antonismbass Posted May 12, 2015 Share Posted May 12, 2015 Hi All, I have a Gallien Krueger MB500 bass head. On Sunday I connected my MB500 to a bass cab at a rehearsing studio. It started making a distorted sound (I had not connected my bass to it at that time) so I quickly switched it off. When I tried to switch it back on I couldn't get any sound from it. (The cab is fine as I used it with a different head later). This is what is happening when I try to switch it on now: -The power switch LED has no colour. I know blue is for ok and red when there is a problem, but I don't know what no colour means. -The mute and boost buttons do turn red when I press them. -There is lots of intermittent (1 short 1 long) hiss from the headphone output, but no bass signal when I connect my bass. The mute and boost buttons flash with the same rhythm. -I did tried replacing the fuse but nothing changed Any ideas on this? I'm confident with soldering and checking components but I have no idea where to start from. Many thanks, Antonis Quote Link to comment Share on other sites More sharing options...
PlungerModerno Posted May 13, 2015 Share Posted May 13, 2015 How long ago did you purchase the amplifier? Was it bought new? In any case I'd look at contacting GK to see do they have a recommended service person. That way you wont void the warranty. If it's a few years old dropping GK a line won't hurt either. Sorry I don't have specific advice - it doesn't sound good but could be as simple as a part failure (e.g. capacitor or opamp). Quote Link to comment Share on other sites More sharing options...
antonismbass Posted May 13, 2015 Author Share Posted May 13, 2015 I bought it not long ago from a fellow basschatter, but I'm pretty sure that it's old enough to be out of warranty. I have emailed GK, but I'm not expecting much. Thanks for the reply anyway Quote Link to comment Share on other sites More sharing options...
antonismbass Posted August 2, 2015 Author Share Posted August 2, 2015 Just an update on this in case anyone else has the same problem: I emailed Gallien Krueger who presumed that the problem is in the power-amp section. They suggested that I sent the unit for inspection to Polar audio who are the UK distributors. However Polar audio charge £30 inspection fee + £10 return postage (also £25 for every 15min of work). So I decided to give the unit to Guitar Aid in Putney (London). They confirmed that there is a problem with the power-amp section but they couldn't fix it and the cost to replace the section is about the same as getting a new amp. I emailed Gallien Krueger again to give them an update and ask them if there is anything they can advice but they didn't reply. Quote Link to comment Share on other sites More sharing options...
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