_3926.JPG

    IMG_3927.JPG

    Sorry for all my dysfunction with this tuner! Thanks for all the help so far.
     
  9. 39cross

    39cross AK Subscriber Subscriber

    Messages:
    908
    Location:
    Beverly, MA
  10. hotdogst

    hotdogst Active Member

    Messages:
    101
    Yea, I saw that thread. Those are the lamps for the dial of the tuner, not the meters. The dial lamps are burnt out as well though.
     
  11. hotdogst

    hotdogst Active Member

    Messages:
    101
    Wait, does the light just diffract up through the clear bottom of the meter enclosures?
     
  12. 39cross

    39cross AK Subscriber Subscriber

    Messages:
    908
    Location:
    Beverly, MA
    Yes indeedy!
    The two leads drive the meters. No lamps in there.
     
  13. hotdogst

    hotdogst Active Member

    Messages:
    101
    So much angst for nothing! I didn't even need to take the faceplate off. Once I track down some lights I'll post up some pics.
     
  14. R-2-R

    R-2-R AK Subscriber Subscriber

    Messages:
    2,163
    That's whats called a...'live and learn' process. Hey it could've turned out a lot worst.
     
  15. 39cross

    39cross AK Subscriber Subscriber

    Messages:
    908
    Location:
    Beverly, MA
    As long as nothing was broken, you did OK. You can contact member dwojo about the lamps, he should be able to help you.
     
  16. hotdogst

    hotdogst Active Member

    Messages:
    101
    For sure. Always fun to get something old and grungy looking pretty and working right again. And I got in touch with dwojo and he hooked me up. It looks great!

    The alignment seems to be off by about .3Mhz across the whole dial. I think I remember seeing in a thread somewhere that a good cleaning might be all it needs. Is this accurate? I should probably clean it per the sticky anyway.

    Also - the "Signal" meter never really seems to dip below 3, even when it's totally not even close to being tuned to anything. Is this normal? I feel like it should have a greater range of movement.

    r IMG_3992.JPG
     
  17. Punker X

    Punker X AK Subscriber Subscriber

    Messages:
    3,971
    Location:
    Panic in Detroit
    In reference to the meter.. Might just use as is, probably in meter driver. Could be cap or caps throwing off a bias or a leaky transistor.
     
  18. hotdogst

    hotdogst Active Member

    Messages:
    101
    Yea, that was my thought, that there's a bad cap or something throwing it off a little. I'll probably leave it as-is for the time being but it would be sweet to get it back to it's original state at some point.
     
  19. Erika7700

    Erika7700 New Member

    Messages:
    1
    Hi guys.
    I'm following the topic, I also have the dial lights burned on my ST-7300 and worst in my SU-7700 too, how many lights are there on the dial? Are they really 0.63V 0.25A tipe Fuse Lamps? What parts should I remove to access the lights?

     
    Last edited: Feb 25, 2017

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