Gibson Skylark Grouding Questions

msmith1 · 23rd September 2005, 07:15 PM

I just inherited a "vintage" Gibson Skylark GA5T Amp. It sounds pretty good but there is a definite hum and ... (this is the bad thing) when it is swithed off the metal and my guitar go hot! its a low voltage but definitly a tingle! Attached is a link to the schematics. I want to ground the chassis and I am checking for shorts. I probably need to install new isolated input jacks. What else do I need to watch for or is there a good reference. This is my first "project' amp. I am new at this so keep it simple, please. Thanks.http://www.harpamps.com/gibson/pg_0089.jpg

Giaime · 23rd September 2005, 09:07 PM

It's easy that the 0.02uF capacitor in the primary of the power transformer is leaky or shorted. Remove it, it's not needed, and replace the power cord with an earthed one, 3-prong.

While you're here change all other capacitors.

amperex · 23rd September 2005, 09:15 PM

Although no leakage issues of line voltage, a new 3-prong cord replacing the stock two prong power cord removed all audio hum on our Gibson Hawk.

23rd September 2005, 07:15 PM	#1
msmith1 diyAudio Member Join Date: Sep 2005	Gibson Sklark Grouding Questions I just inherited a "vintage" Gibson Skylark GA5T Amp. It sounds pretty good but there is a definite hum and ... (this is the bad thing) when it is swithed off the metal and my guitar go hot! its a low voltage but definitly a tingle! Attached is a link to the schematics. I want to ground the chassis and I am checking for shorts. I probably need to install new isolated input jacks. What else do I need to watch for or is there a good reference. This is my first "project' amp. I am new at this so keep it simple, please. Thanks.http://www.harpamps.com/gibson/pg_0089.jpg

23rd September 2005, 09:15 PM	#3
amperex diyAudio Member Join Date: Feb 2005 Location: MI	Gibson amp Although no leakage issues of line voltage, a new 3-prong cord replacing the stock two prong power cord removed all audio hum on our Gibson Hawk.

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23rd September 2005, 09:07 PM	#2
Giaime diyAudio Member Join Date: Oct 2004	It's easy that the 0.02uF capacitor in the primary of the power transformer is leaky or shorted. Remove it, it's not needed, and replace the power cord with an earthed one, 3-prong. While you're here change all other capacitors.

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