Tmg Posted July 9, 2023 Share Posted July 9, 2023 (edited) Amp now Fixed - I took it into Orange and it turned out to be a dodgy treble pot. Big thank you to Joe Gray @ Orange for getting it sorted! Hi all, Over the last few months I've been having problems with my terror bass head. When I go through the pre-amp I'm only getting a fraction of the volume from the amp and sometimes nothing at all. But if I plug in through the send of the effects loop I get the full 500 watts of the power amp! So it's got to be a problem between the pre-amp and the power amp. I've tried changing the valves and lost faith in my local amp tech guy, as I've taken it to him twice now, only for me to get it home and find it's exactly the same. Any body here had a similar problem? At the moment I've managed to get over the problem by running a 'two tones revolt bass pre-amp' into the power amp, which to be honest I really like the sound of, so will probably carry on with this set up, but I'd still like to get the amp fixed. Any ideas? Cheers Tony Edited October 20, 2023 by Tmg Problem solved Quote Link to comment Share on other sites More sharing options...
northcountrybob Posted July 10, 2023 Share Posted July 10, 2023 How old is the Terror Bass? I'm very familiar with the old ones, not familiar at all with the new ones. Quote Link to comment Share on other sites More sharing options...
Tmg Posted July 10, 2023 Author Share Posted July 10, 2023 Hi, It's only about 2 years old. The newer model. Quote Link to comment Share on other sites More sharing options...
northcountrybob Posted July 10, 2023 Share Posted July 10, 2023 Maybe try emailing Orange. The old TB is pretty much an AD200 preamp into a class D power amp, but it has quite a few quirks. A preamp issue shouldn't be too hard for a tech to sort out. Could be a power rail that has failed, dodgy switching jack in the send of FX loop (sounds like you've ruled out the return jack), bad pots, bad solder joint, bad push on connectors (if there is any) or a failed component like a JFET. If the tech thinks it's fine maybe it's intermittent, or is that not your experience? Where are you based? 1 Quote Link to comment Share on other sites More sharing options...
Tmg Posted July 10, 2023 Author Share Posted July 10, 2023 My first action was to email Orange and they gave me a guys details but he was miles away. I'm in Barnwell, about 16 miles away from Peterborough. So I took it to my old tech guy in Bedford but after he'd had two attempts i thought I'd ask around before taking it anywhere else. It has been intermittent in the past, but I think my techs hearing there's a signal and thinking he's fixed it, but it's not even at a ¼ of the volume. Quote Link to comment Share on other sites More sharing options...
dannybuoy Posted July 10, 2023 Share Posted July 10, 2023 When my old Mk1 OTB died, I took it into PMT in Cambridge, who then sent it onto Orange for a repair. It was 2nd hand and well out of warranty, and if I recall correctly all I had to pay was the courier charge! 1 Quote Link to comment Share on other sites More sharing options...
Tmg Posted July 10, 2023 Author Share Posted July 10, 2023 Maybe I'll give that a go, thanks. I must admit when I first contacted Orange I offered to send it to them, even offered to run it down to their factory in Borehamwood, but it fell on deaf ears 😑 Quote Link to comment Share on other sites More sharing options...
northcountrybob Posted July 11, 2023 Share Posted July 11, 2023 The old terror basses we're sometimes a bit touchy. When they went for repair Orange used to replace every PCB in the amp and send them back out under warranty. Most common failure is "shoot through" on one of the output transistors; it shorts out and takes the mains fuse with it. The new ones should be more reliable. The first prototype for the MKII actually became the Little Bass Thing I think. If Orange don't fancy taking a look, I'd recommend JPF Amps on Demark St in Central London. 1 Quote Link to comment Share on other sites More sharing options...
Lozz196 Posted July 11, 2023 Share Posted July 11, 2023 19 hours ago, Tmg said: Maybe I'll give that a go, thanks. I must admit when I first contacted Orange I offered to send it to them, even offered to run it down to their factory in Borehamwood, but it fell on deaf ears 😑 That’s poor, thought Orange had better customer service than that. 1 Quote Link to comment Share on other sites More sharing options...
