Members thinderik Posted September 19, 2009 Members Share Posted September 19, 2009 All right so this amp is supposed to be really easy to bias. Which is making me feel like an even bigger twat. I bought a $70 dollar DMM because the second/distortion channel on this amp sounded good after warming up but ended up getting way to crazy/buzzing/moaning...(im really bad at describing it). So I figured I'd check the bias, what could it hurt. For those of you not familiar with this amp. On the back it has 3 holes where you attach the DMM's leads. The two to the left are bias the the two to the right are the balance. Set the Bias for .04v and the balance for 0v. there are screw's on either side of the holes to adjust bias and balance. Well I would turn the screw and it would not move out of the ooo.o mv range. The DMM works I used it to check batteries. I'm probably going to bring it into the shop on monday if i can't resolve this issue by myself. The amp sounds fine on the clean channel it breaks up nicely. It just worries me I can't check the bias and that my tubes are getting cooked to fast. Thanks for any help =) Link to comment Share on other sites More sharing options...
Members SoldierStape01 Posted September 19, 2009 Members Share Posted September 19, 2009 I can't really see the pictures all that well but are you certain that you have the DMM on a DC reading setting??? I know that is a stupid question sometimes they are just on the wrong setting.... Link to comment Share on other sites More sharing options...
Members thinderik Posted September 19, 2009 Author Members Share Posted September 19, 2009 yah sorry about the pictures they were taking with my phone. And not a stupid question, but it was on dc. After taking it out of auto mode i tried adjusting the settings the range but couldn't get anything. Link to comment Share on other sites More sharing options...
Members mike42 Posted September 19, 2009 Members Share Posted September 19, 2009 Are you sure your probes are actually touching the contact points in the amp? It would be good to know what's actually behind the panel. Are those actual sockets, or just openings for the probe to go in and contact an internal component? Do you feel the probe contacting something? Link to comment Share on other sites More sharing options...
Members thinderik Posted September 19, 2009 Author Members Share Posted September 19, 2009 Are you sure your probes are actually touching the contact points in the amp? It would be good to know what's actually behind the panel. Are those actual sockets, or just openings for the probe to go in and contact an internal component? Do you feel the probe contacting something? you make a very valid point. It's something i was thinking about as i was ramming the probes in there. I didnt actually RAM them in there but pushed them back as far as they could go. They felt as though they were making contact. But something it's something that I'll mention if i have to drop it off monday. Link to comment Share on other sites More sharing options...
Members SoldierStape01 Posted September 19, 2009 Members Share Posted September 19, 2009 Instead of trying the adjustments with a DMM.. You can attempt a by-ear adjustment with the following instructions: The tube BALANCE and BIAS of your Link to comment Share on other sites More sharing options...
Members FlyingZ Posted September 19, 2009 Members Share Posted September 19, 2009 I have the same amp. Just setting the probes in works fine and if the amp is working you should have some voltage. Your meter can read millivolts right? The "The Twin" dirty channel secret: Turn the bass all the way off. My main amp for 20 years and again in 3 hrs. Link to comment Share on other sites More sharing options...
Members thinderik Posted September 20, 2009 Author Members Share Posted September 20, 2009 Man you guys have been soooo helpful =). I mean right now it sounds good...awesome actually. I'm just a worry wort and like to know that things are working correctly. And it bothers me i dont get a voltage reading. I love this amp and will never get rid of it but it will probably take a back seat when my Mesa DC-3 shows up =). I'm gonna bring it to the tech on monday and have em check it over. I got it second hand and should have it checked out before i start gigging it really hard anyways. Thanks again for all the tips and help! Again if your ever around jersey (central jersey) PM me for a beer! Link to comment Share on other sites More sharing options...
Members analorgy Posted September 22, 2009 Members Share Posted September 22, 2009 I have one of these. The bias pots they used are cheap ass.Replace it, then bias.Bass off is a good idea too. Although the clean channel makes a fine bass amp. Link to comment Share on other sites More sharing options...
Members SoldierStape01 Posted September 22, 2009 Members Share Posted September 22, 2009 What was the word from the tech Derik? Link to comment Share on other sites More sharing options...
Members FlyingZ Posted September 23, 2009 Members Share Posted September 23, 2009 I just now looked at the pic. All you need is a good meter that can read millivolts. Link to comment Share on other sites More sharing options...
Members thinderik Posted September 23, 2009 Author Members Share Posted September 23, 2009 I am the great procrastinator... I did not bring it in yet. I'm gonna wait till my DC3 arrives on thursday. Then i'll have my back-up / new amp =). All very good advice and tips so far. I'll keep you all posted as to what the outcome is =). Also my DMM that i "had" (i returned it for a much smaller one) was crazy good supposedly. But I think its the bias pot maybe. I'll keep you all posted! Link to comment Share on other sites More sharing options...
