Mike: Your problem with the Astron 35 will most likely be a bad solder joint on the collector tab of one of the (4) 3771 transistors.
We keep reminding people that have problems with Astrons that this is where to look because it is a VERY common failure mode with those supplies and how they solder the buss wire from collector to collector. If you take a pair of pliers and grab the joint at each transistor and pull on it, you will most likely find one that will simply pull off. All it takes is for one of those transistors all wired in parallel to have a bad collector solder joint and all of the source current from the supply tries to flow through the Emitter-Base junction of that one transistor that has the bad solder joint. Bingo !!! Immediate current limit mode !! Ron WW8RR -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Mike Perryman Sent: Thursday, April 28, 2005 2:11 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: Triplite supply is a linear regulator type. I ordered the re-fit kit (regulation board, and 4 2N3771 transistors)... when it arrives, I plant to try and revive a RS35M that crowbared anytime any load was applied.... just look at it funny, and it would trip!! I guess we shall see how it goes.. This supply was removed about 2yrs ago from the now defunct Metro-Vision ATV System (RIP) in Springfield, VA. I read Skipp's comments, and decided the 44 bucks was worth a shot. I was, however, stunned to learn that Astron won't process a credit card to pre-pay. Had to send a check by snail-mail... still waiting. 73 mike -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of skipp025 Sent: Thursday, April 28, 2005 2:01 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Triplite supply is a linear regulator type. I'm also running the same supply, the non rack mount version. (Just mounted and secured on a rack shelf) I tested the supply pretty well, it still works fine and runs very cool for the remaining duration of its stay. Got to love that burst electrolytic smell and goo. Too bad the crowbar didn't fire. Before Astron's latest pc board upgrade (which uses my suggested pre-regulation circuit approach), they also needed a crowbar circuit that worked. (the early crowbar design was much subject to mis-fires and not-at-home no fire operation). Both the regulator pre-regulation and crow bar circuits in newer Astron Supplies have been re-engineered and updated. I now consider the current generation of Astron Analog DC Power Supplies to be much more reliable. cheers, skipp > DCFluX <[EMAIL PROTECTED]> wrote: > I should mention that I run a 40 amp tripplite > power supply non-rack version. > > About a year ago it blew the PA and controller on my 64 repeater. For > some reason the crow bar refused to fire and short out the supply > > The problem was electrolytic capacitors that were 16V in areas where > 25 volts and alot of ripple are present. Tripplite is famous for not > giving out schematics, but what I can tell is these caps were > filtering the AC voltage from the transformers secondary tap for the > main PCB. You can also put a voltmeter on AC and touch the output > terminals and measure the "ripple" I think it was at 350mV for me > before exploding and about 15mV now. > > I don't know what failed first but I had the capacitors explode and > spray electrolyte on everything in the case. I had to replace all the > active components on the PCB, the 4 pass transistors and the 2 > capacitors on the PCB, used 35V parts this time. > > Feel the face of the power supply, if it is about 130-140 degrees, you > may have a problem. I thought it was normal, but on repair the face is > running fairly cold. > Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
