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DingDing
09-21-2015, 02:10 AM
Hello,
My brother has a pair of gorgeous looking model 19's that were not working properly, so we investigated them this weekend.

67132

One of them were working properly, but on the other the diaphragm in the compression driver was teared and the low frequency driver had a rub. We mounted the low frequency driver the opposite direction and the rub went away. It will be reconed if it doesn't get any better and the compression driver will get a new diaphragm. The L-pad on the working unit were also given a run with some DeOxit Faderlube F5. It turned out very well.

The crossover network on the other speaker (the one with a blown compression driver diaphragm) shows some weird behavior. There is continuity between ground and all other used ground lugs. For example, there is continuity between ground and the hot wire going to the compression driver and low frequency driver.

67133

What can be the cause of this? Broken capacitors?

He doesn't want to "upgrade" the speakers. He only wants them "restored" to "original" condition, but with better caps if that's the problem and both crossovers will be restored.

I can swing a soldering iron, but I don't know how to troubleshoot crossover components so I need advice on what to measure and what to buy. Maybe Mundorf caps and tighter tolerance resistors would be a good start?

DingDing
09-21-2015, 11:13 AM
So I found the schematic for the N1201-8A XO network.

67144

I can read most of it, but what does the arrow pointing towards the resistor in the top left corner mean?

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Set up a shopping cart with parts express, using Dayton Audio's 1 % 250V precision audio capacitors which are metalized polypropylene.

67145

The idea for the resistors is



SPEC / ORIGINAL

REPLACEMENT



R2, R4 = 3.9 Ohm 10 %

4 Ohm 1 %



R5 = 2 Ohm 10 %

2 Ohm 1 %



R6 = 3 Ohm 10 %

3 Ohm 1 %




Is replacing the 3.9 Ohm 10 % with a 4 Ohm 1 % an issue? Can't find a good way to combine resistors to achieve 3.9 Ohms.

As for the capacitors, the idea is



SPEC/ORIGINAL

REPLACEMENT



C1 = 8 mfd, NP

2 x 4 mfd



C2 = 16 mfd, NP

1 x (15 + 1) mfd



C3 = 21 mfd, NP

1 x (20 + 1) mfd



C4 = 6 mfd, NP

2 x 3 mfd




Is the above plan good to go or are there any concerns? Also, say you want 6 mfd, would 2x3 or 5+1 be better or are they equivalent?

The coils and variable pots will be left as is.

Don C
09-21-2015, 12:48 PM
I can read most of it, but what does the arrow pointing towards the resistor in the top left corner mean?


That's your L-pad. The arrow shows that it is variable.

Alien_Shore
09-24-2015, 08:03 PM
This might be helpful to you:
Model 19 Ground Bypass (http://www.hostboard.com/forums/f700/178218-model-19-ground-bypass-mods-revisted.html)