Just to add this note:
All 723 devices contain zener diodes that can and will produce low level
noise RF 'hash' which can be eliminated by adding bypass caps at the
appropriate pins of the 723 device.
Just be sure to check the case type of the device vis-a-vis 8 pin IC or
round metal case types as the pin-out is different for each type.
I have seen cases where an improvement of 6dB-10dB to the noise floor on 2m
results from supplies without OEM bypassing of the devices, such as some
Astrons and other older generic 3055 type supplies.
73...Jordan VE6ZT
----- Original Message -----
From: "Jim Aspinwall via FlexRadio" <flexradio@flex-radio.biz>
To: <flexradio@flex-radio.biz>
Sent: Saturday, June 14, 2014 11:25 AM
Subject: Re: [Flexradio] FlexRadio Digest, Vol 110, Issue 13
Like Ed says - the supply/components, once you have them, are quite
valuable.
Three key elements make this a not-bad supply to start with, any
version/rating, and highly recoverable from any of a few common failures:
- Long-standing 723 regulator - a highly flexible, reliable, FAST, can-be
precision regulator. Yes, there are other newer components with a variety of
qualities but you "can do just about anything" with a 723 - I've been
building 723-based supplies since the mid-70s. Anyone can build a solid
regulated supply from the many app notes for this device.
- Along with the 723, aside from the custom transformer, off-the-shelf
components - no fancy switching regulators, caps, inductors, tricks. If you
can't find a handful of 2n3055 and some big caps you're not looking hard
enough.
- custom transformer - brute force tailored for 18-22 v AC source for the
regulated section, a separate winding for the regulator source voltage, and
there is a LOT of iron between the mains and secondary
I challenge all but the craftiest folks to deal with and repair switchers.
I'm good with electronics but I prefer simple and obvious to custom highly
compact designs.
A few simple problems/issues I've have with the Astrons - all of which can
be solved with after-market parts and 30-60 minutes on the bench:
1. Main supply caps - common issue with any supply - replace or add too them
2. regulator supply cap - I usually rip this thing out and replace with 4700
ufd to beef up the raw DC to the reg chip itself, adds stability
3. on-board driver transistor failure - usually open - easy replacement with
any mid-power NPN
4. MOV shorts - a 99 cent part is not the best surge protection anyway
5. crow-bar vs. fold-back limiting - this is debatable - hopefully you fuse
your loads properly and this never kicks in. Either method is appropriate
depending on whether you're using the supply in a monitored/home environment
or 50 miles away at a repeater site and can't reset it.
I would not use this supply in the BB battery backup mode or to float
batteries. If you need to do this get a good 3-4-stage charger and battery
isolator.
Additionally, I learned not quite the hard way that my rigs and mobile amp
should not share the same supply. I found I was starving my Flex running my
ALS-500M on the same supply. A separate 50A Astron runs the amp and the rigs
run off another supply and battery backup.
________________________________
From: "flexradio-requ...@flex-radio.biz" <flexradio-requ...@flex-radio.biz>
To: flexradio@flex-radio.biz
Sent: Saturday, June 14, 2014 10:00 AM
Subject: FlexRadio Digest, Vol 110, Issue 13
Send FlexRadio mailing list submissions to
flexradio@flex-radio.biz
To subscribe or unsubscribe via the World Wide Web, visit
http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
or, via email, send a message with subject or body 'help' to
flexradio-requ...@flex-radio.biz
You can reach the person managing the list at
flexradio-ow...@flex-radio.biz
When replying, please edit your Subject line so it is more specific
than "Re: Contents of FlexRadio digest..."
Today's Topics:
1. Re: Power Supply Advice (Ed Toal)
2. Re: Power Supply Advice (alacat)
3. Re: Power Supply Advice (Neal Campbell)
4. Re: Power Supply Advice (Robert Lathrop)
5. Re: Power Supply Advice (Hanford R Wright)
6. Re: Power Supply Advice (Paul)
7. Re: Power Supply Advice (Hanford R Wright)
----------------------------------------------------------------------
Message: 1
Date: Fri, 13 Jun 2014 13:55:05 -0500
From: Ed Toal <n...@tds.net>
To: Ted Groke <w2...@comcast.net>, Jerry Falletta
<w2txb.je...@gmail.com>
Cc: FlexRadio Reflector <flexradio@flex-radio.biz>
Subject: Re: [Flexradio] Power Supply Advice
Message-ID: <539b4909.2090...@tds.net>
Content-Type: text/plain; charset=UTF-8; format=flowed
The problems with Astron linear power supplies have been known for
years. However, they can be modified inexpensively to be a good unit.
Info is still available at http://www.w5bwcelectronics.com
<http://www.w5bwcelectronics.com/>.The needed board can be had from
http://farcircuits.net <http://farcircuits.net/>. A description of my
modifications is on http://madisondxclub.org under INTERESTS -> PROJECTS.
I thought those power supplies were far too valuable to junk out.
Ed, N9MW
_______________________________________________
FlexRadio Systems Mailing List
FlexRadio@flex-radio.biz
To opt out of the Reflector:
http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
_______________________________________________
FlexRadio Systems Mailing List
FlexRadio@flex-radio.biz
To opt out of the Reflector:
http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
