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Mark Levinson No.27 amplifier,,,NEED HELP
Mark Levinson No.27 amplifier,,,NEED HELP
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Old 29th November 2020, 08:07 PM   #231
Mark levinson is offline Mark levinson
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Join Date: Jan 2020
I just thought that the new 1900uf valve should be white. Unfortunately, I do not have a complete service manual �� there is only the beginning of the gle, the disassembly of the 27th is described and that's it.
just looked for new mellory for $ 60, so I thought to change them or something. I wonder how the replacement affects the sound do not know?
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Old 29th November 2020, 09:34 PM   #232
Mark levinson is offline Mark levinson
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Join Date: Jan 2020
Quote:
Originally Posted by Hans Polak View Post
So there is a little Gremlin sitting and waiting in your amp, ready to attack once everything is ready for use.

Hans
Hans, I'm having trouble setting up... Please help me.
P7 earth L1.678v. R1.7v
P6 earth L1.734v R1.77v
P6-P7 L3.45v. R3.46v
P11 earth L0.02mv R0.02mv
Constant output voltage R12.2mv L0.05mv

What should I do can you explain in detail? I configured P11. I set the quiescent current to 20mv what's next?
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Old 30th November 2020, 01:22 PM   #233
Hans Polak is offline Hans Polak  Netherlands
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Location: Blaricum
Hi Mark,

Almost everything seems O.K.
With 40mA per output transistor, this adds up to 160mA for 4 pcs.
Between WH13 and WH14, you should measure 160mA x 0.22R = 35mV.
The 20mV that you specified is that possibly between P16 and WH13 ?

Have you also set Vreg+ and Vreg- to be within 0.1V in absolute value?

When that's all done, there's normally nothing left to be adjusted.

I am a bit puzzled why LS out measures 12.2 mV, that's a bit on the high side.
With R3 you could bring this to zero volt if you like.
To achieve that, take out R3 and replace it by a pot ,somewhat larger than 100k.
Turn the pot until you have zero volt out. Take the pot out, measure it's value, and replace R3 with a fixed resistor of this measured value.

Hans
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Old 30th November 2020, 03:20 PM   #234
Mark levinson is offline Mark levinson
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Join Date: Jan 2020
Quote:
Originally Posted by Hans Polak View Post
Hi Mark,

Almost everything seems O.K.
With 40mA per output transistor, this adds up to 160mA for 4 pcs.
Between WH13 and WH14, you should measure 160mA x 0.22R = 35mV.
The 20mV that you specified is that possibly between P16 and WH13 ?

Have you also set Vreg+ and Vreg- to be within 0.1V in absolute value?

When that's all done, there's normally nothing left to be adjusted.

I am a bit puzzled why LS out measures 12.2 mV, that's a bit on the high side.
With R3 you could bring this to zero volt if you like.
To achieve that, take out R3 and replace it by a pot ,somewhat larger than 100k.
Turn the pot until you have zero volt out. Take the pot out, measure it's value, and replace R3 with a fixed resistor of this measured value.

Hans
No, Hans, I didn't set up the current correctly. I have between wh13 and wh14 41mv. Now in 30 minutes I will reduce it to 35mv.
Hans, please tell me how to configure vreg+ vreg-? I read that you need to output a voltage of + - 65 volts.
I will return to the 12.2 mv quiescent current later, first you need to alert everything.
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Old 30th November 2020, 06:59 PM   #235
Hans Polak is offline Hans Polak  Netherlands
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With the two pots encircled in green adjust resp. Vreg+ and Vreg- to +/-63Volt, to within 0.1 Volt.

I assume that with the 12.2mA you mean 12.2mV, right ?

Hans
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Old 30th November 2020, 07:09 PM   #236
Hans Polak is offline Hans Polak  Netherlands
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Oops, forgot the image.
Attached Images
File Type: jpg IMG_20201017.jpg (862.9 KB, 46 views)
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Old 30th November 2020, 07:11 PM   #237
Mark levinson is offline Mark levinson
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Hans, I set up the quiescent current, but it was higher.
Hans but in the service manual to 27 it is written 65v and in the service manual 27.5 it is also written 65v.
At what points should I measure + -63v, I do not understand.
Yes, 12.3 mv in the other channel 0.02 mv

Last edited by Mark levinson; 30th November 2020 at 07:14 PM.
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Old 30th November 2020, 07:30 PM   #238
Mark levinson is offline Mark levinson
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Quote:
Originally Posted by Hans Polak View Post
Oops, forgot the image.
Hans, I attach a screenshot from 27.5 and from 27. And so de in post 190 you wrote that the current is worth putting 39.6 mV.
Hans that in the end will be correct? 35 mV or 39.6 mV 🙂
Attached Images
File Type: jpg Screenshot_20201201_001725.jpg (673.2 KB, 48 views)
File Type: jpg IMG_20201201_002554.jpg (429.4 KB, 44 views)
File Type: jpg Screenshot_20201201_002315.jpg (409.5 KB, 43 views)
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Old 30th November 2020, 07:56 PM   #239
Hans Polak is offline Hans Polak  Netherlands
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Location: Blaricum
You are right, 65 Volt is the right value, sorry for the typo, good that you checked.
My earlier 180 mA was deducted from the ML23 with 45mA per transistor, but reading your manual, 40 mA was advised instead.
But it does make hardly a difference, so either 35mV or 39mV is O.K.

The +/- 65 volt should be measured at P1 and P4.

Hans
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Old 30th November 2020, 08:43 PM   #240
Mark levinson is offline Mark levinson
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Join Date: Jan 2020
Quote:
Originally Posted by Hans Polak View Post
You are right, 65 Volt is the right value, sorry for the typo, good that you checked.
My earlier 180 mA was deducted from the ML23 with 45mA per transistor, but reading your manual, 40 mA was advised instead.
But it does make hardly a difference, so either 35mV or 39mV is O.K.

The +/- 65 volt should be measured at P1 and P4.

Hans
So there will be no effect on the sound from 35mv or 39mv? Then I'll leave 35mv
Vreg+ - 65v is set exactly ��.
I also read in the service manual that the constant voltage at the output terminals is up to 30mv within the tolerance, so I should not worry?
Or should there already be 0 mv at the output terminals at 27.5?
Attached Images
File Type: jpg IMG_20201201_014123.jpg (434.7 KB, 40 views)

Last edited by Mark levinson; 30th November 2020 at 08:46 PM.
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