i'm a beginner, go easy on me, literally copying saarmichels amp: LJM Audio
bought the same smps and same L20.5 modules, wired them IDENTICALLY as he did (sans the switch at this point in time on the bench)
however the smps had to be modded to be 110V from the ebay vendor (grey wire in pic)
when i kill AC to the mains on the smps, it takes like 2-3m to discharge to below 2 VDC on the output (without the amp connected), and with amp connected, its much quicker, but still enough in the line to make choppy music through the amp, with the music cutting in and out until it finally dies (takes 15-20s)
is this normal? am i missing a bleeding resistor somewhere? did the 110v mod bypass something unexpected?
also, based on stock images, its possible i'm missing a potential inductor as well?
any help would be greatly appreciated!
bought the same smps and same L20.5 modules, wired them IDENTICALLY as he did (sans the switch at this point in time on the bench)
however the smps had to be modded to be 110V from the ebay vendor (grey wire in pic)
when i kill AC to the mains on the smps, it takes like 2-3m to discharge to below 2 VDC on the output (without the amp connected), and with amp connected, its much quicker, but still enough in the line to make choppy music through the amp, with the music cutting in and out until it finally dies (takes 15-20s)
is this normal? am i missing a bleeding resistor somewhere? did the 110v mod bypass something unexpected?
also, based on stock images, its possible i'm missing a potential inductor as well?
any help would be greatly appreciated!
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All sounds normal to me. If the amp has a low quiescent current draw then it will run for quite a while on stored energy in the PSU caps. There may not even be any bleed resistor, it could be your meter discharging the reservoir cap.
The real issue is that the amp needs an effective speaker muting circuit to disconnect the speakers at power off. Such things should really be a part of a design rather than something that needs to be added later.
The real issue is that the amp needs an effective speaker muting circuit to disconnect the speakers at power off. Such things should really be a part of a design rather than something that needs to be added later.
Many of these switch-mode power supplies turn on and off with an enable signal, in a similar way to an ATX PC power supply - you ground the right wire to turn it on. Then the outputs come up/down in a fast, clean way. Perhaps it's not engineered to behave as well when switching the AC line on and off. I cant see what the little blue connector is / does at the edge of the board - is this the "enable" input?
You did say "sans the switch". Perhaps if you hook that part up?
Many PSU vendors support a variety of designs using just one PCB layout. I notice your 110V unit has a couple of inductors the stock photo doesnt, so I'd say the missing components are not needed for the design you purchased. I wouldnt worry about that part...
Efficiency is paramount in SMPS designs; bleeder resistors on the PSU board detract from that measurement. So these vendors leave that part to the system engineer to choose an appropriate value for a bleeder - and include it as part of whatever it is the PSU is powering. Perhaps this wasnt considered by LJM Audio; I didnt see a schematic right at the link you posted, but you can check for a bleeder as part of the amp design.
You did say "sans the switch". Perhaps if you hook that part up?
Many PSU vendors support a variety of designs using just one PCB layout. I notice your 110V unit has a couple of inductors the stock photo doesnt, so I'd say the missing components are not needed for the design you purchased. I wouldnt worry about that part...
Efficiency is paramount in SMPS designs; bleeder resistors on the PSU board detract from that measurement. So these vendors leave that part to the system engineer to choose an appropriate value for a bleeder - and include it as part of whatever it is the PSU is powering. Perhaps this wasnt considered by LJM Audio; I didnt see a schematic right at the link you posted, but you can check for a bleeder as part of the amp design.
yeah, so i'm using the L20.5 amplifier, and the power supply actually has a speaker protection circuit that the blue connector in the lower right i connected to, maybe it doesnt have the proper mute you've talked about
that is a built in speaker protection circuit, here is a quote from the vendors page
Open-loop half-bridge structure, instantaneous output current up to 2-3 times the normal current, output voltage of about +/-58V, with short circuit, overcurrent, overvoltage protection, and the midpoint voltage amplifier speaker protection, power amplifier midpoint voltage abnormal shutdown output voltage.
the switch used in saarmichels post is just a AC on/off, so i've just been using a kill switch on my power strip
yeah, im getting all the proper voltage and such from it, so i assume it's working properly on that end, but the bleeding is slow, so i didnt know if something was missing or being bypassed
yeah, worth noting when this is connected to the amplifier, it dies quickly, however, when it gets turned off, the speakers still play some as the reserves empty
here is maybe some further detail on the SMPS: Page Not Found - Aliexpress.com