M49 Clone with 5840W

[Tubemooley]

Tubemooley here. Has anyone built Oliver Archut's M49 mic circuit? See attached. I think I see a discrepancy. See the dot connecting grid 2 and grid 3 to the plate voltage? I'm not sure that's a good idea because grid 3 is internally connected to the cathode. Who knows the answer to this? Thanks. Big mouth Dana out.

 

[Tubemooley]

I have four different 5840 datasheets but I have not located the 5840W datasheet.

 

[gyraf]

Yup, the -W version seems to be differently wired..: https://www.radiomuseum.org/tubes/tube_5840w.html

See also - https://groupdiy.com/index.php?topic=49897.0

/Jakob E.

 

[pucho812]

I built the m-49 with 5840W tube recently. I still need to do testing on it.  I had a similar question concerning the schematic.

The schematic via the website and documentation is shown for a different but similar subminiture tube.

According to Dennis @ AMI, you will omit pins 4 and 8 if using a 5840W tube as provided in the kit.  If you plan to cut those leads, leave at least 5mm to not crack the tube. I shorted my leads and added heat shrink over them.

 

[Bonnie1]

The schematic via the website and documentation is shown for a different but similar subminiture tube.

Not sure I'am reading your statement correctly, however The schematic and documentation on Tab-funkenwerk.com is correct for 5840, 5840w and ac701. As per Oliver's design. 

Tubemooley, it's generally best practice and most efficient to contact AMI with any questions regarding Oliver's designs and info. on AMI/TAB's website.

 

[pucho812]

Not sure I'am reading your statement correctly, however The schematic and documentation on Tab-funkenwerk.com is correct for 5840, 5840w and ac701. As per Oliver's design. 

Tubemooley, it's generally best practice and most efficient to contact AMI with any questions regarding Oliver's designs and info. on AMI/TAB's website.

looks like the schematic has been updated since I last saw it. My comment about omitting pins 4 and 8 are still valid though.

 

[CJ]

looks like the W version has the supressor grid loose, so yes, tie it to the screen. could probably tie it to the cathode and not notice much difference.

you can use other mini tubes >

https://groupdiy.com/index.php?topic=50731.0

 

[Tubemooley]

OK. Thanks for all the input. I e-mailed briefly with Dennis before placing my order. I didn't get the feeling that they were interested in providing tech support. I can contact them and ask. I have a 5840W so the third grid is not connected to the cathode. I can ohm out the leads. I suspect that it is true. I do not expect to have to change out this tube for years. I will let you know how this pans out. Thanks.

 

[EarthTone]

Hey @Tubemooley Did you ever sort this out? I am about to do an m49 with Dany’s board and likely will use the commonly available 5840w tube.

 

[Tubemooley]

Sorry for the late reply. I don't have time to visit the GDIY regularly any more. I did sort this out. I take notes on everything and I have hundreds of photos of each build. I e-mailed with Dennis two weeks after this initial post. He said do not use tube pins 4 and 8. Let me know if you need more on this. tubemooley_at_yahoo_dot_com
1 = grid 1
2 = cathode, grid 3 this is the cathode
3 = filament
4 = cathode, grid 3 do not connect
5 = plate
6 = filament
7 = grid 2 this connects to the plate in Oliver's M49
8 = cathode, grid 3 do not connect

 

[terry setter]

looks like the W version has the supressor grid loose, so yes, tie it to the screen. could probably tie it to the cathode and not notice much difference.

The 6205 is the version of the 5840 that has the suppressor grid independently wired. I haven't been able to confirm that the suppressor grid wiring in a 5840W is any different than a standard 5840, though I've spent a bit too much time trying.

Anybody certain about this?

 

[rock soderstrom]

The 6205 is the version of the 5840 that has the suppressor grid independently wired. I haven't been able to confirm that the suppressor grid wiring in a 5840W is any different than a standard 5840, though I've spent a bit too much time trying.

This is in line with my experience. Even the European close relatives of the 5840W, the EF72 and EF732 have G3 hardwired to the cathode.

 

[k brown]

https://groupdiy.com/threads/6205-vs-5840-tube-wiring-in-royer-sdc.29991/
Built my Royer-modded Okatava MK-012 with 6205s.