How to open E-V TRX12B speaker to change caps? - Page 2 - diyAudio
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Old 18th June 2017, 06:39 AM   #11
Lojzek is offline Lojzek  Croatia
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Check with multimeter for short circuit of the tweeter circuit. If it sounds then there is no capacitor in series with it.
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Old 18th June 2017, 09:30 PM   #12
djk is offline djk
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The cap was external on the steel frame 12TRXB.
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Old 19th June 2017, 01:12 AM   #13
nfafan is offline nfafan  United States
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Quote:
Originally Posted by djk View Post
The cap was external on the steel frame 12TRXB.
Yowza, means these have no caps at all installed, just the "Brilliance" control which I guess is a basic pot of some type...

Thanks all for the replies!
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Old 19th June 2017, 10:27 PM   #14
djk is offline djk
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" means these have no caps at all installed"

Only if you were foolish enough not to read and follow the instructions.

The stock value was around 3F (IIRC), I suggest an 18dB network, 3.3F+0.25mH+10F.

It is very difficult to repair the tweeter in these very old EV (aftermarket parts are largely junk).
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Old 20th June 2017, 12:40 AM   #15
nfafan is offline nfafan  United States
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Quote:
Originally Posted by djk View Post
" means these have no caps at all installed"

Only if you were foolish enough not to read and follow the instructions.

The stock value was around 3F (IIRC), I suggest an 18dB network, 3.3F+0.25mH+10F.

It is very difficult to repair the tweeter in these very old EV (aftermarket parts are largely junk).
Nope, no instructions... I have almost zero in the sense of info on these, having picked them up at an audio/video "junk store".

The pics I posted are just as they looked upon getting them home and taking the 4 screws that held the back panel to the cabinet; simple lamp cord wire from the + and - posts on the external driver frame going to the + and - screw posts on the exterior of the back panel.
That plus the integrated wires to the rotating "brilliance" pot. Nothing else.

I have since poked around the net and found E-V "data sheets" (part nos. 53343 and 534611-422) discussing their 12" coax/triax drivers, and they make mention that for a 12TRXB there is the so-called "Mechanical Crossover: 2000 cps" and an "Electrical Crossover: Integral 3500 cps". (I assume cps = Hz.).

No further details on anything else in terms of caps, crossover circuits, how/if wired; nada.

The EDS pdf is too large to attach to this post, so I can't prove I haven't been sniffing furniture stain in a brown paper bag...

Are you suggesting I add what you are describing into the + path to the speaker terminal to create the missing crossover circuit? If so, can you explain further?

Thanks in advance!!
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Old 20th June 2017, 01:01 AM   #16
srinath is offline srinath  United States
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I had similar ones. They're somewhere I cant get to them now.
But there was a foil on one, and the other one had an external XO.
The foil one had a slider switch in the foil for brilliance/presence etc etc.

And in mine, it was installed in a sealed back nice wooden cabinet. Ummm, how're you supposed to adjust that ? Oh unscrew the back and use up 3hrs to listen to this 1 song with a but more treble ??? Gotcha.

Thanks.
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Old 20th June 2017, 01:30 AM   #17
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There was a cap somewhere, half a century ago...
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Old 20th June 2017, 02:16 AM   #18
paba is offline paba  Canada
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Carefully remove that metal label with the Ev logo. Use a sharp knife edge maybe a little heat. My EV wolverine Lt-15 had a little cap inside as the high pass to the horn tweeter. I replaced with better quality but larger cap and it doesn't fit inside. i kept the ev labels and original caps if i ever need to reverse the change but my ears are so happy now. And i dont see the back of drivers so my eyes don't care.

Cheers
Paba
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Old 21st June 2017, 03:21 AM   #19
nfafan is offline nfafan  United States
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OK, no caps... Removed driver from cabinet, pried off foil label - hidey hole but no caps inside. And no caps under frame, guess this is all free-ranging drivers(?).

Label pried off...
Click the image to open in full size.

No seams in bell-housing can be seen.

Click the image to open in full size.

Small bracket inside... and after removal - no caps...

Click the image to open in full size.

No caps hiding under frame or woofer cone...

Click the image to open in full size.

Any suggestions as to how to add a crossover to this if for nothing else but to protect the drivers would be appreciated!
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Old 21st June 2017, 11:14 AM   #20
irext is offline irext  Australia
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The lugs with the braided wire are the woofer connections. The lug in the centre will be the + to the HF driver. It would appear that an external cap would have been connected between the LH lug and the middle lug but someone (butcher) has removed it and replaced it with a shorting link. Probably because it had dried out and become open cct and they didn't understand the ramifications of shorting it out. The HF section may well now be damaged. Try connecting the input wires (Red and Black) to the outer most lugs and a 1MFD bipolar or film cap between the Red outer lug and the centre lug and have a listen. You should hear some output from the HF section if it isn't fried. If you are lucky and it's o/k you can experiment with different values for the cap. It definitely should have a cap in place.
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