Defect capacitor on JBL 4344 ??

[Ian Mackenzie]

Ian, one question please: Are you sure this capacitor is linked to the 2421 horn ? Would it be the 2405 instead ?
Because I have noticed (with my measurement device) a significant difference of level between the 2405 level between the 2 speakers.
Thanks
Damien

That is probably the tolerance between the 2405 drivers , the L pads or your measurments.

Yes I am sure.
http://www.audioheritage.org/vbullet...46&postcount=4

[Madien3388]

By doublechecking the 3145 Xover schematic and seeing your previous picture of the gooped capacitor (printed as C7 on PCB) we can understand that only C7 in HF section is equal to 3µF

A new problem with UHF

http://audioheritage.org/vbulletin/s...3144+schematic

I'm not sure to have understood well... Could you please explain in more details for newbie ;-)
Thanks
Damien

[ratitifb]

[Chas]

Now that's a clear answer! Nicely done.

[Madien3388]

Thanks! I thought you were saying that the gooped capacitor did have the good value.
Now it is clear. Indeed the only 3 microfarads capacitor is for UH.

Regarding the UHF, I can have the same level between the two 2405 by adjusting the L-pads. I think one of the 2405 may have indeed a lower level, or the L-pad is not as good as it used to be. But everything's working normaly.

[Madien3388]

As I am quite stubborn when I have something in my head, I have realized that in the first picture, we can see easily the solders on the pliers.

If I use a solding iron (50 watts), is it possible to remove all the solder within each plier ? I do not see that as difficult but I may be wrong : by touching the solder a few seconds, the solder should go and relieve the plier, shouldn't it?

If there is still some solder on the rod after having removed the plier, I could use the solding iron one more time with a mechanical solder sucker ?

As we say: you have to target Mars to reach the moon... I am motivated

[Chas]

Some may think this is a heresy, but given the situation your in....you could simply cut the capacitor lead on one side between the body and the board to remove it from the circuit for testing purposes and splice it back together afterward.

Not pretty, I know.

[ratitifb]

you could simply cut the capacitor lead on one side between the body and the board to remove it from the circuit for testing purposes and slice it back together afterwards.

good idea that I have not dared to suggest
(but take care to don't lose the small piece of wire soldered on PCB when heating and resoldering with a strapp ... don't overheat capacitor !)

Regarding connecting part and to avoid overheating on the PCD Cu layers ... it should be better to remove all connecting parts directly from PCB and replace them by new ones ...

After having removed all wires with soldered connecting parts you have time to heat and clean/replace all different elements.

[Madien3388]

Another solution, quite similar, would be to cut the cables. Bring the board to a shop able to do a good job : then they would remove all connecting parts directly from PCB and replace them by other ones ...
But is it still possible to find the rods soldered on the PCB and also the same pliers ? And I think it is required to have a special tool to install the pliers on the cables.

[grumpy]

Personally, if I was going to remove the board, I'd hold the crimped on connector
(part with the wire on it)

with small needle-nosed pliers at the crimp, heat the bottom of the connector and
male tab on the board, then separate the connector from the male tab once the
solder melts (may need to 'wiggle' the connector from side to side while pulling).

Then clean up the tabs/connectors with solder wick (copper braid intended for this
use), so that the connectors will slip back onto the spade lugs later.

Cutting all the wires, and then re-installing new connectors would also work if the
proper crimp tools were available, and there is some slack in the wire such that
a few cm less would not be a problem.

[ratitifb]

if the proper crimp tools were available

an alternative only is to solder wire in crimp area ...

[4313B]

I have realized that in the first picture, we can see easily the solders on the pliers.

That's because those faston connectors are crap after 30 years if left unsoldered. Just heat them up and pull the female fastons off the male fastons. It's nice to see that someone took the time to solder those puppies together.

[Madien3388]

That's because those faston connectors are crap after 30 years if left unsoldered. Just heat them up and pull the female fastons off the male fastons. It's nice to see that someone took the time to solder those puppies together.

Many thanks to all of you for your help, I really appreciate. I would like to be able to help you one day in return but obviously I have less electronic skills than you have.

4313B, the way you describe it, it seems quite easy to remove the solder from the pliers (of course if I do it carefully).
According to other pieces of advice, there is some risk to do that because it could damage the PCB due to the high heat of the soldering iron. What do you think ?
Perhaps, as the solder is in the middle of the female faston (as seen in the picture), it could be difficult to have access to it ?

The best would be to remove the solder of the pliers as you describe, hopping that the pliers will be able to enter in the male faston without having to replace them by new ones.
Damien

[Madien3388]

Has anyone got the book "solder for the dummies" ?
I have found this soldering iron. I'm not crazy, I won't do anything if it is too risky. So if you could tell me if it is the correct tool to try to remove the solders on the pliers, it would be great.
My only goal is to remove the solder on the pliers so that I can disconnect the pliers from the filter. I will let a professionnel shop testing the capacitor.

Here are some pictures. There is a "potential balance" in the back. I have no idea of the temperature of this solering iron. Is it better to use it at the lowest temperature ?
Tomorrow a friend of mine will give me another else soldering iron. So, more chance to find the good one.

Have a nice week-end
Damien

[grumpy]

That will do. The temperature on those is set by the tip that is installed.
Should be a "6" if it is 'normal' "7" would be hotter than is normally used
for circuits. If you unscrew the collar at the base of the chrome shaft, the
tube holding the tip slides off. ... look at the end opposite the point.

connection on the back is for grounding... used with sensitive circuits
(not this).