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Old 26th December 2012, 05:27 PM   #31
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Hi I also have a MC10L with a slightly different problem, I changed the Chinese tubes for Svettlana EL34 from Karltone (matched set of 4), the bias voltage was way high after i turned it on for the first time with the new tubes and there was a slight smell of buring, still i turned to bias voltage down to 400mv. All has been fine for a few month but now there is no voltage across the bias adjustment for V1 and V4.
Any idea's where I start before putting the chinese tubes back in. Top off show no sign of burn resistors etc
Thanks
Bob
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Old 13th May 2013, 04:15 PM   #32
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Hello All,

I wanted to give some updated Feedback: Since I have replaced the tubes one year ago, the amplifier is working fine. I like it.

Best Regards
Ralf
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Old 22nd December 2013, 01:31 AM   #33
Hi_Q is offline Hi_Q  England
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For those with MC10L or T, I have added a cold test routine (Pages 26 to 40) to the original document that I put together. You can verify most resistances and check out the primary windings of the output transformers without removing any covers! Try that with solid state gear!
Two links (hope they work) giving the choice of PDF or WORD document.

Just copy the one you want and paste it into the address bar of your browser.

homepage.ntlworld.com/lez/YAQIN MC10/A LOOK AT THE YAQIN MC10L.doc

homepage.ntlworld.com/lez/YAQIN MC10/A LOOK AT THE YAQIN MC10L.pdf
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Old 23rd December 2013, 11:43 AM   #34
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Location: Schwerte, Germany
Default adding a subwoofer output to the Yaqin Amp

I thought about adding a subwoofer output to the Yaqin Amp. This is because although I have appropriate loudspeakers, the acoustic in my living room is not adequate. My appartment is under the roof of the house, and the middle and high frequencies are reflected from the walls, so the bass is a little bit weaker.

I thought the best would be to connect two resistors together to the sub-amp output for an active subwoofer, while the other ends go to the volume poti. Any other proposal?

Best Regards
Ralf
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Old 29th December 2013, 04:30 PM   #35
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Default Biaspotentiometers

I have also a Yagin MC-10L , bought 3 years ago . Haven´t used it until now
and are now doing some upgrades . Asked myself : what happens if the wiper
on one of the biaspots loose contact ? Perhaps uncontrolled high current through that related EL 34 !? So I added a 180 K metalfilmresistor between the wiper and the leg connected to the biassupply ! The guitarampguru , Kevin
O´Connor shows this in one of his books . This mod slows down the potreaction a little and gives the EL 34 grid (5) full bias and chokes the tube ..... if the wiper
should lift ..... loose contact . To me these pots seem tiny and perhaps another
mod would be to change all four of them to a little larger cermet-type.
I´m trying to add a 750 ohm , 3W , screenresistor to each powertube . But
if possible without taking everything apart ...... Can I cut the ultralinear screencables at the side of the outputtransformer and solder in the resistors
there ? ( with some shrinkisolation at the ends ? ) Or must these resistors be
close to the pin 4 at each socket ? Thanks for some answers . Steven
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