Yaqin MC-100b schematic diagram

[aristocrat]

Hi there to all you experts out there. I have recently bought a Yaqin MC100b integrated amplifier from eBay. I have not hooked it up yet since I have read in quite a few forums that some of the bias from the factory were set wrong and the amp works for a few months and either blow resistors/caps or valves. I was wondering if any of you have had such experience from Yaqin amps and if any of you had owned or still owns the MC-100B and if you have a circuit diagram? As you can see from my introduction, I am a novice at valve stuff and would like to know how to "tune" the bias - either current or voltage to the valves. If any of you have some suggestions, I would very much appreciate it. Cheers.

[halx00]

You might find this useful.
I have one of these amps, a most excellent sound.
Using one in the UK means I need to step down the mains 240volt supply or the heaters run at 7.4v and every thing is a bit stressed. I use a buck transformer this works very well.

Duncan

sorry about the quality, email me if you want the original jpeg. 1.24Mb

[aristocrat]

Hi Duncan, many thanks for the circuit diagram which tells me to adjust the bias to 60mA. I will go ahead and get a step down transformer so the elements don't get stressed and prematurely burn out. Cheers, Spencer

[Tube_Dude]

Hi aristoctrat and other owners of the Yaqin MC-100b.

One exemplar of this amp have passed for my workbench and I have remarked that it was lethal for the operator.

The power supply electrolytic capacitors, situated outside the case, are without isolation at the top and in two of them there was the full HT rail ( ~ 500 V ).

Please inspect with a voltmeter, the voltage between the chassis and the top of the capacitors and if you measure the same voltage, make some insulation in plastic and glue it to the top of the capacitors.

A very dangerous amp...

Regards

[crategus]

Originally posted by halx00
You might find this useful.
I have one of these amps, a most excellent sound.
Using one in the UK means I need to step down the mains 240volt supply or the heaters run at 7.4v and every thing is a bit stressed. I use a buck transformer this works very well.

Duncan

sorry about the quality, email me if you want the original jpeg. 1.24Mb

Hi Duncan,
Could you send me the original jpeg (bartek at hfm dot pl)? Thank You in advance!
Crategus

[ChopperCharles]

I had heard the MC-10L blew parts (resistors) due to incorrect bias settings, not the 100B.

Supposedly if you buy from the Canadian dealer, each unit is tested and adjusted before it is shipped, and it comes with a 1 year full replacement warranty and 2 years of free labor after that. Plus it comes with a translated manual.

I just bought the MC-100B from that guy.... so I'll let you know more when it gets here!

Charles.

[Koifarm]

Originally posted by aristocrat
Hi there to all you experts out there. I have recently bought a Yaqin MC100b integrated amplifier from eBay. I have not hooked it up yet since I have read in quite a few forums that some of the bias from the factory were set wrong and the amp works for a few months and either blow resistors/caps or valves. I was wondering if any of you have had such experience from Yaqin amps and if any of you had owned or still owns the MC-100B and if you have a circuit diagram? As you can see from my introduction, I am a novice at valve stuff and would like to know how to "tune" the bias - either current or voltage to the valves. If any of you have some suggestions, I would very much appreciate it. Cheers.

I sold several Yaqin MC100B. The bias was always set between 40 and 45 mA with the bias on 60mA the tubes will burned out after 500 hours. With the 40/45 mA bias they will last for more then 2000 hours. The sound is the same.

[crategus]

Hi,
Hope I receive MC-100B soon.
Anybody upgraded it? Any suggestions- maybe are there modifications "must to do" (ok, first for sure will be isolating capacitors and changing pot for alps)?
Regards

[ChopperCharles]

I just got a 100B Yaqin/Yaoin amp as well, and I'm really really pleased with it so far. I can;t believe how much better this thing is compared to my old sony tuner. i'm hearing details i did not know existed. Very, very pleased. But... it brought to light how inadequate my speakers are...

Charles

[keithgreenhalgh]

I also have a 100b. Very happy with it got instruction on bias adj in chinese. I was wondering when setting the bias voltage on the test points if it mattered if it was set for triode mode or ul mode? I set mine in ul mode. Hopefully it wont make a difference. Any comments?