AX-700

Tested the old caps from the 3rd amp today. They have remarkably good values considering their age, in some cases better than the new Nichicon FG replacements. To give a comparison I randomly measured 1 new (Nichicon FG or MUSE) cap in each value where I still have one on hand. I haven't remeasured the 18000µF filters yet, the amp is still doing a burn in. I'll check them tomorrow after rechecking the idle current and DC-offset.

µF/v = µF/ESR-ohm
-----------------------------------------------
2200/6.3 = 2264/0.08
2200/6.3 = 2426/0.09
(new FG 2200/6.3 = 2466/0.06)

1000/25 RBG = 993.3/0.00
1000/25 RBG = 1003/0.00
(new FG 100/35 = 876/0.04)

1000/25 Elna = 847.3/0.05
1000/25 Elna = 862.9/0.07
(new FG 1000/25 = 913.7/0.04)

680/80 Nichicon MUSE = 683.2/0.04
680/80 Nichicon MUSE = 694.6/0.05
(don't have any more new Elna's on hand to compare)

220/35 Elna = 183.8/0.22
220/35 Elna = 188.6/0.22
(don't have any more new FG on hand to compare)

220/6.3 Elna = 185.3/0.15
220/6.3 Elna = 185.5/0.15
(new FG 220/10 = 216/0.25)

100/16 Elna = 104.0/0.7
100/16 Elna = 101.5/0.7
100/16 Elna = 105.4/0.7
(new FG 100/25 = 98.7/0.28)

100/6.3 RBG = 94.0/0.26
100/6.3 RBG = 95.2/0.25
(used FG 100/25)

100/6.3 Elna = 92.5/1.1
100/6.3 Elna = 94.1/1.2
100/6.3 Elna = 94.1/1.1
100/6.3 Elna = 94.4/1.1
100/6.3 Elna = 92.7/1.2
(used FG 100/25)

33/16 Elna = 35.6/1.4
33/16 Elna = 38.5/1.4
(new FG 33/16 = 34.7/0.64)

22/16 Elna = 22.9/1.3
(new FG 22/25 = 23.4/1.2)

22/16 Nichicon NPE = 24.2/1.1
22/16 Nichicon NPE = 24.6/1.1
(new MUSE 22/25 NPE = 26.5/0.96)

10/25 Elna = 10.3/1.6
(new FG 10/50 = 10.5/0.91)

10/16 Elna = 10.5/1.5
10/16 Elna = 10.5/1.4
(used FG 10/50)

4.7/50 Elna = 4.83/1.5
4.7/50 Elna = 4.78/1.6
4.7/50 Elna = 4.84/1.6
4.7/50 Elna = 4.66/1.5
4.7/50 Elna = 4.54/1.5
(new FG 4.7/50 = 5.05/1.6)

0.33/50 Elna = 0.312/7.2
0.33/50 Elna = 0.320/5.7
0.33/50 Elna = 0.320/7.2
(new FG 0.33/50 = 0.369/5.4)

(RBG = Rubycon Black Gold)

The results sure make me think that this amp doesn't seem to have been abused, or even used very much for that matter.

Cheers,
James
 
Awesome job! :tresbon:

Probably you don't need to replace the two 18,000uF main caps! :thmbsp:

A few Elnas only seem to have "drifted" a bit their capacitance values. The Nichicons and Rubycons BG still good.

Nice shoot out! :thmbsp:
 
A few Elnas only seem to have "drifted" a bit their capacitance values. The Nichicons and Rubycons BG still good.

Also interesting is that none of them showed any signs of leaking, unlike at least a few of each of the other amps that I recapped.

Cheers,
James
 
That's probably one of the best kept AX-700's around.

Thanks for the kind words. It's making me very happy that the amp is turning out so well. The guy that this is going to is a very good friend and really apprieciates good music. I'm looking forward to getting it into his hands, I want it to be very good for him.

James
 
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NOS capacitors

I don't plan on replacing them for now. But speaking of which, do you suppose that these are legit (not fakes)?

http://www.pcm63.com/?93,elna-marantz-custom-series-18000uf-71v

If so they would seem to be a perfect replacement, even if they do say Marantz on them.

Frankly, I would avoid these, we'd need to see the manuf. date. I might be wrong, but it seems to be manufactured long ago (NOS) and would need reforming before using it (please, read the 5 first answers/comments). And I've seen people complaining also at Badcaps.net (audio forum) about these NOS "custom" caps...

eBay too, is plenty of these never used caps. If replacing the main caps, I'd buy newer Nichicons or other Nippon Chemi-con ones - 18,000uF/80V like...
 
Frankly, I would avoid these, we'd need to see the manuf. date. I might be wrong, but it seems to be manufactured long ago (NOS) and would need reforming... If replacing the main caps, I'd buy newer Nichicons or other Nippon Chemi-con ones - 18,000uF/80V like...

Good to know. Thanks.

James
 
I let the amp run about 36 hours no load, opened it and discharged the main caps. they now measure (average of 3 tests):

17140µF/0.03 ohm esr
17940µF/0.04 ohm esr

So they both came up a good bit.

Cheers,
James
 
Before I closed up the amp I rechecked/reset the idle current, it had drifted up about 0.5mV on each channel.

This last Sunday I bought a pair of ca 1986 Canton Karat 200 speakers on the auction site and they just arrived an hour ago. They are a bit dirty and dusty but are basicly in great shape, especially considering the low price that I paid for them. Both measured 3.8 ohms. So I decided to check them out with the amp, and they sound great together.

These are a bit smaller than the Karat 60's, 8" woofer instead of 10" and smaller mid & tweeter but the same good sound. I really like the combination of these Yamaha amps and Canton speakers. They sound very clear and well balanced, great bass for their size without being boomy, very clear and clean mids & highs. I think that when I can get them for a low price I'll just keep on buying them both and get them into the hands of people that need some good sounds.

