Members Da Utha Cajun Posted May 4, 2015 Members Share Posted May 4, 2015 Hello everyone .My Name is Brannon May and I'm form Cajun Country. South Central Louisiana. I just joined up and am happy to be here. I have been searching for a week or so for information on adjusting the bias on my Orange TH100. I've always adjusted my own bias on all my amps. But this time Orange has done a really good job of keeping schematics, maintenance info and any info other how the user should operate the amp. I can come up with my own voltages with math, I a couple sets of biasing probes and I am not bad at all with electronics. But I still would like to know what the manufacturer recommends/suggests. I did contact orange directly and asked for this info but they were not about to give out this info. Does anyone out there have this info or possibly know the right direction to point me in to find it? Any help would be much appreciated. I have 4 new power tubes coming in any day now. Thanks for reading my post!! Link to comment Share on other sites More sharing options...
Moderators isaac42 Posted May 4, 2015 Moderators Share Posted May 4, 2015 Welcome to the board, Utha. Or would you rather we called you Cajun? I spent some time not too far away from your area a couple of years ago, playing with a band from Baton Rouge. I don't know anything about your amp. I found the owner's manual on line. It says that the bias should be checked, but "Bias checking must be carried out by a qualified engineer." Manual here. I don't see any reason why EL34 tubes in an Orange should be biased differently from EL34s in other amps. After all, the tube specs don't change. Sorry I couldn't be more help, but, again, welcome. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted May 4, 2015 Members Share Posted May 4, 2015 It may be fixed bias even though the site doesn't state that. You definitely want to order matched sets. If the amp is currently working you could just test what you have now and use it as a guideline. The amps are fairly complex and work at multiple wattage settings. I'd just measure them all and keep it written down in a pocket inside the head so it doesn't get lost. You may want to dig around on these sites for additional info. http://forum.orangeamps.com/viewforum.php?f=3&sid=ad38deefd49ecf498b2bffd7fce47936http://www.orangefieldguide.com/ In general the hottest you'd ever want to bias those tubes is 31ma plate current. Any hotter and that will likely glow red when you play and melt down. 25~28ma is more likely the range but like I said, Id test what they are now with the current tubes then just set the new ones the same. Link to comment Share on other sites More sharing options...
Members Da Utha Cajun Posted May 5, 2015 Author Members Share Posted May 5, 2015 Hi there Theodor and Guru. Thanks for the info. Actually I have been to those sites you posted links to. But I found nothing resembling what I am looking for I've even be on the phone with Orange trying to pull the info out of a couple service techs. And again nothing. I'm actually familiar with biasing amps. I just like to have at least very basic specs on the equipment I am working on. I remember when buying the amp I cam across that info plus I have the amp out of the housing now and I've located all 4 pots. Guess Im just going to have to trust in my math skills to get this done with no specs in hand. Because I am not driving 3 hours to the nearest "certified Tech" so I can leave my amp with him for a couple months. I'll have it all done in an hour. THEN I'll be willing to drive out to the tech to fix my mistakes...... Probably... Anyway. Thanks for the replies. I appreciate you guys looking into this for me. Link to comment Share on other sites More sharing options...
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