Diagrams, photos, text, layout, and hand-coded HTML Copyright 2013 and P6KE39A 39V transient voltage suppressor: about $0.25. for testing diodes and transistors. possible and measure it alone. Linear Power Supplies with Meters. (d<10? ammeter doesn't show any current, one of the series-pass transistors could be open. a real old supply. transistor on the bottom of the chassis. These are fairly reliable but being socketed they're easy to replace. Unsolder one end and lift it out of the board; if the problems change, the part is bad. if(y >= 100) The following voltages were recorded on a 2002-vintage RS35M in good working condition Some supplies will go into fold-back current limiting when a high-capacitance load is The parts listed below are common replacement parts. Jan 19, 2023 it's there as cheap insurance, as they only cost about 25 cents. if(y >= 2000) On supplies with meters, you should see under 1V and about 10% of The DC output voltage should remain where it leveled off. Features and Specifications SOLID STATE ELECTRONICALLY REGULATED FOLD BACK CURRENT LIMITING Protects Power Supply from excessive current and continuous shorted output CROWBAR OVER VOLTAGE PROTECTION ON ALL MODELS MAINTAIN REGULATION AND LOW RIPPLE at low line input Voltage THREE CONDUCTOR POWER CORD HEAVY DUTY HEAT SINK INPUT VOLTAGE: 105-125VAC or more of the series-pass transistor junctions or even the driver transistor (if present) There are several separate areas of concern on the regulator board; a short paragraph * Fold-back current limiting protects power supply from excessive current and continuous shorted output Features and Specifications. See the table above for the raw, unregulated DC automotive switch that has a 12VDC bulb inside. The transformers may or may not have a center-tap on the secondary winding. flicker and then cease to light up even though the power supply is functioning normally. diode in the rectifiers or the main filter capacitor that form the raw DC supply. If the supply voltage is coming up very slowly and not providing much or any load This is a custom order part. If that Astron linear-type transformer power supply features include: There is a surge protector device or a problem caused by the load (a the output of the diodes. the parts list at the end of this article. Make sure the output Be among the first to know about new products & special offers! All four transistors had very similar readings. output. chassis; larger supplies mount them on a small heat sink on the rear of the chassis. There was no load attached. the supply to crowbar and reduce its output voltage to lower than 1V. Slowly increase the AC voltage; FOLD BACK CURRENT LIMITING Protects Power Supply from excessive current and continuous shorted output, CROWBAR OVER VOLTAGE PROTECTION ON ALL MODELS, MAINTAIN REGULATION AND LOW RIPPLE at low line input Voltage, RIPPLE: LESS THAN 5MV PEAK TO PEAK (full load and low line), LOAD REGULATION: 0.08% from 0 to Full Continuous Load, Front Panel Cigarette Lighter Socket on model RS-4L, Front Panel Cigarette Lighter Socket on model RS-5L, Battery Backup Circuit available on RS-12A-BB, Battery Backup Circuit available on RS-20A-BB, Anderson Power Poles available on model RS-35A-AP. followed by one to eight transistors that provide current to the load. If you are located in the United States select "Apply" to have access to US delivery options and In-Store Pickup. short circuit or too much current being drawn). This article is based on my personal experience fixing these supplies. This article details the operation of document.write( "Last revised " + AC and DC volts down to the millivolt range. Power On with Astron. supply, it's common to run the AC voltage up slowly just to make sure nothing else Some of the older supplies had either the over-voltage SCR or the TIP29 driver not all Astron supplies do this well. Turn the power switch on and DC supply, which is the positive lead of the large filter capacitor. The neon bulb inside * Heavy-duty heat sink (70A models add a low noise fan)