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[Greg Ruddell]

Hello and welcome:

The first thing to do is go into your account and change your alias to your real name per the posting rules.

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Your post is quite well written, BTW. Make sure the (2) woofers are in polarity with each other. You can go by wire colors, but I'd suggest placing a 9 volt battery on the input and make sure both drivers move in the same direction.

If they were not in polarity, remeasure and see if that fixed it. If they were in polarity, try reversing polarity of the tweeter leads and see if that fixes it.

Oh yeah, unfortunately I do have experience fixing JF80's...

Just wanted to report what I know now that I have finished repairing my 6 JF80's. These were grouped into pairs of close serial numbers, but all of them had the smae rcf drivers which were all in great shape as well as the original horn drivers which were also in great shape.

Two of the LF crossover boards looked fine with no visible damage to components, but the still sounded different from each other and all others sounded different from all others. I think it's a case of varying degrees of capacitor damage or decay.

I replaced the 15 Uf cap with a 15 Uf cap on the upper board.
I replaced the 21Uf cap on the upper board with a 22 Uf cap (can't get a 21 anymore).
I replaced the 15 Uf cap on the lower board with a 15 uf cap
I replaced the 4.7Ohm 25 watt resistor on the top board with a 4.7 Ohm 25 watt resistor
I replaced the .033 Ohm 25 watt resistor on the top board with a 0.33 Ohm 25 watt resistor

I was surprised at how they all sound almost identical now. They sound brand new. Really punchy bottom end and crisp pristine highs like they are supposed to have. Of course they need eq. or processing, but not much.

[Bob Leonard]

It's a well known fact that once an electrolytic reaches a certain "age" it needs to be changed. That can vary depending on manufacturer, use and environment, but regardless that age tends to be somewhere around 10-15 years. How old are your cabinets, and correct, you can't buy 21MFD electrolytics anymore??

[Greg Ruddell]

It's a well known fact that once an electrolytic reaches a certain "age" it needs to be changed. That can vary depending on manufacturer, use and environment, but regardless that age tends to be somewhere around 10-15 years. How old are your cabinets, and correct, you can't buy 21MFD electrolytics anymore??

Bob, I think the oldest pair is probably at least 15 years old. The serial numbers are very early. The other two sets are probably at least ten years old. All of theses boxes would have been used at the edge of their envelope in terms of duty cycle and probably beyond on occasion. The sound company was well established and had some large KF rigs that they provided for large events. On the whole the jf80'S were very well looked after cosmetically, even had the original road cases for them which they generously gave us. I ordered some new grills for them through my distributor and luckily EAW still has them.

[David Morison]

I replaced the .033 Ohm 25 watt resistor on the top board with a 0.33 Ohm 25 watt resistor

Typo?
Am not familiar with the exact circuit but I'd think that an order of magnitude change might be problematic if that wasn't a finger-slip.
Cheers,
David.

[Chris Davis]

Just wanted to report what I know now that I have finished repairing my 6 JF80's. These were grouped into pairs of close serial numbers, but all of them had the smae rcf drivers which were all in great shape as well as the original horn drivers which were also in great shape.

Two of the LF crossover boards looked fine with no visible damage to components, but the still sounded different from each other and all others sounded different from all others. I think it's a case of varying degrees of capacitor damage or decay.

I replaced the 15 Uf cap with a 15 Uf cap on the upper board.
I replaced the 21Uf cap on the upper board with a 22 Uf cap (can't get a 21 anymore).
I replaced the 15 Uf cap on the lower board with a 15 uf cap
I replaced the 4.7Ohm 25 watt resistor on the top board with a 4.7 Ohm 25 watt resistor
I replaced the .033 Ohm 25 watt resistor on the top board with a 0.33 Ohm 25 watt resistor

I was surprised at how they all sound almost identical now. They sound brand new. Really punchy bottom end and crisp pristine highs like they are supposed to have. Of course they need eq. or processing, but not much.

Thanks for filling us in with your outcome.  I wish more people did that.  It never fails to amaze me how much of a difference fresh caps can make when restoring speakers.

[Greg Ruddell]

Typo?
Am not familiar with the exact circuit but I'd think that an order of magnitude change might be problematic if that wasn't a finger-slip.
Cheers,
David.

Ah yes. It's a typo David. Thanks for catching that. It should have been 0.33 Ohm. 

[Greg Ruddell]

Thanks for filling us in with your outcome.  I wish more people did that.  It never fails to amaze me how much of a difference fresh caps can make when restoring speakers.

My pleasure Chris. It was a valuable learning experience for me. I really didn't expect that kind of dramatic result.

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