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Old 23rd October 2011, 09:04 AM   #111
niekos is offline niekos  Netherlands
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Location: Houten, The Netherlands
Yesterday i adjusted my bias to 0,350V after warming up for 10 min, values were all under 0.3v before adjusting.
All was fine after adjusting, listeing to some music sounded nice (as always).
But after that session I turned of the amp, and later that I evening I turned the amp back on. It started warming up, until after say 20 sec the fuse (not in the back of the ) but in my central fuse box.
I tried the adjustmend again, now setting the value to 0,300 V, after turning the value very low. All seemed fine, but now it happened again
Should I go lower? Or should I check something else? Should I maybe suspect my multimeter?
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Old 23rd October 2011, 12:24 PM   #112
data is offline data  Australia
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Are you talking about the fuse box in the house/apartment? if so I would look elsewhere other than the amp, adjusting the bias in the amp from .3mv to .35mv in my mind couldn't trip or blow a house fuse, unless the circuit in the house is on the very ragged edge of It's limits with all that's in use and then it would be getting tripped all the time by other appliances.

Or are you talking about in the amp?

I have never seen any fuses in the circuit of the Yaqin apart from the one in the IEC socket

Last edited by data; 23rd October 2011 at 12:31 PM.
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Old 23rd October 2011, 12:36 PM   #113
niekos is offline niekos  Netherlands
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Yes, in my house. It is related to my adjustments since it does not happen when I do not turn on the amp. Also, when I turned down the voltage to very low values, I was able to power it up again. So, it must have something to do with my adjustments?
I did try to power it up again after my adjustments, I did not have the problem. The difference however was that the amp was already warmed up.
A fuse is located in the IEC connector, but this one is not blown.
Actually, it was not a fuse that was blown, but the RCD was triggered. My Amp is not grounded from the IEC inlet btwI noticed when I opened the housing.
The voltage where I live (Netherlands) is approx 230V.
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Old 23rd October 2011, 01:19 PM   #114
data is offline data  Australia
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Not grounded?

Sounds like one of the earlier models, they addressed this issue in later models.
I would rectify this issue with the amp if I where you.
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Old 23rd October 2011, 04:35 PM   #115
niekos is offline niekos  Netherlands
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I will, I did not open the amp before, so I was not aware. I will also add the other modifications (100k 2W restistor for caps), maybe also replace the currently placed samsung caps 470uF with something better.
Any suggestions?
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Old 23rd October 2011, 05:19 PM   #116
data is offline data  Australia
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With the larger caps I couldn't find anything better that would fit, but the 22uf caps can be replaced with Jensen's, I think they will fit and are a very good cap. Have a look anyway, they may have something to fit Tobias Jensen Production A/S - Radial electrolytic capacitor, screw terminal looks like they have 220uf/400v radial caps that are 035x054 in size, might like to see if that is similar to the larger ones in it Tobias Jensen Production A/S - Radial electrolytic capacitor, solder terminal

Space is a big problem with this amp if wanting to upgrade some parts.

Benefits can come from upgrading the 0.1uf coupling caps and the resistors in the signal path too.

Though the main thing is to make it safe.

Last edited by data; 23rd October 2011 at 05:32 PM.
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Old 23rd October 2011, 05:50 PM   #117
Hi_Q is offline Hi_Q  England
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Normally RCD's operate if there is a leak to earth but as you do not have an earth on the amplifier itself, perhaps there is a leak to chassis then to earth via other equipment that is plugged into the amplifier inputs? Adjusting the bias from 0.3V to 0.35V should not cause the RCD to operate. Can you use your multimeter to do a resistance check between the metal chassis and the mains input connector of the amplifier, just to confirm there is no leak to chassis from either of the input pins. With respect to the capacitors, I obtained some spare ones manufactured by EOS, their type number is B43504-A2477-M, if you can still get them.
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Old 24th October 2011, 12:02 AM   #118
atsc is offline atsc  Australia
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Default Good to see this Amp still having its followers

Hope you can fix the RCD problem. Sounds like it may need looking at by a professional. They don't seem to be the most reliable of beasts and it always seems to come from the adjustable bias?

BTW I took my partners son's nano iPod and connected it to the 10L on the weekend while they were visiting my apartment. Turned it up. We listened for a while (through quite basic Kenwood home theatre speakers). We went to her place. A little while later he said "I want one of those things". I said you mean the Amp? He said yes as it sounds so good. Even my partner separately said (while listening to her budget ipod doc with the same nano) "Your system sounds so much better". Later Mr. 12 looks at my high quality headphones and drools. Looks like I have some budding audiophiles.

We are about to buy a bigger house and I need to drive some (base level) Magnepan speakers in the theatre room so I guess I am shopping for a KT88 amp in the same vein. Any recommendations based on the fact I love the stock standard Yaqin 10L? I know the Magnepans need huge watts/currents so will a KT88 power them enough or am I looking at something bigger? I dont want to go to transistors or Class D. I just don't like the sound.

I need to strike while the iron is hot and Christmas approaches...
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Old 12th November 2011, 10:10 AM   #119
niekos is offline niekos  Netherlands
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I seem to have fixed it
The amp was grounded after all (did not examine it well), I added the extra resistors for the caps, and replaced the pre amp tubes with russion 6N1P-EV-OC (voshkod) and now all is fine again
Better then before I would say, I think these new tubes sound better than the original tubes I had
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Old 14th January 2012, 02:12 PM   #120
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Hi, I'm new to this whole "forum" thing but as a MC10L owner need some help and hope to find some here. My amp is as good sounding as I'd hoped - I've already got a MENG EL 84, which I love - but between 5mins and and hour of switch on the left channel fails - it sounds like the input has earthed, the same sound you get when you touch the and of a jack plug connected to a guitar amplifier, but louder. After being switched off for 30 secs everythings back to perfect!? Anyone out there got a suggestion please??
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