[R-390] SP600JX17 - drift

[Chuck Rippel]

All very true and good points Barry.  A good bit of the drift problem may be 
caused by the chassis expanding with heat.  The SP-600 chassis is not the 
most robust on on the block and not near as immune to flexing as say, the 
R390/or the "A" variant.

The regulator I install keeps the filament voltage dead on and even 
compensates for resistance changes in the actual tube filaments to maintain 
the same current flow value.  The radios still drift.  I would suspect they would 
drift if you regulated every voltage applied as the problem does not appear to 
be electrical in cause.

The radio still drifts.  Les Locklear pointed out in a conversation we had last 
night that you can pass your hand over the VFO tube on top and if the BFO is 
on and a station tuned it, the receiver will "pull" just a tad.

I accept the drifting as a part of the personality of the SP-600 family of 
receivers.  BTW having the special tube shield on the VFO oscillator tube that 
anchors to the main chassis has little effect on drift.  That the original is there 
or its been replaced with an IERC makes little difference.

> I suppose this really belongs on the Hammarlund list, but here's my 2 cents
> worth anyway:
> 
> As heavy as the SP-600's are, the chassis are not all that solid.  If you've
> ever picked one up wrong, you may have noticed that they can twist a bit.
> 
> In addition to the "brace" on that tube shield (why all the quotations
> marks, Rod?), 

I didn't get the "quotes thing" either.
-----------------------------
Chuck Rippel, WA4HHG
R390A List Co-Administrator
Reply to: R390A@R390A.com

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1968 Contract Dittmore-Friemuth R390A #38
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1967 Contract EAC R390A #5295
1967 Contract EAC R390A #5591
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