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Old 8th April 2010, 11:21 PM   #1
alecu7 is offline alecu7  Canada
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Default New problem with Music Angel KT88

Hello all the experts out here,

I bought this amp a few months ago on eBay. 2 weeks ago while listening to it for over 2 hours, I noticed heavy smoke coming from the left side of the amp. One of the hv capacitors blew up. It is 220uF/250v. For the last 2 weeks, I have been reading intensely about mods and other people problems yet I could not find a suitable schematic for my amp. First of all, my amp has 7 tubes: 4x kt88, 2x 6n8p and 1x 6n3. All the schematics I found has 8 tubes.

Also if you notice the power PCB, there is a modification done (by the factory, not me) with the yellow wire. Maybe I got a lemon. Anyway, I need your advice: should i replace the capacitor(s) with 220uF/400v? Would this solve my problem? I also want to eliminate the Triode/UL switch but I need a good schematic for that. Any other suggestions please help me so I can enjoy again “the sound of the music”.



Thanks,

alecu7
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Old 9th April 2010, 01:00 AM   #2
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Its worth changing the capacitor for the one you suggest and power it up again.
If it works then great. If not then more investigations are needed.

It could be the cap died of old age or it could be something else has killed it.

I would replace the other cap on that board too.
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Old 9th April 2010, 01:01 AM   #3
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Replacing the bad capacitor will of course be necessary. Replacing both of them with good brand name units is also a good idea. Going up to 400V parts is probably a smart move provided you can find capacitors that will physically fit. A 400 volt part will probably be a little bigger, so take careful measurments to assure they will fit.

Another thing I would do is to reduce the value of the two voltage divider resistors across the capacitors from 220K to 100K 2 watts. This will help assure that you are below the internal leakage of the capacitors themselves which is necessary for them to do their job of equalizing the voltage. There's some talk, with diagrams, of the Music Angel KT88 here.
Music Angel KT88 correct circuit
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Last edited by HollowState; 9th April 2010 at 01:27 AM.
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Old 9th April 2010, 01:47 AM   #4
alecu7 is offline alecu7  Canada
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What would be a good brand name for those capacitors? Could I get it from Digikey? I buy a lot of stuff from here. I'll measure tonight the physical dimensions on the capacitors.

Still no schematic for my 7 tube amplifier. Anybody?

Thanks,
alecu7
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Old 9th April 2010, 02:30 PM   #5
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Quote:
Originally Posted by alecu7 View Post
What would be a good brand name for those capacitors? Could I get it from Digikey?
Panasonic, Nippon, Nichicon, Mallory, Sprague to name a few. I'm unfamiliar with Digikey's product line so you'll have to look.
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Old 9th April 2010, 03:08 PM   #6
Svein_B is offline Svein_B  Norway
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The amp you have is the Music Angel YC-808MK KT88.

The XDSE 800 is the more common version, with lots of info available on this and other forums.


You are not the first one with blown caps in the YC-808 after a week or two. The PS caps seem to be a bit close to, or under, the required voltage ratings.

Attached is a picture where the suspect caps are identified.

(Sorry, I have no schematic for this one)

SveinB
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Old 9th April 2010, 04:23 PM   #7
alecu7 is offline alecu7  Canada
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Quote:
Originally Posted by Svein_B View Post
The amp you have is the Music Angel YC-808MK KT88.

The XDSE 800 is the more common version, with lots of info available on this and other forums.


You are not the first one with blown caps in the YC-808 after a week or two. The PS caps seem to be a bit close to, or under, the required voltage ratings.

Attached is a picture where the suspect caps are identified.

(Sorry, I have no schematic for this one)

SveinB


That's great. This is the amp I have. I already bought 2pcs. 220uF/350V for the caps on the left side. I never thought to change the ones on the right side. But that's great. Thank you.
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Old 9th April 2010, 04:25 PM   #8
alecu7 is offline alecu7  Canada
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Quote:
Originally Posted by HollowState View Post
Panasonic, Nippon, Nichicon, Mallory, Sprague to name a few. I'm unfamiliar with Digikey's product line so you'll have to look.
Digikey link: Digi-Key - 493-1225-ND (Manufacturer - UVR2V221MRD6)
There are 220uF/350V and are Nichicon. Hope there are ok. Thanks,
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Old 9th April 2010, 06:15 PM   #9
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Quote:
Originally Posted by alecu7 View Post
Hope there are ok. Thanks,
Electronically they are fine. Hope they are not too tall so you can mount them on that board as the originals were and have it fit in the amp.
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Old 10th April 2010, 07:19 AM   #10
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Default chinese tube amplifiers

here is what the manufacturer states on his page: ( as usual overestimates himself):
We engage in power amplifier research and production more than 10 years.
Produce high-fidelity the electron tubes amalgamate work putting (gallbladder) , electron tube earphone , grade electron tube ago, before put stone work behind gallbladder, grade before Hi-Fi is pure, grade after being pure, AV home theater work is put, the progression yard mixes the Chinese percussion instrument in front of the Karaoka disc, the advanced work of sound appliances in the car is put, the stereo work of the computer is put, high-grade power amplifiers , such as Dolby AC-3 series ,etc.. The products are sold to the American-European developed country and all parts of the world mainly. And get the favorable comment.
Our factory especially pays attention to talents, the designer comes from the electronic university of every famous brand , engaged in the specialized electronic engineer of stereo . Our factory has already passed national 3C and CE authentication . The staff pass vocational training on duty. It is self-contained to measure, the raw materials select for use and import Japan , U.S.A. , Germany, Taiwan and domestic famous factory raw materials, through screening strictly, wearing out, quality is first-class. The after-sale service is perfect, for many years, gain the favor of the counterparts people from all walks of life!
Warmly welcome all old and new customers messenger write to us the connection , negotiate. Our factory can produce other electronic products according to customer's request development in addition!

first class capacitors: no they are fake as many other components or pre used and cleaned
... one gets what one pays for
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