King Tut Posted January 28, 2020 Share Posted January 28, 2020 (edited) Yesterday i picked up a lovely AH250 GP12 SMX. This prompted me to do some research and found some info that related to one of my other Trace heads - an AH300 GP7 SM that I picked up off here some years ago. I've used it a few times, no problems, bags of power and not too heavy. Apparently, some of these amps have a power amp called the 'Bipolar Bear' - easy to spot as it's written on the board and has two big heatsinks that are easy to spot. Apparently this board can be troublesome and as well as being prone to failure, it can also take your speaker out in the process. I was gonna sell this amp but I'm reluctant to pass a potential problem on to someone else, or to risk my own speakers - particularly my Barefaced Big Baby! So - questions - there's a fix know as the Clive Button Mod which should have been applied when they went back to Trace for servicing (who does that?!). Is there an easy way to tell if this mod has been done to my amp? Could I assume that if my amp hasn't failed by now, it's not likely too and it's safe to use/sell on? I'm reluctant to spend a fortune on the thing as it doesn't hold a huge amount of value as it is, and i have plenty of other amps . . . . . . decisions, decisions. Anyone have any thoughts? Edited January 28, 2020 by King Tut Pics added 1 1 Quote Link to comment Share on other sites More sharing options...
Deedee Posted March 3, 2020 Share Posted March 3, 2020 I think I read something about this years ago. Just searching through some old threads and @VTypeV4 refers to the Clive Button module in the thread linked below. I wonder if he can shed any light? I think it may actually be a replacement board. https://www.basschat.co.uk/topic/237838-trace-elliot-gp7-sm300-amp-head-infoopinions-please/ Quote Link to comment Share on other sites More sharing options...
King Tut Posted March 3, 2020 Author Share Posted March 3, 2020 23 minutes ago, Deedee said: I think I read something about this years ago. Just searching through some old threads and @VTypeV4 refers to the Clive Button module in the thread linked below. I wonder if he can shed any light? I think it may actually be a replacement board. https://www.basschat.co.uk/topic/237838-trace-elliot-gp7-sm300-amp-head-infoopinions-please/ It's actually the Clive Button mod as in modification. It's detailed on one of the previous threads. My tech has carried out the work for me. Used the head for five gigs last week and all is good! Quote Link to comment Share on other sites More sharing options...
Deedee Posted March 3, 2020 Share Posted March 3, 2020 28 minutes ago, King Tut said: It's actually the Clive Button mod as in modification. It's detailed on one of the previous threads. My tech has carried out the work for me. Used the head for five gigs last week and all is good! Aha! What is required exactly? I saw something about a grounding issue? Quote Link to comment Share on other sites More sharing options...
Paul S Posted March 3, 2020 Share Posted March 3, 2020 Bipolar bears - what a great band name! 1 1 Quote Link to comment Share on other sites More sharing options...
Stub Mandrel Posted March 3, 2020 Share Posted March 3, 2020 I may be wrong, but I think the 'Clive Button' version was the four-mosfet power amp design as used in the keyboard amps which is relatively bullet proof compared to the bipolar design. Quote Link to comment Share on other sites More sharing options...
King Tut Posted March 3, 2020 Author Share Posted March 3, 2020 2 hours ago, Deedee said: Aha! What is required exactly? I saw something about a grounding issue? There's an earth connection that needs a star washer to prevent it coming loose. Another gizmo needs covering in heat resistant compound and a couple of transistors need changing. 1 Quote Link to comment Share on other sites More sharing options...
King Tut Posted March 3, 2020 Author Share Posted March 3, 2020 50 minutes ago, King Tut said: There's an earth connection that needs a star washer to prevent it coming loose. Another gizmo needs covering in heat resistant compound and a couple of transistors need changing. Deets should be attached. Trace_Elliot_GP7_150-300watt_SM.pdf 1 Quote Link to comment Share on other sites More sharing options...
