PapaMidnite Posted January 9, 2009 Share Posted January 9, 2009 Hey I have a Dean Markley CD60 amp with 3 12ax7's and two 6l6's .When biasing today Tube # 1 read 526Plate voltage andbias current set to 37 .Tube # 2 Plate 526 Bias 0 .I switched test leads still the same .tube #two[0] I tried different tubes. Same Tube # two [0] Please advise Thanks Link to comment Share on other sites More sharing options...
layboomo Posted January 10, 2009 Share Posted January 10, 2009 Hey I have a Dean Markley CD60 amp with 3 12ax7's and two 6l6's .When biasing today Tube # 1 read 526Plate voltage andbias current set to 37 .Tube # 2 Plate 526 Bias 0 .I switched test leads still the same .tube #two[0] I tried different tubes. Same Tube # two [0] Please advise Thanks First thing I would check for is a bad screen grid resistor on tube #2. Edit :although I'm not familiar with that exact amp it sounds like a pretty standard fender layout.....the screen grid resitor will be a 470 Ohm usually located right on the tube socket for 6L6 tubes. When output tubes go bad they often take a screen grid resistor with them. It's a good habit to get into when you change your tubes to put fresh screen grid resistors in when you bias the amp.....they are cheap and it can't hurt! Link to comment Share on other sites More sharing options...
PapaMidnite Posted January 10, 2009 Author Share Posted January 10, 2009 First thing I would check for is a bad screen grid resistor on tube #2. Edit :although I'm not familiar with that exact amp it sounds like a pretty standard fender layout.....the screen grid resitor will be a 470 Ohm usually located right on the tube socket for 6L6 tubes. When output tubes go bad they often take a screen grid resistor with them. It's a good habit to get into when you change your tubes to put fresh screen grid resistors in when you bias the amp.....they are cheap and it can't hurt! Thanks Layboomo .That's exactly what happened .I think I'm going to replace both .It has also developed a hum as soon as it comes off stand by ,Gets louder when volume is turned up ..... Link to comment Share on other sites More sharing options...
layboomo Posted January 10, 2009 Share Posted January 10, 2009 Thanks Layboomo .That's exactly what happened .I think I'm going to replace both .It has also developed a hum as soon as it comes off stand by ' date='Gets louder when volume is turned up .....[/quote'] Well ......next in line would be the filter caps and if they are 10 or 15 years old you might want to swap them out as well. Link to comment Share on other sites More sharing options...
PapaMidnite Posted January 10, 2009 Author Share Posted January 10, 2009 Well ......next in line would be the filter caps and if they are 10 or 15 years old you might want to swap them out as well. Thanks layboomo 470's did the trick biasing at 37.I can't believe I did not notice the difference before .Now onto the Caps It has 5 # 1 -420v #2- 212v #3-420v #4-356v #5-277v Looks like 3 are bad, Cause they are 47uf450volts in the amp now .Question where can I get them? Link to comment Share on other sites More sharing options...
layboomo Posted January 11, 2009 Share Posted January 11, 2009 Thanks layboomo 470's did the trick biasing at 37.I can't believe I did not notice the difference before .Now onto the Caps It has 5 # 1 -420v #2- 212v #3-420v #4-356v #5-277v Looks like 3 are bad' date=' Cause they are 47uf450volts in the amp now .Question where can I get them?[/quote'] Hi sorry I didn't get back to you sooner....snow and a leaking hot water heater....ain't life grand? if you can get a hold of the schematic that might make crossing the caps easier,but mouser http://www.mouser.com/ has most values and sizes in stock. Ken @ Watts http://www.turretboards.com/ is very helpful and can most likely hook you up with whatever you need. Link to comment Share on other sites More sharing options...
PapaMidnite Posted January 11, 2009 Author Share Posted January 11, 2009 Layboomo E mail me and I'll send schematic .Can't seem to get it to this site Comeau@sbcglobal.net Link to comment Share on other sites More sharing options...
PapaMidnite Posted January 12, 2009 Author Share Posted January 12, 2009 Thanks for the info layboomo.Caps on order.Sorry to hear about hot water heater.Snow sucks Link to comment Share on other sites More sharing options...
kingbuzo Posted February 1, 2012 Share Posted February 1, 2012 dean markley cd-60 i know that this thread is very old...but thought i would give it a try anyways it has to do with the same amp and there isnt too much info online regarding it.... problem....developed bad hum when standby on....replaced both GT-6L6 power tubes(one looked blue and bad)....just bought 2 GT-6L6CHPD(sounds way better....but still hummmm....checked resistors by tubes... both at 470. i have the amp all apart and want to replace the 5 caps (few of them had broken plastic casings)..the caps i have are different than papamidnight's my are #1-450v #2-450v #3-500v #4-350v #5-350v....they are grey in colour with black writing "TTAA" on the side..... what are the correct replacements ? or comparable? why are the values different than papamidnight's? also, there is only one pot on the board....how do i adjust bias for both tubes? one pot for both tubes? what is the correct bias setting for this amp ? 37 ? there is no test leads on the back, where do i hook up test leads to get bias reading? another note...there is a sticker on the side with "BF MP DT PD " written on it....with some other letters crossed out....maybe a factory mod? not sure.... i know there are alot of questions here but there is not a lot information and/or schematics on this amp... if the moderators of this site would like me to start a new thread ....then i will, thank you for helping =) Link to comment Share on other sites More sharing options...
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