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Woofer buyer warning


dynaco_dan

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Hi there;

There is, for those who want to run right out and buy 4 - A-50 compatible 15 ohm woofers, used on ebay right now.

Ebay 220153517759 has 4 listed at this time.

It is mentioned in the write-up that 3 of the 4 are good, but one has a buzz or such.

Based on my experience, only consider the auction to actually have 3 salvageable woofers.

There is not much chance that the 4th is salvageable, but if you are the winner, I will talk you through troubleshooting it.

I have seen oodles of them, actually hundreds, so I should have said hoodles of them.

Do not consider it serviceable at this time.

Remember that a Dynaco classic 10" woofer from A-25, A-35 and A-50, if there is even the slightest faint buzz, it is damaged, however slight.

When I say damaged, it should not be considered of any monetary value to you.

I might be able to repair it, but no promises.

Also these woofers require special packaging in order to arrive unscathed.

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  • 1 month later...

I just bought a pair of A25's off eBay. I hooked them up and found that one of the woofers was producing very distorted sound. I pulled of the grills on both and checked each woofer. Gently pushing on the cones yielded two distint results. The 'good' woofer traveled back and forth effortlessly and produced no sound. The 'bad' woofer felt resitive and made a scratching noise. The 'good' one sounds stunning and I want to get the other sounding as good. Can you provide me with any advise? Can this be fixed? Are replacement drivers available?

TIA,

Jim

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Vern,

Thanks for the reply. I was afraid that would be your answer. I may just bid on another pair and see what this seller will do for me. According to his ad these were in perfect working order. I just thoght there may be a fix that I was not aware existed.

Thanks again,

Jim

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Hi again;

With your physically resistive woofer, very likely the voice coil is burnt and the wires have un-wound a bit in the gap.

If the woofer did nothing at all, then we might have tried surgery, mental surgery first.

Even the slightest of buzzes is call for rejection.

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Back again;

There is a set of raw Dynaco drivers on the auction block now.

One woofer is stated as it has been repaired and the repair will not affect the sound.

I've downloaded the photo of the affected area.

Only time will tell if there will be any audible problems.

IMHO I would not accept a glue job as something to just ignore or take lightly.

It may seem real petty, but there is now a slight imbalance to the cone.

It may also add a false resonance.

If that woofer was thrown in at no extra charge, then it is worth it.

In perfect working order may not have taken into account shipping damage.

These woofers require special shipping methods not usually used by sellers.

A portion of your auction and shipping charge is due to you for that woofer.

When I previously mentioned a slight buzz, I was not clear enough.

A slight buzz may be some bubbling on the voice coil form or on the top surface of the coil insulation.

I can try to talk someone through checking out something like this problem, otherwise the woofer is burnt and of no value to you.

post-101040-1193540941.jpg

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I pulled out the offending woofer just to be certain that there wasn't any mechanical reason for the resitance. I found nothing rubbing against the cone. Your prognosis of a burnt voice coil seems to be on target. Now I need to see what the seller is willing to do to fix this problem. You said that there were some raw drivers up for aucton. Did you mean on eBay? I will be looking for a replacement as well.

Thanks again,

Jim

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>I pulled out the offending woofer just to be certain that

>there wasn't any mechanical reason for the resitance. I found

>nothing rubbing against the cone. Your prognosis of a burnt

>voice coil seems to be on target. Now I need to see what the

>seller is willing to do to fix this problem. You said that

>there were some raw drivers up for aucton. Did you mean on

>eBay? I will be looking for a replacement as well.

>Thanks again,

>Jim

Hi Jim;

Sorry, if I was right, Jim.

If you haven't done anything to the woofer, please don't destroy it yet.

If you have the time and energy I would suggest disecting the driver as follows, please and take photos and post them here.

There is not much opportunity for members to see what I saw hundreds of, back in the early '70's.

Peel up the outer perimeter of the rubber surround from the frame.

Un-solder the two tinsel leads from the terminal strips.

Out of doors, very carefully use acetone and a natural hair brush to moisten around the perimeter of the spyder and the frame.

It should disolve the glue and you should be able to remover the entire cone assembly in one piece in about 30 seconds.

Various views will be of interest to some members here, please.

Ebay usually has a few woofers on at any one time.

