hello everyone
I have an unknown original amp(no schematic) with a double push of 7868.
these lamps are at the end of life and I have in stock 2x4 6p41s.
I would like to know if any of you have already made swap 7868 / 6p41s and if he can give me some ideas for implementation and modification.
thank you
I have an unknown original amp(no schematic) with a double push of 7868.
these lamps are at the end of life and I have in stock 2x4 6p41s.
I would like to know if any of you have already made swap 7868 / 6p41s and if he can give me some ideas for implementation and modification.
thank you
You need much more negative voltage for g1 (need ~cca -65V for 6P41S bias) than the amplifier can give it. Perhaps you could use the high voltage winding of course with the modifications, and certainly with the change in the value of the adjustment elements for bias.
This is an interesting thread.
I just recently picked up a Rowe (juke box) amp with very knackered 7868's.
Ok so simple solution is to get a set of 6P14's. When they arrived I put them on the curve tracer and couldn't quite believe the phenomenal performance, thinking this will need much more bias than the standard 14 Volts. Being a bit busy I put it to one side but made a mental note that probably a conversion to auto bias is most likely the optimum solution.
I just recently picked up a Rowe (juke box) amp with very knackered 7868's.
Ok so simple solution is to get a set of 6P14's. When they arrived I put them on the curve tracer and couldn't quite believe the phenomenal performance, thinking this will need much more bias than the standard 14 Volts. Being a bit busy I put it to one side but made a mental note that probably a conversion to auto bias is most likely the optimum solution.
New Sensor currently manufactures 7868s.
What does Rowe's bias supply circuitry look like? If it's a simple tap on the rectifier winding that's 1/2 wave rectified, install a 1/2 wave voltage doubler.
What does Rowe's bias supply circuitry look like? If it's a simple tap on the rectifier winding that's 1/2 wave rectified, install a 1/2 wave voltage doubler.
Last edited:
i'm very happy with your Rowe amplifier but mine is not a Rowe ! 😀
after investigation,mine is the same to Hitone H300 but with no phono,no grave/aigue correction,no balance etc etc etc ...
the shematic
after investigation,mine is the same to Hitone H300 but with no phono,no grave/aigue correction,no balance etc etc etc ...
the shematic
6P41S is a high current tube.
It has about the same anode with 170 V screen voltage than 7868 has with 400 V (Ug1 = 0 V).
As a PP-UL amplifier, 6P41S works best with some 300 V supply voltage and 4k load impedance. Some 20...25 W is available.
It has about the same anode with 170 V screen voltage than 7868 has with 400 V (Ug1 = 0 V).
As a PP-UL amplifier, 6P41S works best with some 300 V supply voltage and 4k load impedance. Some 20...25 W is available.
Already discussed.
6P41S is totally different tube, even though looks kind of similar. Since your amp can provide higher swing, you can try 6L6 tubes. In such case it may work, with less feedback as the result.
7868 tubes - replace with 6L6's?
6P41S is totally different tube, even though looks kind of similar. Since your amp can provide higher swing, you can try 6L6 tubes. In such case it may work, with less feedback as the result.
7868 tubes - replace with 6L6's?
Yes, OS 7868s are very scarce. However, (repeat) New Sensor is currently producing 7868s.
Find an EU dealer that carries New Sensor's product. You should not have to pay the price New Sensor shows. The "blurb" that follows below is taken from the site of excellent U.S. dealer Jim McShane.
Find an EU dealer that carries New Sensor's product. You should not have to pay the price New Sensor shows. The "blurb" that follows below is taken from the site of excellent U.S. dealer Jim McShane.
why persist in wanting to keep the 7868 while the 7591 is exactly the same with a different broaching.
the 7868 will not be manufactured long, it has only to see the number of adapter sold on the net to convert magnoval support in octal .deja on the hitone, in the 60 ", he had changed the 7868 for the 7591 and I do not think it's the only ones who did it.
to finish, actually I find EH in Europe, but twice the price of usa ...
the 7868 will not be manufactured long, it has only to see the number of adapter sold on the net to convert magnoval support in octal .deja on the hitone, in the 60 ", he had changed the 7868 for the 7591 and I do not think it's the only ones who did it.
to finish, actually I find EH in Europe, but twice the price of usa ...
That's correct. I suspect that New Sensor could not conveniently source Novar bases, but Magnoval bases were available. The pin circle is the same, but Magnoval pins are bigger than Novar pins. Given the "tired" state of many units' sockets, the fatter pins can be a blessing. Be warned that once current production 7868s are used, going back to OS tubes, without replacing sockets, is not an option. Given the very, very, poor availability of OS 7868s, the socket issue is theoretical, not practical.
New Sensor will make the tubes, as long as a market exits. There are some units where installing Octal sockets and 7591s will not work, due to space considerations. Profit is a very powerful motive.
Well, the EH 7868s really require a magnoval socket. At least, with the 7591A, you have 3 choices for vendors, and they aren't choosy regarding sockets. I've been getting good results with the EH parts. I intend to try the 6P41s some time to see what I can squeeze out of them. Too bad the documentation on that tube is so poor.
Are there available any datasheets for these 6P41S? Frank doesn't appear to have them handy...
Best regards!
Best regards!