Astron schematics

Discussion in 'General Technical Questions and Answers' started by N1BUZ, Sep 8, 2012.

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-rl
ad: l-gcopper
ad: Subscribe
ad: L-rfparts
  1. N1BUZ

    N1BUZ Ham Member QRZ Page

    I need a schematic for an Astron Model SS-25 power supply, astrons site sucks
    and I urge all hams to boycot astron triplite and any other company that does not support us. Why because even the rig manufacturers provide schematics, so should they. My ss25 blew a cap need to know what it was as well as the
    the part beside it.
  2. K8JD

    K8JD Ham Member QRZ Page

    I installed hundreds of astron supplies and in every box was a sheet with the schematic on it !
    Did you just throw away yours?
  3. K9STH

    K9STH Ham Member QRZ Page

    One thing to do is to tape the schematic inside the cover just as soon as the box is opened! That way, you will have the schematic available when you need it!

    Glen, K9STH
  4. K8JD

    K8JD Ham Member QRZ Page

    I had a thick folder in a desk drawer in my bench filled with the schematics & parts lists for various power supplies, voltage and polarity convertors made by Astron etc...
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    In my experience, if you want an Astron schematic, just call them and ask and they'll send it to you. And as others have said, usually when you buy one new, it comes with the schematic.
  6. KM3F

    KM3F Ham Member QRZ Page

    I think your in over reaction mode just because you don't have a drawing, on the first thread post.
    Go to a website called
    Click on Astron and go down the page until you come to your size.
    There is all kinds of info on these supplies for mods, repairs etc.
    The only difference between a 20 and a 35 amp or other sizes would be the transformer and rectiifer current handling and the pass transister dissapation design rateings.
    Caps, regulators and many componants are still all the same for 14 volt operation no matter the current capacity.

    Good luck
  7. W9GB

    W9GB Ham Member QRZ Page

    Ransom --

    Information is available, from Internet sources and the amateur radio community.
    ASTRON is the one of the better companies for documentation support.

    Dumbing down "appliance mentality" ... means the typical 21st century radio amateur is just another consumer (No tech talent) ...
    for manufacturers and support adjusted to this mentality.

    NOW, you are dealing with a Switch-Mode Power Supply (SMPS), not the easier the repair Linear power supply designs.

    Repeater Builder Technical Information Page -- Astron, SS-25 and SS-30 share large number of parts
    ANYTHING you ever wanted to know about Astron can be found there.

    From Eric Lemmon, WB6FLY:

    The MU1 intergated circuit (IC) used in the Astron SS-30M power supply
    is the "workhorse" Pulse Width Modulation (PWM) chip TL494CN (33 cent part).

    The IC is mounted on a module that is about 1.25 inch by 1.75 inches and
    has nine header pins on one end that are soldered into the main PCB.
    All of the reference numbers that begin with "M" are mounted on this module.
    I examined the parts on the module and identified them as follows:

    MC1 - 50 uF 10V electrolytic
    MC2 - 0.1 uF Mylar
    MC3 - 0.022 uF Mylar
    MC4 - 0.001 uF Mylar

    MR1 - 10 k
    MR2 - 8.2 k
    MR3 - 2 k
    MR4 - 15 k
    MR5 - 150 k
    MR6 - Zero Ohm Jumper
    MR7 - Not Used

    MD1 - Not Used
    MD2 - Not Used

    The switching frequency is fixed, and is set by MC4 and MR4, which are connected to IC pins 5 and 6 of the TL494CN.
    With those values, the switching frequency works out to be about 73 kHz.

    I could not identify most of the resistors on the main PCB, because the designators were under the components and could not be seen.
    I did notice that diodes D23 and D24 were not used; the 12 VDC cooling fan is controlled by a thermal snap switch on one of the heat sinks.
    A similar thermal switch, on the other heat sink, will open the AC input line when triggered.

    Neither thermal switch appears on the schematic which came with the unit.
    As is typical with Astron schematics, it is "representative" of the circuitry, but it is by no means perfectly accurate.
    Last edited: Sep 9, 2012
  8. WA7KKP

    WA7KKP Ham Member QRZ Page

    Don't complain -- most hams don't even look inside their radios or power supplies, so having a schematic is quite often a waste of time, effort, ink and paper. Most times corporations won't post service info because the consider their schematics/repair manuals proprietary, and would rather have the customer send it in for service.

    Astron is well - known for their power supplies, and they have used a standard design with the LM-723 and NPN pass transistors in darlington for years. Why? It's simple, and almost bullet-proof. Having home-brewed regulated power supplies over the years, the design really can't be beat.

    If you are "Technically inclined" as I have been for 40 years (my bread and butter) . . . get the service manuals for everything you own. Most of the new stuff with surface-mount stuff is beyond my skills, but at least I've got it for someone who can handle SMT with the proper tools.

    Gary WA7KKP
Thread Status:
Not open for further replies.

Share This Page