|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
73.68.175.222
Folks, my malfunctioning preamp among others is using 4 x 6s3p-ev tubes. I read that in some circuits they're interchangeable with the EC86, but in some they're not. The Vincent sa-7 owners have had good luck substituting the Soviet ones with ec86. I did that too. Everything was good, until I got a loud hiss in one channel a few weeks back.
Now, is it possible that the ec86 caused this? Before this particular set I'd been using different varieties of ec86 for 9 months, never had a single problem.
Attaching the diagram, the upper one is 6s3p-ev
Thanks
Follow Ups:
Looks like EC86 connects pins 6 & 8 to the control grid. If your preamp is wired for 6s3p this means the grid and cathode are connected when you plugin a EC86. Not sure how it worked at all.
Edits: 01/10/21
Check how your sockets are wired. If it worked previously with an EC86, then the socket intended for the 6p3s must not have been connected at pins 6 and 8. These high Gm tubes can easily oscillate without gridstopper at the right pins.
Hey Spantou, the unit is still on its way, but I did some investigation, and found out that the pins 2,3 and 9 are connected on 6s3p-ev. 6 and 8 are unused. Does that make sense for the ec86 replacement?
I see no problem, other than the potential for oscillation, which you and other users have not experienced in this amplifier.. As shown in the basing diagrams, the pins used (and unused) should make it possible to substitute the EC86 in place of a 6s3p-ev, so Vincent designers probably considered and enabled this substitute.
.
Thanks, I'll take a look when it's back.
Originally it came with 6s3p-ev tubes, but if they're incompatible with the ec86, shouldn't it be malfunctioning from the beginning?
Yes. If pins 6 and/or 8 were connected to the cathode for the 6s3p, then the EC86 should not have worked from the beginning, meaning that 6&8 are unconnected. My understanding is that EC86 oscillates easily and the three connections (2,6&8) for the grid was one measure to suppress that, but two of those connections are now unconnected in your setup when you use EC86, if our assumption is correct for how the socket is wired..
We are just guessing, but one theory is that "hiss" is caused by oscillation due to a connection that previously worked, but became oxidized or "dirty" recently, probably pin 2.
Checkout exactly how the sockets are wired, clean the sockets and pins and let us know if the problem persists with the EC86 (on the one channel only, correct?)
Glad you got the problem fixed.😊 Sorry the problem was apparently in a "black-box" module that you can't access.
They already fix it. The noise-canceling module called Vimala (the ones that have Flohbaum printed on them) was responsible for the left channel malfunction. They have them plenty in stock, which makes me believe this is a common problem, nobody's talking about it because of the resale value. Can't be sure, of course.
Thanks Spantou, at the moment the pre is at Audioadvisor, hopefully they'll do the job right. But when it's back, I'm going to investigate its wiring, I've been in contact with quite a few owners of this unit, and everybody's using ec86 without problems.
The pins and sockets are clean, before I sent it for repair, I cleaned everything and tried a brand new set of the original tubes with no luck. I hope they'll fix it this month.
Will let everybody know about the results.
Attaching a couple of pic for fun
From the FAQ at the top of this page.
It sucks to get old. It really sucks to get old and bitter.
I'm very sorry, but don't see the connection between ec86, 6s3p-ev and McShane's post.
If you're referring to the dirty pins/sockets, that's not the case.
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: