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Cheap and Good 5v 1A supply
Cheap and Good 5v 1A supply
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Old 25th September 2021, 03:49 PM   #1
phase is offline phase  United States
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Default Cheap and Good 5v 1A supply

Recently while working with a $2 Bluetooth board, I found myself digging through my drawer of wall-warts, and found a Motorola 180-0711 power supply from an old Palm PDA.

The sound was so much better than the smps I had been using, I decided to open this linear supply and see what it had going on.
The supply not only had a regulator, but a pair of inductors, multiple capacitors, an ic, additional diodes. While I haven’t traced the circuit to analyze things further, I did add a snubber to the main diode, replaced the main cap after the diode, and added an X cap for the incoming A/C.

Highly recommended for users of 5v line level devices, are available for around $10-$15 on the auction site. These are about 20 years old and will likely need the caps replaced, but are a relatively good bargain imo.
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Old 25th September 2021, 03:52 PM   #2
jean-paul is offline jean-paul  Netherlands
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5v is 5V!

Linear PSU's outperform modern SMPS in many many cases. Now nearly at the end of the analog era many excellent regulators are produced that outperform that classic linear regulators. The old designs were not hampered by low part count and were often RF proof which is very nice. Their efficiency is not that good and some can be noisy (but way less than standard SMPS!). So a combination of a transformer, diode bridge and linear regulator can be lower in noise and lower in loss with todays regulators. There was a time that ALL wall warts/adapters were either transformer/unregulated or transformer with a regulator based.

Of the old designs the ones with LM723 are quite OK compared to modern regulators but only with regards to low noise.
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Last edited by jean-paul; 25th September 2021 at 04:01 PM.
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Old 25th September 2021, 04:14 PM   #3
jjasniew is offline jjasniew  United States
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Cheap and Good 5v 1A supply
I've been perusing for a 5V linear. My most probable buy; POWER SUPPLY 5V 3AMP LINEAR by HUGHES POWER PRODUCTS | eBay

However, I'd like the system to run on battery power too, which means dropping 15-20V at whatever current my pi plus I2S converter takes. Maybe have to dissipate 15-20W somewhere / somehow... Most probably, I'll be forgetting the battery power idea and just going with the AC powered linear. I could tap the battery string (2 12 volts) which would leave me ith "only" 7W to burn somewhere.

$22, new old stock, free ship, 3A will probably do it nicely.
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Old 25th September 2021, 04:16 PM   #4
jean-paul is offline jean-paul  Netherlands
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These are based on LM723 and they’re sold under various names but most are 100% equal. They can be very good. Some have slightly humming transformers though. Hard to find here but I have a few. New caps seems a wise choice.

For 5V 1A the ldovr TPS7A4700 PSU outperforms them while still being affordable. Smaller, lower loss/heat/noise.
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Last edited by jean-paul; 25th September 2021 at 04:23 PM.
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Old 25th September 2021, 07:22 PM   #5
phase is offline phase  United States
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I should have mentioned that with the smps I was also using the P089ZB filter. Turns out the compact Motorola wall wart is the best of itís kind and size that I have used. I just ordered another for $8.

That open chassis from Hughes Power Products looks like it could use a case, would likely be ok if it had the caps replaced since it looks quite old, as that company name predates the modern internet. I have a few similar to that here too, but theyíre for higher voltages.
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Old 25th September 2021, 08:03 PM   #6
jean-paul is offline jean-paul  Netherlands
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PO89ZB is nice but it is a plaster to an issue best avoided.

I think nearly all linear adapters vary from old to very old so replacing caps seems the first thing to do. The open frame PSU's have the bonus that they have an integrated heatsink. I have one new in box Power ONE 5V 1.5A version which is one of the best 5V PSU's I have seen.
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Last edited by jean-paul; 25th September 2021 at 08:07 PM.
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Old 25th September 2021, 09:18 PM   #7
phase is offline phase  United States
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Good to know regarding the Power One units, I have one of those I picked up at a surplus shop.
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Old 25th September 2021, 10:23 PM   #8
Fsatsil is offline Fsatsil  United States
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Maybe check eBay for used Accopian power supplies.
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Old 25th September 2021, 10:31 PM   #9
phase is offline phase  United States
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If you could make those clunky full chassis type PS units smaller and a available for $8, then Iíll be listening.

I mentioned the above unit as it was compact, performed well, and seemed more appropriate for those more basic devices that tend to be single 5v powered than a lab project.
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Old 26th September 2021, 01:01 AM   #10
v4lve lover is offline v4lve lover  Netherlands
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Cheap and Good 5v 1A supply
Quote:
Originally Posted by jjasniew View Post
I've been perusing for a 5V linear. My most probable buy; POWER SUPPLY 5V 3AMP LINEAR by HUGHES POWER PRODUCTS | eBay

However, I'd like the system to run on battery power too, which means dropping 15-20V at whatever current my pi plus I2S converter takes. Maybe have to dissipate 15-20W somewhere / somehow... Most probably, I'll be forgetting the battery power idea and just going with the AC powered linear. I could tap the battery string (2 12 volts) which would leave me ith "only" 7W to burn somewhere.

$22, new old stock, free ship, 3A will probably do it nicely.

Just picked up 3 of those from a local guy for Ä10 Ive seen these under four brands already. So i dont think that module is actually made by Huges, or there was some defacto standard for these kind of modules.
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