On 10/7/2010 3:28 AM, alexeban wrote:
> Even so, the GRC 106 linear amplifier had a linear regulator to feed 2
> 4CX250, 26 VDC filaments, in parallel with no problems. There are types of
But the 4CX250s have low powered, oxide coated cathodes. The larger
tubes are 225 watts for oxide coated cathodes (YC156) and nearly 400
watts for the 4CX3000A7. Some in the 3000 to 5000 watt range run as much
as 500 watts for the thoriated tungsten filaments.
Aren't we taking about different animals here?
73
Roger (K8RI)
> linear regulators that don't latch up at start conditions. In that case, the
> regulator was there to protect the tubes from surges in the vehicular power
> system.
> Alex 4Z5KS
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Jim W7RY
> Sent: Thursday, October 07, 2010 7:34 AM
> To: Jim Thomson; amps@contesting.com
> Subject: Re: [Amps] Switching Supplies for High Current Filaments
>
> Nope! A linear type. And yes, the power supply was on. It was a 20 or 35 amp
>
> supply.
>
> 73
> Jim W7RY
>
>
>
> --------------------------------------------------
> From: "Jim Thomson"<jim.thom@telus.net>
> Sent: Wednesday, October 06, 2010 9:26 PM
> To: "Jim W7RY"<w7ry@inbox.com>;<TexasRF@aol.com>;<amps@contesting.com>
> Subject: Re: [Amps] Switching Supplies for High Current Filaments
>
>> ## The typ cold resistance of a light bulb is 10% of the hot resistance.
>> On tubes, it's
>> even worse, typ 12%. On the few switcher's we experimented with.. all
>> had
>> a built in ramp up
>> feature on start up. IE: with no load on the switcher's output, the
>> output Vdc would ramp up
>> anyway. With a load ALREADY connected [oxide tube only]... the switcher
>> is
>> then turned on... and it goes
>> through it's ramp up feature. Between that and the current limiting
>> feature... the switcher will
>> not cro-bar itself. But this only worked if the switcher's output
>> current
>> rating was aprx double the
>> tubes rating. IE: tube fil was 3.6A.... a 8A switcher will just
>> work...a
>> 5 A switcher would not work.
>> --------------------------------------------------
>>
>>> Agreed! Ever try to hook a headlamp across an Astron power supply?
>>> Pretty
>>> tough to do..
>> ## was the astron turned on 1st..... then the headlamp connected ? Or
>> did you
>> hook the headlamp to the astron 1st.... then turn on the astron ? Is the
>> astron a
>> switcher type ?
>>
>>> 73
>>> Jim W7RY
>>>
>>>> --------------------------------------------------
>>> From:<TexasRF@aol.com>
>>>>>> So, for any regulated and current limited power supply, there needs to
>>>>>> be
>>>> a
>>>> method of starting at low voltage and ramp it up as the tube warms up.
>>>>
>> If it was actually a current limited supply, not a current
>>>> shutdown
>>>> design, all would be well and the tube could warm up with a constant
>>>> rated
>>>> current source. A regulated current design instead of voltage would be
>>>> wonderful.
>> ## On my little lab type switcher supply, the current limit can be
>> adjusted to any value.
>> If set for normal rated tube current [ + maybe 1%] it will perform just
>> like you wanted.
>> You can cro-bar the output all you want, and all it does it put out the
>> max
>> current you dialed
>> in. So this type of switcher will work as well.
>>
>> ## None of these switcher's will work on a thoriated tungsten tube like
>> a
>> 3-500. The B-
>> return for any thoriated tungsten tube is via the CT of the conventionl
>> fil
>> xfmr sec.
>>
>> Jim VE7RF
>>
>>
>>
>>
>>>> By the way, that 10% resistance figure applies to light bulbs as well.
>>>> The
>>>> hot resistance can be estimated by r equals voltage squared divided by
>>>> wattage rating. That is the well known power = e squared divided by
>>>> resistance formula turned around backwards. The cold resistance can be
>>>> measured with
>>>> a VOM or DVM.
>>>>
>>>> 73,
>>>> Gerald K5GW
>>>>
>>>>
>>>>
>>>> In a message dated 10/5/2010 11:01:14 P.M. Central Daylight Time,
>>>> jim.thom@telus.net writes:
>>>>
>>>> Date: Tue, 5 Oct 2010 07:34:41 -0700
>>>> From: Patrick Barthelow<apolloeme@live.com>
>>>> Subject: [Amps] Switching Supplies for High Current Filaments
>>>>
>>>>
>>>>
>>>> Are there any sensibly priced switching supplies (even surplus) that
>>>> are
>>>> small and light, that could power some of the QRO tubes
>>>> with high current filaments? Would, say, a 5v, 30A switcher which
>>>> could
>>>> power a pair of 3-500Zs, be economically
>>>> competitive with a 5V 30A transformer, and even if it is not directly,
>>>> it
>>>> might still be worthy of consideration
>>>> if it was small enough, and light enough to significantly lower size
>>>> and
>>>> weight in an RF deck?
>>>> Would cold start surge current be a problem for switcher implementation
>>>> for filaments?
>>>> Best Regards,
>>>> 73, de Pat Barthelow AA6EG apolloeme@live.com
>>>>
>>>> ## This was 1st tried on a GS35B 6m amp. The inrush current was so
>>>> great that the
>>>> switcher thought it was being cro-barred... and went into shut down
>>>> mode
>>>> !
>>>> A bigger
>>>> switcher was used..and that worked, but the 2nd one was almost double
>>>> the
>>>> capacity
>>>> of the 1st one. Also, I believe my buddy had to use a Dc-dc isolation
>>>> converter in their some where, to
>>>> solve yet another problem.
>>>>
>>>> ## In the end, with numerous other problems, like heating of the air
>>>> variable load cap, the RF deck was scrapped,
>>>> and a new one designed from scratch. 2nd version used 2 x GS35B's...
>>>> and
>>>> this time, 2 x separate conventional
>>>> fil xfmr's used, one per tube. The problem with a pair of 3-500Z's
>>>> is.... the B- return is via the CT of the conventional
>>>> fil xfmr. We gave up on the notion of using switcher's for fil
>>>> supplies on oxide tubes. Some have had better success,
>>>> so it can be done with oxide tubes. Then you have an adjustable,
>>>> regulated supply. They will not work on a directly
>>>> heated thoriated tungsten tube. On some of the switcher's... hash and
>>>> noise was across some of the HF bands...and
>>>> a bitch to filter out completely.
>>>>
>>>> ## hammond makes a 5V @ 30A [with CT] conventional fil xfmr...for 2
>>>> x
>>>> 3-500Z's. Runs barely luke warm. It's priced
>>>> way below what a dahl is.... and readily available in the usa, through
>>>> the
>>>> usual distributor's. Comes in 2 x version's ,
>>>> with or without bell end housings, IE: bell housings or open frame.
>>>> They
>>>> measure 5.5 V no load.. and 5.0 V with a 30A load.
>>>> Last I checked a few years ago, it was aprx $45.00 . Their is only
>>>> one
>>>> primary, 115 vac. You can also get it in 5v @ 15A .
>>>> They also make a 7.5 vac @ 21 A. A friend in W6 land got his
>>>> YC-156
>>>> fil xfmr from hammond. The YC-156 fil xfmr was a
>>>> torroidal type.
>>>>
>>>> later... Jim VE7RF.
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