Altec 604E Super Duplex conundrum - diyAudio
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Old 26th February 2013, 06:37 AM   #1
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Default Altec 604E Super Duplex conundrum

Lads...in a bit of a pickle here...

Had a set of Altec 604E Super Duplex units w/N1500 x/overs foisted on me today.

While one unit is tickety-boo the other unit has suffered the insult and injury of having some boob apply polyurethane to the backside of the surround ( I imagine in some misguided attempt to compensate for some form of voice coil rub).

Although the LF/MF unit coil tests ok for continuity the resistance reading of about 5 ohms is definitely off. The other non-handicapped 604E LF/MF coil measures at 11.5 ohms.

A play-test with a very low output signal applied to the LF/MF unit confirms almost zero cone excursion, but there is undistorted sound (I didn't dare subject the unit to anymore output as I didn't want to burn out the coil).

It's obvious this horrendous hack job must be remedied...so my question is how?

I am contemplating using acetone or some other agent to soften that gawd-awful foam, but am concerned that in doing so, I may likely damage the surround and/or the cone material.

Suggestions, insights?
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Last edited by devilsindetails; 26th February 2013 at 06:44 AM.
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Old 26th February 2013, 06:45 AM   #2
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Mods...could you edit my glaring header sp mistake? Thks.
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Old 26th February 2013, 02:39 PM   #3
DaveCan is offline DaveCan  Canada
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I think that driver needs a trip to GPA

http://www.greatplainsaudio.com/
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Old 26th February 2013, 02:52 PM   #4
Zen Mod is offline Zen Mod  Serbia
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yup - if coil is south , then no use of cleaning da mess on surround
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Old 26th February 2013, 03:03 PM   #5
Pano is offline Pano  United States
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Title fixed, thread moved to Multi-Way
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Old 26th February 2013, 03:33 PM   #6
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Gentlemen......GPA, of course, is the go-to source for Altec repairs if money was not an obstacle...but I am inclined by nature to investigate this a little further.

So my question remains...what agent could I use to soften and remove the polyurethane foam without damaging the original surround material and cone material?

Thanks, Leo
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Old 26th February 2013, 03:35 PM   #7
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Quote:
Originally Posted by Zen Mod View Post
yup - if coil is south , then no use of cleaning da mess on surround

Zen Mod. Are you saying that if the resistance reading on the LF/MF coil was higher than spec (instead of lower) that it might be salvageable?
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Old 26th February 2013, 03:41 PM   #8
Zen Mod is offline Zen Mod  Serbia
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I'm saying that - if Rdc is erring more than 10% in any direction (from regular value ) , you can call that voice coil Dodo

so - as I understood - that one measuring 5 something is way off , so there is no point thinking about it's cone/surround condition - it needs complete recone

so Dave mention GPA

if other cone is in very good shape - leave it as is ; if it's in so-so shape - recone it , too

those spks are well worth your trouble

I think that boyz at GPA will check AlNiCos routinely

if all that is too much for ya , just send them to me , for proper disposal , free of charge
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Old 26th February 2013, 10:24 PM   #9
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Looks like the foam was a too late botched attempt to fix a cracked surround.
The cracked surround probably led to a scraping voice coil, which partially shorted out judging by the resistance you measured.

Too bad.
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Old 26th February 2013, 11:23 PM   #10
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Cured urethane foam is impervious to any solvent I know of. Acetone will attack most other older adhesives though; beware. Your DCR reading is odd, maybe the crossover is trashed and the two voice coils are paralleled?
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