Deedee Posted March 3, 2020 Share Posted March 3, 2020 Many thanks for that. 👍 Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted March 3, 2020 Share Posted March 3, 2020 Evening, folks.. The two boards look similar but they're easily identifiable by a few bits.. The main heat sinks on the bi-polar bear are separate but it's a single bigger one on the CB, also the main caps are physically larger and the gizmo mentioned above is a transistor that has something to do with controlling the fan - has its own heat sink. As I recall, they're a direct drop in replacement - I did my own on the 4808 years ago. I never had any bother with it (although I had some bad joints on the pre-amp board) and it had plenty of power too.. Quote Link to comment Share on other sites More sharing options...
King Tut Posted March 3, 2020 Author Share Posted March 3, 2020 13 minutes ago, VTypeV4 said: Evening, folks.. The two boards look similar but they're easily identifiable by a few bits.. The main heat sinks on the bi-polar bear are separate but it's a single bigger one on the CB, also the main caps are physically larger and the gizmo mentioned above is a transistor that has something to do with controlling the fan - has its own heat sink. As I recall, they're a direct drop in replacement - I did my own on the 4808 years ago. I never had any bother with it (although I had some bad joints on the pre-amp board) and it had plenty of power too.. The easiest way to identify the Bipolar Bear amps is that they have "The Bipolar Bear" written on them. Dead giveaway! Also two big heatsinks mounted on the board as @VTypeV4 said. Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted March 4, 2020 Share Posted March 4, 2020 17 hours ago, King Tut said: The easiest way to identify the Bipolar Bear amps is that they have "The Bipolar Bear" written on them. Dead giveaway! Also two big heatsinks mounted on the board as @VTypeV4 said. I'd forgotten that, ha! - Clive button ones have 'clive button' on them too.. 1 Quote Link to comment Share on other sites More sharing options...
Stub Mandrel Posted July 7, 2023 Share Posted July 7, 2023 A disgruntled Clive Button posted on Facebook today to stress that despite a currently popular video, he did NOT design the Bipolar Bear. 2 Quote Link to comment Share on other sites More sharing options...
VTypeV4 Posted July 7, 2023 Share Posted July 7, 2023 My SMX having a little service sometime last year. It's CB power stage can clearly be seen and is still working great - plenty of horsepower. 😀 1 Quote Link to comment Share on other sites More sharing options...
DGBass Posted July 8, 2023 Share Posted July 8, 2023 I've had a few GP 7 SM's in bits for a rebuild, 150's and 300's and the split heatsink output boards are the bipolar variant. They arent dissimilar to the MAG 180 and Mag 300 design in later Ashdowns, one heatsink is positively charged, and one heatsink negatively charged. They should never touch or sparks will fly and components are likely to pop. The only reall issue I ever see with these bipolar boards is that some loose their ground screw because the locking washer either wasn't fitted in the first place or due to years of vibration. The screw in labelled GND1( see pic) and is in the left front corner of the board. I always give this screw a turn with a screwdiver to see if its loose. If it is, renew the locking washer. If not its probably ok. Another curious but common issue with the SM amps is the standby switch circuit. The big green resistor next to C10 is often fitted hard to the board, overheats and burns out. This causes no output because the standy circuit dies. Both are easily fixed. Anoth tip is to keep the cooling fan clean and make sure the heatsink fins dont clog up with dust. Bipolar output transistors can be prone to thermal runaway if the aren't kept cool. Mosfets will shut themseleves down in that scenario. Fans on the bipolar SM's tend to run noisier and faster than the ones on their mosfet brethern's amps. The 300 watt mosfet board is very stable, and the only issue i see with them is vibration causing dry solder joints on the coupling caps over a long time. On earlier models, the board is usually not screwed down at the front right corner and sort of floats losely on a plastic post allowing that corner to flex too much. Later SMX models like the one in the picture were properly screwed down at all four corners. The mosfet boards also tended to have thermostatically controlled fans so they run quiter and smoother and only spin up to full speed when the amp is hot. Thats why later SMX's are more desirable than standard SM's, they usually have the more reliable mosfet output and all the previous niggles earlier SM's suffered have for the most part been ironed out. 3 1 Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted July 11, 2023 Share Posted July 11, 2023 My SMX is one of the early ones so it looks just like the SM printed graphic style except more bells and whistles. I must open it up and check no bipolar bear is lurking in there and all corners secure. Quote Link to comment Share on other sites More sharing options...
