Flex Posted December 30, 2010 Share Posted December 30, 2010 (edited) Hi all, Have a problem with my trace. It is a british built (1995 model) unit but that said here's what happended and what I have found. Last night at rehersals we cranked it up a notch. My trace was set to About 7 on Output ( high bass, low highs - reggae setup on EQ). anyway 30 mins in and ... whats that smell?? Looked at the amp and smoke trickling out. This morning I have removed the amp from the case and found the 'HIGH FREQUENCY VOLUME' pcb card is a bit (alot) burnt. This dial on the back of the amp was set at '7' I noticed this morning :/ My question is if I remove the power feed to this card is it likely to effect the amp? As I presently play reggae the high frequency is not a major issue, I will look at replacing the PCB at somepoint. Any help would be appreciated in resolving this fault. Many thanks Pete Edited December 30, 2010 by Flex Quote Link to comment Share on other sites More sharing options...
icastle Posted December 30, 2010 Share Posted December 30, 2010 Unless you can ascertain for certain that the cause of the defect was actually located 100% to that particular PCB then you are very likely to fry something else and increase the cost of repair. You really need to get it to an amp tech I'm afraid. Quote Link to comment Share on other sites More sharing options...
MarkBassChat Posted December 30, 2010 Share Posted December 30, 2010 Pete, Do you mean the switch on the back of the amp (see attachment)? It is a switch that switches several resistors in series with the horn. Most probably it was not contacting correctly. You can simply set it to minimum value. If you need, you can disconnect it but, as ICastle says, you should be sure that this is the only problem with the amp. I had exactly the same problem with rare TE 1225 combo. I had to replace the switch (and clean the board). Mark [attachment=67466:switch.jpg] Quote Link to comment Share on other sites More sharing options...
303monkey Posted March 15, 2012 Share Posted March 15, 2012 Hi there Does any on know if these 12 way switches are Break b4 Make or Make b4 Brake/Shorting or Non-Shorting rotaries Quote Link to comment Share on other sites More sharing options...
Jeff Posted April 2, 2014 Share Posted April 2, 2014 Hi I just joined because I to have the same amp with the same problem and I need to share what I found. Let me ask you this. Were you using a mono speaker cord? I looked at how the amp is wired and I wouldn't believe it if I hadn't seen it with my own eyes! Both the output jacks are labled "Speaker 8 Ohms" but they are not the same. The amps + and - output go to the tips and sleeves of both jacks but the High Frequency Volume control places a selectable resistance [b]from + to the[i] ring [/i]of the upper jack!!! [/b]I'm guessing that this was some wacky attempt of having the horn volume on the amp not the cab. The idea being you use a stereo speaker cable where the tip goes to the woofer and the ring going to the horn. The HFV puts resistance in series with the horn turning it up or down. BUT here's the problem... When a mono speaker cord is plugged into a stereo jack the sleeve of the plug shorts the ring to the sleeve. So when you plug a mono cord into the upper jack instead of putting the resistors on the HFV in series with a horn it is actually putting that resistance [i]IN PARALLEL WITH THE SPEAKER[/i]!!!! So with an 8Ohm speaker cab and your HFV on 7 your load is 8Ohm(speaker) in parallel with 6.6Ohm(resistor) The resistors were getting more of the power than the speaker. UNBELIEVABLE!!! unbelievable that these two jacks are both labeled "Speaker 8 Ohms" with no distinction I don't know if you did any damage to the amp but if you have a standard 8Ohm speaker that uses a standard mono plug use the bottom jack and disregaurd the HFV. If you have a cab that uses a stereo cable with the tip to the speaker and the ring to the horn use the upper jack. How the user is supposed to know that is beyond me but this amp is either poorly designed or poorly labeled. Take a look at yours, same thing? One wire from HFV to tip of upper jack one wire to ring of upper jack. Personally I'm gonna remove it. Like I said I don't know if it hurt your amp but if you got lucky and it didn't I'd remove the HFV Thanks Jeff Quote Link to comment Share on other sites More sharing options...
jjscreeds Posted April 2, 2014 Share Posted April 2, 2014 (edited) I have just had my gp12 smx amp apart for a different reason and checked this out as i had read your post, mine isn't connected to the speaker outputs at all, the high pass filter control on the back is only on the send and return and doesnt control anything on the speakers . Maybe someone had modified it for a specific reason. Edited April 2, 2014 by jjscreeds Quote Link to comment Share on other sites More sharing options...
Jeff Posted April 3, 2014 Share Posted April 3, 2014 Ooops I just noticed my amp is a gp7 not a gp12. Sorry Quote Link to comment Share on other sites More sharing options...
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