Vintage Products

Re: Beovox 3702 Restoration

HarryPierce — Tue, 14 Feb 2012 14:08:13 GMT

Sorry, I didn't mean it like that...I think it is a great idea. Where do you source the velcro stuff? Thanks!

Re: Beovox 3702 Restoration

Rich — Tue, 14 Feb 2012 13:24:45 GMT

Seriously, six or eight of these per speaker and problem solved. That's what I'm using on my second pair of M70s.

Re: Beovox 3702 Restoration

HarryPierce — Tue, 14 Feb 2012 13:09:19 GMT

Because this would be too easy

Re: Beovox 3702 Restoration

Rich — Tue, 14 Feb 2012 12:24:43 GMT

Good work, and congrats!

Why not use velcro?

Re: Beovox 3702 Restoration

HarryPierce — Mon, 13 Feb 2012 21:51:54 GMT

Just wanted to give a quick update on my progress: I put everything back together. Here a shot of the installed recapped crossover with terminals in the back. I put the terminal in a location covering the original cable feedthrough so I would not have a hole to plug in the back wall:

One note regarding using a hole saw on the back panel: The side walls are exactly 15 mm thick, i.e. this needs to be taken into account when marking the center spot for the hole saw. Otherwise it is easy to accidentally cut into the side walls if one wants to stay next to the wood slat that holds the crossover...

Here a shot of one of the speakers after reinstalling the woofer:

I am listening to Herbie Hancock's Maiden Voyage...very nice! It seems the mid and treble speakers are in good condition. Both speakers sound the same, i.e. it appears this worked out nicely!

Thanks for your help and input!

Now on to the broken cover. Seems the previous owner was not able to restrain his curiosity and broke one of the covers while trying to pry it off...Something for the next weekend...;-). I am thinking of using small magnets to hold them in place once they are fixed instead of the double sided tape...

Re: Beovox 3702 Restoration

HarryPierce — Tue, 07 Feb 2012 23:50:31 GMT

mine say Type 6263 on the back...I am waiting for the terminals...more after the weekend

Re: Beovox 3702 Restoration

Søren Mexico — Tue, 07 Feb 2012 21:55:15 GMT

Sorry Rudy, took it from memory, at first I had it right, but then I thought it was wrong and changed it.

So you have the same type as I, the 6233. did you test them yet or are you waiting until you get the terminals in place.

Re: Beovox 3702 Restoration

HarryPierce — Tue, 07 Feb 2012 21:30:57 GMT

Are you sure you read the second one correctly? Mine looked exactly like yours. From left to right (on your pic) I had 5uF, 12uF (25V), 75 uF, 25uF, 75uF. I replaced them with 4.7, 12, 68+6.8, 22+2.2, 68+6.8.

Re: Beovox 3702 Restoration

Søren Mexico — Tue, 07 Feb 2012 15:42:03 GMT

HarryPierce:

The dent in the tube only goes about 3 mm down....do you think this is really a problem? Seems really hard "party operation" would be necessary to cause scraping...I tried to bend the dent back out, but the material is quite elastic, and I was afraid I might distort the overall shape of the tube...

As it only goes 3 Mm down I dont think it will be a problem.

BTW can you post the caps and resistor values from your crossover, I think they are diff. from mine.

I have left to right, 5 uF, 25 uF, 75 uF, 12 uF, 75 uF

Re: Beovox 3702 Restoration

HarryPierce — Tue, 07 Feb 2012 11:19:22 GMT

The dent in the tube only goes about 3 mm down....do you think this is really a problem? Seems really hard "party operation" would be necessary to cause scraping...I tried to bend the dent back out, but the material is quite elastic, and I was afraid I might distort the overall shape of the tube...

Re: Beovox 3702 Restoration

tournedos — Tue, 07 Feb 2012 04:26:02 GMT

Søren Mexico:
About the lacquer on the mid range, there are some special brands out there, but I dont know anything about it, so maybe another member could give some advice about it.

I don't think it needs anything. Certainly not paint! That would increase the mass of the cone a lot and it wouldn't sound the same any more (and so will a handful of dog hair ).

