Genz Benz Shuttle 6.0 Problem (Almost No Output)

[Pedronious]

Hi Everyone
This is my first post on the forum, although I've often used it as a resource for reviews and opinions over the years because of the experience and knowledge of the members.
I'm now hoping that I can get some advice on a specific problem with my 6 year old Genz Benz Shuttle 6.0.
It hasn't had heavy use at all - a couple of dozen gigs, about the same number of practices and usually used at home for quiet practice.
It had functioned perfectly until I fired it up a couple of weeks ago. I thought initially that there was no audio output, but after turning all the controls to maximum I found that there is a very slight output signal. This affects both speaker outputs (also tested with different cabinets) and the headphone outputs, but the DI seems unaffected where output levels are just fine.
I changed the 12ax7 preamp tube, just in case (and because it was easy for somebody like me with no electronics knowledge!) which made a slight change to the output, but still nowhere near useable.
All the lights and controls on the front seem to work as before, and the gain LED glows as expected.
I've taken the amp into my (very helpful) local guitar shop but their technician said that being a Class D amp and not his area of expertise, it would probably need a board replacing, but since Genz Benz is no more, the chances of getting such a part are slim.
I have a good friend who is very experienced in electronics who says that, although not knowing about guitar amplifiers (he prefers building keyboards, Theremins and MIDI modules), if schematics were available he may stand a chance of figuring out what may be wrong. It appears, though, that schematics aren't available on the Internet.
So, my questions are, does anyone have a rough idea of what may be wrong with the amp, and if so, is it repairable?
Or should I cut my losses and start looking for a new amp?
If anybody has any suggestions for good engineers or repair technicians, I'm in Kent in the UK, so local would be great.
Any help would be most gratefully received.

 

[B-string]

@agedhorse He is the man that engineered your amp and can walk you through some of the basics. Further repair info if needed. He will probably pop in but you can also PM (Start a conversation) with him as that is his prefered method over doing this in the open threads.

 

[agedhorse]

The first thing to try is to jumper from the effects send to the effects return with a short 1/4" cable and see if that works. If so, just cycling the return jack should take care of the problem.

You can also try playing your bass into the effects return jack, if you have output (volume will be lower than through the full preamp), that is good info. to have as well.

 

[Pedronious]

Hi B-string and agedhorse
Thank you both so much for such a quick reply!
I've tried jumping from send to return but the volume is still the same level and very quiet. I've also tried going into the return socket and, as you say, is even quieter, even with my G&L which is the loudest bass I own.
Does that help narrow down where the fault may lie?
Thanks again for your help

 

[agedhorse]

How quiet are you talking about?

Do you have a known good speaker you can try the amp with? How about a known good bass.

I have a hunch that there may be something else involved here.

 

[Pedronious]

The volume level is like being next to somebody listening to it on headphones, and that's with all controls on max.
I also have a Laney 1x15" which I have used previously along with the GB 1x12", and that produces the same results, and with swapping around the speakon sockets that I connect them to.
I've also tried a few different basses (passive and active) and leads, as well as a couple of different mains cables just to be sure.
Does that help? Is there anything else I could try to test where the fault may be?

 

[Jeff Genzler]

The volume level is like being next to somebody listening to it on headphones, and that's with all controls on max.
I also have a Laney 1x15" which I have used previously along with the GB 1x12", and that produces the same results, and with swapping around the speakon sockets that I connect them to.
I've also tried a few different basses (passive and active) and leads, as well as a couple of different mains cables just to be sure.
Does that help? Is there anything else I could try to test where the fault may be?

So that we can be of better assistance could you PM me your contact info and together Andy and I can see how we can get you up amd running again quickly.

 

[Pedronious]

It has been a few weeks but the problem is solved!
My friend, who is an electronics engineer, offered to take a look and see if he could diagnose where the problem may be, before I sent the amp away for repair. He narrowed the problem down to being around the master volume pot on the pre amp board and found that it had a constant resistance of about 5 ohms. On closer inspection, with a magnifying glass, he found a small metallic fibre across the two active pins, shorting it out! So by simply removing the offending article the amp is now good as new again, and it had it's first outing last night (with trying out my newly acquired Manson Merlin).
I suspect that this is a pretty unique problem, and the chances of such a piece of material finding its way inside the amp head and blowing around to finally rest in such a position are slim to say the least. Maybe, if any lesson is to be learned from this it is that perhaps the first thing to try is to blow everything clean first, as in this case, nothing had actually failed at all.
My friend did say that on the plus side he's done a lot of reading around the subject and now know how op amps work, even though he didn't need to know in the end ;-)
Many thanks to B-string, agedhorse and Jeff Genzler for all your help, advice and the best after sales service that I've ever had!

 

[DWBass]

Not a knock on Genz Benz but I found the pots very susceptible to foreign matter. Had a 3.0 and a 6.0. Sent the 6.0 in for pot cleaning once and not long after I got it back the scratchyness returned. I just dealt with it. Really hoping if GB returns, they use a different type of pots. Other than that, great amps.

 

[agedhorse]

Pots in general can be vulnerable to problems because they are a mechanical part with surfaces exposed to the environment. Some corrosive atmospheres can be the cause, including salt (marine), dust and sulphur dioxide.

While it's frustrating, fortunately the numbers are pretty small compared with the number of pots used.

 

[Godbody]

I just made another thread about my Shuttle 6.0 before seeing this one, I'll crack open the amp tonight and see what's going on in there.

This sounds very similar to my issue.

 

[BassmanPaul]

I just made another thread about my Shuttle 6.0 before seeing this one, I'll crack open the amp tonight and see what's going on in there.

This sounds very similar to my issue.

Unless you have serious electronic chops I would not open the amp. If you did would you really know what you are looking at??

 

[Godbody]

Unless you have serious electronic chops I would not open the amp. If you did would you really know what you are looking at??

Yes, I would.

 

[JReno]

It has been a few weeks but the problem is solved!
My friend, who is an electronics engineer, offered to take a look and see if he could diagnose where the problem may be, before I sent the amp away for repair. He narrowed the problem down to being around the master volume pot on the pre amp board and found that it had a constant resistance of about 5 ohms. On closer inspection, with a magnifying glass, he found a small metallic fibre across the two active pins, shorting it out! So by simply removing the offending article the amp is now good as new again, and it had it's first outing last night (with trying out my newly acquired Manson Merlin).
I suspect that this is a pretty unique problem, and the chances of such a piece of material finding its way inside the amp head and blowing around to finally rest in such a position are slim to say the least. Maybe, if any lesson is to be learned from this it is that perhaps the first thing to try is to blow everything clean first, as in this case, nothing had actually failed at all.
My friend did say that on the plus side he's done a lot of reading around the subject and now know how op amps work, even though he didn't need to know in the end ;-)
Many thanks to B-string, agedhorse and Jeff Genzler for all your help, advice and the best after sales service that I've ever had!

Not my intention to revive a zombie thread, but your post just saved the day for me. Had my bass and amp(Shuttle 6.2) in the shop trying to diagnose this exact same issue with no luck until I found this thread. After a number of different tests, I advised the tech to do exactly as you said and simply blew some canned air through all the ports. Boom. Problem solved. Felt like an idiot for how simple this fix was. Still love this amp. For anyone else having similar issues, definitely try doing this first.