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Old 2nd May 2013, 06:18 PM   #1
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Join Date: Jan 2006
Location: Athens GREECE
Default weird solid state problems

...Been working with almost 5000-6000 amplifiers all my life that one was a first .

Akai AM 2400 it will never get more simple than that amp is pretty straight forward 1980 technology in mint condition and all capacitors have been replaced and upgraded ...very good cleaning and that's about it .

on start up a loud hiss or burst of high level including low freq signal sounds for about 10 sec after that amplifier works perfectly

Bias was proper , offset down to almost zero , capacitors replaced , soldering in perfect condition , all voltage present according to the schematic , all auxiliary voltages also very fine , output relay was also replaced anyway .

In a few words anything possible to be checked was already done .

The very loud hiss was there on each and every start up ...

To cut the long story shorter it was the mains switch the switch cons where badly damaged the amplifier featured bleed resistors so on every start up the switch was struggling to ''load '' the caps after that probably the switch presented a high resistance and probably produced some ark but the big capacitors filtered everything so it was impossible to understand what happened .

By the way all Sanyo plus 55 i come across the latest 4-5 years have the same problem.

Feel free to add your solid state weird problems

Kind regards

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Old 4th May 2013, 06:06 AM   #2
Zero D is offline Zero D  United Kingdom
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Join Date: Aug 2009
Hi, that "could" have been one of "those" things that never got tracked down So kudos to you for finding the solution

Another issue can be, Amps that have their voltage rails going to the low current devices first on the PCB, rather than high current. It can lead to some wierd turn situations !
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