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Accidental short of 12V to gnd on the FAN header

giljones88@...
 

I released the magic smoke with an accidental short of the 12V pin on the FAN header (yes, ouch!).  The schematics do not show the route the 12V takes to that point.  What is the likely component, or PCB trace that might have gotten fried?  The receiver still works, although at reduced sensitivity because the bandpass relays are not working.  Transmit does not work.  If this is not a user-fixable event, is there an individual, or shop, that would repair the unit?

Another question:  In the assembly of the rear panel cooling fan, should the air be blowing on to the PA heat sink?  If I install the fan I received with the label facing outwards, it sucks air out of the enclosure.  Routing the wires through the hole in the panel is also awkward, because they originate from the top of the fan, not the right side as shown in the picture in the manual.  Reversing the fan so the label is inward allows the wires to easily be threaded through the hole, and blows air on the heat sink.

Thanks for your help,

Gil, AA9FT

Ron / W4MMP
 

Hi Gil,
The first question is what revision PCB do you have?   The original has no revision marks.  The second release has a "C" mark near the LED.   The latest has "Ver 4.x" near or under the LED (it is hard to see).  That will tell us which schematic to examine.  

Depending on what fried,  you may be able to repair it with a cut and jumper approach.   As for Multus SDR,  repairing the rig,  I will need to check with the team.

The fan is intended to blow out of the enclosure.  This evacuates the heat verses blowing heat all around the components and helps keep the Si5351 oscillator stable.  I don't understand the issue with the fan wire routing.  When looking from the back of the rig, position the fan so that the wire leaves the fan from the top right side.  Put the heat shrink over the wire before passing through the hole that to the right of the fan.
--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP

 

Gil, there are two schools of thought regarding airflow and both will claim with absolute certainty they’re right. 

Too few or misplaced ventilation holes/slots will starve a fan if it's sucking fresh air through the enclosure over the unit and exhausting “spent” air out the back. 

If the fan is incapable of pushing air against the static pressure of the components inside the case because of its placement or too few ventilation holes/slots the fan will “bog down” and move little air. 

In both cases, good laminar flow at appropriate static pressures for that fan is the goal. It’s not just “air”...

So the real answer, like many things, is: “It depends.”  

Because you likely have little in the way of data on the fan, the case, the existing static pressures and any test gear, have a good close look at the placement of the fan in relation to the heat sink and those in relation to the ventilation holes/slots. My guess is the fan is pretty low “power” fan (in its ability to overcome static pressure) and is likely quite close to the heat sink. It may be better to orient the fan so that it blows “out” of the back rather than sucking cool air and pushing it “into” the enclosure. 

My $0.02 worth in isolation. 

73,
Robert VE7ZN

On Apr 6, 2020, at 8:50 AM, giljones88@... wrote:

I released the magic smoke with an accidental short of the 12V pin on the FAN header (yes, ouch!).  The schematics do not show the route the 12V takes to that point.  What is the likely component, or PCB trace that might have gotten fried?  The receiver still works, although at reduced sensitivity because the bandpass relays are not working.  Transmit does not work.  If this is not a user-fixable event, is there an individual, or shop, that would repair the unit?

Another question:  In the assembly of the rear panel cooling fan, should the air be blowing on to the PA heat sink?  If I install the fan I received with the label facing outwards, it sucks air out of the enclosure.  Routing the wires through the hole in the panel is also awkward, because they originate from the top of the fan, not the right side as shown in the picture in the manual.  Reversing the fan so the label is inward allows the wires to easily be threaded through the hole, and blows air on the heat sink.

Thanks for your help,

Gil, AA9FT

--
73,

Robert VE7ZN

giljones88@...
 

Hi Ron,
The board is Ver. 4.3. 
The fan is labeled "SB, DC BRUSHLESS FAN, DC 12V, CE", a different label than pictured in the manual.  Attached is a picture of the fan mounted backwards (label facing inward, and air blowing inward).  Note the position of the wires.  If you reverse and rotate the fan, the wires come out of the top of the fan cage, unlike the picture in the manual.  This must be a fan from a different source.  The wires can be routed through the hole with the fan mounted opposite, but it doesn't look as neat.

Thanks,

Gil

giljones88@...
 

Thanks, Robert, for the perspective!  I'm not surprised it is a complicated issue.  I will take your advise and Ron's to mount the fan blowing outward, and put up with the slightly awkward route of the wires from the top of the fan into the hole.

73,  Gil

Ron / W4MMP
 

HI Gil,
Yes, the fan I have here has the wires coming out the right bottom (not the right top).  I had not noticed that before.  But still routing the wire up to the hole should not be a problem.  Yes, the fan really needs to blow outward.  There are sufficient vents in the enclosure to provide sufficient air flow.  Also, it is located almost directly behind the PA heat sink which draws cool air around the heat sink and out the back of the rig along with along with just a tad of air from surrounding components.  Yes as Robert pointed out the fan certainly does not create a wind tunnel :).  But it does prevent a build of heat inside the rig.  The Proficio can run all day long without a fan ( in a case or not). Again the idea is to evacuate heat quickly so that other components do not become heated,   not cool the heat sink.

