Decoding the Mystery: Understanding Astron PSU Failure Mode
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- Опубліковано 30 гру 2023
- In this video, I share some up-close details about the Astron RS-35M-AP Linear Power Supply. I ended up replacing the regulator board, but it wasn't as easy as that sounds. There might have been mistakes made along the way!
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I am happy that you got the multiple issues sorted with Mr Hollywood, Jeem.😊
However, I don't think I'll ever buy one of these amps with the poor design and quality control of them. I agree with everything you said and yes, for a premium brand, you simply shouldn't get the issues and flaws.
Good luck with it and happy new year from the future in 2024, Jim.🍻🤠🇦🇺
Well that's the last astron I buy. Thanks for the info and the hard work.
Astron used to put binding posts on their 12amp and 20amp supplies, The main failure I saw was the 723 chip going bad, so I started installing a socket. whenever replacement was needed. I heard recently that 723 ic's were no longer being made, and Astron had redesigned their regulator board. Thank you Jim!
I grabbed a pack of them, can';t remember if it was mouser, or amazon. Thankfully mine was socketed.
I'm glad you solved it and shared the solution with us!!!
nice work. glad you figured it out. i have fixed many power supplies over the years .lost count. started in 1976 or so. been fixing them building them. not just 13.8V ones either. most Astron ones have them bolt studs for power. the newer ones have power poles. they have insulating caps for them TO-3 transistors. I add heat shrink to AC leads . easy to do. most of them supply's are that way. most of failures I see is power surges and made with cheap sub standard parts. and over loading . like buying a 15 amp to run a Icom 7300. at full power that peak 21/22 amps. I add MOV or GDT surge protection often. some of that old thermal compound goes bad and dries out making transistors heat up to much. I clean them and re due. using thermal camera to check them. also some times them bridge rectifiers go bad. mostly on Pyramid and China brand ones. with that one in video with them 2 rectifiers mounted to cabinet bottom ,If you have them go bad replace them and add a piece of aluminum or copper to work as a heat sink and use that thermal compound. I have bigger replacements I use. never had a replacement bigger one fail yet. you would love the 200 amp cont./250 amp surge one I bult. it linear 723 IC based and 30 2N 3772 transistors. fan cooled. 4 50 amp transformers. 240V ac in. made in 1988 around. never failed. big and heavy. 1 person can't lift it.
73's
Thanks for watching my struggles! I think the original problem was a bad solder/short in one spot, barely making bad touches ! In my troubleshooting (admittedly, blazing a trail), I also induced another problem initially.
You can 3D print covers for the transistors and cover for the power posts.
I have a Astron RS-12A I picked up at Goodwill. With no load it measures 14 volts, but as soon as any type of load, no matter how small, it drops to 7 volts. When I get time I need to tear it apart.
Good videos on repairing the power supply. These have been around forever.
You can check the pass transistors pretty easy, don't even have to take the cover off. Next, I'd replace the 723 chip (hopefully yours is socketed.). Those are cheap components and not involved to replace.
Check out SevenFortyOne's channel, he has a couple of good videos on his troubleshooting process for Astron's.
Ron - I went and grabbed them off thingiverse, I have covers on all of it now. Transistors, and the posts on the back. Thanks for watching!
Thanks for the video, Jim. I really needed closure on that problem.
Happy to help Jim. More lessons, anytime you are up for it. 73 & Happy New Year!
Thank you for the assist. I'd probably still be swearing at it...Happy New Year!
I have had this model for 35 years without issues. Thank you Jim! And happy New Year!🎉
Always good to take pics during disassembly specifically if you don't have a good manual. I would also always replace the pass transistors in pairs if they are set up as a darlington pair. Just my thoughts from my experiences. It was definitely a learning experience. Great series you ought to put it together as one. thanks Jeem! 73
Jeff, I have NO idea why I didn't. That would have been easier than all those labels. Yeah, when I smoked one of the transistors, I looked up the parts, and they weren't crazy expensive, I figured I'd just get all of them, and eliminate the issue from cropping up later.
