Discussion in 'Exclusively Sansui' started by SanthoshA, Sep 21, 2017.
Not on the example I restored.
What condensers can be used on replacement of "Black flags" with a small capacity from 2-47pf?
Either 'Silver Mica' types, or C0G/NPO ceramic types - I have used both (in different amplifiers) but I personally prefer 'C0G/NPO' ceramic, for their small size and good performance, as a bonus they are also cheaper than Silver Mica, at least where I can get them from.
Note that there are other types of ceramic capacitors - these are no good, it must be 'C0G/NPO' type ceramic.
Silver Mica like this (500V rating is commonly available)
C0G/NPO Ceramic like this (100V rating is usually as high as these go in the low values needed)
What of ceramic condensers it is better, multilayered or single-layer?
The ones in the link are multilayer, I have not investigated the use of any other type.
Some light reading for you
How you solved a problem with replacement of assembly 2SK129? What changed for?
Zero at the exit changes because of it? Output transistors can flow and influence it?
I have never needed to change a 2SK129 - ever.
It is very unusual for a 2SK129 to be the cause of high DC offset - in the vast majority of cases the problem lies elsewhere.
What can serve as the reason of lack of constancy of zero at the exit? Zero drifts in great values. From it the background in loudspeakers appears.
Disconnected a payment of the driver from the preliminary amplifier. Malfunction flees by the driver. Current of shift is exposed. Remains only 2SK129. Therefore I ask that there is no constancy.
I agree, its not the 2SK129, I have never ever had to replace one either.
Replaced all transistors 2SA992 and 2SS1845, did not help.
How much DC offset do you have (in volts) at the output - I think you are saying it varies a lot - please say by how much in volts.
Have you checked the power supply voltages? - are they stable? are they the correct voltages? - this is the first thing to check.
Only tension in one shoulder 68B, in another 68.5B comes to the driver. It walks depending on tension in network, it without stabilizer a little.
At the exit it is not possible to achieve stable zero. Tension jumps to 200 mV.
Are both channels like this? or just one?
In one channel jumps a little more, than in another.
Have you reconditioned the driver boards? - including replacing all the 'Black Flags' ? and the trimmers? - and in general given them the same treatment as you should have seen here on AK in various AU-X11 (and AU-X1) threads.
Did not change "Black flags" and trimmers yet.
Washed out trimmers and greased. It is possible to expect it from condensers?
I strongly recommend you replace them.
They can make a difference to this kind of problem, providing they are 'new' replacements.
But DO replace the Black Flags as soon as possible.
On replacement ceramic multilayered C0G/NPO condensers "Murata" and trimmers are acquired.
Tomorrow-the day after tomorrow I will make replacement. I will unsubscribe about results. Can you and are right.
Really the modern ceramics is better "Black Flags"?
Sounding of the amplifier will not be worse from it?
Definitely more reliable.
The black flags are degrading - you can tell when you remove some of them as they have become swollen and pitted with age (and I guess maybe heat also).
They are a liability and were not used in many amplifiers. Its only a matter of time before they cause serious issues. I am not even sure that many are in the signal path. The recommended replacements are very high quality and will be extremely stable.
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