Maynuo M8811 inside pic

[crt]

Just get my Maynuo M8811 Progammable DC Supply 
here is the picture inside it (sorry for poor quality photos)

1. SyncMOS SM5964
2. Analog Devices AD7718B
3. Burr Brown DAC7631E (2 pcs)
4.. BU508A (4 pcs)
5. Texas Instrument REF5025
6. Bunch of  Texas Instrument OPO7C
7. Texas Instrument LM324 (2 pcs)
8. Yangjie Electronic KBU8D (2 pcs)
9. On Semiconductor LM7805/7812/7912
10. Some of IRF740 an TIP41C

[saturation]

Nice!  You've also zeroed in on key parts immediately, very nice executive summary.  Its listed as a 'source meter' so now how is  performance?  The spec sheet says output with 10-100uA stability.

[cosmos]

Was it well calibrated when you got it?

If not then calibration can be initiated by doing (note you need a  6.5 digit meter as reference) 

"shift" "up" "Down" "enter"
it then asks for a key:
enter "6666" and  "enter"
display shows CAL

here are four types (that I know of) of calibrations:

readback V "V-set" button + connect a 6.5 digit voltmeter to the Vout terminals, M8811 generates the voltages, just enter what the external meter shows + "enter".

readback I "I-set" button + connect a 6.5 digit amp meter with 3A  range to the Vout terminals, M8811 generates the currents, just enter what the external meter shows  + "enter". (if calibrating a higher current version of the M88 series be sure to use an amp meter that can do near the full range setting, M8811 is rated at 5A and mine calibrated with 2.4A)

remote sense "Recall" button + connect a 6.5 digit voltmeter to the Vout terminals and connect the remote sense there too, M8811 generates the voltages, just enter what the external meter shows  + "enter".

DVM "Save" button + connect a 6.5 digit voltmeter to the Vout terminals and to the DVM inputs, M8811 generates the voltages, just enter what the external meter shows  + "enter".

power off and on again and calibration is done.
You can do the calibrations one by one.

[cosmos]

I wrote a bit about the M8811 in another tread.

https://www.eevblog.com/forum/suggestions/maynuo-bk-precision-dc-power-supplies/msg260250

[saturation]

Thanks cosmos, I missed your review.  Recently I find on this forum that if you log on but do not read all the new posts at the same time, the next time you log on the new posts shown are now new relative to the last log on, so all those prior posts are not listed.  I will ask mods what to do.

[cosmos]

It was perhaps a mistake to write in the other tread, there was no other related to the M8811 at the time so I put it there. Shaping it as a review I later realised I should have made a new tread instead of having it end up under suggestions for Dave to review.. sry

[crt]

@saturation

I just get them, so i even not playing with them 
anyway, how to do a proper test on this DC Supply ?
p.s
(i have a scope (poor one) and DC Electronic load


@ cosmos

I did not doing any calibration
6.5 digit Multimeter ?! ==> look's like i will leave them as-is

at first power on, it show about 0.0011V and maybe take about 15 minutes to settle 0.0000V

Have you try to use software/pc connection to control M8811 ?
it showing "working normally" but i can not set Voltage neither Current via PC software knob
I already mail maynuo, but till now (3 days) still no response   

[metalphreak]

You should see the RX/TX status indicators on the software constantly blinking when it's connected properly.

Double check the baud rate and ID number set in the software matches the power supply. Also check the COM port and that the drivers for the USB cable have been installed properly.

[saturation]

A sample of thorough test was done by many members on different supplies within the forum archives.  I think we discussed it also on the Power Designs precision supplies since they are close to source meters by today's definition of their capabilities.

Essentially, confirm all the specs of your unit: load and line regulation, input protection, overload protection etc., to insure it lives up to its spec sheet; cosmos has done quite a bit in his review.  In addition check the overshoot voltage at turn on.

Since this unit is sold as a 'source meter', it should act close to a theoretical current or voltage source and provide stable low ripple output at 30V and A ~0, since you cannot get zero amps in real life, see how low  can be A before the unit cuts off.  Since the resolution is 10-100uA, you should be able to dial down to uA levels and lower while outputting 30V.  Likewise the reverse check response at 5A, V~0.   

Enjoy your tests!

@saturation

I just get them, so i even not playing with them 
anyway, how to do a proper test on this DC Supply ?
p.s
(i have a scope (poor one) and DC Electronic load


@ cosmos

I did not doing any calibration
6.5 digit Multimeter ?! ==> look's like i will leave them as-is

at first power on, it show about 0.0011V and maybe take about 15 minutes to settle 0.0000V

Have you try to use software/pc connection to control M8811 ?
it showing "working normally" but i can not set Voltage neither Current via PC software knob
I already mail maynuo, but till now (3 days) still no response   

[crt]

Essentially, confirm all the specs of your unit: load and line regulation, input protection, overload protection etc., to insure it lives up to its spec sheet; cosmos has done quite a bit in his review.  In addition check the overshoot voltage at turn on.

