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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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5th Oct 2022, 3:00 pm | #21 |
Heptode
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 539
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Re: Homebrew PSU Problems
I purchased a linear PSU kit from Banggood based around the LM317. Performance was weird and erratic. I dug out an old genuine Nat Semi one from the spares box and all the problems vanished.
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Alan G6PUB, BVWS |
5th Oct 2022, 6:02 pm | #22 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,302
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Re: Homebrew PSU Problems
Going back to the question of are they fakes, check the voltage between the adjust pin and output, this should be 1.25V, if it reads about 0.7 then you have been sold a simple transistor and it's working as an emitter follower, this will give a variable output but with no protection.
Just a thought Peter |
5th Oct 2022, 7:26 pm | #23 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
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Re: Homebrew PSU Problems
Quote:
0.663v on diode check Cheers Jay
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Help!! I've been electrocuted by a glass thing that glows Last edited by Radio Scotland; 5th Oct 2022 at 7:30 pm. Reason: extra info |
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6th Oct 2022, 9:20 am | #24 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,302
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Re: Homebrew PSU Problems
I actually meant when the regulator is on and working but a diode test of 0.6 certainly looks like you have been sold transistors labeled as regulators, fakes in other words.
Peter |
6th Oct 2022, 9:29 am | #25 |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,088
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Re: Homebrew PSU Problems
It would also be of the opposite polarity!
LM317 has its adjustment pin 1.25V -ve to output terminal, whereas an NPN transistor would have the base 0.6 V positive to output terminal (emitter). I've never had any problems with the LM317 except a bit of noise. And I've used lots - they're one of National Semiconductor's triumphs! |
6th Oct 2022, 10:15 am | #26 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
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Re: Homebrew PSU Problems
Wouldn't be the slightest bit surprised, Bought them direct from china a few years ago, I'm actually planning on using the LM338 But they seem to have vanished in the post
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Help!! I've been electrocuted by a glass thing that glows |
6th Oct 2022, 11:25 am | #27 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
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Re: Homebrew PSU Problems
Yup surprisingly enough they seem to be genuine, As tha'ts the voltage I'm getting between adjust and the output
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Help!! I've been electrocuted by a glass thing that glows |
7th Oct 2022, 7:42 am | #28 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,302
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Re: Homebrew PSU Problems
Interestinger and interestinger,
At this stage I would try the following Try an LM317 from a different source. Try the regulator circuit on a bench power supply, not the battery charger, to narrow down the problem. And try as Sideband says in post 13 to mount the capacitors as close to the regulator as possible. Peter |
7th Oct 2022, 11:01 am | #29 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
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Re: Homebrew PSU Problems
Quote:
Jay
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Help!! I've been electrocuted by a glass thing that glows |
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8th Oct 2022, 10:20 pm | #30 |
Nonode
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,171
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Re: Homebrew PSU Problems
Are you using your homebrew PSU to charge batteries?
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8th Oct 2022, 10:23 pm | #31 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
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Re: Homebrew PSU Problems
No. It's just a general power supply for projects etc.
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Help!! I've been electrocuted by a glass thing that glows |