Polk model 7a crossovers

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brcarman
brcarman Posts: 27
in Vintage Speakers
Trying to repair or replace the crossover on a model 7a speaker, are they same as model 7, and can anyone recommend where to buy the capacitors especially the 4uf 50vac
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  • F1nut
    F1nut Posts: 49,794
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    Monitor 7, not model.

    The Monitor 7 is the 7A.

    Sonic Craft has everything you need.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Gardenstater
    Gardenstater Posts: 4,182
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    brcarman wrote: »
    Trying to repair or replace the crossover on a model 7a speaker, are they same as model 7, and can anyone recommend where to buy the capacitors especially the 4uf 50vac

    There are some minor differences but so far I have not heard of anything but 12 uF mylar capacitor in the high pass (tweeter) circuit and a 34 uF electrolytic capacitor in the low pass (midwoofer) circuit.

    Are you sure about that 4 uF or did you perhaps misread it?

    What is your serial # and/or manufacturing date (often put on the crossover and sometimes the midwoofers)?
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • brcarman
    brcarman Posts: 27
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    Thankyou for answering, and yes it is 34 uf havnt removed the old so could only see the 4, in trying to find capacitors it's the vac can't find, I did find the 12 uf in a higher voltage dc, would prefer to fix myself if can find what I need, but there are used model 7s crossovers on ebay, the tag on back reads model 7a and the serial number is 11178, I so much! Appreciate any help thankyou, Bill r
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  • Gardenstater
    Gardenstater Posts: 4,182
    edited February 2023
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    Those are quite earlier than my Aug 1979 7B which were 19XXX (can't remember exact). Do you have 2 fuses on the terminal cup?

    The metallized polypropylene capacitors you are best going with for an upgrade are going to be quite a bit larger and 200V and above. You won't likely find below 200V rated ones. The resistors you are best off replacing with something like Mills/Vishay wirewound non inductive or the like and it is advisable to go with 10W or even 12W to handle the heat better and run cooler for less thermal noise. You probably have 4.5 Ohm and 2.7 Ohm 5W ceramic (sandcast) resistors but I have seen some early ones with 4.7 Ohm and there may be others. I even saw one with one 10W and one 5W
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • brcarman
    brcarman Posts: 27
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    I have a 4.7 ohm, 10% and 2.7 ohm 10% resistors, my peerless tweeters works but didn't work in the box connected to crossover, the base sounded muffled and the 34uf cap looks like it's bulging, I don't know anything about upgrades, back to factory specs ok with me, but whatever I have to do to get them sounding good, and there are two fuses on the back, I believe they are worth fixing?
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  • Gardenstater
    Gardenstater Posts: 4,182
    edited February 2023
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    Absolutely worth fixing. There were some Monitor 7 (don't remember if 7A or B ) crossovers for sale on eBay. You could always snatch them up if they are still there. Upgraded caps and resistors sound amazing though, as well as internal wiring which you can always do all that later.

    Just checked and there are two pairs on eBay but both are single fuse 7Bs 40XXX and 22XXX, so if you went with those you would no longer be original.

    You could transfer your 4.7 Ohm resistors over. Problem is that I do not know for sure if inductors were the same in the earlier ones like your 7As. We don't have any early schematics. If you have the MW6500 drivers which I am fairly certain you must, I can't really forsee any problem with going with the 7B crossover.

    https://www.ebay.com/itm/325513956918?hash=item4bca24ce36:g:kE4AAOSw6-dj1AOE&amdata=enc:AQAHAAAAoNzyxJjra5/g2DM9Ns9fz66KwcizSM+cG/1gMBBIhbogIrM3y2VU+S1BAQX2ysQusqT1mrQbn5MMCIAi3ePC+MP7MeWdtj8gOs5wiqaOlNJJuiCggxVB0FICWpMe95B2746HptOfOBl9tSMeIESee4O95jcn0rGpkcjVi3euDZpwVGNgdkAO6URC/kGXl5tMGHAoI5FsgUWnrUnZviGgTy8=|tkp:Bk9SR5bL85PFYQ