Back to the problem at hand.  Here is the schematic: https://multussdr.groups.io/g/main/files/Multus%20SDR%20Proficio/Proficio%20support%20files/Schematics/schematic-4-3.pdf.  Take a look at sheet #3, top left.  JP1 is for constant on (5V or 12V).  TX-FAN is for switching fan on/off with TX.
I do have a question.   The fuse should have blown when the 12V was shorted to ground.  The fuse supplied with the Proficio is a 2 amp fast blow.  These fuses blow if you just look at them the wrong way ;).  The rig should have been protected from a short circuit.

--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP

giljones88@...
 

Hi Ron,

I have a bunch of power cords with this type of barrel connector on my workbench, and unfortunately the one I had plugged into the Profico was a 5A - fused Rigrunner outlet.  I did not notice a fuse on the board, or in the schematic.  The schematic does not identify the trace from JP1 back to the 12V power connector.  Could I jumper a wire from the 12V power to the 12V pin on JP1?  What other components (upstream from JP1) might need 12V brought to them?  

Thanks and 73,  Gil AA9FT

Ron / W4MMP
 

Hi Gil,

Lets back up just a bit.   First perform a physical inspection of the PCB.   You may have said and I missed it, but look for any damaged traces.  If you do find a damaged trace,  scrape the trace down to bare copper before and after the damage.  Then solder a length of #28 or smaller wire between the two bare areas.  That is step one.   Now apply power (with the fuse in place).  If the fuse holds then there are no shorts.  Step three,  break out the DVM and follow the schematic from J1 through the regulators.  Make sure there is 5V(B), 5V and 3.3V.   Once that is confirmed  focus on the 12V.   I believe you mentioned the relays are not working.   Looking at the back of the PCB and with the DVM check to see if 12V is supplied to every relay.   I don't know if there is one common trace supplying 12V to all the relays or multiple traces.   At any rate, all the relays end up on the 12V buss.  Check the relays and let me know what you find.

On 4/6/2020 18:02, giljones88@... wrote:
Hi Ron,

I have a bunch of power cords with this type of barrel connector on my workbench, and unfortunately the one I had plugged into the Profico was a 5A - fused Rigrunner outlet.  I did not notice a fuse on the board, or in the schematic.  The schematic does not identify the trace from JP1 back to the 12V power connector.  Could I jumper a wire from the 12V power to the 12V pin on JP1?  What other components (upstream from JP1) might need 12V brought to them?  

Thanks and 73,  Gil AA9FT
-- 
73,
Ron / W4MMP

--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP

giljones88@...
 

Hi Ron,

I located the damaged trace.  It was on the bottom of the board, from the area under the fan to a via right next to the PA, Q5.  After repair of the trace, and checking that it was not shorted to ground, I plugged in the fused power cord.  The LED came on for about a second, then went out.  The current draw for the board was about 0.5 A.  Rechecking the voltage regulators showed that U1 was fine, with 5.0V(B) out.  However U3 and U5 were not outputting any voltage.  I lifted the output leg of U3, and found that U3 itself was fine--5V out.  Something on the board connected to the 5V output of U3 is shorted.  I lifted the input leg to U5, and the short is still there, so it is not U3.  Unless you've seen something like this before, I'm at a loss to identify what it is.  All of the 12V components now have the correct voltage applied.

Thanks,

Gil

Ron / W4MMP
 

Hi Gil,

Well, the good news is the The PSoC (U16) is probably OK (it is the only chip attached to 5V(B).  And the 5V regulator is shutting down on either current overload or thermal trip.

The bad news is that all other devices are attached to 5V.  Just a couple of thoughts.   Check the area in and around JP1 to determine if the 5V trace is OK.  Check for viable signs of a short to ground.  A second thought is lift Q4.  That device is in the area of the 12V trace damage.   If neither of those ideas pan out,  I'm sorry to say that one or more of the chips attached to the 5V buss are fried. If that is the case trouble shooting will be difficult as each chip will need to be lifted one at a time, until the short is found.  If you decide to tackle that job,  lift U14 last.  It is bear to replace. 

You can return the board to me if you like but I can't guarantee a timely repair.  I will need to do the above and then order the defective part(s). 

On 4/8/2020 10:00, giljones88@... wrote:
Hi Ron,

I located the damaged trace.  It was on the bottom of the board, from the area under the fan to a via right next to the PA, Q5.  After repair of the trace, and checking that it was not shorted to ground, I plugged in the fused power cord.  The LED came on for about a second, then went out.  The current draw for the board was about 0.5 A.  Rechecking the voltage regulators showed that U1 was fine, with 5.0V(B) out.  However U3 and U5 were not outputting any voltage.  I lifted the output leg of U3, and found that U3 itself was fine--5V out.  Something on the board connected to the 5V output of U3 is shorted.  I lifted the input leg to U5, and the short is still there, so it is not U3.  Unless you've seen something like this before, I'm at a loss to identify what it is.  All of the 12V components now have the correct voltage applied.

