Polk monitor 7b diy repair and upgrade.

I have a pair of Polk monitor 7B's that I use as my main speakers but there was a surge that fried my amp and in turn my speakers so I have repaired (it was beyond my capabilities so I took it to a shop. Shout out to pro tech repair) and now its time for the speakers and my goal is to repair and upgrade them with solen caps along with milles resistors. I was wondering if I could get any advise past the basic it needs to be done.
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Comments

  • pkquatpkquat Posts: 422
    What's "fried" on your speakers?

    For caps, the majority here favor Sonicaps, www.soniccraft.com . They also carry Mills resistors. For a slightly lower cost option, Clarity caps are often suggested.

    Other recommendations are to use Loctite Power grab to secure the magnets. The glue can fail with age and a wrong bump. The power grab can also seal any seams in the cabinet as needed.

    Replace the wood screws holding the drivers with machine screws and hurricane nuts. (There are also "Larry's Rings" from a member here, but they are currently out of stock for a while. These are more handy for SDA speaker where there are many more drivers and screw holes.)

    Some people also dynamat the speaker baskets.

    If you are not looking to mod these, you may get more hits in the "Vintage Speaker" section. That is a good section to search.
  • hammy1750hammy1750 Posts: 20
    edited April 1
    Thanks. Should I glue the cones if I am getting new one from Polk. The old ones ripped to shreds from the amp. And the caps are 34 and 12 so I don't know what company would make the best capes for the price (my Bridget is less than 80 for all 4 caps) that the budget just for Thebes's caps the full budget isn't less than 200 and preferably less than 180
  • NightfallNightfall Posts: 6,841
    edited April 2
    hammy1750 wrote: »
    Thanks. Should I glue the cones if I am getting new one from Polk. The old ones ripped to shreds from the amp.

    Woah. Can you post pictures?

    Edit: Unless you mean "ripped to shreds" figuratively and not literally.
  • hammy1750hammy1750 Posts: 20
    For one of the cones it was literal also here is a few pics of the speakers taken fully apart. I am curently ordering parts for the repair.


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  • hammy1750hammy1750 Posts: 20
    If any one wants I can't make a video because i some what know what I am doing (that's a very big some what) and other people could watch and if any one decide they want to do the same upgrade/repair they could se what I didn't wrong and do it better. Just like this post or comment if you want a video of the build.
  • pitdogg2pitdogg2 Posts: 6,575
    edited April 25
    Man that had to of had some SERIOUS voltage go through it. Are the inductors melted? What does the pcb look like?
  • hammy1750hammy1750 Posts: 20
    the coils were chard black and the one that blew out was not in one peace (i don`t have any pics of the part its all in the trash) the one that stayed in i think only stayed in because it melted to the cavity it sits in.
  • hammy1750hammy1750 Posts: 20
    edited April 27
    the parts for repair are in the mail so here is a current parts list for the
    'budget repair' budget as in 200 for the whole thing (not replacing tweeters they some how survived... i hope) every thing but The speaker cones where ordered on amazon.

    2x mills 2.5 ohm 12w resistors
    2x mills 4.5 ohm 12w resistors
    2x solen 33uF 400v capacitors
    2x solen 12uF 400v capacitors
    20ft Harmony audio 4 gauge black wire
    2x duel fuse holder (cheep Chinese no brand)
    2x Parts express wire terminals (2 pairs)
    2x Polk speaker cones for the 7-bs

    There might be More parts but I can't think of them right this second burn i will update this if I remember (I am as of now not ceiling the cones but I might in the future I am already at the 200$ budget)
  • hammy1750hammy1750 Posts: 20
    edited April 27
    Also with the voltage it looks like it sent 1200 Vdc into the speakers. It's a late 1970's ps audio elite inatagrated 55 watt amp and a house wired in the late 50's to early 60's. a power surge went threw the amp. It blew the fuse on literally all of my equipment except The speakers and the amp. So everything was unharmed exept the speaker said and the amp where booth need to be total the rebuilt. :( (I really need a surge protector)
  • pitdogg2pitdogg2 Posts: 6,575
    edited April 27
    let us know how you like the Solen caps in the high pass. Many have tried and taken them out because of shrill screechy uncomfortable sounds.
    Those might be BIG CAPS space will be at a premium. Try to leave the resistors up off the board for better airflow around.
  • hammy1750hammy1750 Posts: 20
    edited April 27
    I have a very warm amp so I'll post how it sounds (I will also record it playing) any segestions on songs to run threw it?
  • motorhead43026motorhead43026 Posts: 1,792
    ^^Anything sung by Yoko Ono.
  • heiney9heiney9 Posts: 23,341
    Also, normally people delete the fuse block. It didn't seem to help you anyway.

