[AMPS] Alpha 76 and 78 tube conversions
Tom Hix
w4th@hotmail.com
Sat, 02 Feb 2002 02:05:13 -0600
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<P>I dont know if any of you builders have ever paid any attention to the Svetlana gi7b/gi7bt triodes, but if you haven't you should. These are really neat tubes, and I can supply them at a great price. </P>
<P>I believe these tubes would possibly be a good solution for many of the people who own the older Alpha amps like the 76 and 78 series, who dont want to pay $1200.00 to $1500.00 to retube their amps. These tubes are really heavy duty. A pair of them will give you about 1200 to 1400 watts depending on voltage and drive. There is an article on my site about the conversion a friend of mine did on an older Dentron amp that ran 4 572b tubes. He put in a pair of the gi7b tubes and was able to make a real nice amp out of it. He gets about 1200 to 1300 watts out on the pair of gi7b tubes. </P>
<P>Since the 8874 tubes for the 76 and 78 series Alpha amps have gone up so high, I am constantly getting calls from people wanting to know if there is a substitute they can get for the 8874 tubes. Of course there are no direct replacements, but these gi7b tubes might just be a good choice as replacements for the 8874 tubes.</P>
<P>I really hate to see anyone have to rework a perfectly good amp like the alpha 76 or 78, but the price on the 8874 tubes have gone up so much that you can actually buy a good amp for what it would cost to retube these amps. I get calls every week from Alpha 76 and 78 owners facing this very situation. Most of them tell me they will just have to stop using their amps because they are not willing to spend the money to retube their amps. They will either have to set them aside or find another tube they can replace the 8874 with. So it is a real dilemma for these owners to decide what to do. Turn the amps out to pasture or replace the tubes with something they can afford. </P>
<P>I am not an amp builder. I wish I knew a lot more about building amps or reworking existing amps, but I am to old, fat, dumb and lazy to learn know. BUT.....I know many of you folks on this list are the very best at building and repairing amps.</P>
<P>SO..............Here is what I am thinking of doing. Just to see if the gi7b tubes can be a decent replacement for the 8874 tubes. If someone who knows what they are doing has an amp that has the 8874's in it, and they want to change those out and would like to try the gi7b tubes, I will sell you, for my cost, a pair of these gi7b tubes, and a matching set of sockets.</P>
<P>The person who wants to do this can take a look at what I send them and determine if the tubes and sockets will physically fit into the cabinet. If they will then he can pay me for the tubes and sockets at my cost......all I ask is that when the conversion is completed that the person who does the work, will send me a schematic of the conversion and a full set of pictures detailing each step of the conversion. I want this so I can share it on my web site with all the other amateurs who want to change out their 8874 tubes to something else like the gi7b. So if you know what you are doing, and have a good digital camera and can send me the pictures of the project via email, then contact me. I would love to see if this could be done, and I know the entire group of older Alpha owners would really appreciate finding out if there is another tube they can use, and what it will take to make it happen.</P>
<P>If any of you are interested in trying this, just send me a reply and we will see what we can work out. I have no idea if any of this is even feasible or not, but I sure do wish I could help out these guys with these beautiful old amps.</P>
<P>Thanks for your time and comments will be welcome.</P>
<P>73</P>
<P>Tom Hix..................w4th<BR><BR><BR></P>
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<P><FONT color=#ff0066>Tom's Tubes: Your Russian Tube Connection. Specializing in Amateur Amplifier Tubes, Heavy Duty Antenna Tuners, Remote or local ladderline & coax antenna switches. </FONT></P>
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