Randall amp problem.

[Mr. Bill]

To me it sounds like a design problem. If it were as simple as a pot replacement, everyone would have already figured that out by now, but it sounds like there are a lot of amps with this problem.

Sometimes when an amp is designed, the parameters are chosen for what the average signal, frequency, etc. will be. But in the real world, when the actual parts are put together sometimes those parameters are exceeded and the amp will fail. Eventually the factory will find the problem and will issue a technical service note that informs the field of what to change to fix the problem. If you have been working with a Randall service center, they will know if this is a common problem and if there is a factory fix. It's sorta like a software upgrade, sometimes a bug will turn up in a program that isn't found until after the release.

From what you describe, it could be that the amp is going into a parasitic oscillation when the master is turned up past 5. This would be at a frequency that you can't hear and the speaker can't reproduce. The amp uses all of its' energy reproducing this ultra high frequency so the guitar signal gets lost and dies out. Or it could be a specific part that just can't handle the amount of signal that it is getting.

As has been suggested here, you should contact Randall to get the most current information regarding your amp.

[mosman]

I contacted Randall but they just didn't want to know. I checked out the amp on the Randall Forum and Youtube and there's heaps of people on both sites with the same problem. The shop where I bought it eventually gave up sending it back and forth to the service center ( 4 times) and refunded my money. Here's something interesting though: I play fast 3 chord Johnny Ramone style and it's only then that the problem occurs. The guys at the shop called and told me they couldn't replicate the problem after trying for some time but when I went in I made it happen after only a few seconds of chainsaw style thrash. It turns out even though they were playing it at the same volume I was, they were doing Stairway To Heaven or Hotel California type stuff and with that you can go all day and have no trouble. When I started bangin' away and made it happen so quick they realised what was going on but still never found a solution. I don't have the amp anymore but I'd still like someone to come up with a definitive answer.
Randall sure don't have one.

[olrocknroller]

I just fixed a solid state amp (a major, American-built brand) for a buddy of mine, and it was dead easy. I got him to duplicate what caused it to cut out, and when it did, I tapped around on the chassis with my finger, and voila, it came back on... bad ground. I opened up the box, and found that the manufacturers have gone to automotive style push on connectors for a lot of key circuit board connections. Sure enough, I found one that was loose, closed it up a little with a pair of needle-nose pliars, and reassembled. He reports it runs on "10" now quite happily.

Hope that your problem is as easy to fix...when you said it cuts out at "5", that just might be enough vibration to cause the same problem.

Olrocknroller