hello, i have a k 4040 since many years, and i may peplace 1 EL 34 time to time, in a few years, i change approximatyively 20 tubes !! and i saw on different forums that it is a well known problem . i tryed different kinds of EL 34 ,as others people and my question is :
the 4040 sounds great, but seems have a probem because i never seen another ampli to burn so much tubes! (i’m electronician and never see that in another ampli ).
have you some possibility to do a mocification .
i find KT77,is it possible to reaplaces the EL 34 .
cheers,77
Sorry, we do not have any experience with this modification.
thank you, vel for the replay.
i bought and try 8 x KT77 in replacement of the EL34 without problem, and now the 4040 sounds great and hope the KT77 will be better, i let you know in a few time.
otherwise, can you give me the ref. number of the alimentation and the output transformers, please.
cheers,77
power transformer: TR4040
output transformer: ZD043
thank you again,VEL417, my 4040 is still working very fine with 8 KT77 instead of the EL34’s and i can now order the transformers.
cheers,77
Hello
I have the same problem with my K4040. I built this kit twelve years ago.
I changed a few part to avoid these problems.
In the first time, I changed the resistors R97 to R104 by 10ohms/5W instead of 10ohms/1W carbon.
I noticed that at startup (after 10 minutes that the red led blinked), the current which cross the R97…R104 can be too hight.
In my case, a lot of resistor was burned before the vaccum tube EL34.
When I changed the resistor by 10ohms/5W, I have never had EL 34 dead. (sorry for my english; it’s not my mother tongue)
In the second time, I changed the capacitor C25 (470µF/25V) by a 1000µF/25V for increase the time of delay.
I notice also some micro arcing inside the EL34, with 470µF. I think that the EL34 is not enough hot before that the high voltage turn on.
Regards
hi, silans,
i thank you for the replay, i think to replace resistors is a good solution, but these resistors are also a fuse for each EL34 and when the EL34 is really in short circuit, it can cause some other problems.
for the capacitors, good idea.
i think to try your solution soon, using the KT77 “gold lion” because they seems better than EL34 and sounds very great.
cheers,77 
hello, guys,
i’m coming back to inform you of what happens with the 8 kt 77 i use since 4 months instead of the el 34 :
amplifier is working very fine with great sound and never burning resistors.
the kt77 are gold lion . hope it help, and appreciate if someone having the same problem with micellaneous el 34 can try and post results.
cheers, very good new year to all the forum .
Hello
can you post the link, which modification have you used?
Thanks
usually if an amp burns that many valves that quickly the bias is set just too high, if you know the anode voltage you could try online bias calculators for a more optimal point, or just make the bias colder.
hello, guys, a new thank to all for your replays. i’m coming back :
my K4040 is working fine with his KT77 “GOLD LION” replacing the EL34 without any modification, just i had to modify the bias, and that’s all.
hope this help the owners of K4040 tubes burners !
cheers,77