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I noticed today that the tweeter in one of my Dynaco A-25 speakers is not putting out any sound. I took the tweeter out of the speaker system and it works, but when I put it back in the system it does not. So I figure it must be the crossover. All the solder connections look clean, So could it be the five position switch or the capacitor. I should probably replace the capacitor any way. Could the switch also be bad? I do not have equipment to test these components. Any advice would be appreciated.
Follow Ups:
I know your question is how to best troubleshoot and repair the tweeter connection.
May I suggest you replace both tweeters? When I rebuilt my A-25's I replaced the tweeters with a modern replacement. Major upgrade. Are the speakers still A-25's? I don't know but they sound great. The stock tweeters paid for half the new tweeters cost.
Thanks for the suggestion. I have done that with other Dynaco speakers I have had. I replaced the tweeters with modern Seas tweeters in another pair of A-25's and used Morel tweeters in a pair of A-35's. But the A-25's I have now are in perfect cosmetic condition and I want to keep the original.
Hi Tadlo,
When I look at the A-25's crossover there are a total of 8 spade lugs between the input jacks on the back of the speaker to the woofer and tweeter counting the spade lugs on the drivers themselves. A way to write those off as not being a problem is to solder the wires without the lugs to the terminals. I'm sure for mass production and less driver damage due to the solderers ability spade lugs were chosen for the speed of building and the ease of replacing the drivers. I soldered mine. It's a better connection sound wise anyway......Mark Korda
That seems like good advice, but I am pretty sure the problem is the capacitor. When I by-passed the capacitor the tweeter worked.
And rebuild both crossovers. You could have that done for not too much. A25's are nice and worth it as I see it.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
Hi Tadlo,
The way I test my A-25 tweeters without anything special is that I take a fresh 9 volt battery and put a wire from the positive terminal of the battery to the positive lead of the tweeter and vice versa with the negative terminal(s). If the tweeter is working you will hear a distinct clicking sound.
If the tweeter checks ok use the 9 volt battery on each position of the switch, the positive side with a wire attached to each 5 positions of the switch and see if you get the clicking noise. Keep the negative battery wire connected to the negative tweeter terminal and use that positive wire attached to the battery as a probe and touch each wire from all 5 resistors and the capacitor and I think you can find the culprit in your crossover. All the guys before me covered the cleaning.
I have an example of the A-25 crossover in my hand and I can easily follow the positive ends of the cap and resistors by following the wires from the red binding post on the back. My cap is non-polarized 8 uF 25 volts and if any of the previous guys think the 9 volt battery will do any harm they should speak up. I just wait to hear the clicking tweeter sound then back off. I have not damaged anything yet....good luck and go find that problem...Mark Korda PS...It's the same as a continuity test with a multimeter. If you do have a multimeter you could attach the wires of the battery to the cap for a minute or so then use your multimeter and measure the caps DC volts and watch your meter to see if the cap holds some voltage and slowly dissipates it. You know it's best to replace it but it might be a fun experiment anyway...Mark.
Thanks for the information and advice. Before I saw your battery suggestion I tried using the wires from an amp with music playing at a low level. The tweeter definitely is working. It seems that the signal is getting through the resistors and that the only thing interrupting the signal to the tweeter is the capacitor. Is it possible when a cap fails for it to totally interrupt a signal trying to get through it?
Hi, just jump the cap out with a piece of wire etc and play at a low level again and see if it works.
Thanks. That is basically what I did.
The switch is dirty. Get some contact cleaner, spray it in the slots and switch it back and forth a dozen times or so. Do the same to the other speaker.
Thanks. I tried De-oxit but it didn't fix the problem.
No expert here, but if it were my problem I would try to eliminate the switch as a possible cause before replacing the capacitor. A little
De-Oxit or similar, working the switch a little, trying different positions should tell you something.
It never hurts to replace the capacitor, but watch your hands in that tight space while soldering. I nearly became part of the circuit once.
Thanks. I tried De-oxit and it did not fix the problem.
You could try bypassing it. Alligator clips would suffice for a test.Dave
Edits: 12/04/16
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