edster00 Posted March 20, 2003 Share Posted March 20, 2003 My normal routine is to turn on my 2 channel system on Fri. evening when I get home from work and leave it on until Sun. evening when I am through listening for the weekend. I listened to a few hours of music Fri. night as usual, and went to bed. I put in a CD Sat. morning and I noticed I was getting reduced volume out of one speaker. I shut everything down and checked all my connections etc. and fired the system back up. Still ~½ volume from one channel. I swapped the tubes from one Moondog to the other...same problem. I thought it may be the preamp so I swapped R & L interconnects from the pre to the amps...didn't help. My next thought was it could be something wrong with the speaker, so I put in my Monarchy SM-70 and that balanced out the volume. Does anyone familiar with the Moondogs (or not) have any ideas what might be wrong and cause ½ volume (power) in the Moondog? TIA! Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 20, 2003 Share Posted March 20, 2003 Not really sure what could be the problem but it sounds like the perfect chance for me to get to hear them without buying. As you know there are special rates for such service as in free !! of coarse this a wishfull thinking on my part ! I'm sure its a cap or resistor went south or even a bad connection there such simple designs it can't be hard to trace ! Craig Quote Link to comment Share on other sites More sharing options...
leok Posted March 20, 2003 Share Posted March 20, 2003 I agree .. cap or resistor went South. There's not much in the Moondog so NOSValves will find the problem real fast .. or anyone with tube skills may find the problem pretty fast. Last time I helped someone out with a similar problem on a Dynaco ST-70, it was a resistor. I was pretty fast. leok Quote Link to comment Share on other sites More sharing options...
edster00 Posted March 20, 2003 Author Share Posted March 20, 2003 Everyone is saying the same thing...I guess I will pull the bottom plate and take a look inside . I guess it may be time I learned how to solder! I will practice on something else of course! Thanks for your timely replies both on and off the BB! Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted March 20, 2003 Share Posted March 20, 2003 Hey, Ed. Sorry to hear about your Moondogs. Do have and know how to use a multimeter? If you have a copy of the schematic, go through and check the voltages on the 6SN7s and 2A3. Plate voltage on the 2A3 (taken between plate and cathode) should be in the 300 VDC range, or about 350 taken between the plate and circuit ground. My plate voltage is reduced a bit, since I sometimes use vintage 2A3s, with a max plate/cathode voltage of 275 (spec for the tube is 250). These would be the first things to check, and you can start breaking it down from there. Also check your filament supply voltages. It also sounds like you leave your amps on for a fairly long time at a stretch. Over time, this will begin to takes its toll. Do you have a tube tester? Check those tubes! If you can't find the problem, Craig could find it really fast, I'm sure. Or if you know anyone near you whose got a tube tester, maybe they could help out. I'd be happy to check them for you, but I'd hate for you to pack them up and send all the way to Texas! If you wanna try to trouble shoot over the phone, I'd be happy to try to help you out. We'll get it fixed! Erik Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 20, 2003 Share Posted March 20, 2003 Edster there are moondog gods that forbid newbies from testing there skills on something as awesome as a set of moondogs. They will reach up and zap you with B+ for being so unfaithfull to the moondog god !!!! Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted March 20, 2003 Share Posted March 20, 2003 Yah! Craig is right, Ed. I remembered you said you haven't done very much of this before -- I'm sorry if I seemed to just take something like for granted. DO NOT attempt this if you haven't experience. Voltage measuring can be lethal if you're not sure about what you are doing. I apologize! Send to Craig ASAP! Check the tubes if you can, but stay away from that B+ monster. Erik Quote Link to comment Share on other sites More sharing options...
