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I just looked a little closer into this Electromuse amp I am working on it is supposed to be made by Valco they did not put model numbers on these amps so finding a schematic is proving to be a pain. So here are the tubes one 6F6GT,7 pin below that is a glass tube without any numbers it is a 8 pin tube next to it is a metal tube 6F6,and a glass tube next to it 5Y3GT does anyone recognise this set up ?? this amp was made between 1940 and 1950 it had a 10" inch speaker I wish someone would make a web site where you could enter the tubes and get the schematic out HAHAHA here is a pic of the amp maybe someone knows what model it is I just need a schematic so I can rebuild it
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Im not sure from your description how many tubes in total, four right?
Is it 6SL7 into two 6F6 and a 5Y3 rectifier? Search on electromuse 10a
Also, it sounds silly but you can sometimes fog a glass tube with your breath (cold and unplugged) and see the faint markings. Also check on the top of the tube for marking, not just side.Comment
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Have a look at this gibson ga-9:
Its got 6SJ7. Another possibility for four tubes.Comment
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I found a schematic for a Electromuse but it does not have a model number it says they did not put model numbers on the Electromuse made by Valco. anyway on the schematic it has a, 6J5GT labeled preamp 2, mine has a 6f6GT, in that spot.below that on the schematic has a, 6SH7 GT labeled preamp 1, mine has a tube with the markings gone except I see a faint 7 on the top so I think mine has a 6SH7 in that spot, next to it schemo list a 6V6GT,labeled power amp mine has a 6F6 metal tube, last one on schemo, list 6X5GT,labeled rectifier Mine has a 5Y3 in that spot.Question do these tubes on the schematic do the same function as the tubes in my amp? and do you think I found the right schematic I plan on replacing all the caps and maybe even the resistors and tubes, I just need to know if I can use this schematic to do the job. I am off to compair the tubes on the schematic and the ones in my amp if I can find them on the charts.Comment
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The above would be a pentode 6sh7 in pre1, a triode 6J5 in pre 2, and 6v6 pentode as power, plus rectifierOriginally posted by RitzRed View Post
However, you have two 6F6s which are both power pentodes (very similar to 6v6), the 5Y3 is the rectifier, so the mystery tube that ends in "7" has to something like a dual triode for your preamp. That is why I suggested you look at the gibson, or have a look at the link below. I think this guy has drawn the scheme and a layout and took pictures...
Electromuse10Alayoutv1.jpg photo by ktduck | Photobucket
One other thing: Yes, this guys schemo shows 6V6s and you have 6F6, but that's okay, you can substitute them. The pinouts are the same, the voltages will likely be close to expected. However, dont trust me or some guy on the internet, verify what you have with the info he has.Comment
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thank you very muchComment
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It took a while ,But the schematic on the link you sent is spot on to my little amp!Thanks a million ! except the 6F6GT and the 6F6 are 6V6,s in the schematic .the tube I could not identify on my amp is a 65L7 on the schematic everything else is spot on to the schematic.I followed every wire from pin to pin,or tube to tube. I tried to replace the multi (can)capacitor with orange drop caps, that did not stop the buzz. so I tried replacing the 2 paper cap with orange drop type caps, that took out the buzz, but after plugging it in for a little while the transformer got hot. do you have a good place to buy capacitors and resistors? I did not have the right value caps, but close. I am sure that did NOT cause the transformer to heat up, so I think I might have shorted something out when I was trying it out I also tried plugging one of my guitars into the amp after I got it to stop buzzing I did not get any sound out of it. What I need to do is find a place to buy resistors and caps, so I can order a bunch to have around. I have 7 different tube amps I bought to make into harp or guitar amps. they are all different and came out of different type vintage tube musical devices like old organs record players P.A. systems so I have allot of part needs let me know if you know of a electronics parts source other than tubes and more thanks again that schematic was a life saverComment
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Probably the tube is 6SL7 (twin triode) not 6fiveL7...Originally posted by RitzRed View Post
Regarding replacing the filter caps with orange drops...you are off on the required capacitance to a large degree. Your filters should be somewhere in the tens of microfarads, which coupling caps are probably around two-hundredths of a microfarad. Please note, older caps used different markings (mmf, mf) as opposed to the "u" micro character that we use now.
