[time-nuts] newbie question Thunderbolt supply

Sun Aug 26 16:36:20 UTC 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:
>>>
>>>
>>>
>>>
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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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