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Author Topic: Fixing a Yamaha G100 112 ii  (Read 18905 times)

phatt

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Re: Fixing a Yamaha G100 112 ii
« Reply #45 on: September 21, 2015, 09:49:47 AM »
 :dbtu: :dbtu: :dbtu:

Someone once stated that 90% of electrical problems are in connections,, whether they be plugs or soldered joins like you found it's all connections. The trick is finding them. :grr
Phil.

DrGonz78

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Re: Fixing a Yamaha G100 112 ii
« Reply #46 on: September 21, 2015, 02:56:31 PM »
I love those old Yamaha amps! Nice work Dropanchor  :dbtu:
“A person who never made a mistake never tried anything new.” -Albert Einstein

g1

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Re: Fixing a Yamaha G100 112 ii
« Reply #47 on: September 22, 2015, 08:14:04 PM »
-I don't notice a difference in sound coming from the speaker when I adjust the output waveform when following the directions in the manual.  Is this something I'm just going to need an scope to measure?
You can't follow the directions for this part without a scope, so you were not following the directions.  ;)
-I can't get the center voltage down to ~45v as directed in the manual.  When the trimmer is fully counter-clockwise it only gets down to ~53v.  I'm afraid to turn it fully clockwise because I'm afraid I might blow something, but as it is fully counter-clockwise the amp still sounds great!
This reading is affected by the previous waveform adjustment.  Try moving the B4.7K pot either way and see if it helps you get the center voltage adjustment closer.

DrGonz78

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Re: Fixing a Yamaha G100 112 ii
« Reply #48 on: July 16, 2020, 02:35:22 PM »
UPDATE: I had posted not accurate information about this amp, refer to post 12. This amp has a cap coupled output and without a load on the output it will float at 50v as the cap will not be able to charge up. I must have missed this bit on the schematics and did not realize. Hopefully this post will prevent any further confusion if referencing this thread while working on their amp.
« Last Edit: July 16, 2020, 02:36:38 PM by DrGonz78 »
“A person who never made a mistake never tried anything new.” -Albert Einstein