Vintage Headphone repair, help needed

I have some vintage Superex Stereophones, model Pro B-VI (with a google search only find an ad in a paper dated 1973 referencing them). They have both a tweeter and a woofer in each ear, and I believe the resistors in the crossovers have gone bad. The high end drops out now and then to pop back in after a short while or after a minor volume adjustment - other than that the volume is crystal clear. Am I right in assuming the resistors could be the issue? The other components in the crossovers are just inductor coils, which are know are for the low pass, so it can't be those. I know instructables isn't a electronics repair forum, but I wasn't too sure of where else I could ask and find knowledgeable people. I love this site. :) I.W.

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g.begnozzi2 years ago

Hello I.W. are you still there?
I'm right now fighting me too with this Pro B-VI.

Did you fix it?

I'm facing the same issue as your, my headph. they have two caps 0.0022uF (see pic) and the issue it is not due to a caps fault. because I see watching your picture, that you haven't caps at all.

Moreover, I can't understand what exactly the inductor is because I tryed to figure out how this cross over works and watching at the pcb I can't understand it. Is pehaps this double inductor, used as a trasformer?

schema_1.jpgPad_2 IMG_20150131_140702.jpg
westfw9 years ago
It's more likely to be the capacitors that have gone bad. Electrolytic caps have a finite lifetime...
crisams westfw7 years ago
You are right about that but in incredibleweirdo pcb picture the capacitor is missing. I have the same model Pro B-VI and the capacitors are there , I will make a picture of my pcb and post it. I hope this will help.
incredibleweirdo (author)  westfw9 years ago
Yeah, that would have been the easy one to figure out, but there are no capacitors in there.
guyfrom7up9 years ago
if you open it up does anything look burnt, melted, cracked, etc?
incredibleweirdo (author)  guyfrom7up9 years ago
No, everything looks hunky dory. As a matter of fact, I've no need to open them at all - the shells are clear plastic. Another thing I forgot to mention - the resistors only have 3 stripes, not 4. Red, Red, and Green. I'm thinking 220k? There's a gap where the 4th stripe for the tolerance would be.
Those are old carbon-composition resistors. The tolerance band: gold means +/- 5%, silver means +/- 10%, and none means +/- 20%. A lot of old carbon-composite resistors have three bands, if you've spent much time dissecting old electronics. Old resistors weren't nearly as accurate as modern ones. And wouldn't red-red-green be 2.2 M ohm? Unless it's old paint, and actually supposed to be yellow.
incredibleweirdo (author)  CameronSS9 years ago
I figured that out, and was coming to edit my post when I saw your reply. Yeah, not 220k, 2.2 M ohm. Not sure why I didn't pull my multimeter out before, but I just did, and +/- 20% would make sense, as the one I tested read 2.0 M ohm. Still wondering what could be causing my problem, though. :\
can u post a photo?
incredibleweirdo (author)  guyfrom7up9 years ago
This is a view of the pcb in one of the ears with the shell removed.
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