[Boatanchors] Globe (WRL) V-10 VFO - Problem with voltage regulation

[Garey Barrell]

The parts list shows R4 as a 4.7k @ 1W.  The B+ is shown as 185 VDC on Pins 5 and 6 of the 6CB6.  So 40V drop to the 0A2 
is about 9 mA.  The 6BH8 is drawing about 9 mA when keyed, so doesn't leave anything for the 0A2.  I'm not surprised it 
didn't fire!  A 2700 ohm @ 2W would be a better choice.  With the higher line voltages today you'd have enough to 
regulate without overloading the 0A2 when the VFO is unkeyed.

Dropping 40V across the 1.5k would result in 26 mA keyup and 17 keydown, well within it's limits.  BUT, you would leave 
as much as 1W in that 1.5k resistor.  Really ought to be a 2W.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>

Jerry wrote:
> Hi Lee
>
> Many thanks.  Will get to it tonight.  Did you also add a low value resistor with the silicon diode to compensate for the extra 8-10v drop from the old selenium?  My V-10 had two large selenium stacks in series so it could have been as much as a 20vdc drop across them bringing the B+ from 175vdc to 155vdc.  I though this may have been part of the problem so I only put in a 220 ohm resistor to drop it by about 7 volts.
>
> 73 Jerry
> K1JOS
>
> -----Original Message-----
> From: L L bahr [mailto:pulsarxp at embarqmail.com]
> Sent: Friday, November 08, 2013 17:56
> To: D C _Mac_ Macdonald
> Cc: boatanchors at mailman.qth.net; Jerry
> Subject: Re: [Boatanchors] Globe (WRL) V-10 VFO - Problem with voltage regulation
>
> Jerry,
>
> This is your LUCKY DAY!!!!  I know exactly what the problem is as I had the same problem with my V-10.  I bought it off of the E-pay place and of curse it did not work.  I too replaced the selenium rectifier with a diode and changed out the filter caps.  Then I turned it on and my 0A2 would not strike.  The problem is people have diddled with these VFOs and tried to rebuild them.  There big mistake was the circuit diagram is wrong!!!!!  That dropping resistor they show as 47k cannot work.  If you use ohms law, the 47k defies science.  There is no way the 0A2 can fire with a 47k resistor in there. WRL might have meant a 4.7k.  However,  I put in a 1.5k 1 watt and it fires off nicely and the resistor stays cool and everything is now happy!!!
>
> Lee, w0vt
>
> ----- Original Message -----
> From: "D C _Mac_ Macdonald" <k2gkk at hotmail.com>
> To: "Jerry" <jsternmd at att.net>
> Cc: boatanchors at mailman.qth.net
> Sent: Friday, November 8, 2013 4:10:22 PM
> Subject: Re: [Boatanchors] Globe (WRL) V-10 VFO - Problem with voltage	regulation
>
> Try the regulator to give you 105V regulated with the specified dropping resistor.  I'd bet the VFO would run just fine with the lowered B+ voltage.  IIRC that's the 0B2.
>
> 73 - Mac, K2GKK in OKC
>
>
> Sent from my iPhone
>
> On Nov 8, 2013, at 15:51, "Jerry" <jsternmd at att.net> wrote
>
> I found a V-10 in great shape but someone had cut the line cord close to the chassis which made me worry that there were some potentially serious issues with the VFO.  The inside looks new, however before applying power, I checked to make sure the power transformer was not shorted.  The xfrmr works fine supplying filament 6.2vac and separate 175vac to a half wave selenium
> (65ma) that I replaced with 1n5408 plus a 200ohm dropping resistor.  I also replaced the two 30uF lytics and left the large (~10mH) choke between the two filter caps as it was not shorted either.  Thes B+ supplies the plates to 6BH8 and 6CB6 using a 0A2 voltage regulator.  I cannot get the 0A2 to strike at 175vdc from the filtered supply.  I replaced the 0A2 twice with
> known tubes and still not striking.   The dropping resistor between the B+
> and 0A2 is 47K, 1W per the schematic but in the VFO I found a 560 ohm 1 watt instead.  I cannot tell if this was done by the previous owners to get the
> 0A2 to strike earlier or if this was a factory mod not documented on my
> schematic.   Can anyone offer advice?
>
> 73 Jerry
> K1JOS
>