The special coatings are usually there to stiffen the cone or to repair/prevent rips. It think Visaton is one brand, perhaps you can find the marketing material somewhere and decide if it would be useful in this case.

Re: Beovox 3702 Restoration

Søren Mexico — Tue, 07 Feb 2012 01:17:55 GMT

Rudy, on your shimming pic I see that the "tube" around the coil has a bend in it, as these drivers has a long pull, this may give distortion or "scraping" when adding a lot of bass or plaing very loud, test it before taking of the dust cap again. And dont kill the messenger

Re: Beovox 3702 Restoration

Søren Mexico — Tue, 07 Feb 2012 01:10:11 GMT

Rudy, took a look more on this pic. The "tube" around the coil has a bend at the top, and as these drivers has a long pull, this may give "scrathing" when having a lot of bass or plaing very loud. I know its bad news, but try it out before you start taking of the dust cap again. And dont kill the messenger

Re: Beovox 3702 Restoration

Søren Mexico — Tue, 07 Feb 2012 00:28:58 GMT

HarryPierce:
I still did not put the woofers back in. I am discussing right now the philosophical question whether to insert cable terminals into the back panel of the speakers or leave everything original with the cables directly soldered on to the crossover...Right now I am leaning towards the terminals and using nice modern cables.

I would go for the terminals, all other speakers I have repaired has terminals, and its a lot easier to get the drivers out with terminals.

I didn't get my caps from Martin yet, so I could not preceed, Parts Express wants me to buy for at least USD 50.00 and then they charge me more or less the same for shipping to Mexico, so I will just have to wait until I get up there, or try again with Martin.

Now please get on with it, I'm real curius abaut the result.

About the old caps, they are bipolar, but just marked with plus and minus, because in some positions they use the shield as ground connection.

About the lacquer on the mid range, there are some special brands out there, but I dont know anything about it, so maybe another member could give some advice about it.

Very good job and lovely pics. Congrats

Re: Beovox 3702 Restoration

HarryPierce — Mon, 06 Feb 2012 23:54:51 GMT

I thought I would post an update about my 3702 project: I basically followed Soren's advice. First I removed the old foams as good as I could and cut off the dust caps:

The next step was to glue on the new foams (I used the ebay store Soren recommended - very fast and nice quality). Here it was important to not put too much glue on the foam. One wants to avoid that a significant amount of glue gets squeezed out from inbetween foam and cone since this can get messy. I had to remove the foam the first time and take 50% of the glue off, then put it back on:

Attached to cone. I simply pressed the foam on the cone going around the cone again and again and pressing them together. After ~5 min the foam remained stuck down (less glue works better...)

The next step was shimming. It turned out that laser printer transparencies are perfect. These woofers took two strips (~0.13mm thickness) in three locations. After putting them in the speaker cone was almost immobilized, but would still move if pushed.

Next step: Glueing the foam to the cage. Here I used a perfectly matching dinner plate to hold it down during drying:

One day later, I glued the dustcaps back on. A thin layer of glue does it (glue is still white in the pic):

On to the cross overs (again followed Soren's advice, and bought from Parts Express; a nice experience):

Here the old crossover:

And here after cap exchange:

I tried to match the original capacitances as good as possible, i.e. I used some combinations in parallel, since the original values were not available.

Strange thing: The original caps seemed to have been mostly ordinary polar electrolyte caps. I guess one can make an argument that that may work since the signal is mostly true AC without DC component, i.e. the electrochemical dissolution of the electrodes under reverse bias should reverse itself during the next halfwave at opposite polarity...I measured the ESR and capacitance of the old caps. Most seem to have survived well...all except the 12uF ones were at spec.

The next step was cleaning off the doghair from the sticky midrange speaker (quite a mess!!). Ethanol finally did it, but most of the sticky laquer came off in the process:

I am wondering if I should leave it like this, or paint them again with some glossy black??

I still did not put the woofers back in. I am discussing right now the philosophical question whether to insert cable terminals into the back panel of the speakers or leave everything original with the cables directly soldered on to the crossover...Right now I am leaning towards the terminals and using nice modern cables.