Marantz 2275 Restoration - 1974

Discussion in 'Audio Visual' started by aokman, Oct 25, 2009.

  1. mtma

    mtma Member

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    Yeah the factory ones are a lighter blue colour than the photo of the LED face on the last page. Which was my only qualm, since a pure blue as in the LED mod photo doesn't go well together with that model of Marantz imo. But aokman already said that the photograph exaggerated the colour.

    I didn't mean to stir people up about it! apologies aokman if I've offended you.
     
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    aokman

    aokman Member

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    lol doesn't bother me the slightest :cool:
     
  3. itachi46

    itachi46 Member

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    hey aokman i just been tinkering with my amp and while adjusting the bias the fr01 fuse blew... so im like wth? maybe i shorted something by accident with my meter... so i pop in another fuse and it blew it again.. any idea what this fuse does? and what could be the problem ? >.<

    edit: it seems like i have a short between j708 -j703 and j704-j707 on the left channel...

    edit2:
    [​IMG]

    ^what are those? on my right channel they show about 900 ohm (but it keeps increasing?) of resistance and my left channel shows 0 the one that sparked was the left channel.
     
    Last edited: Nov 16, 2009
  4. TERRA Operative

    TERRA Operative Member

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    They look like diodes?
     
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    aokman

    aokman Member

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    to do the idle current adjustment you need to measure Mv between J703 and J704. You didnt have the meter on resistance or something did you?

    Have you tried setting the ajustment pot to fully counter-clockwise before replacing the fuse? those 2 components you pointed out are diodes :)
     
    Last edited: Nov 16, 2009
  6. itachi46

    itachi46 Member

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    yep i was doing dc 200mV and all of a sudden POW! it seems like the diodes are shot... their giving me 0 resistance both ways. >.<

    now question is.. wth happened to kill both diodes :(

    edit: and question 2 is.. what are the specs for these diodes.. i cant find them on the manual -.-
     
    Last edited: Nov 16, 2009
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    aokman

    aokman Member

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    the only 2 diodes i see on the schematic are H715 and H716 which are WZ-150 Diodes 15v +-15%

    not sure what would happen but have you tried unplugging the amp modules and seeing if the unit will come online without poping the fuse?
     
  8. itachi46

    itachi46 Member

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    h715 through to h721 are all diodes which are on the board itself not wired >.< and yeh i was going to test that next... im just thinking even if i replace the diodes if the problem lies somewhere else.. its just gonna break the diodes again :(
     
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    aokman

    aokman Member

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    ill need to look over the schematic some more, its layed out very weird and those diodes are not in it, maybe a hotfix, as the only part i can see is H001 to H004 transistors which are shown connecting between those terminals but with an extra connection being a transistor...

    It is possible i guess that one of those transistors has blown and shorted. I would unplug both amp modules and power it up again and see if the fuse holds.
     
    Last edited: Nov 17, 2009
  10. itachi46

    itachi46 Member

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    what would it have taken to blow the power transistor? (i assume their the thingies int he middle with heatsinks?
     
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    aokman

    aokman Member

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    it could be the diodes if they are shorted or the transistors but it depends what your meter probes actually shorted out on.

    unfortunately you cannot be 100% sure of if a diode or transistor is ok while its still in the circuit...

    a guide for diode testing also:

    http://www.electronicrepairguide.com/testing-diode.html

    heres a general thing i go on when it comes to power issues:

     
  12. itachi46

    itachi46 Member

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    well im going to try the amp without the left channel plugged in... if it doesnt blow the fuse atleast i know for sure its the left channel... then i suppose i can cut one of the legs of the diode and test it.
     
  13. skipppy

    skipppy Member

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    sweet post im bit of fan of oldschool audio gear myself

    My pride and joy is a Luxman r-1120

    [​IMG]

    120rms per channel :)

    i had to replace my globes to but i went the orignals
     
  14. goodguy82

    goodguy82 Member

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    pic is not working btw...

    Anyways, i had a luxman R2200 i think. Luxman makes really good sounding amps:thumbup:

    Aokman: amp looks bloody good mate.
     
  15. 3Tone

    3Tone (Banned or Deleted)

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    aokman you have inspired me! I just got my hands on one of these for $20!!!

    [​IMG]
    Yamaha DSP-A1000

    Fortunately it looks like everything works perfectly so all it needs is a clean up.

    Can i ask you what you used to clean the insides? Looks like there is heaps of dust inside it.
     
  16. MrSmoke

    MrSmoke Member

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    haha ive been meaning to take a look at my old National Panasonic RA-6500 for a while.....still works great but 1 input is dead and and front panel lights dim when playing music and the pots have a bit of crap in them...idk, the lights still work and its fair old so maybe ill just leave it....still sounds great :D
     
  17. itachi46

    itachi46 Member

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    just tested my diodes (yes 2..) they both seem to be "open" now i have 2 issues...

    1what the heck are the specs of these diodes?
    2 if they both got fried... isnt there probably something else that caused them to get fried :(

    edit: oh and it turns on just fine with the left channel module off.
     
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    aokman

    aokman Member

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    are you seeing a different reading from the diodes on the other amp module? im trying to find some info on them... aparently if there is a problem in the bias circuit it will cause

    according to one of the guys on the other forum a open bias circuit can throw the outputs to full open power and short out and blow fuse.
     
    Last edited: Nov 17, 2009
  19. itachi46

    itachi46 Member

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    thx coz im looking at the circuit diagrams and stuff and they seem to not exist.. :S damn ninja diodes.

    havnt tested the other amp module.. but.. will do that tomorrow.
     
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    aokman

    aokman Member

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    Sorry for the lack of updates guys, been flat out at work and Left 4 Dead 2 :wired:

    Anyway i put tonight aside and i managed to get all the front end wiring back in place, finished wiring in the DC converter board and after some hair pulling i got the tuner pulley system back together :D

    I decided to go with all the original colors in the unit except with LED's

    Anyway heres a couple of pics and a teaser of things to come ;)

    [​IMG][​IMG][​IMG]
     

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