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.
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.
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.
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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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.
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.
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.
For 5V 1A the ldovr TPS7A4700 PSU outperforms them while still being affordable. Smaller, lower loss/heat/noise.
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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 it’s 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 they’re for higher voltages.
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 they’re for higher voltages.
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.
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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Just picked up 3 of those from a local guy for €10 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.
>Ive seen these under four brands already.
Yep, it seems identical to the SOLA liste here, used. SOLA SLS-05-030-1 POWER SUPPLY **FREE SHIPPING** 780333861188 | eBay
I bought the SOLA one, even though it was used. Looked like it was built better...
Yep, it seems identical to the SOLA liste here, used. SOLA SLS-05-030-1 POWER SUPPLY **FREE SHIPPING** 780333861188 | eBay
I bought the SOLA one, even though it was used. Looked like it was built better...
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It is industrial (read: military) stuff made by several OEMs, that is why they are almost identical. Old but good, no LDO and one needs a casing/IEC inlet.
@phase: 5V 1A is often not enough for streamers and then the linear 3A open frame PSU's may come in handy. The ready built Astron PSU's are also good (but difficult to find in the EU) for 12V applications. Please note that these manufacturers all jumped to SMPS long ago so more recent devices are in fact SMPS.
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My point in illustrating these more unique power supplies was that they appeared to be more of the exception for small (1A) supplies, with more of the benefits found in the larger commercial supplies.
If you’ve ever taken apart the typical (traditional) wall wart, you will usually only find a diode and a single cap. These have what appears to be a proper filter circuit using inductors, multiple caps, etc.
If you want to talk about larger supplies then maybe this thread isn’t for you.
I had purchased another one of these last week to play with, and will attempt to map out a schematic after I receive it.
If you’ve ever taken apart the typical (traditional) wall wart, you will usually only find a diode and a single cap. These have what appears to be a proper filter circuit using inductors, multiple caps, etc.
If you want to talk about larger supplies then maybe this thread isn’t for you.
I had purchased another one of these last week to play with, and will attempt to map out a schematic after I receive it.
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Mine actually have an output overvoltage crowbar present. Which is a nice feature if you want it to be bombproof, The 723 is a giant of a regulator kit too, said to be immune to RF which is nice.
Just bought them because i had to buy something, I was there for the tubes. Got me a master carton of 15CW5 for my birthday yesterday!
Just bought them because i had to buy something, I was there for the tubes. Got me a master carton of 15CW5 for my birthday yesterday!
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I think they all have the crowbar circuit. LM723 is very low noise even compared to todays regs but noise is only specified from 100 Hz to 10 kHz. Todays regs are much more wideband .... Please let's write stuff as intended. 5V 3A it is. Today I visited a flea market where I found a few linear PSU's of which one is a 13.5V 2.5A. They are not all scrapped it seems 
v4lve lover, if you can use the 12/15V 6A version... I am looking for the 5V 3A version...
v4lve lover, if you can use the 12/15V 6A version... I am looking for the 5V 3A version...
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