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Re: K4DPK VFO Stabilizer

 

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Nigel,

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I would like to avoid switching/bucking DC-DC regulators.? Sometimes they seem fine only to discover a spur or two some time after a mod is made.

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Just me, but I think all vacuum tube gear should run without grounded heater returns.? In audio stages, it¡¯s so much easier to balance out hum that way.?

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Yes, it¡¯s possible to un-ground the heaters but have a look at the collision of parts and wiring under a TR-4Cw.? Adding a dedicated wiring string for the heater return on all tubes would be a nightmare.?

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Paul, W9AC

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From: [email protected] <[email protected]> On Behalf Of nigel patterson G3YDT
Sent: Thursday, January 18, 2024 3:31 PM
To: [email protected]
Subject: Re: [DRAKE-RADIO] K4DPK VFO Stabilizer

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Paul

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I have not read the other suggestions, but two come to mind

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1. Can you unground one side of the AC for heaters.? Normally it is a twisted pair.? I used a bridge to pull down the heater voltage on a R4C from 7.0 to 6.5. (It had forfeited some tubes for transistors)

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2. There are very cheap DC to DC converters (sometimes called regulators or step up or step down (buck) but are adjustable for output voltage) from China on the internet, for $5.? So rectify your heater voltage - half wave may be OK.? The two sides of the converter are electrically isolated.

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I used one also on a drake R2C using a replacement mains transformer that did not have a 12.6V output.? So boosted from 6.3V.? If there is interference put the ferrite beads on the wires.

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Nigel

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On Thu, Jan 18, 2024 at 8:09?PM Jim Shorney <jimNU0C@...> wrote:


Even better, use a 317T regulator *with recommended external caps*. Better specs and you can set the voltage to exactly what you want.

73

-Jim
NU0C

On Thu, 18 Jan 2024 11:52:15 -0800
"jerry-KF6VB" <jerry@...> wrote:

> On 2024-01-18 11:17, Paul Christensen wrote:
> > I'll soon be installing a K4DPK VFO stabilizer in my TR-4Cw.? The
> > stabilizer works on 10-14 VDC.? Since there's no low voltage in the
> > TR-4Cw, I'm curious how others have attempted the supply voltage
> > dilemma,?
>
> *** I had a similar requirement for my KWM-2.? I used a half-wave
> rectifier
> off the filament circuit, feeding a TO-92 three-terminal regulator.?
> Which
> has far better ripple rejection than a zener diode.
>
> Actually, I wound up using two half-wave rectifier circuits;? one for
> a BHI noise reduction module inserted in the audio stream, and the other
> for a DC fan.
>
>? ? In the case of the KWM2, there was an empty tube socket on the
> chassis,
> meant for a noise blanker option.? This had most of the signals I
> needed,
> including a switch closure for the "NB" position on the front panel.? So
> now when I click to "NB", the band noise goes down.? I mostly leave it
> in
> "NB".
>
>? ? ? ? ? ? ? ? ? ?- Jerry, KF6VB
>
>
>
>
>



--

73

-Jim
NU0C
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