    https://www.ebay.com/itm/325513956918?hash=item4bca24ce36:g:kE4AAOSw6-dj1AOE&amdata=enc:AQAHAAAAoNzyxJjra5/g2DM9Ns9fz66KwcizSM+cG/1gMBBIhbogIrM3y2VU+S1BAQX2ysQusqT1mrQbn5MMCIAi3ePC+MP7MeWdtj8gOs5wiqaOlNJJuiCggxVB0FICWpMe95B2746HptOfOBl9tSMeIESee4O95jcn0rGpkcjVi3euDZpwVGNgdkAO6URC/kGXl5tMGHAoI5FsgUWnrUnZviGgTy8=|tkp:Bk9SR5bL85PFYQ

    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • brcarman
    brcarman Posts: 27
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    The other numbers on resistors are 7806 trw pw5, and 7745 trw pw5 on the 4.7 ohm one, I'm not up on all the terms, but took hobby electronics in high school, and these look easy to repair soder to me,
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  • Gardenstater
    Gardenstater Posts: 4,182
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    Yes. It should be very easy for you then. The pw5 means 5Watts
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • F1nut
    F1nut Posts: 49,794
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    Don't buy used crossovers, fix yours.

    The first thing you need to do is clean the ends of the fuses as well as the fuse holder clips. They oxidize over time. The eraser on a pencil works well for that. You should also verify the fuses aren't blown. Do you have a VOM?
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • brcarman
    brcarman Posts: 27
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    Ty for answering me I don't have a meter but looks like I should get one, I'll recheck the fuses and condition of holders
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  • brcarman
    brcarman Posts: 27
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    Thankyou both, I think I have enough to go on, and will leave ya all alone, for now lol my sincere appreciation, was about to pull my hair out after trying just find caps all day
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  • Gardenstater
    Gardenstater Posts: 4,182
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    No problem. I'm guessing you want to find out how they sound stock before upgrading. I can tell you the parts list to basically use the components I used (Sonicaps capacitors and Mills resistors) if you are interested. I purchased them all from Soniccraft.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • brcarman
    brcarman Posts: 27
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    Would appreciate Any info, and sounds like that sonicraft is the go to place, I pick up a near mint pair of pioneer pm60s a bit back, and am anxious to see how these polks compare, one speaker sounded good far as could tell but the other one no tweeter sound and bass was awfull
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  • brcarman
    brcarman Posts: 27
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    Also would like to do my own repairing, because those pioneers are old too ,so thinking just a matter of time till they will need crossover work too
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  • brcarman
    brcarman Posts: 27
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    Looks like 1nut was right and I was rt too lol, from your info and the serial number mine must be 1978. They have the little factory holes in the tweeters, gonna take one nuts advice and recheck the fuses and connectors, and both your advice and hit up soniccraft tomorrow. Thanks a bunch guys!! I'm 59 and not to social media savvy, you have made my first experience excellent, Bill r
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  • F1nut
    F1nut Posts: 49,794
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    Bill, it's F1nut.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • bcwsrt
    bcwsrt Posts: 1,591
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    Posts = ~48,000
    Respect = 0

    😳🙄😂

    And while we’re at it, it’s Sonic Craft. 😉😋
    Brian

    One-owner Polk Audio RTA 15TL speakers refreshed w/ Sonicap, Vishay/Mills and Cardas components by "pitdogg2," "xschop" billet tweeter plates and BH5 | Stereo REL Acoustics T/5x subwoofers w/ Bassline Blue cables | Rogue Audio Cronus Magnum III integrated tube amp | Technics SL-1210G turntable w/ Ortofon 2M Black LVB 250 MM cart | Sony CDP-508ESD CD player (as a transport) | LampizatOr Baltic 4 tube DAC | Nordost & DH Labs cables/interconnects | APC H15 Power Conditioner | GIK Acoustics room treatments | Degritter RCM
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  • xschop
    xschop Posts: 4,684
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    F1nut wrote: »
    Bill, it's F1nut.