As always, use caution, in that there is 2 different brands of 10" woofers, Seas and Scan and also the original 8 ohm A-25 woofer and 15 ohm A-50 woofer, which is identical except for the label marking for the impedances.

Usually there is a photo of the label and just look for the 8 ohms and you can't go wrong.

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Vern,

The seller has contacted me and may be providing me with a replacement woofer. If I don't have to ship back the blown woofer, then I will provide you with an illustrated dissection of the speaker. I enjoy providing any useful information to these forums, since I have learned so much from them.

I will let you know the outcome of my negoiations.

Jim

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Hi Jim;

Good luck with a price/goods adjustment.

A Dynaco single woofer should be shipped as follows.

They have the 1/2 roll rubber surround which protrudes beyond the frame about 1/2" or so.

I've written here previously about how Dynaco shipped the OEM woofers to our warantee depot.

I do not have a photo of the ones I have on hand, sorry.

I will try to describe the process, as simple as possible.

Place at least 3 equadistant bolts, about 1 1/2" - 2" long, with nuts which when mounted correctly into the screw holes will keep the surrounds above any flat surface, just like spider legs.

A piece of any guage wire connected, even crudely, between the two terminal strips, will prevent the back and forth motion of the cone in transit as well.

Now the speaker can be placed against a piece of cardboard, a few inches larger that the woofer frame, or plywood and wrap it with shrink wrap or Saran Wrap.

This prevents anything from touching the surround/cone in transit.

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Vern,

Thanks for the information. I am going to supply this to the seller just in case he is unaware of the process. I will keep you informed as to my progress.

Thanks again,

Jim

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Hi Jim;

If you saw what Dynaco used to ship their woofers, it is so simple.

They used what looks like blind end crimpon electrical connectors, less the metal insert.

One per hole which kept the surround adequately clear of the cardboard frame they made for shipping them.

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Guest fetzenpeter

Christian from Paris to Vern

Hi Vern, here I am again ! Glad to have found you again !

I am the one with burned woofer and tweeters of an A-25.

Meanwhile I found and bought a pair of woofers "SEAS made in Scandinavia, 25 TV - EW", and Dome-Tweeters "Type Dome H-087". Both pairs come from discarded A-25 and are, I was assured, in good functioning condition.

I would love to simply screw them into my old cabinet, and connect them up to the wires.

The screw holes would fit nicely ! But I am uncertain if I should do so.

Why ? Because the cross-over arrays from the same A-25s where the woofers/tweeters came from, and which I received in the bargain, look a bit d i f f e r e n t from mine.

Especially there is a "Jensen electrolytic cross-over capacitor" "5 uF, 50 WVDC, 25 WVAC", round and in a golden metallic color, like a battery,

whereas in my own old cabinets what seems to be the capacitor is yellow plastic with a box-like shape, and is marked "14,7 uF/10/100".

Finally the speaker wiring for the newly acquired woofer/tweeter is black-red / black-white, whereas for my own cabinet the cables are black-red / black-blue.

And: Outside the cross-over array is a "Made in Denmark" imprinted below the 8 Ohm, which does not figure on mine.

Could you please tell me whether I may hook these SEAS woofers/tweeters into my old cabinet without further ado ? Do you need any additional information to tell me ? Should I open my other cabinet and have a look at the woofer/tweeter in there ?

Best regards, and thanks again for your help,

Christian from Paris

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Vern,

I got the replacement and installed it in the cabinet. What beautiful sound these 33 yr old speakers make! Per your directions, I did manage to dissaemble the bad woofer and found that the voice coil (?) surrounding the magnet was burnt and had split in two places. If you think it would be of use, I will take some pictures and upload them to the forum.

BTW, I would have written back sooner, but the url for the site changed when it migrated to the new software.

Thanks,

Jim

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Vern,

I got the replacement and installed it in the cabinet. What beautiful sound these 33 yr old speakers make! Per your directions, I did manage to dissaemble the bad woofer and found that the voice coil (?) surrounding the magnet was burnt and had split in two places. If you think it would be of use, I will take some pictures and upload them to the forum.

BTW, I would have written back sooner, but the url for the site changed when it migrated to the new software.

Thanks,

Jim

Hi Jim;

A few photos at different angles would be great, thank you.

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