Thanks,

Gil
-- 
73,
Ron / W4MMP

--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP

Ron / W4MMP
 

Hi Gil,
Any progress?
--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP

giljones88@...
 

Hi Ron,

I'm working on a homemade 4-lead milli-ohmmeter to measure resistance across each IC on the board.  Hopefully I can pinpoint the shorted one and only have to remove that one.  I'll also need to get up to speed on desoldering an SMD IC--I presume I'll need a hot air rework station.

Thanks,

Gil

giljones88@...
 

Hi Ron,

Using a home-made milli-ohm meter, I've found that pin 3 of U4 may be shorted to ground.  The schematic shows it as "MMG3" , but that gives no results in a search in Digi-Key.  The device "MMG3014NT1" showed up on a google search, and looks similar in Digi-Key.  Is this the same device?  The imprint on top of it is "M3H21N  A6AGA"

Thanks,

Gil

Ron / W4MMP
 

Hi Gil,

That is a very good candidate for replacement.   Yes, the part number is MMG3H21NT1.   Also that is an easy component to lift from the board.  With your iron turned up high,  heat the tab and gently and carefully lift the tab just until it is off the board.  Now heat the all the legs at the same time and remove the MOSFET.   Now check for the short.   Let me know.   I have a couple of them laying around here somewhere.   If the MOSFET is bad,  I will put one in envelop and get it off to you. 

On 4/22/2020 17:05, giljones88@... wrote:
Hi Ron,

Using a home-made milli-ohm meter, I've found that pin 3 of U4 may be shorted to ground.  The schematic shows it as "MMG3" , but that gives no results in a search in Digi-Key.  The device "MMG3014NT1" showed up on a google search, and looks similar in Digi-Key.  Is this the same device?  The imprint on top of it is "M3H21N  A6AGA"

Thanks,

Gil
-- 
73,
Ron / W4MMP

--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP

giljones88@...
 

Hi Ron,

U4 was definitely shorted.  When I removed it and powered up the board, I still found excessive current draw on the 5V line.  R6 was getting hot.  When I independently provided 5V power to the board at the fan header, I found it was drawing about 450 mA, and U2 was getting hot.  I don't have a hot air gun yet to remove U2, but I'll definitely need one of those in addition to U4.  Do you have any of those on hand?  I can get them both from DigiKey if not.

Thanks,

Gil

Ron / W4MMP
 

Hi Gil,

I'm sorry that you are experiencing these troubles.   Finding fried chips can be difficult and time consuming.   Since you are sure the chip is fried,  you may want to take a shot at removing the chip with your iron.  But it goes without say (but I will say it anyway), you must be extremely careful when doing so.  The a number of videos on the internet that show how do this with just an iron.  Do an internet search and you find them.  Yes, I have the chip in the shack somewhere, I'm sure.  Let me know when you have the chip off the board and the current/voltages are all back to normal.  

On 4/23/2020 12:52, giljones88@... wrote:
Hi Ron,

U4 was definitely shorted.  When I removed it and powered up the board, I still found excessive current draw on the 5V line.  R6 was getting hot.  When I independently provided 5V power to the board at the fan header, I found it was drawing about 450 mA, and U2 was getting hot.  I don't have a hot air gun yet to remove U2, but I'll definitely need one of those in addition to U4.  Do you have any of those on hand?  I can get them both from DigiKey if not.

Thanks,

Gil
-- 
73,
Ron / W4MMP

--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP

giljones88@...
 

Hi Ron,

My friend, JP, KC9KKO, lent me his hot air rework tool, and I was able to remove U2 successfully, using 325C hot air.  Independently powering the 5V line results in a steady 96 mA current draw.  After re-installing U3 and powering the board with 13.8V, I see a steady current draw of 116 mA.  The LED is lit steady, and when connected to a computer, MSCC connects to it without complaint.  Unless you suggest some other diagnostics, and 116 mA is not out of line, then I think U2 and U4 are the only two chips I'll need.

Thanks,

Gil

Ron / W4MMP
 

Hi Gil,

Looks like you have nailed the issues.  I will get both devices in the mail to you.   If you have your order number,  please provide it so I can look up your shipping address.

73,
Ron / W4MMP
On 4/23/2020 19:01, giljones88@... wrote:

Hi Ron,

My friend, JP, KC9KKO, lent me his hot air rework tool, and I was able to remove U2 successfully, using 325C hot air.  Independently powering the 5V line results in a steady 96 mA current draw.  After re-installing U3 and powering the board with 13.8V, I see a steady current draw of 116 mA.  The LED is lit steady, and when connected to a computer, MSCC connects to it without complaint.  Unless you suggest some other diagnostics, and 116 mA is not out of line, then I think U2 and U4 are the only two chips I'll need.

Thanks,

Gil

--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP

giljones88@...
 

Thanks so much for your help.  My original order number is 69, and my address is also correct in QRZ.com.

73 and Stay Safe!

Gil

Ron / W4MMP
 

Hi Gil,
Any update on the status of your rig?
--
Thank you for your support and business,
73,
The Multus SDR,LLC Team,
Ron / W4MMP