Since this unit is sold as a 'source meter', it should act close to a theoretical current or voltage source and provide stable low ripple output at 30V and A ~0, since you cannot get zero amps in real life, see how low  can be A before the unit cuts off.  Since the resolution is 10-100uA, you should be able to dial down to uA levels and lower while outputting 30V.  Likewise the reverse check response at 5A, V~0.   

I had try test with 30V (no load) ==> voltage starts to drop about 0.00096A
But How to test 5A at V~0 ?

I will try to put them on DC LOAD to see dynamic response

[crt]

Dynamic response at 8VDC
0.1A @ 1mS
2.5A @ 1mS

Voltage turn-on
@30V/5A

Don't know is this  or 

You should see the RX/TX status indicators on the software constantly blinking when it's connected properly.

Double check the baud rate and ID number set in the software matches the power supply. Also check the COM port and that the drivers for the USB cable have been installed properly.

I have install USB driver and RX/TX was blinking constant
here's screenshoot

[saturation]

Thanks!  Its better if you load the PSU to make these tests, since you have a DC electronic load, that's ideal.  You could set the e-load to constant voltage at 30V, then gradually reduce the output current from the PSU until it cuts off.  Your report of ~ 1mA sounds reasonable, but is it to spec?  That's a test of the unit as a voltage source.

Likewise set the eload for constant current at 5A, and reduce the PSU output voltage until it cuts off.  That's a test as a current source.

That turn on voltage looks good, no spikes.  Try it at a small voltage you might practically use, like 1.25V, and insure it doesn't spike.  Repeat the off-on procedure many times to insure switching multiple times and the discharging output capacitor does not cause it to glitch.

Essentially, confirm all the specs of your unit: load and line regulation, input protection, overload protection etc., to insure it lives up to its spec sheet; cosmos has done quite a bit in his review.  In addition check the overshoot voltage at turn on.

Since this unit is sold as a 'source meter', it should act close to a theoretical current or voltage source and provide stable low ripple output at 30V and A ~0, since you cannot get zero amps in real life, see how low  can be A before the unit cuts off.  Since the resolution is 10-100uA, you should be able to dial down to uA levels and lower while outputting 30V.  Likewise the reverse check response at 5A, V~0.   

I had try test with 30V (no load) ==> voltage starts to drop about 0.00096A
But How to test 5A at V~0 ?

I will try to put them on DC LOAD to see dynamic response

[free_electron]

BU508 ? what the hell is that doing in a linear supply ... those are switching transistors designed for horizontal deflection and SMPS in old Tv's .

those things have virtually no gain and need humongous base currents to kick em on...  weird design...

[cosmos]

I do not have the unit here so I can not make better pictures (I am on vacation).

I found this picture from when I had it open, (shrunk size 7:1 for posting here so hope details are still ok).
The BU5 legend of the part is visible and the package seems to fit BU508 too.

The text beside the large capacitor is interesting, it seems to say it can be mounted with 63V 10000uF or 160V 4700uF or 250V 2200uF.

If the target is only to have a single robust (and low cost?) bipolar transistor type (load sharing) that can handle large currents and voltages up to 200V+ with margins, and where the base current anyway goes to the load then the BU508 might still be a sensible alternative.

Soldering quality leaves a bit to be desired.

[Christe4nM]

I think we're looking at a full wave bridge rectifier here.

[cosmos]

I am not talking about the rectifier, the BU5xx is the one at the right upper corner.
As I said, I can not make new photos now and this was the best example I found showing both the BU5 legend and the silk near the larg cap, sorry that the rectifier seems to be the component of interest.

[metalphreak]

The text beside the large capacitor is interesting, it seems to say it can be mounted with 63V 10000uF or 160V 4700uF or 250V 2200uF.

They probably use a common board for all the different variations. They do a PSU that goes to 75V and I believe one that hits 150V as well.

[Christe4nM]

I am not talking about the rectifier, the BU5xx is the one at the right upper corner.
As I said, I can not make new photos now and this was the best example I found showing both the BU5 legend and the silk near the larg cap, sorry that the rectifier seems to be the component of interest.

My bad, I read BU...8D on the rectifier and assumed that was the component you were talking about. (Which indeed seems to be the component of interest ) Stupid really, since I should now by now that there will be no component markings where the hole for the screw is and ..BU8D is different from BU5x

[crt]

Thanks!  Its better if you load the PSU to make these tests, since you have a DC electronic load, that's ideal.  You could set the e-load to constant voltage at 30V, then gradually reduce the output current from the PSU until it cuts off.  Your report of ~ 1mA sounds reasonable, but is it to spec?  That's a test of the unit as a voltage source.

Likewise set the eload for constant current at 5A, and reduce the PSU output voltage until it cuts off.  That's a test as a current source.

That turn on voltage looks good, no spikes.  Try it at a small voltage you might practically use, like 1.25V, and insure it doesn't spike.  Repeat the off-on procedure many times to insure switching multiple times and the discharging output capacitor does not cause it to glitch.

