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[email protected] owhatagoosiam@gmail.com is offline
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Default Yamaha Stagepas 300 failure mode

On Thursday, April 21, 2016 at 4:53:41 AM UTC-4, wrote:
I have seen the following problems occuring on StagePas 300 :

People change cables w. "standard issue 10m cables, 6,3mm Jack ends" because they need longer cables. This won't ever work; Most industry standard cables having 6.3mm jacks are meant for guitars and other relevant instruments,Conductors inside are thin and coaxial having enormous capacitance and very large resistance.


You need to order your technician or build yourself a pair of REAL Loudspeaker (twin-lead and sufficient thickness for 150W power handling) cables having mono 6,3mm jacks end to end. You won't burn your amp that way.

also -

I have noticed a problem w. my set that showed after 15 mins of operation the following problem:

Sound cut off, replaced with low frequency hum (thus amplifier is still active), Limiter led (red on bar graph) stuck ON, Turning it off and after a few minutes back on solves the problem.

That problem was traced down to an 7915 voltage stabilizer on the main preamp/psu board, having an output of -8V instead of -15 on normal operation and after 15 minutes that voltage fell to 0 volts. Replacing the 7915 with another fixes the problem (solid -15V on output). My Stagepas 300 has an 7915 with plastic casing (too large heat resistanse to heatsink, I guess, and a semiconductor fatigue resulted to that problem). It looks that using a metallic 7915 is possible as the heatsink is electrically isolated from the rest of the circuit on my revision, if in doubt use some mica - plastic ring isolator there.

Cheers.


Mak,
Did you replace the 7915 chip yourself or did you have it done in a shop. I don't trust myself to make this repair but the cutting out problem has made the Yamaha unit totally unreliable so I really need to try it. Any tips would be greatly appreciated.
Thanks J