unclej Posted January 15, 2005 Report Share Posted January 15, 2005 a little amp just came into the shop for repair and i've run into something that i havent' thought of before. it's a recco amp, japanese made for an american company and i can find absolutely no information on it. the problem is that the output tube is so old that all of the markings are gone so i can't even test it let alone replace it if need be. so given the fact that the other two tubes are 6av6's is there a source somewhere that would tell me what the other likely is? and if there's no magic book with a chart in it for this purpose how do you calculate what it should be? i'm guessing that this will come up again and i'd like to learn to solve the problem without having to ask again. Quote Link to comment Share on other sites More sharing options...
Southpa Posted January 15, 2005 Report Share Posted January 15, 2005 I used to own an all tube Teisco amp from around the mid 70's. The main output tubes were 6L6GC but I can't say if they were the originals. I'll bet most of those Japanese makes from that era used similar components. I found only one review from Harmony Central regarding Recco amps. Here is the link: http://www.harmony-central.com/Guitar/Data...2_Combo-01.html The person left an email addy and the review is fairly recent. Contact him/her and see if they can give you the numbers off the tubes in their amp. Quote Link to comment Share on other sites More sharing options...
unclej Posted January 15, 2005 Author Report Share Posted January 15, 2005 thanks southpa...harmony central was the first place i went and his amp is considerably larger than this one. i expect mine is crankin' a whoppin' 4 to 6 watts. but i will e-mail him to see if maybe he found some history that i didn't on the company. maybe if i run some review on teisco and some others i'll find one similar with a tube chart. excuse me while i play sherlock. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted January 15, 2005 Report Share Posted January 15, 2005 You can possibly figure it out from the circuit, if it's worth the effort. If you can figure out the pinout and measure the voltages at each pin, then all you have to do is find a power tube that fits those voltage and bias levels with that pinout(sounds simple, no? good luck!!) . Those 7-pin preamp tubes would be enough to make me to shy away from attempting any repairs without a schematic. Just call me chicken! What's your hourly rate on tube repairs? It sounds like it might be cheaper to send my stuff to you than it is to work on it myself. Quote Link to comment Share on other sites More sharing options...
unclej Posted January 15, 2005 Author Report Share Posted January 15, 2005 hey..give the rookie a break and you probably wouldn't want to do that yet anyway. i just had time to look at it again and it's actually the rectifier tube that i need. the power transformer goes straight to it and then on to the 6av6's. but once i replace a couple of caps and a big ole burnt out resistor i should still be able to use your idea. and i've got plenty of time...it gets really lonely out here in the country. Quote Link to comment Share on other sites More sharing options...
lovekraft Posted January 16, 2005 Report Share Posted January 16, 2005 Just kidding, man, do what you do - I just try not to work on anything I can't make a little money on, and do the customer justice. I don't always make friends with that approach, but at least I make all my enemies up front, not after they've gotten a huge bill! You might want to trace this circuit out, both for your own experience, and to figure out what everything is doing in there. The 6AV6 is a high-mu triode (like half a 12AX7) and two diodes, all with a common cathode (6AV6), a pretty oddball tube for an amp - it was usually used in tube radios, as a detector/AGC/amp, and I don't think I've ever seen one in a guitar amp, so I won't be any help to ya with this one, I'm afraid. Good luck with it! Quote Link to comment Share on other sites More sharing options...
ansil Posted January 17, 2005 Report Share Posted January 17, 2005 Just kidding, man, do what you do - I just try not to work on anything I can't make a little money on, and do the customer justice. I don't always make friends with that approach, but at least I make all my enemies up front, not after they've gotten a huge bill! You might want to trace this circuit out, both for your own experience, and to figure out what everything is doing in there. The 6AV6 is a high-mu triode (like half a 12AX7) and two diodes, all with a common cathode (6AV6), a pretty oddball tube for an amp - it was usually used in tube radios, as a detector/AGC/amp, and I don't think I've ever seen one in a guitar amp, so I won't be any help to ya with this one, I'm afraid. Good luck with it! ← hmm perhaps using it to get some diode clipping in the tube amp.. sounds like blasphemey i know but there were quite a few people who did it back in the day. Quote Link to comment Share on other sites More sharing options...
unclej Posted January 18, 2005 Author Report Share Posted January 18, 2005 hey lk, i knew you were kidding and actually there's method to the madness. i'm charging a basic bench charge to check it out, trouble shoot it and such. then if it needs parts i'll charge for those and for the time it takes to install them. all of the rest of the time used at this point is eduation expense. i didn't even charge the ampeg guy for anything except parts. i've been working on his guitars for years so i've made money off of him and he was good enough to let me learn on his amp. anyway, as always thanks for the help and encouragement. i'm gettin' there. Quote Link to comment Share on other sites More sharing options...
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