    H9
  • pitdogg2pitdogg2 Posts: 6,575
    hammy1750 wrote: »
    I have a very warm amp so I'll post how it sounds (I will also record it playing) any segestions on songs to run threw it?

    I think you meant to say you HAD lol so warm it toasted your speakers almost to the point of inferno :p :p

    just teasing So what will you be driving the speakers with now?
  • hammy1750hammy1750 Posts: 20
    Same amp I had it full restored (more of a compleate rebuild with every part replaced) but it's all new original parts and I kept it's great sound shout out to pro tech repair in Akron Ohio USA they did a great job
  • heiney9heiney9 Posts: 23,341
    edited April 27
    A complete rebuild with every part replaced and it's still all original? An oxymoron there. No need to post a video.

    H9
  • hammy1750hammy1750 Posts: 20
    It's all original parts from the 70's for the amp just the parts have never actually been used.
  • hammy1750hammy1750 Posts: 20
    welp that just my luck. I get the speakers working and they sounded Amazing not harsh at all and after about 20 min of playing (i was half way threw side A of tubular bells) when the left Chanel of my newly redone amp heavily distorts. so basically it might be a short time until i can get some music pumping threw the new parts. :(

    i do not be leave it was the shops fault it sounds like a dud cap or loose wire. (the distortion sounds like the mid to highs oscillating on and off and the sound is to distorted) but i tested the speakers and there both work great i just don`t have an amp to drive them now.
  • pitdogg2pitdogg2 Posts: 6,575
    Umm and how is that not the shops fault if they did a complete rebuild? Many shops will run the repair for many hours(days) through tuff loads to make sure their work is satisfactory.
    Hopefully this amp is still under warranty from said shop.
  • hammy1750hammy1750 Posts: 20
    edited April 29
    my current plan it to (when the amp is fixed) run this list of albums threw the speakers.

    Tubular balls by Mike Oldfield
    Maynard Ferguson (I don`t know the album name at this second)
    wish you where here by Pink Floyd
    quadrophenia by The Who
    Harder they come by Jimmy Cliff
    some random grateful dead songs
    this is the list so far there will be more added in a later post
  • hammy1750hammy1750 Posts: 20
    ya but some times stuff just happens with 30+ old new stock parts
  • hammy1750hammy1750 Posts: 20
    also to any one attempting a repair or upgrade on a pair of monitor 7b speakers this will help A LOT trust me on this one 6pnwsw35n4xu.jpg
  • F1nutF1nut Posts: 37,319
    The inductor values for the 7B as follows,

    Small - .4mH
    Large - 1.55mH

    It should also be noted that the leads from the fuse are now severely oxidized on this model and I would suspect all of the vintage Polk speakers with fuses mounted on the binding post cup. This is an issue that should be addressed.
  • machonemachone Posts: 694
    ^^^ The leads on my 1A's were green. I ended up eliminating the fuses.
  • hammy1750hammy1750 Posts: 20
    edited May 3
    I went with 2 fuses per speaker that are slightly underrated because of my amps problems but for new amps I would agree and eliminate the fuse (the fuses are in cerise)
  • hammy1750hammy1750 Posts: 20
    I am taking my amp to the shop today so I will be able to get some recordings on the sound quality hopefully soon. I will also record strate into a recording box run after the amp for comparison (it will all be in flak or wave files)
  • pitdogg2pitdogg2 Posts: 6,575
    fuse only protects the tweeter section normally so does the second fuse protect something else?
  • F1nutF1nut Posts: 37,319
    7B fuse leads....579c4uuujjrj.jpg
  • hammy1750hammy1750 Posts: 20
    From the scamatick the + wire goes strate into a the fuse meaning it protects every thing. Also any one who has a pair of 7b or any pair of 30+ year old speakers I recommend new fuses
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