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24th March 2006, 10:07 AM
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#1 |
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diyAudio Member
Join Date: Jan 2002
Location: Mumbai (Bombay), India
 
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EL34 CCS help
THe pic attached is the CCS.
A friend assembled the CCS boards and discovered a problem. The circuit has a "direct connection" between the 6SL7 and the 6SN7 stage. This means the CCS will have about 261 volts at its collector. The current is about 14.5 mA . So dissipation is about 3.8 watts in the MPSA340 used there. This is too much for the MJE340. Note that if the stage was " ac coupled " with a dc blocking capacitor in between then the cathode would be at just about 7 volts. FYI... this is the amp http://www.diyaudio.com/forums/attac...amp=1136905599 The power supply http://www.diyaudio.com/forums/attac...amp=1100080737
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24th March 2006, 10:50 AM
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#2 |
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diyAudio Moderator Emeritus
Join Date: Jan 2003
Location: Near London. UK
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MJE340 is rated at 20W dissipation (with heatsink). Just add a heatsink with 8C/W thermal resistance or better.
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