Infinity Quantum 4 - Neither mid range driver is working. Repository of repair tutorials?

[pswayze]

Hey everyone,

I received a set of hand-me-down Infinity Quantum 4 speakers. The surrounds had basically evaporated so I purchased a kit off of ebay and replaced them, hoping that's all that would be required to get them up and running. Hooked up to my receiver, it seems that neither midrange driver is doing anything. Both mid range drivers measure 7.2 Ohms on the terminals so neither are an open circuit. I'm unsure how to test for any other issues with the mid range drivers. I see people suggesting to clean the potentiometers but do you need to remove them? Or soak them with pot cleaner in situ? I guess I have lots of questions.

• Is there some obvious reason that neither mid range driver would not be producing sound?
• I see a few big capacitors inside the cabs. Do they need to be replaced?
• Is there a way to remove/access the electronics? It looks like the whole thing is glued together permanently.
• Do the pots need to be removed to be cleaned? How do you get them out?
• Are there repair/troubleshooting tutorials that I've missed?

Thank you for your assistance!

 

[goodolpg]

Are the EMITs working?
It appears the EMITs and Mids are protected by the same fuse.
I'm thinking those dome mids are among those known to have tinsel lead breaks but you got a reading so it seems they should work.
As for the pot, to really clean the pot, the cleaning solution must get INSIDE the pot to where the corrosion is. Some pots have slots, some you may need to shoot (use the small straw) down into to the pot where the connector leads come through. Then work the pot in both directions, full range end to end many many many times.
Good luck.

 

[pswayze]

Are the EMITs working?
It appears the EMITs and Mids are protected by the same fuse.
I'm thinking those dome mids are among those known to have tinsel lead breaks but you got a reading so it seems they should work.
As for the pot, to really clean the pot, the cleaning solution must get INSIDE the pot to where the corrosion is. Some pots have slots, some you may need to shoot (use the small straw) down into to the pot where the connector leads come through. Then work the pot in both directions, full range end to end many many many times.
Good luck.

I assume EMIT == tweeter? Both tweeters work fine. There is one external fuse on each cab and they are good. Hmmmm.....

 

[goodolpg]

Yes, EMIT is tweeter.

http://www.infinity-classics.de/models/Quantum-series-1976/index-Quantum.htm Quantum 4 page
http://www.infinity-classics.de/technik/manuals/Quantum_4_technical_sheet.pdf Quantum 4 schematic

 

[tubed]

I'd remove the mids and test for sound.
If working I'd bypass the pots with a 1 ohm resistor and enjoy until you've got the pots working again(or replaced).

 

[savatage1973]

Work "backwards" from the driver back to the crossover, all the way back to the speaker input jacks. You know you are getting power to the speakers (the other drivers work). You have tested the midrange drivers and established that they are not "open", so should function. Now just "connect the dots", checking for continuity as you go--at some point you will lose continuity--that will be where the problem lies.

 

[slimpikkins]

Agree with tubed 100%. If they are measuring 6-8 ohms they should make music. Bypass or clean the pots. To clean them they most be removed from the circuit and taken apart. Great speakers, well worth the effort, I have a pair and like them a lot.

 

[chef free]

It's the pots, it's always the pots when the mid domes test "good". They are easy to remove but you probably don't need to remove them, just dribble some DeoxIt D100 into the pots and work them back and froth 50 times or so...