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  Astron Linear Power Supply
Main Filter Capacitor Values

By Robert W. Meister WA1MIK
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I have repaired several Astron supplies that had high amounts of ripple voltage on the cap or at the supply's output, or poor voltage regulation with a small load. They all used snap-in capacitors. There was no indication of physical damage until I removed the old cap. That's when I discovered a scorched area between the cap and the board, usually at the positive terminal. This terminal was also loose, and at times the capacitor would measure the proper value before removal.

Astron linear power supplies usually mount the main filter capacitor to the chassis with a clamp. The regulator board mounts to the top of the capacitor, either soldered directly (snap-in terminals) or held in place with #10 screws (screw terminals).

In general, SL supplies use snap-in capacitors. Most 35A and larger supplies use screw-terminal capacitors. I have 20A supplies with each type. Older supplies (pre-2000) at any current rating probably used screw-terminal capacitors. The variety in value among supplies of the same current rating is likely due to parts availability and cost.

If you have to replace a screw-terminal capacitor, you may find that the snap-in terminal style is more plentiful and far less expensive, however they are also physically much smaller, usually requiring a different clamp to hold them in place. The standard lead spacing for snap-in capacitors seems to be 10mm but the diameter and length do vary, so try to match those when selecting a replacement. The physical dimensions are more critical in SL-series power supplies where small size is a factor.

You may have to drill holes in an older regulator board to accept a snap-in terminal cap. The newer regulator boards already have these in addition to multiple slots or holes to accommodate the various screw-terminal spacing. Observe the polarity and double-check it before you solder the new cap in place. Fold the terminals over onto the circuit board foil before soldering them to provide some mechanical strength.

Astron 14V Linear Supplies:

Astron 14V linear power supply main filter capacitors are all 25VDC. The capacitance value is approximately 1.5K-2K uF per ampere of load current.

742KPerhaps 12K?

Astron 28V Linear Supplies:

Astron 28V linear power supply main filter capacitors are all 50VDC. The capacitance value is approximately 1.2K-1.5K uF per ampere of load current.


The above information was obtained from the Astron linear power supply schematics on repeater-builder.

Contact Information:

The author can be contacted at: his-callsign [ at ] comcast [ dot ] net.

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This page originally composed on 26-Jun-2016

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This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.