New problem with Music Angel KT88

[tubesteve]

gallbladder is really used for tubes in chinese language, its no joke. so the machine translated correct..
There are some smart here, but not too much probably not in the tube business. What i have seen how some do it: buy a book with schematics inside. Translate that into hardware.
what they are not aware, that in that (funny) book, most circuits are printed with a lot of errors as resistor values, voltages, or so, plate to gnd via resistor, etc...

so far, i never trusted chinese quality also my company not, and thats why we are here

 

[tubesteve]

quality

i just remember a story from some time ago:
a bigger manufacturer had sent his DVD recorder to us for testing, function and safety. in the report we said, it didnt work as their customer wanted. After that, they came several times to our Lab. we gave them hints how to fix the problems. nothing happened. then one day, when their manager was with them in our lab, i asked him, why their engineering could not do the job. he said: we have 2 engineeing teams, one good, and one bad. i asked: which is now this team, working on the DVD recorder? he answered: the bad team.

 

[tubesteve]

just found a manufacturer, built quality looks rather nice:
they have a selection of different tube amps, prices in china looking ok.
À­·Æ¶ûµç×Ó¹ÜÒôÏ쳧

 

[alecu7]

Hello all,

Got my capacitors yesterday. The 820uF/500V are really big. Diam 50mm x 63mm long. Which terminal should I connect? I'm thinking (-) and (C) but I don't know what's the difference between (-) and (A) or difference between (C) and (D). Anybody could shed some light please?

Thanks,

 

[Ian444]

(-) and (A) are probably internally connected, check with a multimeter. Same for (C) and (D).

 

[alecu7]

(-) and (A) are probably internally connected, check with a multimeter. Same for (C) and (D).

You're right. (-) and (A) are bridged together. Same for (C) and (D). I don't know what is the purpose of (B). It's not electrically connected to any of the pins. Maybe just for mechanical stability on circuit board.

 

[tomchr]

Maybe just for mechanical stability on circuit board.

Bingo! Or Panasonic markets another line of caps where the fifth pin is used as the center point of two caps in series.

For your cap, even though the pins are bridged internally, I'd still connect both pins to the circuit. - Or bridge them externally with a piece of wire, then run one wire to the PCB. You never know how strong the internal connection is...

Good luck. Hopefully, this is all that's needed to get that sweet gallbladder sound again... 🙂

~Tom

 

[alecu7]

I didn't have too much luck in fixing the problem with my amp. I'he replaced the 4 HT capacitors from thepower supply, replaced 2 resistors in parallel with the capacitors but hte amp is not working. What happens now is that after the power on delay, the left kt88 are very bright while the kt88 on the left channel are normal brightness. I'm worry about this.
I'm wondering if there are any good people around Toronto area where I can take my amp and have a look at it.

Thanks,
alecu7

 

[Tekko]

I could fix it, but i doubt intl shipping would be worth it.

Wasent there some kinda warranty on the amp when you bought it that you could have used to get it fixed ?
Tho you voided it the moment you stuck a screwdriver into the screws.

 

[alecu7]

I could fix it, but i doubt intl shipping would be worth it.

Wasent there some kinda warranty on the amp when you bought it that you could have used to get it fixed ?
Tho you voided it the moment you stuck a screwdriver into the screws.

Thank you for your intention.

Shipping cost would be more than the price of the amp. This is the same reason why I don't send the amp back for repairs and this is why I'm looking for somebody locally.

 

[thoriated]

gallbladder is really used for tubes in chinese language, its no joke.

Sure there's not some sort of undisclosed reference or context in there?

 

[Edriz]

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

Sorry about starting up an older thread. I have the YC_808 and am trying to bias the power tubes. A photo in alecu7's post on the 1st page of this thread shows 4 bright blue post and 2 larger ones seperate from the board. When I tried biasing, the 1st blue pot seemed to adjust tubes 1&2, the 2nd blue pot adjusted tube 3&4. Is this right? I would think one pot per tube and the 2 larger pots off the board would be balancepots? Would someone please help me with what each of the blue pots adjust and the 2 larger ones. I'd sure appreciate it.

Ive had the amp about 10 days now and really do think the sound quality is really good. Once I have enough hours on the original tubes, I was thinking about swapping in some EH's but before i can do that, I would like checking the bias with these tubes and be able to adjust bias when putting new tubes in. Again, I would really appreciate any assistance and thank you for whatever information I can get.

 

[JSMARTINS]

Music Angel KT88 rebuild

Hello,
I decided to buy this amplifier due the low price and because of good reports that i read in the internet.
I received the amplifier and liked the sound but after about two month the power transformers burned so i decided to make a full rebuild the amplifier.
I have attached some pictures of the process.
Now the amplifier is sound much better but this is almost a new amplifier.
Please excuse my poor english.
Best Regards

 

[JSMARTINS]

Here is more pictures

 

[JSMARTINS]

To bias the power tubes i'm using a Tentlabs bias module that allow me to use any kind of KT88, 6550, KT120, EL34, EL156. I just have to adjust the plate current i want to the tubes and the module automatically adjust the current for each tube even if i use not matched tubes.

I tested several power tubes and choose the EL156. These tubes have a very musical and natural sound.
I always use the tubes in triode mode.
I change the front stage circuit to accept several types of tubes like ECC85, 6DJ8, ECC81, ECC82. Now i'm using Philips PCC88. The driver tube i choose the 6FQ7. These are much better tubes than ECC82 in driver stage, but i had to make some changes.
Here some more pictures.

 

[JSMARTINS]

The power supply was built all over again with a much better transformer from ordered from ASL, FRED diodes, filter choque, Muldorf Eletrolitic caps bypassed with PIO caps. I add one more filter stage with MEC50 eletronic modules for front and driver stage.
The filament of PCC88 and 6FQ7 was DC supplied with a separated power supply.

All original eletrolitic and PP caps was replaced with better ones.
The original volume pot and input selector was replaced with APLS Blue line pot and silver contact switch. The input signal wire was also replaced by silver cable.

I must try in the near future new coupling caps, maybe PIO but i must select the small onesas possible because i have reduced space inside the amplifier.
This amplifier have zerohum and noise even when i use my Lascala horn speakers.
Normally i use this amplifier with my Quads ESL/ESL63 with excelent results. I would like to try new output transformers, maybe Lundall or Eletra Print?
I leave here some more pictures.

 

[gfs]

hello, je possède moi aussi un xd-800mk3 KT88.J'ai remplacé toute les capa non polarisé X2 ~ d'origine par des mkp wima =.Et cela sonne mieux , pas de modification de schéma. Par contre , faite attention au sens de la grille de protection de fond . Au niveau des visses de fixation des pieds de l'amplificateur , elles sont un tout petit peu trop longues. Un mauvais positionnement entraine à la mise sous tension un défaut châssis/carte . L'appareil se met en sécurité . J'ai du mettre les écrous à l'extérieur et tout est rentrée dans l'ordre.

 

[AllenB]

TRANSLATION

hello, i also own an xd-800mk3 KT88. I replaced all the original non-polarized X2 ~ capa with mkp wima =. And that sounds better, no schematic modification. On the other hand, pay attention to the direction of the bottom protection grid. At the level of the fixing screws of the feet of the amplifier, they are a little too long. Incorrect positioning causes a chassis / card fault on power-up. The device goes into safety. I had to put the nuts on the outside and everything is back to normal.

Veuillez noter qu'il s'agit d'un forum en anglais.