Vintage Monitor 5jr

hoverboard

I just picked up 4 of these at a thrift store last week for $100....

3 of the 4 work/sound great!, but i knew when i bought them there might be a problem with the 4th one....the visual problem is that it is missing the fuse terminal block that is supposed to be affixed to the terminal cup on the back of the speaker.

I called Polk TechSupport(nice and helpful!) to see if i could get that part, but none were available. However, they suggested I put a fuse in-line on the black wire going from the tweeter to the crossover.
I did that, and the tweeter seems to be ok, although it doesnt seem to sound as good as the other 3 speakers do.....

But, I hadn't hooked that 4th speaker up until then because i was afraid to without a fuse in place. So i didnt know until putting a fuse inline on that wire that there is another problem...the woofer/driver does not work at all. So, I need help figuring out the next step/s to take to get it working. My visual inspection is that everything seems ok, and the black and white wires are connected to the terminals on the driver.

One strange thing about this speaker is that the crossover/terminals inside are different than the other 3....on the 3 working speakers, there are 3 terminals( inside near the crossover ) with the black and white wires going to/from the tweeter and driver, but on this non-working 4th speaker, there are 5 terminals by the crossover. Since this one is different than the other 3, did i do something wrong in the placement of that fuse? It is definitely inline on the black wire that goes from tweeter to crossover, and when i bypass it, the woofer/driver still doesnt work....

Anyone have any ideas on what to do to get this driver working? Thanks

Attached are some pics of whats described above.

pitdogg2

Need many more pictures of the whole speakers. Not all Polk's were fused but they all had the same cup that made them appear to of had fuses. more pictures of cross overs wires and drivers

in the second picture is a little yellow disc. that is the polyswitch (fuse) they started using after the external fuses. those are what protects the tweeter. remove the fuse you put in.

soundfreak1

First switch the "bad " driver with one of the ones that work and see if it works tjere if so the issue is elsewhere if still dead that you need to replace it before going further.at least you will know where to begin.

boston1450

Is the driver froze up ? WELCOME TO CLUB POLK ALSO

hoverboard

pitdogg2 wrote: »

Need many more pictures of the whole speakers. Not all Polk's were fused but they all had the same cup that made them appear to of had fuses. more pictures of cross overs wires and drivers

in the second picture is a little yellow disc. that is the polyswitch (fuse) they started using after the external fuses. those are what protects the tweeter. remove the fuse you put in.

so, maybe this one is just different, and doesnt need the inline fuse, since that is there?

i will try to take some more pics

hoverboard

soundfreak1 wrote: »

First switch the "bad " driver with one of the ones that work and see if it works tjere if so the issue is elsewhere if still dead that you need to replace it before going further.at least you will know where to begin.

dang, thats a simple tshooting step, i shoulda thought o that already

hoverboard

boston1450 wrote: »

Is the driver froze up ? WELCOME TO CLUB POLK ALSO

no, it will move if i push on it... and thanks for the Welcome!

westmassguy

hoverboard wrote: »

no, it will move if i push on it... and thanks for the Welcome!

Welcome to CP. Put a meter on the bad woofer's terminals, and check for resistance. If it's a MW6502, it should read somewhere around 3.5 ohms. If you get no reading then the coil is most likely bad. New Replacements are available from Polk Customer Service, or check eBay for used parts. The fused units are the older model. The others which have pop-rivets installed where the fuse holder would have been, are newer. Polk did away with circuit boards on some of the newer Monitor 4s and 5s, opting for simple point to point wiring, which you have.

hoverboard

hoverboard wrote: »

no, it will move if i push on it... and thanks for the Welcome!

Well, upon further check this morning, it IS sort of frozen....if i push on it from the back, it will kind of pop, and move forward, but when i let go, it will pop back and not want to move when pushed from the front.

Also, resistance measurement is not good, definitely not 3.5 ohms as suggested.

Lastly, I took a good one and put it in this ones place and it works/sounds just fine....

So am I looking at definitely a bad driver now? or is there any hope for it? Physically it looks fine...just something not right behind the coil?

westmassguy

Probably magnet shift, which is unfortunately very common with the older Polk drivers. The glue they used back then deteriorates. You can build a jig to attempt to re-align the magnet, front and back plates, or look for a used one on eBay, or as I said, by a new replacement from Polk. If you do a search of the forums, there's plenty of info on the subject, as well as instructions for building the jig. However, since the coils DCR value is off, you might just want to replace it. What was the model # of the woofer?
I'd also recommend gluing the other three magnet assemblies to prevent them from shifting. You can use JB Weld, 10 min epoxy, or what I use, Locktite Power Grab clear adhesive.

hoverboard

Thanks for the info. It is the mw6502....well, i'd love to save $ by trying to fix it if thats the problem, but sounds a little more involved than i may be able to do....im kinda clueless as to how to take it apart....i can research that and also will research new driver pricing!

Msabot1

No movement when lightly pushed from the front sounds like a blown coil to me...get a replacement.