[R-390] SP600JX17 - drift

Wed, 9 Jan 2002 15:26:43 -0800 (PST)

Chuck,

The 6C4 Oscillator at V4 is "braced" to the the chassis with a "thumb" screw, "brace" and "sheild"
combination.

If you move this tube the oscillator frequency moves.

I have seen this tube shield and "brace" arrangement replaced with "heat dissipating tube shields"
without this "brace" arrangement.

This is not recomended, unless the "mechanical stability" of the "Brace" is reinstated somehow.

This also is a potential source of "drift" before "warm up" has stabalised.

Rodney
VK2KTZ

--- Chuck Rippel <[email protected]> wrote:
> One thing to keep in mind is that SP-600's, even after recapping and taking 
> the extra step of adding the mod which regulates the filament voltage to the 
> top 4 tubes, still drift quite a bit until the entire chassis heat saturates.
> 
> As to setting the input line voltage, the best way to determine the correct A/C 
> Line input voltage (@60 cycles!!!!!) is to monitor the tube filament voltage at 
> your tube of choice other than the rectifier, regulator or the (12AU7??).   Set 
> the line input voltage to a value that yields 6.3VAC at the tube filaments.  That 
> puts the other voltages right about where they need to be.
> 
> > > << PS: if the input volts are too high, then the 0A2's get very hot,
> and very
> > > bright !!! No wonder  they drift, and stop regulating....
> 
> > > Rodney
> > > VK2KTZ >>
> 
> -----------------------------
> Chuck Rippel, WA4HHG
> R390A List Co-Administrator
> Reply to: [email protected]
> 
> To learn more about R390A's visit:
> http://www.R390A.com
> 
> 
> 1968 Contract Dittmore-Friemuth R390A #38
> 1967 Contract EAC R390A #2808 with outboard Sherwood SE-3 Sync. Detector
> 1967 Contract EAC R390A #5295
> 1967 Contract EAC R390A #5591
> 1967 Contract EAC R390A #1023
> 
> All in regular use as premier Shortwave Broadcast DX Receivers
>        -and-
> Vintage AM Amateur use
> --------------------------------
> _______________________________________________
> R-390 mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/r-390

__________________________________________________
Do You Yahoo!?
Send FREE video emails in Yahoo! Mail!
http://promo.yahoo.com/videomail/