Rick: Looked at your homebrew PS and it's almost the same as the one I have
here. I use a 30 ampdarlington pass transistor and the 7815 drives the base of
the pass transistor. The "crowbar" is simply
a 10 watt 15 volt zener diode that will become a dead short and blow a fuse at
the input of the passtransistor. The darlington device has a 1.4 volt drop
from base to emitter, thus the output voltage is13.6 volts, which is just under
a full charged 12 volt battery (13.8 volts).
When the 78xx devices fault, the output goes to zero. That is what I like
about them. We tested theproto-type for 24 hours in a oven set to 120 degrees
F and then for another 24 hours in a freezer.This was to insure operations as a
repeater power supply. These power supplies ran for several yearson a mountain
top in East Tennessee at the K4EAJ repeaters without the first fault.
I like you design too. Should be very dependable.
Clayton N4EV
From: Rick - DJ0IP / NJ0IP <Rick@DJ0IP.de>
To: 'Discussion of Ten-Tec Equipment' <tentec@contesting.com>
Sent: Thursday, February 26, 2015 5:33 PM
Subject: Re: [TenTec] 252Mo supply
I'm always amazed to see people running power supplies without a crowbar.
This is about as dangerous as driving on "slicks" in a snow storm and not
wearing your seat belt.
A crowbar is a dirt simple circuit to homebrew and add to any power supply.
It will cost less than $10 and can save hundreds of dollars in potential
damage to our radios.
When I got my first Omni in 1979, I couldn't afford the matching P.S. so I
home-brewed one.
Here is a brief description:
http://www.dj0ip.de/ten-tec-stuff/homebrew-p-s/
Not shown in the schematic is the Circuit Breaker / Switch plus power
indicator lamp on the AC input side.
I just uploaded this tonight.
I can make some pictures and upload them later.
This power supply is 35 years old and still in operation today.
NO EXCUSES, PEOPLE! If you do not have a crowbar on your power supply, add
one!
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Douglas via
TenTec
Sent: Thursday, February 26, 2015 10:13 PM
To: tentec@contesting.com
Subject: Re: [TenTec] 252Mo supply
I'd not use a 2N3055 substitute for a pass transistor in the 252M supply.
The 2N3055 only has a collector current rating of 15 amps. There are better
subs out there with higher ratings. I believe the original transistor used
in these single pass transistor supplies was a 2N5301. It's collector
current rating is 30 amps.
It's available here:
http://www.mouser.com/ProductDetail/Central-Semiconductor/2N5301/?qs=Ypxpq5e
NvNU0NwYSSi8qxw%3D%3D
The 252M supply can be adjusted fine for 12.1 V.
Perhaps you were warned against using this supply because it has no built in
over-voltage protection. When that pass transistor shorts, the output can
rise to something like 30 volts, really doing a job on your transceiver.
Ten-Tec originally sold an optional over-voltage protection crowbar circuit
in a small external box. I've one in use with my 252M supply.
The 252 M(O) supplies do have a crowbar circuit for over CURRENT protection,
the so-called electronic circuit breaker.
73,
Doug/WA1TUT
Date: Thu, 26 Feb 2015 10:37:14 -0600
From: Chris Howard w0ep <w0ep@w0ep.us>
To: tentec@contesting.com
Subject: Re: [TenTec] 252mo supply
Message-ID: <54EF4BBA.5050002@w0ep.us>
Content-Type: text/plain; charset=windows-1252
My bridge rectifier seemed to be ok.
But the big pass transistor was reading dead short between collector and
base.
I replaced that with another 2n3055 that I had on hand.
That seems to have done the trick.
Chris
On 2/9/2015 1:24 PM, Chris Howard w0ep wrote:
>
> Thank you Ralph!
>
> I hooked the Omni up to a Pyramid linear supply that I have here. I
> can run up to about 10 watts and then the voltage sags enough to cause
> the frequency to change. So, I am ok if I stick to lower power.
>
> I'm going to dive into the 252mo supply and see what is what.
>
> Do you think it would be better to get a switching-type supply?
> Should I be worried about noise on the power line?