For caps of all types (In the US), try: Mouser, tubesandmore.com, digikey among many many others.Comment
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I cleaned off the capacitors in my electromuse amp and found out they are all Mica so that was good news I guess the paper covered in plastic are unreliable but Mica ones are VERY RELIABLE! I am waiting for a couple of the .25MF and a .1 MF big paper caps to get here I am going to buy a bunch of assorted caps and resistors so I don,t have to wait on themComment
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Originally posted by RitzRed View Post
Just in case there is any lingering confusion on old cap markings, have a look at this handy conversion table:
http://www.justradios.com/MFMMFD.htmlComment
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Is there any difference in witch tubes you use for a rectifier tuber like is a 6AX5GT better than a 5Y3??Comment
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Neither is "better", just different. The 5y3 is looking for a 5Volt-2A heater supply, the 6AX5gt is looking for a 6.3V 1.2A heater supply. The pinouts are different, although they are both full wave rectifiers, so they have the same elements. Other characteristics are not too different, but it really depends on what you are trying to do. You can't just plug one in place of the other, that wont work. You could, possibly, modify a circuit to make one work in place of the other, but it begs the question: why bother?Originally posted by RitzRed View Post
The tube data sheets for many many tubes can be found at:
Frank's electron Tube Data sheetsComment
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Neither is "better", just different. The 5y3 is looking for a 5Volt-2A heater supply, the 6AX5gt is looking for a 6.3V 1.2A heater supply. The pinouts are different, although they are both full wave rectifiers, so they have the same elements. Other characteristics are not too different, but it really depends on what you are trying to do. You can't just plug one in place of the other, that wont work. You could, possibly, modify a circuit to make one work in place of the other, but it begs the question: why bother?Originally posted by RitzRed View Post
The tube data sheets for many many tubes can be found at:
Frank's electron Tube Data sheetsComment
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thank you the reason I asked about the difference in these tubes is I noticed in some old amps they have one or the other in the rectifier spot I am trying to figure out like if they make the amp sound better . or a better way of putting it is if I have a chance to buy amps and one has the 5Y3 rectifier and the other one has a 6AX5GT rectifier does one of these sound better or work better?? the best amp I have is one that has 1 12AU7, 2 12AX7,s 2 6V6,s and a 5Y3GT just wondering if it makes allot of difference in the sound? Also what do you think the 12AU7 tube does or what would it,s funtion do .Comment
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The question about rectifiers is one of those things that can provide endless debate, because to a certain degree you are talking about aesthetics - what sounds most pleasing to you and your musical goals. Electronically speaking, there is a phenomenon called rectifier "sag" (search for it on the forums to see the conversations here on this topic), where the voltage drops due to current increasing resulting in compressed signal. I am not the best person to talk with about this stuff - there are many other posters with more informed opinions. I am mostly concerned with fixing existing circuits. Also, I tend to be a skeptic by nature. I think other things contribute to good music more than rectifiers - such as talent. There has been some great music made on marginal gear - and even more really bad music made on good gear - too much for rectifiers to make much difference. However, I also think that if you find that you like the sound of particular circuits and that works for you, then have at it!
Have a look at what valve wizard says about rectifiers and sag here...
The Valve Wizard
To your question about what a particular 12AU7 is doing, that depends on the circuit, I would kind of need to see the schematic to say for sure. Probably, it is the phase inverter, but it could do something else. What it is is a twin triode, triodes being the basic amplifier building block. They can do many different jobs, such as pre-amp, phase inverter, tremelo oscillator, reverb send, etc. Since the tube has two triodes in it, one half of the tube could be doing one job and the other half doing another, or even half the tube doing nothing at all.
Have a look at triodes here from valve wizard. If you digest this chapter it will make a huge difference in your appreciation of tube amps. Even better, if you take the principles from this and then go back and do some measurements on one of your working amps you can learn a lot.
The Valve WizardComment
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