edster00 Posted March 20, 2003 Author Share Posted March 20, 2003 I do have a Fluke 73III multimeter. It has 2 "knitting needle" type pointy things, 1 on black wire and and one red. I know how to check continuity (I once built a pair of Cat 5 speaker cables), and how to check the charge on a 9V battery with it! If I lick my fingers and stick those needles in an electrical socket it gives me a pretty good jolt too . Now where should I poke those knittin' needle thingys? Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted March 20, 2003 Share Posted March 20, 2003 Ed, There's an old rule about keeping one hand in your pocket while fooling around with one of these amps. Good advice. I practice it carefully. Find a place to stick your black ground lead so you don't have to hold it. knitting needles, OMG. you're just trying to scare us, right? Tom Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted March 20, 2003 Share Posted March 20, 2003 Wow, what a fluke...my dad has several Flukes! Small world. I remember as a small lad taking my dad's knitting needle thingies from his old '60's analog Simpson multimeter and picking my nose with 'em...he was not impressed! Quote Link to comment Share on other sites More sharing options...
jazman Posted March 20, 2003 Share Posted March 20, 2003 Ed, Do not send your Moondogs to Craig! Do not pass GO! Change your rectifier tubes!! If you need an extra GZ37, I can send you one to use. If you want to try two 5AR4s, I have two brown base, made in Holland Amperex tubes you can borrow. Klipsch out. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 20, 2003 Share Posted March 20, 2003 Jazzman your killing me I just wanted to hear them !! That is not fair. I was just joking around for the most part anyway. It is most likely something simple. Craig Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted March 20, 2003 Share Posted March 20, 2003 Ed: If you are going to do this, put a dummy load on the speaker terminals (8 ohm power resistor 5-10 watt job). BTW, you might even try 5Y3 rectifier. They are lots cheaper than the stock GZ37. I use 5Y3s, which are totally adequate for this application. (but they just don't look as cool as the big bottle jobs!) Tom has good advice. Clip that black test probe on ground, and keep your left hand in your lap or pocket. Let us know what your readings are. Do you have a schematic? All you need to know is the pin-out of the tubes. Be Careful! Erik Quote Link to comment Share on other sites More sharing options...
jazman Posted March 20, 2003 Share Posted March 20, 2003 Craig, You should understand that when used in the same paragraph with a reference to a Monopoly game card, there was supposed to be some humor intended. The ultimate intent was, you don't need a brain surgeon for a bump on the head. Last, I have had experience with the problem and the cure. Let's lighten things up, please! Klipsch out. Quote Link to comment Share on other sites More sharing options...
Deang Posted March 20, 2003 Share Posted March 20, 2003 I'd be taking a hard look at those tubes as well. What Edmond says makes sense, and is worth checking. Did you swap all the tubes between the amps, or just the 2A3's? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 20, 2003 Share Posted March 20, 2003 Edmond I was kidding also. I think the lightening up is being directed at the wrong guy ! Quote Link to comment Share on other sites More sharing options...
edster00 Posted March 21, 2003 Author Share Posted March 21, 2003 The first thing I tried when looking at the problem was swap each tube one at a time between the amps to see if the problem would move to the other side. Then I swapped all the tubes to see if the problem would move, and it didn't. That is when I thought it may be something in the preamp so I swapped channels on the interconnects going to the amps. I going to take the bottom plate off and take a peek inside. I am not going to do any "multimetering" with power going into the beast at all. I would love to learn a bit about how to troubleshoot and/or fix some of my gear but I need to have an instructor by my side to show me the ropes first. Thanks for your input guys! Quote Link to comment Share on other sites More sharing options...
Mike82 Posted March 21, 2003 Share Posted March 21, 2003 Hi Edster: If yo get stuck and need a pro to look at it. Modular Electronics on Atlanta St. in Roswell is a good place. They tech is a tube junkie and builds his own stuff. Good luck! Quote Link to comment Share on other sites More sharing options...
edster00 Posted March 21, 2003 Author Share Posted March 21, 2003 Mike, Thanks for the info! I have been looking for someone local who can work on this kind of stuff. Maybe I'll be able to get this fixed quickly and get my system back to "normal". Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 21, 2003 Share Posted March 21, 2003 Edster, You are more than welcome to take a shot of the under chassis and email it to me along with a schematic if you have one and I will spend a few hours this weekend on the phone with you helping you find the problem with your trusty Multi meter. There really isn't that many parts to check so it should be easy to find. I was really kidding about you sending your babies up here if you don't have to. I would just love to hear a SET ! Craig Quote Link to comment Share on other sites More sharing options...
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