Baloney Balderdash Posted July 12, 2023 Share Posted July 12, 2023 Clive Button, ain't that Cliff Burtons cousin? Quote Link to comment Share on other sites More sharing options...
Buddster Posted July 12, 2023 Share Posted July 12, 2023 On 03/03/2020 at 18:03, Paul S said: Bipolar bears - what a great band name! Well, funny you should mention it, there is a band called that in the South Bristol /North Somerset area. 1 Quote Link to comment Share on other sites More sharing options...
Stub Mandrel Posted July 12, 2023 Share Posted July 12, 2023 Interesting follow up - Clive Button says there is no Clive Button mod for the Bipolar Bear! I don't think he wants ANYTHING to do with it! 1 Quote Link to comment Share on other sites More sharing options...
King Tut Posted July 15, 2023 Author Share Posted July 15, 2023 On 12/07/2023 at 22:54, Stub Mandrel said: Interesting follow up - Clive Button says there is no Clive Button mod for the Bipolar Bear! I don't think he wants ANYTHING to do with it! To be fair, I’ve just looked through the details of the file I posted earlier in the thread, including the mod, and there’s no mention of Clive Button anywhere. For those who haven’t downloaded it, here’s the text from the ‘not Clive Button’ mod - now to be known as ‘The Paul Mathews Mod’!!!! Important Notice To make the bi-polar 300 watt bass board reliable the following guidelines must be adhered to. When a board need to be serviced it is advisable to replace both the Output Transistors and TIP31 and TIP32. Also it is advisable to replace TR11 which is situated under the rear of the heatsink. The Output device should only be T2SC4468 and T2SA1695’s The Drivers should be of the same manufacturer as each other to ensure stability. And TR11 is a T2N3904 as listed on the parts list. TR11 need to be completely covered in Heat Transfer Compound (HTC) This is to ensure that it keeps the unit biased correctly even when the unit gets hot. If TR11 is not covered then the fan can cool this component down and give the board a fault reading of temperature and provide and inappropriate bias. When adjusting the bias on the scope, make sure that the crossover distortion is just not visible. Too far beyond this point will over bias the unit. Use a Shake-proof washer under the pcb earth point to ensure a permanent connection and prevent crackling noises in the future. Paul Mathews Jan 2000-01-25 1 Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 18, 2023 Share Posted July 18, 2023 Maybe ask Ashdown to have a look at it? They are servicing Trace Amps these days. Quote Link to comment Share on other sites More sharing options...
ahpook Posted July 18, 2023 Share Posted July 18, 2023 1 minute ago, Chienmortbb said: Maybe ask Ashdown to have a look at it? They are servicing Trace Amps these days. I tried a few months ago and was told they're too busy. Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 18, 2023 Share Posted July 18, 2023 1 minute ago, ahpook said: I tried a few months ago and was told they're too busy. Ah, sorry if I misled anyone. Quote Link to comment Share on other sites More sharing options...
ahpook Posted July 18, 2023 Share Posted July 18, 2023 7 minutes ago, Chienmortbb said: Ah, sorry if I misled anyone. Ooh, sorry - not trying to 'put you right' - just a warning it may not be an option as I believe it once was. Apologies if I seemed a bit blunt ! Quote Link to comment Share on other sites More sharing options...
trellio Posted April 9 Share Posted April 9 Is it a board that can be found in the Series 6 also? I am going to buy a GP12 Series 6 and am worried about it failing because of this. Quote Link to comment Share on other sites More sharing options...
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