>
> Chris
>
>
> On 2/8/2015 9:22 PM, Ralph Arnold wrote:
>> I had the same problem with my OMNI D the PS is bad mine blew the
>> Bridge Rectifer and the 3055 Voltage Regulators were leaky I also
>> replaced the electrolytic cap it was old Now it works like a champ
>> Oh BTW check output with a known good DVM and I also Scoped PS for
>> clean power.(no 60 cy ripple. Im an old USN Aviation Tech KD8BTQ
>> ---Ralph
>>
>> On Sun, Feb 8, 2015 at 11:41 PM, Chris Howard w0ep <w0ep@w0ep.us> wrote:
>>
>>>
>>> I was tuning up the antenna with my Omni-D yesterday afternoon and
>>> everything went completely dead.
>>> I was not high on SWR and not turned up to maximum power.
>>>
>>> Turning things off and on I was able to get the power supply meter
>>> light to come on, but nothing on the rig.
>>>
>>> I have the light in my SWR meter hooked up to the supply also, and
>>> that is not working. I think the supply has problems.
>>>
>>> -- later --
>>>
>>> I jumper the "SW" ports of the connector, plugged in in the supply
>>> and fired it up. Sure enough, the supply lights up but no output.
>>>
>>> Any advice before I dive in?
>>>
>>> Chris
>>> w0ep
>>>
>>>
>>>
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>
>> _______________________________________________
>> TenTec mailing list
>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>>
>>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
>
------------------------------
Message: 11
Date: Thu, 26 Feb 2015 12:19:24 -0500
From: "Al Sirois" <alsirois@roadrunner.com>
To: <tentec@contesting.com>
Subject: Re: [TenTec] 252mo supply
Message-ID: <95D02EADB0D14D3C9E8385CE62176E83@officepc>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Thursday noontime, guys:
My discussions with Paul at T-T some time ago, told me NOT to use the 252mo
supply with the Jupiter or Scout. He said it doesn't keep the voltage about
12.1 VDC.
The 252om is OK for the OMNI-A, B, C, D.
Al Sirois/N1MHC
==============
-----Original Message-----
From: Chris Howard w0ep
Sent: Thursday, February 26, 2015 11:37 AM
To: tentec@contesting.com
Subject: Re: [TenTec] 252mo supply
My bridge rectifier seemed to be ok.
But the big pass transistor was reading dead short
between collector and base.
I replaced that with another 2n3055 that I had on hand.
That seems to have done the trick.
Chris
On 2/9/2015 1:24 PM, Chris Howard w0ep wrote:
>
> Thank you Ralph!
>
> I hooked the Omni up to a Pyramid linear supply
> that I have here. I can run up to about 10 watts
> and then the voltage sags enough to cause the frequency
> to change. So, I am ok if I stick to lower power.
>
> I'm going to dive into the 252mo supply and see
> what is what.
>
> Do you think it would be better to get a switching-type
> supply? Should I be worried about noise on the power
> line?
>
> Chris
>
>
> On 2/8/2015 9:22 PM, Ralph Arnold wrote:
>> I had the same problem with my OMNI D the PS is bad mine blew the Bridge
>> Rectifer and the 3055 Voltage Regulators were leaky I also replaced the
>> electrolytic cap it was old Now it works like a champ Oh BTW check
>> output
>> with a known good DVM and I also Scoped PS for clean power.(no 60 cy
>> ripple. Im an old USN Aviation Tech KD8BTQ ---Ralph
>>
>> On Sun, Feb 8, 2015 at 11:41 PM, Chris Howard w0ep <w0ep@w0ep.us> wrote:
>>
>>>
>>> I was tuning up the antenna with my Omni-D yesterday
>>> afternoon and everything went completely dead.
>>> I was not high on SWR and not turned up to maximum power.
>>>
>>> Turning things off and on I was able to get the power
>>> supply meter light to come on, but nothing on the rig.
>>>
>>> I have the light in my SWR meter hooked up to the supply
>>> also, and that is not working. I think the supply has
>>> problems.
>>>
>>> -- later --
>>>
>>> I jumper the "SW" ports of the connector, plugged in
>>> in the supply and fired it up. Sure enough, the supply
>>> lights up but no output.
>>>
>>> Any advice before I dive in?
>>>
>>> Chris
>>> w0ep
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