Doing some tube swapping the other evening, I managed to arc and open one of the filaments in a Valve Art 5AR4. I had a GE 5AR4 to replace it with (noticeably improved the sound quality, to my surprise) but the cost of replacement NOS 5AR4's got me thinking of substitutes.
5V4 looked promising, a B+ drop of 10-15 volts might be helpful in my particular case, for now I don't use NOS power tubes so I could care less if I strip the cathodes, but when I started looking at my 5V4's in inventory, they all looked wimpy until I came across this guy in the photo below.
The photo is poor (cell phone is the only camera I have here at the office) but it shows a Sylvania manufacture (date code 8012) marked 5V4GA that is definitely NOT a 5V4GA. It has a hardened glass, fat boy, bottle, and a robust plate structure with big boxes on the end of the plates the likes of which I have never seen on a 5V4. It's not a 5R4, 5U4, 5Y3, or any of the other common half wave rectifiers, either.
I've never seen a Sylvania 5AR4, but I wonder if they slipped some 5AR4's out the door marked as 5V4GA.
5V4 looked promising, a B+ drop of 10-15 volts might be helpful in my particular case, for now I don't use NOS power tubes so I could care less if I strip the cathodes, but when I started looking at my 5V4's in inventory, they all looked wimpy until I came across this guy in the photo below.
The photo is poor (cell phone is the only camera I have here at the office) but it shows a Sylvania manufacture (date code 8012) marked 5V4GA that is definitely NOT a 5V4GA. It has a hardened glass, fat boy, bottle, and a robust plate structure with big boxes on the end of the plates the likes of which I have never seen on a 5V4. It's not a 5R4, 5U4, 5Y3, or any of the other common half wave rectifiers, either.
I've never seen a Sylvania 5AR4, but I wonder if they slipped some 5AR4's out the door marked as 5V4GA.
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I have some of the same tubes. Mine are labeled RCA 5AR4. The type number is not the usual RCA stop sign. It is the typical lettering found on a Sylvania tube.
Near the end of the vacuum tube era some vendors were sticking whatever guts they could find into some tubes in order to fulfill military contracts. The most famous of these is the repinned 6AV5 beam pentode being sold as a 6B4G and the 7027A with a plate cap being sold as a 6BG6. I have tested both tubes and they do work. Replacing a DHT with an indirectly heated sweep tube pentode seems like a bigger stretch than a relabled rectifier. Not coincidentaly all of these tubes came from Sylvania.
One of my RCA 5AR4's can be seen here. They seem to be very good tubes.
Near the end of the vacuum tube era some vendors were sticking whatever guts they could find into some tubes in order to fulfill military contracts. The most famous of these is the repinned 6AV5 beam pentode being sold as a 6B4G and the 7027A with a plate cap being sold as a 6BG6. I have tested both tubes and they do work. Replacing a DHT with an indirectly heated sweep tube pentode seems like a bigger stretch than a relabled rectifier. Not coincidentaly all of these tubes came from Sylvania.
One of my RCA 5AR4's can be seen here. They seem to be very good tubes.
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Thanks,
The plate structure in your tube is exactly the same as in my Sylvania marked 5V4GA. I guess it really is a 5AR4.
Until I bought the cheap Ebay KT88 amp, I never had anything that used a 5AR4 so I have never paid much attention to them.
The funny thing is that I had not selected this tube as a keeper for my personal stock - it was in my Hamfest sell inventory with a half dozen other 5V4's. Someboy could have got it for a few bucks! Check the contents of those boxes carefully, guys .....
Thanks again,
Win W5JAG
The plate structure in your tube is exactly the same as in my Sylvania marked 5V4GA. I guess it really is a 5AR4.
Until I bought the cheap Ebay KT88 amp, I never had anything that used a 5AR4 so I have never paid much attention to them.
The funny thing is that I had not selected this tube as a keeper for my personal stock - it was in my Hamfest sell inventory with a half dozen other 5V4's. Someboy could have got it for a few bucks! Check the contents of those boxes carefully, guys .....
Thanks again,
Win W5JAG
I think I got mine at a hamfest for a few bucks. I got all he had (3 or 4). I have been using them for testing out new amps in case that something went wrong.
When shopping the swap meets at a hamfest, remember that the original rectifier tube in some old HP audio oscillators (200AB I think) was an Amperex 5AR4. Sometimes you can see the bugle on the side of the tube through the slots in the side of the case. The power transformer in these things will run a 50 watt guitar amp forever too. The oscillators can often be bought for $10 to $20. Output tubes are 6K6. The newer 200CD oscilator uses SS rectification and 6CW5 output tubes. The power transformer has no 5V winding. I got about 25 of them from a scrap dealer that was selling them by the pound. About $3 each!
When shopping the swap meets at a hamfest, remember that the original rectifier tube in some old HP audio oscillators (200AB I think) was an Amperex 5AR4. Sometimes you can see the bugle on the side of the tube through the slots in the side of the case. The power transformer in these things will run a 50 watt guitar amp forever too. The oscillators can often be bought for $10 to $20. Output tubes are 6K6. The newer 200CD oscilator uses SS rectification and 6CW5 output tubes. The power transformer has no 5V winding. I got about 25 of them from a scrap dealer that was selling them by the pound. About $3 each!
Sorry about that. I walked into a surplus dealers shop and there was 2 or 3 pallets of vintage tube test equipment and a bunch of other equipment on a trailer outside in the Florida rain. It was all destined for the metal recycler. I picked up about 25 HP oscillators, about 10 TV sweep generators, and the power supplies out of 4 Motorola ambulance base station transmitters (1500 volts 1/2 amp) for $100. The oscillators and sweepers gave up their transformers and tubes. So far all of the transformers have been good. Two of the power supplies worked, but their 75 pound constant voltage transformers buzz too much to be used in an audio amp.
I consider all National tubes on a case by case basis. I think they are willing to relabel anything as anything. I got some 7543, supposedly JAN with a federal part number, that FM so badly in my Collins PTO's as to be unusable.
They turned out to be some East German junk that might not even be useful as a plain 6AU6.
Win W5JAG
They turned out to be some East German junk that might not even be useful as a plain 6AU6.
Win W5JAG
secrets..
I hope you are kidding, as this is no ones intellectual property, many old timers share this info with no problems. You must be a tube "roller" with some sort of profit margin in mind..unless again, if you are kidding, my apologies, I thought DIY was alla bout sharing..not harbouring lame secrets.
I hope you are kidding, as this is no ones intellectual property, many old timers share this info with no problems. You must be a tube "roller" with some sort of profit margin in mind..unless again, if you are kidding, my apologies, I thought DIY was alla bout sharing..not harbouring lame secrets.
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