Try it with 5A Load, and current starts to drop about 0.292V

And this is with 1V/5A Load, turn on voltage
(i had repeat 3 times and zoomed, and its have a same behaviour)

about previous dynamic load i posted, it is good or bad ?

[saturation]

Thanks a ton for that crt, the turn on waveforms are good; the key is no overshoot; overshoot can fry your circuit, but not undershoot.

The current sourcing is fine, its a bit on the 'high' side but for practicality is more than fine. 

The application are fairly narrow for that low voltage but if you work in such areas, ultracaps, piezo crystals etc., at least you know what the limits are for that unit.

FWIW, the power designs precision supply can output its rated current down to ~ 3mV before it rolls off, compared to your unit of ~ 292mV.

https://www.eevblog.com/forum/testgear/looking-for-goodinexpensive-bench-power-supply/msg105910/#msg105910

I think robrenz was able to push his output voltage even lower, just because ...

Your dynamic test is good, what it shows mostly is transient response because a true dynamic test must be under load.   You should program the PSU for 10V/5A and the eload to 10V 5A, then 10V .05A alternating say at 1 sec intervals, and check if the PSU actually produces that output and the response waveforms; this can be very stressful on PSU and can damage them if you do this for long periods.  That load will simulate radio transmission [ or cellphones if you set it to 3.5V instead] alternating between send and quiescent.

 

[crt]

Thanks a ton for that crt, the turn on waveforms are good; the key is no overshoot; overshoot can fry your circuit, but not undershoot.

The current sourcing is fine, its a bit on the 'high' side but for practicality is more than fine. 

The application are fairly narrow for that low voltage but if you work in such areas, ultracaps, piezo crystals etc., at least you know what the limits are for that unit.

FWIW, the power designs precision supply can output its rated current down to ~ 3mV before it rolls off, compared to your unit of ~ 292mV.

https://www.eevblog.com/forum/testgear/looking-for-goodinexpensive-bench-power-supply/msg105910/#msg105910

I think robrenz was able to push his output voltage even lower, just because ...

Your dynamic test is good, what it shows mostly is transient response because a true dynamic test must be under load.   You should program the PSU for 10V/5A and the eload to 10V 5A, then 10V .05A alternating say at 1 sec intervals, and check if the PSU actually produces that output and the response waveforms; this can be very stressful on PSU and can damage them if you do this for long periods.  That load will simulate radio transmission [ or cellphones if you set it to 3.5V instead] alternating between send and quiescent.

Awsome Supply that you have     


This is more test below 0,292V @ 5A Load

output setting (max current) ==> reading at DC Load (Contant Current @ 5A)
0.25V @ 5.1A ==> 0.172V @ 4.2740A
0.20V @ 5.1A ==> 0.137V @ 3.4181A
0.15V @ 5.1A ==> 0.103V @ 2.5624A
0.10V @ 5.1A ==> 0.069V @ 1.7077A
0.05V @ 5.1A ==> 0.034V @ 0.8390A

For dynamic test with full load, i think i will skip that 
this is the only supply that i have

[cosmos]

crt:
Thanks for testing:
You might want to redo those 5A readings with remote sense (both on DC load and PSU if possible).
There seems to be about 80mV diff in the reading from set at PSU to reading at DC load and it looks like it could be due to the lead resistance.

[crt]

Your dynamic test is good, what it shows mostly is transient response because a true dynamic test must be under load.   You should program the PSU for 10V/5A and the eload to 10V 5A, then 10V .05A alternating say at 1 sec intervals, and check if the PSU actually produces that output and the response waveforms; this can be very stressful on PSU and can damage them if you do this for long periods.  That load will simulate radio transmission [ or cellphones if you set it to 3.5V instead] alternating between send and quiescent.

The picture that i post before already under load 0.1A @ 1mS // 2.5A @ 1mS with 8V

I have try to put more load 5A @ 1s // 0.05A @ 1s
@500mS/div My scope (DSO8060) is slow as hell  ==> So i can not get better view

crt:
Thanks for testing:
You might want to redo those 5A readings with remote sense (both on DC load and PSU if possible).
There seems to be about 80mV diff in the reading from set at PSU to reading at DC load and it looks like it could be due to the lead resistance.

Sorry for stupid question, but how those connector behind this M8811 works  ?
I had try to push, pull and move it to right/left side but i can not lock the cable
now its seems one of those connector already broken because my stupidity 

[metalphreak]

Pretty sure they are just push in connectors. You press the latch back/up to remove the cable. I put wire ferrule ends on my voltage sense cables to make it easier

[crt]

Pretty sure they are just push in connectors. You press the latch back/up to remove the cable. I put wire ferrule ends on my voltage sense cables to make it easier

Previously, i had try to insert cable (small dimension myabe about 22AWG) but those cable can not be locked 
You mean, i had to push it (orange button)  ==> insert cable ==> release it ?