Cornwall midrange keeps going out

[pigonthewing76]

Hello all. I recently purchased a pair of 79 Cornwalls and when I first hooked them up the midrange horn was out. I messed with the connection and then midrange horn was fine. Now the horn keeps going out again. I switched channels and changed connections and I keep having the same issue with the horn so I know it's not my amplifier. I am not tech savvy so I have no idea how to fix it unless I take it to a audio repair shop. Can someone please guide me in the right direction on how to fix it.

Thanks for your help.

[PrestonTom]

You need to be more specific about your trouble-shooting.

It sounds like you have ruled out the amplifier. Using voltmeter to check for continuity, are the connections within the crossover secure? Are the connections from the crossover to the driver secure (wiggle them). If this is okay, disconnect the wire from the driver to the crossover (disconnect at the crossover side since it may be soldered on the driver-side) and measure the resistance across the driver. It should be 5-10 ohm, then wiggle the leads on the driver to see if the connection is secure (don't open up the driver at this point). Finally, hook up the wire from the driver to the "other" crossover to see if the driver is still intermeittent.

Tell us the results. The good news is that it is most likely easily fixed. The bad news is that an intermittent connection can take awhile track down (sometimes it works and sometimes it doesn't ...)

[Captn Bob]

Playing a long shot - one of my '74 Cornwalls had the same problem when I first got it. I traced the problem to a cold solder joint inside one of the transformers. I peeled back the wax paper, resoldered it and it's been fine for the last 37 years,

I'm not recommending you do this unless you are pretty experienced with such things. The midrange driver on the Cornwall is really hard to damage - PWK used to say they almost never got them back for repair.

You've got good advice above. You should be able to figure it out without too much trouble. Remember, you're just trying to isolate the problem one thing at a time.

Bob A.

[PrestonTom]

With all due respect, it is premature to start taking apart auto-formers.

It is best to follow the decision tree that I outlined above

[WMcD]

Some thoughts.

This seems to be a somewhat typical situation where a new member has bought a used unit, and then finds that something is wrong. Perhaps the problem is why the seller sold them.

PotW, if you find that the midrange is on the fritz, I wonder if you easily detect whether the tweeter is working (or not) too. I'm not sure I could by ear detect whether the tweeter is still working with the woofer sounding -- the tweeter is really only sending tinkling sounds. It is a narrow issue in the long run. However, if both tweeter and mid are not working, it would point to certain solder connections on the crossover board. But this is being overly technical at this point. Rather, I suspect it is just a messed up screw down connection.

It is not clear to me just what work PotW has done wtih connection and taking the unit apart. PotW, what I'm suggesting is something you can do which is just a step above changing a lightbulb. No insult intended in the below but I'm assuming your're new to this..

If you have not done so already, you'll have to open up the box by unscrewing the back panel. Be a little careful because there is wire from the input terminal on the back to the crossover board. You can move the back panel to the side without straining the internal wire connection..

You'll find the crossover board where many wires to the drivers (three pair) and the connection from the input terminal (one pair) come together. The connections to the crossover board are wires with spade lugs. These are the U- shaped pieces soldered or crimped to the end of the the wires which fit under screws on the terminal strip on the crossover board.

It is pretty common that the screw-down connections get loose or corroded over time. I suspect this is your problem.

All you have to do is back off the screws by 1/8th turn. Lefty loosey. And then snug them up. Righty tighty. Make sure the spade U-shaped connection is pushed in under the screw head. as you do this. You'll see. It is simple.

On the crossover board terminal stips from Klipsch I've seen the following is true: The screws holding the terminal stip to the plywood base are Phillips screws (you don't have to work these). The screws which are the electrical connection to the drivers are just slot head. You probably have this typical screwdriver.

I always suggest that if you are taking things apart, you label things with masking tape tabs with lettering and take pictures.

We are interested in what you're doing and so please do post pictures. (I always request that they be reduced to VGA size so as to not burden the system) You will be one of our new experts.

WMcD

[dtel]

Hello all. I recently purchased a pair of 79 Cornwalls and when I first hooked them up the midrange horn was out. I messed with the connection and then midrange horn was fine. Now the horn keeps going out again. I switched channels and changed connections and I keep having the same issue with the horn so I know it's not my amplifier.

I had the same thing happen but with a forte ll, it was the connection at the horn. It looked clean metal to metal on the connection but did the same thing your saying. Cleaned and sanded the connectors a little and it worked ever since. So I guess that could happen at any of the connections after many years. Hope it works, it's easy to try anyway.

[T.H.E. Droid]

The connections between the voice coil and terminals are very delicate and can even be damaged by applying too much heat on the driver terminals. They can also suffer from cold solder joints. If you are not good at soldering or have the correct wattage soldering pencil you should leave the job to an experienced technician.

[Captn Bob]

Agree completely on both counts.