Yaqin MC-100b schematic diagram

[Koifarm]

Originally posted by aristocrat
Thank you gentlemen for such great help. Now, all I need to do is measure the DCV across the test points to measure 0.4 - 0.45V should be fine then? How about the schematics saying an input voltage of AC220V, mine is AC240V since I live in Australia. I have lifted the lid up on the transformers, and they did have stickers saying its 240VAC windings. Should the voltage still be the same across the test points or would they vary due to the input voltage being different? Sorry about my ignorance here. I don't think that matters, but just thought I'd check with the experts here. Cheers, Spencer

You can take the same voltages. This is to simplifie it. Normaly you must measure the anodevoltage( B+), Aquire the max. power rating of the tube and then calculate the biascurrent. There is a excel sheet to do that but to keep it simple use the value above.

Excel calculation


http://www.ict-net.net/load.xls

[keithgreenhalgh]

I'm confussed! Are you saying that I should set the bias to .4 to .45volts giving me a current of 40 to 45 ma. on my yaqin 100B amp.Why would the people building the amp recromend a higher current and how will this affect the power output? Are we sure about this?

[keithgreenhalgh]

Also on the schematic,where are the test points for adj the voltage?

[boboo]

Is that possible for some one to mark those testpoints on the schematic with a red pen and pulish it again?

[boboo]

Originally posted by Koifarm

I have a lot of experience with the MC100B.

You said that you have a lot's of experience with this amp and thats very good because than you can tell me why I got that no bass at all.

It's there but nothing to comapere with my hudred years old harman Kardon 730 twin receiver.
This junk just realy don't satisfy me at all!

[boboo]

Originally posted by Koifarm
[B]

The manual says 550mv-600mv with is a current of 55-60mA thrue a 10 Ohm resistor. You just measure the DC voltage on the testpoints and devide it with 10 and now you have the biascurrent.

40-45mA measures on the testpoinst 40-45 x 10 = 400-450mVDC.
This current has proven that the lifetime of the tubes will be about 2000 hours while 60mA current burned up the tubes in 500 hours. I have a lot of experience with the MC100B.




U(Voltage in Volts)= I(current in Ampere) x R ( resistance in Ohm )

You said that you have a lot's of experience with this amp and thats very good because than you can tell me why I got that no bass at all.

It's there but nothing to comapere with my hudred years old harman Kardon 730 twin receiver.
This junk just realy don't satisfy me at all!

[Koifarm]

Originally posted by keithgreenhalgh
I'm confussed! Are you saying that I should set the bias to .4 to .45volts giving me a current of 40 to 45 ma. on my yaqin 100B amp.Why would the people building the amp recromend a higher current and how will this affect the power output? Are we sure about this?

The higher the current the longer the amp works in class A but the shorter the live of the tubes. A current of 40/45mA is gives no sound disadvantage but give longer tubelive. No less poweroutput.

Originally posted by keithgreenhalgh
Also on the schematic,where are the test points for adj the voltage?

Originally posted by boboo
Is that possible for some one to mark those testpoints on the schematic with a red pen and pulish it again?

The points are there where they always are in de Cathode thrue the ground.

Originally posted by Koifarm

I have a lot of experience with the MC100B.

You said that you have a lot's of experience with this amp and thats very good because than you can tell me why I got that no bass at all.

It's there but nothing to comapere with my hudred years old harman Kardon 730 twin receiver.
This junk just realy don't satisfy me at all!

It is possible that your loudspeakers need a lot of power for the bass because of low impedance and spl. It is also possible that the input impedance of the amp is lower as the other amp. If your source has a to little output Capacitor the low frequenties will cut off.

[boboo]

You wrote

"It is possible that your loudspeakers need a lot of power for the bass because of low impedance and spl. It is also possible that the input impedance of the amp is lower as the other amp. If your source has a to little output Capacitor the low frequenties will cut off."

Okay that’s very understandable even for me :-) but how can I improve the quality? Here is the list what I have on each channel

Okay the speakers it’s mostly all JBL .

In one channel for example I got 2x15” bass split in to two, very low so called air suspension cabinet and high bass closed cabinet.
Than, you got two drivers in a wooden horn low and high come in different size with 2 x 4” which overlap the two drivers and just for coloring the sound.
On the top there is one JBL 075 and four Piezzo discount.

Now the other side is almost the same but there is one 15” sitting in one big cube very low frequented faced to the flour to balance and color the other sides air suspension cabinets sound. I got a very rich sound! That’s why it’s so difficult to find other amps because I’m loosing it.

So what do you think?

[Lowrider]

You dont need to know where on the schema, measure BIAS outside, it is indicated near each output tube (KT88), you also adjust outside, with a small screwdriver...

[boboo]

Originally posted by Lowrider
You dont need to know where on the schema, measure BIAS outside, it is indicated near each output tube (KT88), you also adjust outside, with a small screwdriver...

Yes i have seen that but don't you have to meshure it! How did you know when you are there? Check it with my toung? :-)

You got a lot to learn me Portugal living in Litvania! :-) I'm full of curriousity.