Tmg Posted July 11, 2023 Author Share Posted July 11, 2023 I thought the same! Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted July 11, 2023 Share Posted July 11, 2023 Find the official Orange service centre for your neck of the woods. I wouldn't be surprised if it's the factory if you're in driving range. Even if it's not the closest take it to them and tell them what you know and they will fix it good. 'Lukewarm' does not cut the mustard. Just show up with it. 15 hours ago, northcountrybob said: Most common failure is "shoot through" on one of the output transistors The old old ones used to blow the top off one of the capacitors, I don't think it's that either as OP has a perfectly operational power stage. Quote Link to comment Share on other sites More sharing options...
northcountrybob Posted July 12, 2023 Share Posted July 12, 2023 8 hours ago, Downunderwonder said: Find the official Orange service centre for your neck of the woods. I wouldn't be surprised if it's the factory if you're in driving range. Even if it's not the closest take it to them and tell them what you know and they will fix it good. 'Lukewarm' does not cut the mustard. Just show up with it. The old old ones used to blow the top off one of the capacitors, I don't think it's that either as OP has a perfectly operational power stage. That's true, almost had one hit me in the face once... and the Negative Temperature Coefficient Thermistors used to break off the IEC inlets, and the 6V reg for the heaters in the preamp valves used to to fail. The switching FETs in the supply would short out. The rectifier diodes mounted under the power transformer would expire. The switching IC's driving the power supply FET's would expire. The core in the transformers would come loose and rattle about in the middle of the windings. The posts the power supply PCBs were attached to would break off. Inductors on the output PCB would break off. The switching frequency for the output drivers would come out of calibration (set by two little trim pots). The potential divider on the output PCB that sets a reference frequency that determines the "dead time" of the output FETs isn't set to anything from the driver chip spec sheet. So "dead time" is minimal, which means there's very little time when one output FET turns off and the next in the pair turns on, which increases the risk of shoot through in the output FETs. I'm fairly certain it was also designed around 230V mains, when we have up to 252V here IIRC. The input to the supply is a voltage doubler when switch to 120V for the US, so that makes issues with spicy mains worse I think. My guess is that's partly why some people would have repeat problems even after all the PCB's in their amp being swapped out. Quote Link to comment Share on other sites More sharing options...
Tmg Posted July 17, 2023 Author Share Posted July 17, 2023 On 12/07/2023 at 09:44, northcountrybob said: That's true, almost had one hit me in the face once... and the Negative Temperature Coefficient Thermistors used to break off the IEC inlets, and the 6V reg for the heaters in the preamp valves used to to fail. The switching FETs in the supply would short out. The rectifier diodes mounted under the power transformer would expire. The switching IC's driving the power supply FET's would expire. The core in the transformers would come loose and rattle about in the middle of the windings. The posts the power supply PCBs were attached to would break off. Inductors on the output PCB would break off. The switching frequency for the output drivers would come out of calibration (set by two little trim pots). The potential divider on the output PCB that sets a reference frequency that determines the "dead time" of the output FETs isn't set to anything from the driver chip spec sheet. So "dead time" is minimal, which means there's very little time when one output FET turns off and the next in the pair turns on, which increases the risk of shoot through in the output FETs. I'm fairly certain it was also designed around 230V mains, when we have up to 252V here IIRC. The input to the supply is a voltage doubler when switch to 120V for the US, so that makes issues with spicy mains worse I think. My guess is that's partly why some people would have repeat problems even after all the PCB's in their amp being swapped out. I won't even try and pretend I know what all that means! So a define trip to Orange is on the cards. Thanks everyone 👍 Quote Link to comment Share on other sites More sharing options...
Tmg Posted October 19, 2023 Author Share Posted October 19, 2023 Just to let everyone know, I finally took my amp back to Orange & it turned out that it was just a faulty treble pot! Thanks for all your input! Cheers Tony Quote Link to comment Share on other sites More sharing options...
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