Members FlyingZ Posted September 23, 2009 Members Share Posted September 23, 2009 Also my DMM that i "had" (i returned it for a much smaller one) was crazy good supposedly. But I think its the bias pot maybe. I'll keep you all posted! Um.. no and no There is nothing wrong with the bias pot but your meter is uber fail. You better take it in Link to comment Share on other sites More sharing options...
Members SoldierStape01 Posted September 24, 2009 Members Share Posted September 24, 2009 I have the DMM that is one step under the one you had and it does measure millivolts. I feel you on the procrastination... I am the same way, usually due to lack of monetary funds though. Not by my choice. LOL Link to comment Share on other sites More sharing options...
Members thinderik Posted September 24, 2009 Author Members Share Posted September 24, 2009 Um.. no and no There is nothing wrong with the bias pot but your meter is uber fail. You better take it in The meter i bought could read .oo1 volts even lower i believe. My new one can read the same, just has way less bells and whistles. Link to comment Share on other sites More sharing options...
Members FlyingZ Posted September 24, 2009 Members Share Posted September 24, 2009 The meter i bought could read .oo1 volts even lower i believe. My new one can read the same, just has way less bells and whistles. oh, I guess is was not the one I looked up then. A precise and reliable multimeter you can use with or without a computer. This PC Interface 46-range digital multimeter is a compact, auto-ranging, digital multimeter ideal for testing in the field, lab, shop or home. It measures AC and DC voltage up to 1000V, AC and DC current up to 10A, resistance up to 40M ohm, capacitance from 0.5nF to 4.0uF, and frequency from 10Hz to 4MHz. I just realized this amp is beyond repair, however I will buy it from you for the parts:p Link to comment Share on other sites More sharing options...
Members thinderik Posted September 27, 2009 Author Members Share Posted September 27, 2009 Going to drop it off tuesday. Got my new mesa dc-3 rocks, so the seperation anxiety will be less. I hope this amp is not beyong repair. I mean it still sounds good. Do I have to get a special DMM to read MV? I thought that it would. However I'm frequently wrong. Link to comment Share on other sites More sharing options...
Members FlyingZ Posted September 27, 2009 Members Share Posted September 27, 2009 Have the shop mod it for el34's, it's easy and you will love it. Do I have to get a special DMM to read MV? No, just a better one. Link to comment Share on other sites More sharing options...
Members thinderik Posted September 27, 2009 Author Members Share Posted September 27, 2009 I do like the el34's in my DC'3. Cant wait to see what the shop says. Can you reccomend a meter? Link to comment Share on other sites More sharing options...
Members FlyingZ Posted September 28, 2009 Members Share Posted September 28, 2009 They have some cheap meters here:http://www.parts-express.com/wizards/searchResults.cfm?searchFilter=multimeter Link to comment Share on other sites More sharing options...
Members thinderik Posted October 13, 2009 Author Members Share Posted October 13, 2009 I dropped this beast off at "central jersey music" today. I paid my $60 deposit and told the guy that i had heard the bias pots go bad so he could check it out. Also told him since i got it second hand i just wanted him to look it over and give it a clean bill of health. So hopefully I'll some news to post soon as to the status of this beast. Thanks for all the help thus far =) Link to comment Share on other sites More sharing options...
Members FlyingZ Posted October 23, 2009 Members Share Posted October 23, 2009 Well I just had a tube fry and it took out three of the four 5 watt resistors. The amp still worked with some mild fizziness but only biased to about .02 mv. If this is your problem as well make sure the 5w resistors get changed because it will work without them. Link to comment Share on other sites More sharing options...
Members thinderik Posted October 25, 2009 Author Members Share Posted October 25, 2009 SOOO I'm a complete retard. The bias pot was allright, and worked right off the bat he said. Since I've never biased an amp before i didnt know enough to take the amp OFF standby after warming it up, and that is why i was not getting a reading. He changed a resistor inside that was wrong (wrong how i dont really know), and he switched the fuse on the outside. The fuse on the outside is a 7A i think but he was describing it to me that they have two fuses, one on the outside thats 7a and the inside is like 5 or 4a's. so the one on the inside is going to blow first which defeats the point of having a fuse on the outside. So whatever made sense while he was explaining it. he also replaced input jacks on the outside that i was neglecting to have repaired. all in all $140 dollars. But the main reason i brought it in was no problem to begin with, just user error /facepalm. Link to comment Share on other sites More sharing options...
Members FlyingZ Posted October 25, 2009 Members Share Posted October 25, 2009 I never noticed that My guess: It's AC so if 302 blows it because of a line surge and should just be replaced. If 301 blows its from a shorted winding and a job for a tech. Link to comment Share on other sites More sharing options...
Members FlyingZ Posted November 7, 2009 Members Share Posted November 7, 2009 I recently put 6l6's back in mine and had forgotten how much they suck! I see why some people dislike this amp. Get EL34's in it pronto and you will have what I consider one of the best guitar tones available, especially with a slight ts-9 boost for solo's. Oh ya with the el34's (only) turn the bass on the dirt channel completely off. I guarantee you will love it, especially live. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.