Cheers,
James
 

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Yamaha + Canton = total synergy

Everything went really well. Now, some beer... :beerchug:

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The AX-700 # 3 went to it's new home yesterday. It's kinda hard to see these amps leave sometimes. Kinda like when my kids moved out one after the other. Anyway my friend is happy with the improvement but we decided that he needs some better speakers. And I have these MB Quart 800's sitting around here waiting for some new or repaired tweeters. So I'm giving him the speakers and he's paying for the tweeters to be sent to GermanMaestro for new voice coils, and new caps. Gets the speakers out of my way and should be an improvement for my friend.

Time for a new project. Maybe another 700? Should I?

Cheers,
James
 
700 family

Time for a new project. Maybe another 700? Should I?

Awesome.

Maybe an A-760? :scratch2: X Power Supply, same used in B-6. Seems a nice and versatile amp. If you find it cheap, grab it. :yes:

Others include the A-700 (1983) or 1970's era CA-710 / CA-810... :thmbsp:
 
Awesome.

Maybe an A-760? :scratch2: X Power Supply, same used in B-6. Seems a nice and versatile amp. If you find it cheap, grab it. :yes:

Others include the A-700 (1983) or 1970's era CA-710 / CA-810... :thmbsp:

Well, I'm looking at a number of amps, several AX series, and a couple of A series, but I'm not so sure that I want something with an X Power supply. Seems that they only made them for 2 years, and they are fairly complicated? Anyway, I'm being patient and will see what works out. But definitely something.

Cheers,
James
 
An update on that last amp that went to my friend. He called me a couple of weeks ago and told me that he was getting a lot of noise and some signal drop-out from/with a number of the switches. So I had him bring it back and opened it up. Seemed clear to be a case what Avionic and others have said about the difficulty of getting deoxit deep enough into the switches without taking them apart. I have taken apart the switches on an A-1020 and their delicate nature scared the crap out of me so with this one I had tried to just shoot enough deoxit into the cracks to work. And it did work for a while but clearly not good enough.

So I started with the tone defeat switch. Sorry, no pics at this time, I got so involved and my nerves were so shot that I didn't take any. But I got a surprise when I took the switch apart. It's completely different inside than the earlier switches in the A-1020. A total of 8 parts in that tiny little thing. And one of them is a tiny little Z shaped hook that latches the switch. And I can state that that damn little thing doesn't like to stick around. I darn near lost it twice as I was working at figuring the correct sequence and orientation of all the parts to put the switch back together. Which took me the better part of an hour. And finding that little latch/hook the second time took me 2 hours. I actually thought that I had lost it and was screwed. My nerves were totally shot by the time that the switch was successfully back together.

So for the second switch I found that if I very carefully unlatched the cover and just pulled it off a few millimeters I could get the spray nozzle down into the switch directly above the contacts and spray down into them. Gave it a couple of good shots, snapped it back together and then worked it a bunch and let it set over night. I did this 2 times with straight O.C.X. de-oxidizer and then a third time with some large blasts of De-oxit. This seems to have worked well, all of the switches are dead quiet now. At least I hope that it will work over the long term as I really don't want to have to completely dissemble one of these switches again.

Cheers,
James
 
Hello!

Recently I had the luck to find an AX-700 cheap (80€). It was very dusty and dirty inside out. I did a quick cleaning of the cover, front face, boards and pots, although the bass control knob is still scratchy when I turn it. It functions ok and I don't use it so much but I want to make it perfect. Do you know if it is possible to disassemble the pot and clean the inside of it (as contact cleaner, washer, the lubricant didn't help much)? Or maybe something else could be wrong with it?

I'm planning to recap it in the future but my budget for this month is spent already:) Thanks for the recap list btw, it was very helpful!
 
Hello back,

Cool that you found an AX-700 for that price, it's a better than average price for Europe. They are very nice amps so I hope that you enjoy it a lot.

I haven't dissasembled a poti yet but I think that if you de-solder it it shouldn't be too hard to bend the metal tabs holding the body together and get it apart. It goes without saying that you want to be careful to only bend the tabs as much as needed and be careful not to break one off. That would be bad news.

So far I have never needed to go that far. I use some industrial de-oxidizer ( Rivolita O.C.X.) first. I give the pot a good shot through the open slots in the body and through the little hole on the sides. Then I work the shaft stop to stop 30+ times and let it sit for 15-20 minutes. That gets done 3-4 times and then I repeat the process at least 2 times with DeoxIT D5. This has been enough to get everything working cleanly so far.

I'm happy that the recap list was helpful. Since the last list update I've started using Wima MKS-2 film caps for the 4.7µF/50v and 0.33µF/50v.

Since I last wrote here my daughter decided that she doesn't have space for the black 700 and Canton Karat 60s and won't for at least a year. So I gave her a re-capped AX-300 and a pair of Canton GL-260s. That sys is at least small enough that she can use it with her PC. Next year I'll put something together for her when she can get a larger apartment.

In the meantime the AX-700 along with a re-capped and modded Denon DCD-1290 cd player has gone to a friend of my son. I sold them to him at my cost with no profit and no charge for the work. He found a pair of somewhat rare Canton Reference 6000 speakers to go with them and the system sounds great. The Karat 60s are now in my HT system as fronts until I can afford to buy a pair of Canton CT-800 or CT-1000 speakers.

And I found and bought another AX-700 (the 5th one now) at a very good price at the request of a guy at work. It will also be paired with a DCD-1290 when I get them finished. We haven't decided on just what speakers yet but probably some Cantons as they sound so very good with this amp/cdp combo.

Cheers,
James
 
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