[time-nuts] newbie question Thunderbolt supply

Don Latham djl at montana.com
Sun Aug 26 12:36:20 EDT 2012


Hi all: I'm using buck regulators from our ebay friends, e.g. 130704328176
at a little over $1.00 apiece, settable to 5 v or 12 v or whatever,
capable of 3 A with good heatsink. Foldback protection. Better than a
3-legged fuse, as my good gaffer Argus calls 'em.
Don

Bob Camp
> Hi
>
> The only real disadvantage of a 7812 / 340-12 is it's relatively high
> drop out voltage compared to a 1764 (or similar). Stability of any of
> them will be impacted more by thermal issues than anything else. The
> colder you can keep the 12V regulator, the more stable it will be. The
> +12 is by far the most sensitive supply line on the TBolt.
>
> Bob
>
> On Aug 26, 2012, at 6:46 AM, EWKehren at aol.com wrote:
>
>> Having played with several solutions I found the best is a 12 V 1 A
>> switcher with the output voltage increased to 15 V, check the
>> capacitors and if
>> necessary replace with 25 V. I laid out a PC board that has a TC7662A
>> inverter  followed by a 79L12.  Also on the board is a 7812 followed
>> by a 7805.
>> Putting them in series gives me good thermal distribution. In my
>> opinion every
>> thing else is an overkill.
>> Working with very low noise PLL's I have found that getting rid of
>> switcher
>> noise is much easier than 60 Hz.
>> There are other pin compatible alternatives to the TC7662A, even a 555
>> will
>> work, just more components.
>> Bert Kehren
>>
>>
>> In a message dated 8/25/2012 8:10:07 P.M. Eastern Daylight Time,
>> lists at rtty.us writes:
>>
>> Hi
>>
>> The easy way to do a TBolt supply is to start with  something between
>> 15
>> and 18 volts.  Regulate down to 12 and 5 with linear  regulators.
>> 7805's are
>> fine for the +5. Something like a LT1764 might be  better for the +12.
>> The
>> -12 supply is very low current and does not matter  much. People have
>> had good
>> luck with voltage inversion chips off the +15 and  then something like
>> a
>> 79L12.
>>
>> Bob
>>
>> On Aug 25, 2012, at 6:41 PM,  Edgardo Molina <xe1xus at amsat.org> wrote:
>>
>>> Dear Chris,
>>>
>>> Good afternoon. I am in the process of mounting my TBolt to a 2U 19"
>> rack enclosure and was looking for a decent power supply. I found the
>> Cisco
>> unit and I am ordering a couple of them just in case. It would really
>> be nice
>> if I could have access to the diagram of the upgrade you did on yours
>> to
>> recreate the same performance from the Cisco unit. Please do not feel
>> compromised if it is difficult to share. I didn't mean to be rude and
>> if my  note
>> causes you any discomfort please kindly disregard it. I jumped into
>> the
>> thread because of experiencing the same doubts as the originator of
>> it.
>>>
>>> Redondo Beach? I love visiting there whenever visiting my  brother
>>> who
>> lives in Rancho Palos Verdes. I would invite you lunch anytime  just
>> for the
>> pleasure of meeting you in person.
>>>
>>> Thank  you.
>>>
>>> Regards,
>>>
>>>
>>>
>>>
>>>
>>> Edgardo Molina
>>> Dirección IPTEL
>>>
>>> www.iptel.net.mx
>>>
>>> T : 55 55 55202444
>>> M : 04455  20501854
>>>
>>> Piensa en Bits SA de CV
>>>
>>>
>>>
>>> Información anexa:
>>>
>>>
>>>
>>>
>>> CONFIDENCIALIDAD DE INFORMACION
>>>
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>>>
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>> you.
>>>
>>>
>>>
>>>
>>>
>>> On Aug 25, 2012, at  3:26 PM, Chris Albertson
>>> <albertson.chris at gmail.com>
>> wrote:
>>>
>>>> On Sat, Aug 25, 2012 at 1:06 PM, Jerry <jsternmd at att.net>  wrote:
>>>>
>>>>> I am using a Cisco supply 3 voltage supply  for the T-bolt.  Is
>>>>> there
>> any
>>>>> performance loss if the  +12vdc rail and the -12vdc rail are off by
>>>>> a
>> few %
>>>>> in opposite  directions, e,g  +11.7 vdc and -12.3vdc ?
>>>>>
>>>>> The true nuts here on the time nuts list will tell you that  the
>>>>> noise
>> from
>>>> a switching power supply is bad and that you need a  regulated
>>>> linear
>> power
>>>> supply.   But for most practical  purposes the Cisco supply is a
>>>> good
>> one.
>>>> Being only slightly nuts  myself.  I use the Cisco   supply but I
>>>> built a
>>>> small power adaptor board with matching connectors and some "pi"
>> filters
>>>> made with RF choke and capacitors.  I realy don't  thing the filters
>>>> are
>>>> needed but I wanted a connectorized  installation and a small choke
>>>> was
>> as
>>>> easy to solder in as a  length of wire.
>>>>
>>>> --
>>>>
>>>> Chris  Albertson
>>>> Redondo Beach, California
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-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
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