Well, I did it. The Yamaha relay. I guess you could say that I practiced desoldering with desoldering braid on the Dual, so it only took me about an hour to remove and replace the relay. I put the amp back together, said a quick prayer, threw the switch.
One, two, three..."Clack!"
Perfect. I always worry when I make repairs but this one went without a hitch.
I'll listen closely to see if there's any improvements; there should be, as the contacts are brand new silver-cadmium oxide, rated for a minimum of 100,000 cycles and 15A (not just 10, like Omron or Panasonic) at 30VDC!

nice work.

maybe someday i'll learn how to read a schematic. then maybe i'll be able to do stuff like this.

Scott, that's the beauty of all this. I didn't have to read a schematic at all. For simple stuff like this, it's opening cases, finding the physical location of parts on circuit boards, removal and replacement with soldering skills, and button everything back up. Think about it: all a relay is is a switch. Y'don't need a schematic to replace a switch. The caps on the Dual? Desolder the old ones, replace 'em with new ones. Jeez, if I can do this, anyone can!

I'll tell you right now that any problem with any gear I have is easy to fix as long as I don't have to troubleshoot via a schematic. These two repairs were mechanical in nature. I'm in awe of people who can narrow down an electronic repair to replace a single resistor or transistor on a circuit board crammed with components, after they've studied a schematic and done some probing with a DMM and oscilloscope.

A simple cap replacement. Relay replacement. A spring, a belt, a lever... mechanical repairs = easy. But if I had my tuner suddenly have distortion in one channel, or my CD player have screeching treble, or I can only get partial tape erasure in my cassette deck, I'd be immediately worried that I'd have to find a tech and pay big bucks for his or her skills in diagnosis. And that's something I can't do myself.

Hey Tom, doesn't it feel great ?!
Congrats and keep going...now you got the "bug"...
This weekend i'd replaced in both Rogers speakers crossovers', the high frequency electrolytic caps for polypropylen ones, just to see what happens...and i tell you, the highs are now more liquid and detail than ever. I 'll try the same with the mids and the lows as soon as possible... polypropylen is the way to go...

i guess i shouldnt let this type of thing intimidate me so much. tell you what, next time a problem like this crops up for me, i'm jumping in with both feet.

Scott, like I say, something pretty simple that can be isolated easily is a snap to fix if you can get the part. I was lucky that the repairs were logically deduced with help, the TT caps are common items, and the speaker relay has a modern replacement. The original Panasonic part is no longer made, but Omron and Tyco/Potter & Brumfeld make drop-in replacements.

The thing about this is that I asked questions when I had a problem. I'd read a lot at various stereo forums *ahem* and thought things through, and came up with a solution. It CAN be done!

Alvaro, the feeling is great! Not only did I learn how to use desoldering braid, but I believe I saved about US$200 or so. I'd hate to think of how much it would cost to ship a 44lb/20kg Yamaha long distances two ways without damage, and a delicate turntable as well, and on top of that, labor costs! The total cost for all the parts was just US$14.

Now I'm wondering about recapping my KEFs... They're already ten years old!

i think it particularly important to note that you did your homework and got good advice from trusted sources before attempting the repairs.

That's the spirit, Tom.

You know, I was listening to my L.A. Woman LP this evening, and I found myself asking, "Is the treble sounding cleaner or is it my imagination??"

wouldnt surprise me, if the gear is operating better it should sound better.

IMHO, you should try some film caps on the Kefs. I'm glad that i did that with my Rogers.

Okay.
I finally cracked open the KEFs to see what I had for a crossover. Pretty impressive: two coils, two electrolytic caps, two ceramic resistors, all on a printed circuit board. (Compare that to my Avids' one 8Ω 10W sandbar resistor and an unmarked cap of some sort!) That's the good news.

The bad news is that the circuit board is hot-melt glued to the rear plastic cover panel. There's so much glue on everything, it may as well be a "potted" board! The board's small, and I don't know how I'd get all that glue off without damaging the components or warping or melting the rear panel. The parts are crammed on there really tight.

The caps are:
10 μF 100wvdc electrolytic
4.7 μF 100wvdc non-polarized electrolytic

So, my questions:
1. How do I melt the glue to get the board off without damaging anything?
2. What do I replace the caps with?
3. Should I bother?

The same happens with my Rogers. Everything glued to the PCB.
What i have done was, instead of desoldering i cut off - with a small cut-pliers - the caps leg's and than with a knife or a screwdriver gently but firm insert it between the caps and the pcb in the glued parts and i tried to pull them out.
Than you can desoldering the remains or you cut them close to soldering point and solder the new ones. Et voilá.

About caps, imho try to find good electrolytic polarized from Panasonic with low ESR and for the NP's you have two great choises : Polypropyliene or Film caps.

I have replaced some polarized with non-polarized in passive circuits with no problem what so ever, simply because NP caps will be biased with the proper polarity. But, if you feel more confortable - the price make difference - using polarized ones just go ahead and choose wisely.

Please, read this : http://www.bext.com/replace.htm
http://www.repairfaq.org/sam/cap-*test*-('").htm#ctnpo

BTW, just remember, though, that you need to let caps run in before making any final decisions about them. Some caps can sound awful when new, but eventually smooth out and become winners.

Have fun.

Just an idea :
Why don't you try and do the same i did with the Rogers ? I mean, 4.7 μF NP polypropylene to tweeter and two NP polyester foil (film) in parallel (4,7+4,7 or 4,8+4,8) to mid/bass.

Just an idea...



BTW, A polarized electrolytic cap in a crossover seems strange...did you see it right?

Yes, I'm positive (ha) that one is polarized. One is dark blue aluminum and says "NP" on it, but the other one is light blue with a definitely marked "-" polarity stripe on it.

You can bet that I will be going very slowly on this upgrade. The speakers sound just fine to me now and I do not want to damage anything. I've saved those two web pages to read in detail.

Tom