HOME Forums Music 911 Amp Repair Log – What was wrong and how you fixed it?

Tagged: 

Viewing 2 posts - 1 through 2 (of 2 total)
  • Author
    Posts
  • Jeff Harrisjrokguitar
    Keymaster
    Post count: 8
    #2619 |

    Poor Gain on Randall RG-100ES – I Purchased a Randall RG-100ES off of Ebay and the “red channel” had poor gain even when the treble knob was pulled out. After putting it on a scope I found that the second FET in the red channel gain stage was blown. After I changed that FET she was good to go. Good thing I had a scope on this one.

    • This topic was modified 1 year, 2 months ago by Jeff Harris jrokguitar.
    Jeff Harrisjrokguitar
    Keymaster
    Post count: 8

    Solid State Guitar Amp Dipping in volume – I am a guitarist/worship leader at a church here in Calif. Every Sunday I practice for an hour then play for roughly 35 minutes. Over the last 2 months I have been experiencing my volume fading intermittently and then coming back on its own after a few seconds. I have opened the amp and checked all jacks (effect loop and input jacks) checked with magnifying glass for open or loose solder joints and found nothing. I checked my guitar cable to the amp and my effects loop cables and they all tested around .3 ohms. After having this happen 3 to 4 times, I again opened the amp and investigated. After still finding nothing I decided to check the cables again but this time I flexed the cable every 4 inches or so while it is was tightly clamped and connected to my ohm meter. To my surprise about 18 inches from where one of my effect loop cables plugged into my pedal board there was some type of flaw or intermittent break in the center conductor of the cable. When I would bend that area the resistance of the cable would peak as “Open” and the resistance would change drastically but only for a millisecond. The next day my friend came over and wanted to see my findings but when I measured the cable with my ohm meter I could not make it repeat what I had seen. It tested good. This was really odd to me so I tried the cable again at church and the same thing happened with the intermittent dipping in volume. l let the cable sit for a few days and then tested the resistance again and this time it had the same high resistance when I flexed the cable about 18 inches from tip. What I found was that my cable was definitely bad even though it would often test as good. Changed the cable and problem was gone. This is the first time in 45 years that I have experienced a problem like this.

    • This reply was modified 1 year, 2 months ago by Jeff Harris jrokguitar.
Viewing 2 posts - 1 through 2 (of 2 total)

You must be logged in to reply to this topic.