Jamo 507

[Ptoosh1952]

Bought Jamo 507 Speakers last week. Beautiful cabinets. Cones all good. Unable to test. One speaker has very low volume. Switched out speakers with other. And still low volume. Switched channel on amp. Switch wires later. Tried All the combos but still low volume no life. no obvious signs on crossover. It’s almost like open wires are crossed someplace. can't get To the woofers buried deep in the cabinets. Sure would appreciate any clues.
And by the way the good speaker sounds amazing. Wow. I think it’s called the Denmark sound.
Connected second set of speakers to amp to confirm both channels work as should.
Thanks folks

 

[AllenB]

Is the treble quiet too? If so then maybe either something is shorting the amp output or some internal protection scheme has come askew. Either way I would be examining the drivers and crossover. A meter would be handy.

 

[Ptoosh1952]

thanks, I was thinking the same thing. Just hoping that the Jamo 507s had a quirk of their own .

 

[AllenB]

I ought to mention that if it is a short, it could damage your amp.

 

[Lojzek]

...Unable to test. One speaker has very low volume... Thanks folks

Well, that's something you should work on. How complicated can it be to unscrew drivers and get a multimeter to find voice coil dc resistance of each unit out of circuit. How is the cabinet back side, can you access woofers through terminal/vent opening?

 

[Ptoosh1952]

I appreciate your work in finding that diagram. More then I’ve found. I’ve checked the drivers. They are all ok. I can see the lower woofer. Of course not the top. It appears that the rear cabinet has been glued. I sincerely think the problem is the crossover. I need to remove it . It is extremely tight fit. There is no working room. Poor design in that way. I’m going to take the binding plate off to look at the bottom of the circuit board for some)meshing obvious.

 

[Galu]

On another Jamo repair I came across, the spade connectors on the internal cabinet side of the speaker terminals had become so corroded that they weren't conducting.

 

[Ptoosh1952]

I have been thinking about connections.I’m going to dig into that now. Thanks let you know

 

[Ptoosh1952]

Crossover leaking

The bottom of the crossover board shows corrosion where all of the speaker wires connect. There is no leakage from the inductors, resistors , or caps. Wish I could send a pic . Can’t figure how to attach an image to this posting. Anyone ever had all the speakers wire corroded before. Clean and resolder for sure

 

[AllenB]

I’ve checked the drivers.

You disconnected them at the crossover and measured their resistance?

corrosion where all of the speaker wires connect

A rosin deposit?

 

[Ptoosh1952]

Crossover

Yes rosin. Not tested yet. I have not disconnected the wires yet. I sprayed it all with deoxit and cleaned it all up. I need a better soldering iron anyway. I’m new to this. I learned when I was a kid, 60 years ago from my grandfather, but have forgotten most of it. Also the connectors were all finger tight, pretty loose. Keep the info coming . So far you’re right on the money.

 

[Galu]

Wish I could send a pic . Can’t figure how to attach an image to this posting.

Click the 'Go Advanced' button under the reply box then click on the paperclip symbol in the top line of the menu on the new screen. Now you can browse your computer to highlight, open and then upload the image you want to attach to your post.

 

[AllenB]

Yes rosin.

It's probably not relevant to the issue at hand (and that should be easy to confirm with a meter). As a rule of thumb I'd stay away from such distractions until the problem is fixed.

 

[Ptoosh1952]

I’m going to desolder all of the speaker connects and check the cable before I go further.

 

[Ptoosh1952]

Crossover

One last question. I only gave a multimeter.
I understand that I am unable to get proper reads unless I remove all components from the board. True or false. Or at least remove one side from circuit board.

 

[AllenB]

Great. The resistance function is all you'll need to diagnose a major breakdown. You may not need to pull (any or most of the) components. If you post a picture of each side of the board we can tell you which.

 

[Ptoosh1952]

Crossover

 

[Ptoosh1952]

Crossover

 

[AllenB]

It would be good if you could trace out a schematic, otherwise we would be guessing from the pictures.. so if you could big close up, straight on, all the way to the edges and clear which wires go to which driver and input please.

 

[Ptoosh1952]

Well folks I found that the lower midrange was testing very low . Less then 1 ohm. Disconnected it . Plugged in tower and boom. It’s sounds fab. A little lite in the mids but just great. I see what they mean by the Danish sound. Very nice. Turns out I had not tested all the drivers, sloppy work or just memory issues, who knows. I very very much appreciate all of your assistance and support. Now I’m looking for a mid range speaker for a Jamo 507 Speaker part number 20245. Or equivalent. Will try to reach Jamo direct. Or if yous have any ideas they would be most welcome.