Vintage Products

Re: Beovox S-75 Repair and Restoration

Eugene — Sun, 17 Jul 2011 18:25:49 GMT

Leslie:

You're an expert in electronics Eugene Wish I had this knowledge

No no no Leslie. I am no expert.

The reason I use high temp caps off the power supply is not because I conjured up or simply found a better answer but rather it was a solution I stumbled across reading an old forum post by Martin (Die Boegner). I copy the solutions and ideas of other more than I create or solve on my own.

The other factor I look at when sourcing power supply caps is the "life" of the cap. I personally prefer a 3000 hr plus high temp for my power supplies. Maybe it doesnt even matter so much.

Re: Beovox S-75 Repair and Restoration

Søren Mexico — Sun, 17 Jul 2011 17:21:02 GMT

Peter :

That is my old Beocord 2400 that you are using as your avatar! I can tell by the non matching reels! Now that was a beautifully built machine!

One like that is on my wish list

Re: Beovox S-75 Repair and Restoration

Leslie — Sun, 17 Jul 2011 16:59:25 GMT

You're an expert in electronics Eugene Wish I had this knowledge

Re: Beovox S-75 Repair and Restoration

Peter — Sun, 17 Jul 2011 15:44:16 GMT

That is my old Beocord 2400 that you are using as your avatar! I can tell by the non matching reels! Now that was a beautifully built machine!

Re: Beovox S-75 Repair and Restoration

Søren Mexico — Sun, 17 Jul 2011 12:40:18 GMT

Eugene:
Ok then, so I use "audio grade" on the signal path preamp etc, then switch to a high temp standard for the power supply. I dunno, as tight as a BM 2400 fits up it tends to run a bit warm even under the best of circumstances. Would I be smarter to replace all the caps with "high temps" in a situation like that.

Most caps sold today resist higher temps than the ones used originally some 20-30 years ago, so I do not think there will be heat problems.

The heat problems I've seen is more because of bad or to small rectifiers and bad adjusted, or bad, poties. my BM 2400 ran hot before changing caps, rectifier and some poties, but after repair and adjustment rectifiers and cooling elements only got a little more than hand warm. When I open it again and its running, I will check the temps before asambling and then again when in the closure.

Re: Beovox S-75 Repair and Restoration

Eugene — Sun, 17 Jul 2011 07:03:27 GMT

Søren Mexico:

I've been reading myself dizzy about caps, audio grade, audiophile and so on, conclusion: There are as many opinions as there are brands, and none with a good technical acceptable explination or measureable evidence, so a known brand, "normal" cap, bought where they have some turn around (fresh caps) in my opinion for our use is as good as it gets.

I'm curius about how your tweeter will work out

The 30 dollars cross vs the 3 dollar cross and my ears cant tell the difference. But my walet sure can.

My opinion on cap selection is that it is a bit of a "black art". I am happy with the combination I have been using lately. I like my Nichicon Muse and KW's but I also like my Fujicon high temp standards. The only difference I have been able to pluck off the datasheets when comparing audio grade caps vs standards is the ESR is generally a bit lower on the audio caps.

Ok then, so I use "audio grade" on the signal path preamp etc, then switch to a high temp standard for the power supply. I dunno, as tight as a BM 2400 fits up it tends to run a bit warm even under the best of circumstances. Would I be smarter to replace all the caps with "high temps" in a situation like that.

Re: Beovox S-75 Repair and Restoration

Søren Mexico — Sun, 17 Jul 2011 00:06:43 GMT

I've been reading myself dizzy about caps, audio grade, audiophile and so on, conclusion: There are as many opinions as there are brands, and none with a good technical acceptable explination or measureable evidence, so a known brand, "normal" cap, bought where they have some turn around (fresh caps) in my opinion for our use is as good as it gets.

I'm curius about how your tweeter will work out

Re: Beovox S-75 Repair and Restoration

Eugene — Sat, 16 Jul 2011 22:53:45 GMT

Caps came yesterday so now its is time for the crossover refurb.

Only replacing the caps - nothing else appeared to be damaged or burned and after my S45 experiment I cant justify the cost of buying the expensive poly caps and "audio" grade resistors the resellers want to push on us.

Re: Beovox S-75 Repair and Restoration

Søren Mexico — Sat, 09 Jul 2011 15:35:41 GMT

Good job Eugene

Re: Beovox S-75 Repair and Restoration

Eugene — Sat, 09 Jul 2011 10:44:02 GMT

Every driver got a bead of epoxy around the magnets.

Yes it is put back together, but as it stands it is not fully tested because I disassembled both speakers. The caps will be ordered this weekend. new grill cloth plus some sanding and restaining.

If the repair doesnt work out I can get a new replicated replacement here in the US and I also have a lead on an old stock. No worries at my end. It is a 50-50 shot it will work or fail. Either way it was worth the effort.

Re: Beovox S-75 Repair and Restoration

Rich — Sat, 09 Jul 2011 07:46:55 GMT

Any further news on the tweeter?

Re: Beovox S-75 Repair and Restoration

Eugene — Sat, 02 Jul 2011 23:41:02 GMT

Rich:

That sucks! Good luck on the repair, and I look forward to seeing/reading your writeup.

Yes it does Rich, but that has pretty much been my luck with speakers bought off eBay. But allow this to serve as a warning to all potential future buyers. It certanly no longer appears that magnet failures and slips are confined to the Peerless drivers.

But moving along the photos will ilustrate that I have put the tweeter back together in two pieces now it is just a matter of allowing a preper cure time for the pieces to dry. 24 hours should do the trick. You can also see that I used ISP and swab to clean any excess especially out of the inner ring.

What remains is solving the riddle of finding a suitable centering shim when I join the two pieces back together. Think I found a potential solution, it seemed to work during dry fits. We shall see.

I have also laid a bead of epoxy around the Dynaco bass driver magnet and will most likely bead up the mid and phase link. The cross has been taken out and new caps placed in my basket at Parts Express. But what I wonder is if I couldnt just go ahead and use Nichicon Muse Bipolar instead.

I see no need to spend crazy money buying all new fancy poly caps and crossover resistors. My previous S-45 experiment says spending a fortune on luxary high end caps and resistors is not necessary. A handful of 100 volt electros and leave the rest in place works just as well and costs a hell of a lot less.

Re: Beovox S-75 Repair and Restoration

Rich — Sat, 02 Jul 2011 13:44:42 GMT

That sucks! Good luck on the repair, and I look forward to seeing/reading your writeup.

Re: Beovox S-75 Repair and Restoration

Søren Mexico — Fri, 01 Jul 2011 21:47:31 GMT

What a shame Eugene, hope "by George" you get it working, love these old speakers

Beovox S-75 Repair and Restoration

Eugene — Fri, 01 Jul 2011 19:47:16 GMT

My speakers arrived from Texas today and low and behold one of them didnt work and there was something rattling around. The tweeter had had come apart and had pulled the purple wire off the solder stud.

Oh woe is me !!! Yet another evilBay speaker purchase gone bad.

Makes me want to get out the Tammy Wynette LP's or other hillbillie music and do some cryin in my beer.

Rant aside, I was dry fitting the various tweeter pieces back together and "by george" there is a chance I might be able to put the dang thing back together. I think I have another epoxy kit left from the S45 repair. So it look like I will be putting the epoxy around some more magnets this weekend.

What was kinda cool was the speakers came with the original user manual. I dont remeber that being staed in the auction. Should be an interesting read later this evening.

Now off to the "Honky Tonk" for some beers.