    Yeah Bill, 1nut has a twin, 2nuts. F1nut has no relation.
    Don't take experimental gene therapies from known eugenicists.
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  • Gardenstater
    Gardenstater Posts: 4,182
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    bcwsrt wrote: »
    Posts = ~48,000
    Respect = 0

    😳🙄😂

    And while we’re at it, it’s Sonic Craft. 😉😋

    soniccraft.com (no space)
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • Gardenstater
    Gardenstater Posts: 4,182
    edited February 2023
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    @brcarman Here's some dual fuse 7A crossovers for you with the 4.7 Ohm resistor. Would give you the option of getting up and running and also have 2 crossovers to take your time upgrading. Or buy one and rotate it in and upgrade your bad one followed by the other one. JAT

    https://www.ebay.com/itm/255617683425?hash=item3b84004fe1:g:hJUAAOSwYaRixgNF&amdata=enc:AQAHAAAAoCLIWRnQS2w/dMauEr8GhnfBQ2HvnQy3ExQUnuIgmTrAzvXUsPM5l/HPSAdcbf9Dg+RPE4pOmxIM/efVrjDQiTJd5+V6XwGZh2R92LrIisv9S1a/mvbL8TpHOqARoIXmutQA438LHCUrnHbs+WDHDwUXmEhiSLZdc8CfeYqHTUujg1+dIOW/rxnXkiwVxZGjfXJ8doQ+rD+D8oETfzRuwuI=|tkp:Bk9SR7rwxsbFYQ

    Here's another but sold only by the pair:

    https://www.ebay.com/itm/325012846345?hash=item4bac467709:g:O64AAOSw6Xdh7hjU&amdata=enc:AQAHAAAAoH5L1Gb2YU9xcGwWXDEu65JG5Xme6SeMYjedDZ0qXHKDU7Fca+3PSX1+DKOqmh6nVm/JILeVdYcQus/g0xSZpK+vpln7ug/AvdrOuuC3kObv98LLoq5vS7+mENLWI1gV8bBgWDBkTGCdYLWFlSIVNfr2A50vS5cwSBSyZbLxQfhllj29qZBD78kY1yqjuxDV4lQUpwG6NMonccL/J2A4ODY=|tkp:Bk9SR7zwxsbFYQ
    Post edited by Gardenstater on
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on FacebookShare on Twitter
  • F1nut
    F1nut Posts: 49,794
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    Gardenstater wrote: »
    bcwsrt wrote: »
    Posts = ~48,000
    Respect = 0

    😳🙄😂

    And while we’re at it, it’s Sonic Craft. 😉😋

    soniccraft.com (no space)

    The business name is Sonic Craft as was correctly posted. The correct site address is https://www.soniccraft.com/
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • brcarman
    brcarman Posts: 27
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    Sorry f1nut, no dishing intended
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  • brcarman
    brcarman Posts: 27
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    Hope these pics sent this time
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  • brcarman
    brcarman Posts: 27
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    Thankyou Gardens tater for the links, I think there called
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  • brcarman
    brcarman Posts: 27
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    I guess I had opened two two different discussion pages, I did post pics and answered questions on the other one lol sorry, beginner here, you guys are great 👍 ty Bill
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  • brcarman
    brcarman Posts: 27
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    Help Gardenstater, I posted that I was going with the parts connection stuff, and when I went back to write down that info it was gone! Did that happen because I hit the question answered spot? Hate to ask but could you please repost the parts connection numbers, ty
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  • brcarman
    brcarman Posts: 27
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    Oops the info was still on the other post so no need to repost . I'll improve, I'm not to literate on these forums but learning
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  • ken brydson
    ken brydson Posts: 8,648
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    brcarman wrote: »
    Thankyou Gardens tater for the links, I think there called

    I know it's a typo but...

    axexx115viuh.jpg
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  • brcarman
    brcarman Posts: 27
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    Was I guess a funny typo,lol, but I'll tell you what, Gardenstater went beyond the call of duty to help me, I hope he received my final plan and thankyou to him. He even located All the prices and even part numbers and where to buy them, and I am truly grateful. Bill r
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  • xschop
    xschop Posts: 4,684
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    George's moniker is lengthy. Maybe he won't mind if we call him 1-tater?
    Don't take experimental gene therapies from known eugenicists.
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