Amp tube question

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My 69 Bandmaster Reverb tube chart (on inside of amp cabinet) shows the first (main power?) tube as a 6Z34 (GZ34?), and I have a replacement tube labeled 5AR4/6Z34.
However, the tube in place right now is a BR DGD, and is much larger and has 5 contact pins rather than the 4 of the 5AR4.
I know that someone re-capped this amp back in the mid 70s and also changed out the power transformer.
So are the tubes equal, or is that 5AR4 useless to me?
 
they may have changed to tube sockets as well. if the tube doesn't fit (ie. 5 pins vs. 4 pins), i don't think there is much you can do. you can always get the right socket and change back to the stock socket, if you know how to solder. otherwise i think you're best off replacing the old tube with the same kind. 5AR4 and 6Z34 are interchangeable (usually, if not always), so it sounds like someone did some moding in the 70s.

if you have a picture of the tube placement chart that could be handy too.
 
also in 69 the BMR came with a 5U4GB and not the GZ34. the 5U4GB sagged which is probably why they went with a GZ34. It's also not a good idea to blindly swap different rectifiers, some consume more heater power than others and might damage the amp.
 
BR DGD doesn't sound like any tube type I ever heard of...and a quick check in some tube databases comes up with nothing for that. Are you sure you are looking at the tube type and not the production code? I bet it is a 5AR4/GZ34...but maybe the marking is gone.

Also...some 5AR4/GZ34 rectifiers will have 5 pins and some 4 (nothing to worry about as long as it's the same tube type), and yes, they can come in different sizes (the glass bottle portion).

What's the reason you are looking to replace the existing tube(s)...?
 
No reason for replacing the tube, I just have this spare one sitting around and I'm getting ready to sell the amp. the 4 pin 5AR4 fits in the socket - the pin layout is the same.
Some better light revealed "5AR4/GZ34" on the bigger 5-pin tube.
 
What brand is the spare?
Should be worth some $$ whatever it is.

Do you have any use for it? :)
I have a couple of amps that take a 5AR4/GZ34...but lately I've been running them with 5U4GB tubes...I like the extra sag. ;)
 
I was hoping you would say something like "Mullard - Made In England" or "GE/Sylvania - Made in USA". :cool: :D

Have not heard of "International Servicemaster" before....is that an old production/USA made tube or current production Russian/Chinese tube?
 
GZ34 is the European designation, and 5AR4 is the US designation for the same tube. Sometimes manufacturers use 4-pins, sometimes they use 5-pins, but the tube is an octal like the 6L6. You don't need all 8-pins, so many manufacturers leave off some pins, and they know the amp builder might use the pins on the socket as tie points. But the bottom line is if your chart calls for a GZ34, you can almost use anything there.
The GZ34 drops the least amount of voltage internally, so the B+ in the end is the highest. A 5U4 would drop much more voltage, so the B+ is lower. No harm to the filters or anything else. You lose a few watts, and get some sag, so many people like that idea. I think about the only octal I wouldn't use would be a 5Y3. They just aren't rated for as much Plate voltage as a GZ34, so you could harm the 5Y3 if you just stuck it in there. But there is also a 5R4, 5T4, 5V4; there were a lot of rectifier tubes. The big thing is the suffix to the tube designation. The later versions moved the Plate closer to the Cathode, so there was less voltage drop, and the voltage rating went up slightly. 5U4GA, 5U4GB, and 5U4GT are all slightly different, so there would be different B+ happening, different amounts of sag, and you would end up with different tone. A fun experiment. Just make sure to rebias each time.
 
The box has 'International Components Corp, Huntington, NY' on one flap, and the tube says its made in Germany.
 
Well...don't throw it away. If you don't need it, sell it.
 
I'm pretty confident that "BR DGD" is just the production/date code...
 
Making a mental note to PM ranjam if I ever have any tube questions...:cool:
 
Ranjam is way too technical, even for an engineer!!
The tube is glass. As stated above, it's a small base 5AR4.
If you're interested in it before I Ebay it next week, PM me - $5 + $5 for Priority Mail (US only).
 
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