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Old 7th October 2013, 09:40 AM   #21
Mooly is offline Mooly  United Kingdom
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I wouldn't like to say with regard to just copying another player and without seeing all the component values etc. All the little details come together.

This player is obviously designed (and the gain and response of the stages calculated and correctly configured) to work correctly. If that transistor is normally off under all the conditions that you use the player in then you can remove the transistor.

That has to be the first thing to measure before you alter anything. See if the transistor would conduct under your normal usage. If you remove the transistor then there is a slight influence of that 1800pf cap in combination with the 1k +22uf +47k series chain. The effect is extremely small (negligable probably).

If the transistor conducts under any of your usage conditions such as DVD playback, CD playback etc then you should refit them.
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Old 7th October 2013, 09:59 AM   #22
dazzz is offline dazzz  Israel
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Quote:
Originally Posted by Mooly View Post
I wouldn't like to say with regard to just copying another player and without seeing all the component values etc. All the little details come together.

This player is obviously designed (and the gain and response of the stages calculated and correctly configured) to work correctly. If that transistor is normally off under all the conditions that you use the player in then you can remove the transistor.

That has to be the first thing to measure before you alter anything. See if the transistor would conduct under your normal usage. If you remove the transistor then there is a slight influence of that 1800pf cap in combination with the 1k +22uf +47k series chain. The effect is extremely small (negligable probably).

If the transistor conducts under any of your usage conditions such as DVD playback, CD playback etc then you should refit them.
First thing thanks for the help bro

The 2900 works perfectly finished mod yesterday as well as I changed the OP AMP NJM2068 - I / V
to LM4562
I now only remains to decide which OP AMP to place
BA15218

(This audio circuit diagram of 3910)
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Last edited by dazzz; 7th October 2013 at 10:10 AM.
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Old 7th October 2013, 12:02 PM   #23
Mooly is offline Mooly  United Kingdom
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Thats similar in concept but with very different values. Gain of that stage is 2 and the feedback return is DC coupled.

For the unit you are working on you need to measure the base/emitter voltage across the corresponding points where the transistor was fitted (and that you have now removed). If there is B-E voltage present in playback then it means the transistor was on (conducting) and so should be in place (or a link fitted)... ut then you loose the function of what happens when its supposed to be off. Its there for a reason and whether you remove it or short it out means you loose that function.
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Old 7th October 2013, 01:14 PM   #24
dazzz is offline dazzz  Israel
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Quote:
Originally Posted by Mooly View Post
Thats similar in concept but with very different values. Gain of that stage is 2 and the feedback return is DC coupled.

For the unit you are working on you need to measure the base/emitter voltage across the corresponding points where the transistor was fitted (and that you have now removed). If there is B-E voltage present in playback then it means the transistor was on (conducting) and so should be in place (or a link fitted)... ut then you loose the function of what happens when its supposed to be off. Its there for a reason and whether you remove it or short it out means you loose that function.
Thanks bro
The decision to remove this transistor made
After reading a lot of people did on the 2900 Mod.
So after removing it sounds A lot better
I was just curious about resistors
After your reply
I got the answer I wanted
Thank you.
If you could ask one more question
Now I installed the audio circuit on I / V amplifier LM4562
And buffer AD826
To what OP AMP would you recommend switching from BA15218
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Old 7th October 2013, 01:21 PM   #25
Mooly is offline Mooly  United Kingdom
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The 4562 is as good as anything for most situations. When swapping opamps you need to be aware of stability problems that might arise although there shouldn't be any problems with this. Not sure if you've seen this or not,

Swapping Op-Amps... you have checked to see it's stable haven't you ?
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Old 7th October 2013, 01:41 PM   #26
dazzz is offline dazzz  Israel
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Quote:
Originally Posted by Mooly View Post
The 4562 is as good as anything for most situations. When swapping opamps you need to be aware of stability problems that might arise although there shouldn't be any problems with this. Not sure if you've seen this or not,

Swapping Op-Amps... you have checked to see it's stable haven't you ?
Yes no problem
It works fine circuit
No problems of
op amp oscillation
I researched a lot before all decision on replacing of each OP AMP.
I read your thread now.
Topic of the OP AMP fascinates me



These projects refreshing the electronics studies I learned a few years ago
(Although at the time it was mostly mathematics
And a electrical equation )
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Old 14th October 2013, 02:27 PM   #27
dazzz is offline dazzz  Israel
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Hello

Today i make the order to all the other parts of the finsh project
Its left only one thing to decide



After I changed in the circuit of 2900 The OP AMP

(I/V) NJM2068 to LM4562
(buffer) OP275 to
AD826


Is left to replaced the filter OP AMP's - BA15218F
IC218
IC219
Like all good battle
There are two candidates in the arena
OPA1662 VS LM6172

Who Will Win ?
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Old 14th October 2013, 04:57 PM   #28
Mooly is offline Mooly  United Kingdom
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Impossible to say without seeing how they behave and hearing them
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Old 14th October 2013, 05:43 PM   #29
dazzz is offline dazzz  Israel
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Quote:
Originally Posted by Mooly View Post
Impossible to say without seeing how they behave and hearing them
mooly
I need your professional experience
Is the OP AMP
OPA1662
Can be used in a filter stage ( ic218.ic219 )
?????



I have to decide today whether to order it

Last edited by dazzz; 14th October 2013 at 05:47 PM.
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Old 14th October 2013, 06:08 PM   #30
Mooly is offline Mooly  United Kingdom
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I'm not going to commit myself on that because I haven't used the OPA1662. In theory it should be OK but its your call. Some quirk of the device could become apparent when you test it for real.
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