I have an electrical engineering degree and experience with power supplies and I had to go through the exact same process to get my Astron RS-20M back to life (after it was I who put it out of service by trying to “voltage-charge a lead acid battery with the thing-not good with this machine). So don’t feel as if anyone else would have brought more to the table than you did. A mixed blessing, these Astron power supplies: they last for a while in normal use-don’t ask more of it than intended and careful trying to modify because they weren’t designed to be “modified.” But when they quit you have a devil of a time troubleshooting-they were designed (somewhat) well but not for troubleshooting. It’s all crammed into the case with no convenient test points between stages. I was to the point of scrapping this thing and scavenging parts but tried one more thing and behold, didn’t blow the fuse again and DID show 13.2 volts out. This thing could last ANOTHER 10 years. Worth fixing because they’re so expensive but boy, do they suck up bench time. Keep up the good work!
I had a lot of good help out of a buddy (Hollywood) when I was working on it. It was at the far edge of my skill level. Turned out to be a little more than parts swapping, but glad I got the beast fixed. It was still under warranty, but I just didn't want to hassle with that, and figured it might be a decent enough video while I struggled through it all. Thanks for the good words, and thanks for watching!
I’ve always thought of Astrons as high quality supplies. Looking at the inside of yours, I can’t say I’m overly impressed with their workmanship.
Tom - right?? I thought Astron was high-end gear. Looking in that one (I'm afraid to look in my other one), I was really put out with the functional(ish) job, but sloppy layout and soldering jobs. That damn wire pushing against the transistor solder was just inexcusable.
Cool , good luck with the power supply 😊
The stud or bolt connections can carry much more power than a binding post. Binding post will have melted long before the bolts even get warm. All of my high power lab supplies made by HP have studs/bolts on the back for output. HP used bolts for a reason, current carrying capacity and connection reliability. No matter how hard you try you just can't hand tighten a binding post as tight as you can a bolt and nut. It's so easy to move wiring around and unknowingly loosen the binding post. Try to do that with a stud connection you tightened with a wrench.
Probably so, but I still think exposed hot terminals is poor design. I ended up 3-D printing a cover to go over it, so nothing lands on those studs and shorts them out.
@@FEPLabsRadio That's one thing high current lab supplies have that the Astrons don't, terminal covers.
Well, I won’t be buying an Astron power supply. Thanks for the update.
I have 2, and to be fair, this was under warranty, I took the hard route on it. However, it was not super quality I saw inside. My buddy called it "MFJ quality" on the wiring and solders. I'd say it's Cadillac pricing and Pinto construction.
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Oh gee I just bought one of those, I hope I don’t have the same problems
Bob, I have another one, and it has been flawless since I got it. I hope this was just a glitch in their wiring process, and not all of them are that sketchy. Still, I was not super impressed with what is supposed to be a premium supply. Cadillac money, Pinto quality
God bless Hollywood
Thanks Ape. Jim really did learn quite a lot in that cram session and is an excellent student. 73 & Happy New Year.
@@WECB640 Happy New year to you as well 👍
Nice video Jim and a great update. But, I have to say, I cringed everytime you stuck your fingers in there. Stay safe there nemesis 😉
Looks like 1980's engineering and implementation... not really what you'd expect of a a modern premium product in today's litigation-averse world. You have to wonder when the last time this unit was presented for UL, CSA, or ETL review.
Right? I expected a lot better than what was in there.
Binding posts will carry less current, and are less secure physically. That is, the nuts on the studs take a wrench and stay put better than binding posts.
Plus, it's only 13.8V. On the back. Away from children (right?). So, who cares?
I found 3-d covers that I printed out to pop over those parts. Yeah, no kid around the backside, but I also don't want to bump it against something (or vice-versa) and let the magic out. Call me paranoid.