derrickdj1 Posted August 18, 2016 Author Share Posted August 18, 2016 Thanks guys. Everything is disconnected and the amp unplugged. I will try a find some fuses later today. What ever is worng may be a little simple thing if I can figure out what is going on. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted August 19, 2016 Author Share Posted August 19, 2016 I have thought about this amp for a while and decide to get a new tube amp. I will still get the fuses to see if the old amp is an easy fix. I can always use it another room. Benchwork in shops around here is expensive and I will not pay more to fix the amp than what I paid for it. I'm sure it is most likely a minor problem and if I new more about working on tube amps, a little time may be needed to fix it. Thanks for the kind suggestions. The new amp is the Yaqin MC 13S GD. This is a PP amp and does Class A. It is higher watt than a SET and should have similar power to the old amp to power the RF 7 II's. The amp has 4 EL 34 and 4 12AT7 tube. The EL are the power tubes and 12AT 7 are the preamp tubes. The bias can be measured and adjusted right on top of the amp via the small holes next to the big EL tubes. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted August 26, 2016 Author Share Posted August 26, 2016 Now another story. I got the new tube amp delivered today. I set it up and 15 second after it was on static from the L speaker and pop! The 0.5 fuse blew. I went out a picked up some more and blew 3 more fuse. Between the fuses I rechecked the wires looking for a short, I change two preamp tubes, 12AX7B, since they were not a bright as the other two, 12AU7, changed outlets and wire and pop! on the startup again. Only one fuse left. I notice that one of the power tubes was running a sunny glow before the last pop. I took out all the power tubes, 6CA7T, a nice pretty blue. They were replace with Tung-sol EL 34's. Now the moment of truth. Powered up the amp, 10 s, 20 s, 30 s without a pop. Now sweet music to my ears. Bias as been adjusted to roughly 0.35. I guess the one power tube didn't like the 7000 mile trip, lol. I ended up getting a silver one and not the gold. I would of had to wait much longer for shipping. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted September 6, 2016 Share Posted September 6, 2016 On 8/17/2016 at 8:57 PM, dtr20 said: I don't know much about tube amps, but I was told never power them on without being hooked up to speakers It won't hurt a thing as long as there is no input to the amplifier. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted September 6, 2016 Author Share Posted September 6, 2016 1 hour ago, Don Richard said: It won't hurt a thing as long as there is no input to the amplifier. What exactly happens when there is a signal and no load? Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted September 7, 2016 Author Share Posted September 7, 2016 I was reading some infor that having to load on the amp means the current has to where to go so, it grounds to the plate. This can lead to tranformer damage. It's a bit more technical but, transformer and tube damage are the end result. Quote Link to comment Share on other sites More sharing options...
jdbeachbum Posted September 8, 2016 Share Posted September 8, 2016 Derrickdj1, I just bought the same amp (MC-13s) last week and have used it only once so far for about an hour. The amp is used but in perfect condition. I was wondering what your thoughts are on the Tung Sol EL34B tubes. I know you haven't had burn in time but I'm not crazy about the stock Chinese tubes in regards too muted highs and bass that isn't very tight. The choices out there overwhelm me when I try and research all the different brands available and make a choice what would match my unit. Any input for a rookie tube guy would be welcome! Jack Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted September 8, 2016 Author Share Posted September 8, 2016 The 6CA7 tubes are softer in the bass and for a lack of better words, warm. The Tung-Sol EL 34B will have a bit more power, and tighter bass. They may have a crisper high end. The stock tubes aren't bad from my listening to them. It may be nice to have the 6CA7's and EL 34B. This will give you two slightly different sounds. I originally thought I had a bad tube but, the amp bias out of the package was all the way up and causing the fuse to below befor I even had a chance to set the bias. I like both set of tubes, Yaquin 6CA7 and Tung-Sol EL 34B. I thought the blue bulb would be cool but, the EL 34 B's look a bit better with the lights low, lol. This amp can put out some sound. I really am happy with the purchase. Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted September 9, 2016 Author Share Posted September 9, 2016 I'm getting some hours on the stock tubes: they are pretty good from what I am hearing. With the amps from China, I've read a lot of people wanting to do mods and change out the tubes right away. IMHO, it is not warranted. China and Russia are the worlds largest supplier of vacum tubes. They never abandon tubes when transitors came into fashion. There tubes are rebranded and sold to look like they were made in another country. Quote Link to comment Share on other sites More sharing options...
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