[R-390] HP410B rectifier tubes

[n4buq at knology.net]

It has an EA53 in it.  I glanced at my other meter's (ME-26) 2-01C and it 
didn't appear at first glance that the 2-01C would fit in my HP-410B's 
probe, but I'll give it a second look.  Maybe someone put an EA53 in this 
probe and I'm just assuming a 2-01C won't fit.  It sure would be great if 
it does as the 2-01C is generally a less-expensive tube these days.

73,

Barry - N4BUQ

> Barry,
> 
> You sure you don't want a 2-O1C?  That's what I have in my 410B.  You 
> can use the EA53 but it requires a different plate contact and attaching 
> spring.  Also the filament voltage is different.  Don't know if HP made 
> a design change or if they just allowed for a different repair part.  I 
> have an NOS HP replacement part, 2-O1C.  Let me know if you are 
interested.
> 
> 73,
> 
> Bill, K3PGB
> 
> Barry wrote:
> 
> >Did some more digging.  With the cover off, I can measure the filament
> >voltage for the EA53 while it is in circuit.  I had to crank the resistor
> >quite a bit farther "up" to get 6.3VAC across the filament.  This did 
cause
> >the probe to get really warm like it used to; however, the probe still
> >doesn't check AC properly (low reading).
> >
> >I did some checking in the manual.  It states to check the resistance
> >"below" the ballast tube with the ballast tube removed from the circuit.
> >This should produce 4 to 6 ohms.  If it doesn't, most likely something 
has
> >been "shorted" (I assume it means something has damaged the rectifier).
> >Mine checks a little over 2 ohms, regardless of the setting of the 
variable
> >resistor.  Looks like I probably do have a damaged EA53.  I checked the 
rest
> >of the wiring and some of the test point voltages and nothing was
> >particularly too badly awry.
> >
> >Looks like I'm back to looking for an EA53 :-(
> >
> >Brry - N4BUQ
> >  
> >
> 
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