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#ubitx #ubitx-help #ubitx #ubitx-help

varidur@...
 

Burned main board.

I was a little eager when I was hooked on the battery and I connected the battery wrong with the plus and minus cable ...
 
Has anyone done something similar and managed to solve the problem

R. E. Klaus
 

If you built it per the plans with the diode across the power jack, you may be lucky and just shorted the diode.  I've replaced hundreds of protect diodes in various mobile equipment with no further issues. If you didn't then it's time to break out the multimeter and start checking for shorted semiconductors and ICs.
Roxie -- K1AUS

Jerry Gaffke
 


If you build per the plans and don't happen to have a fuse on the power supply, there is no reverse polarity protection.
Search for "reverse polarity" in this forum to see the various threads.
Here's one:   https://groups.io/g/BITX20/message/35353

Once you pop the diode, you have the full reversed supply to the board.
The only way to be lucky here would be if you had a really wimpy supply that was unable to blow the diode open,
or you happened to have an appropriate fuse on the 12v line from the power supply of 2 or 3 Amps.

If you had the Raduino plugged in when you powered the board up, that will be the major hit.
The LM7805 does not offer any reverse supply protection, so if the Raduino saw reverse 12v,
that would almost certainly blow the Nano, and probably the display and si5351 as well.
Could have been avoided by having a diode where 12v goes into the LM7805, we can afford to lose a little voltage there.
Try plugging just the Raduino into a host computer (no connection to the uBitx) via the mini-USB connector, see if it comes to life.

If you have a very new board from hfsignals, than the TDA2822 is likely socketed and easy to replace.
Most likely blown if it saw a reversed 12v.

The 78L05 at U2 may have blown.

The remainder of the radio is suspect, but may well have survived.


Jerry


On Wed, May 16, 2018 at 08:36 pm, R. E. Klaus wrote:
If you built it per the plans with the diode across the power jack, you may be lucky and just shorted the diode.  I've replaced hundreds of protect diodes in various mobile equipment with no further issues. If you didn't then it's time to break out the multimeter and start checking for shorted semiconductors and ICs.
Roxie -- K1AUS

varidur@...
 

Happy!!!
I replaced the diode and it works again👍👍👍

WA9PWR
 

Generally silicon diodes will fail with a short circuit, protecting the hardware.

Jerry Gaffke
 

This reference suggests silicon diodes generally fail with a short when subjected to over-voltage.
And generally fail with an open when subjected to too much current.
    https://electronics.stackexchange.com/questions/77712/can-a-diode-fail-to-open-position

The uBitx reverse protection diode would likely blow open due to excessive current (and heat)
if the power supply is not fused properly.

Jerry


On Mon, May 21, 2018 at 08:50 pm, WA9PWR wrote:
Generally silicon diodes will fail with a short circuit, protecting the hardware.

WA9PWR
 

Tell that to varidur.  Reverse protection diodes are cheap insurance.

Jerry Gaffke
 

It's certainly possible that it works in some cases.
But without a fuse, that shunt diode scheme is not an insurance policy I'm willing to buy.
Worse than nothing, it gives is a false sense of security.
Please add a fuse between the supply and the shunt diode.

Whether that shunt diode fails with a short or vaporises to an open depends on the supply you hook it up to.
Have you ever seen ham gear running off a car battery?
Have you ever seen what a car battery can do to a crescent wrench?

I'd recommend a series schottky diode for 12v into the main uBitx board (but not for PA-PWR into the IRF510's.)
We can well afford a 0.3v drop there.
Ideally, that diode would be rolled into the next rev of the uBitx board.
A 0.5 amp fuse there would also be a good idea, but the diode protects without any maintenance required.
And if you really care, a 12v LDO such as the LM2940-12 to prevent overvoltage,
this part also gives reverse protection so could do away with the series schottky diode.

The IRF510's should have a 3A fuse in the PA-PWR line.
That's likely enough, as the intrinsic diodes in the IRF510's will conduct if that supply is reversed.
Could burn those chokes on the drains, maybe some traces, but that's about it.
Easily fixed.  A shunt diode on PA-PWR after that 3A fuse is not a bad idea.

But just a shunt diode at the power connector and no fuse?
Bad idea.

Jerry, KE7ER


On Mon, May 21, 2018 at 10:36 pm, WA9PWR wrote:
Tell that to varidur.  Reverse protection diodes are cheap insurance.

David Wilcox
 

I know it's not the best but the shunt diode did protect my MTR 5. My problem was I did NOT have a fuse in the line so the smd diode let the smoke out (opened up as it vaporized). I now fuse all B+ lines (or is that A+ in solid state). Thanks for your comments.

Dave K8WPE

On May 22, 2018, at 2:47 AM, Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:

or

ajparent1/KB1GMX
 

For the life of me I do not understand why the diode is before the fuse.

The fuse should always be first as it needs to operate for all faults even reverse polarity.

Allison

Jerry Gaffke
 

No mention of "fuse" here:  http://www.hfsignals.com/index.php/ubitx-wire-up/
What looks like a fuse at the top left of the schematic is labeled "ON/OFF",
so I take that to be the power switch on the volume pot.

The 26 gauge stranded wire in the wiring harness might be considered an adequate fuse by some.
Unfortunately that comes after the shunt protection diode.  As you so rightly pointed out.  ;-)

Jerry


On Tue, May 22, 2018 at 03:13 am, ajparent1/KB1GMX wrote:
For the life of me I do not understand why the diode is before the fuse.

The fuse should always be first as it needs to operate for all faults even reverse polarity.

david todd <kg9rb@...>
 

The fuse can be looked at two ways. 1.it provides over current protection.
2.it won't provide polarity protection.
Some techs prefer to put the diode before the fuse as a practice to keep positive voltage off the ground plane.

Now the diode installed after the fuse will do the same but if you miswire anything after the fuse,then you will be holding a really neat looking paper weight. The diode only conducts one way and I personally have used this method to protect some of my equipment. A fuse is a fuse. Only protects from current. I prefer to protect my equipment from reverse polarity before it gets into the ground side. I do this because I have repaired many rigs with fuse first, and the owner hooked up the pwr source wrong. You can also wire it in series with ur power cord externally .some chips will fry before u get the display to glow. - 5 or - 12 is a whole lot of hurt to a static sensitive chip. Just my two cents worth.

Everyone has their own way.

73s
Have fun
David
ka9koj




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--------------------------------------------

On Tue, 5/22/18, Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:

Subject: Re: [BITX20] #ubitx #ubitx-help
To: BITX20@groups.io
Date: Tuesday, May 22, 2018, 10:36 AM

No mention of
"fuse" here:  http://www.hfsignals.com/index.php/ubitx-wire-up/
What looks like a fuse at the top left of the
schematic is labeled "ON/OFF",
so
I take that to be the power switch on the volume pot.

The 26 gauge stranded wire in
the wiring harness might be considered an adequate fuse by
some.
Unfortunately that comes after the
shunt protection diode.  As you so rightly pointed out. 
;-)

Jerry


On Tue, May
22, 2018 at 03:13 am, ajparent1/KB1GMX wrote:

For the life of me I do not understand why the
diode is before the fuse.

The fuse should always be first as it needs to
operate for all faults even reverse polarity.

Jerry Gaffke
 

Hmm.
Ground is ground all the way through.

Only exception might be if you try putting a bridge rectifier up front so it still
works if the wires are swapped.   Bad idea.

The fuse is an integral part of polarity protection if using a shunt diode. 

Jerry



On Tue, May 22, 2018 at 10:41 am, david todd wrote:
The fuse can be looked at two ways. 1.it provides over current protection.
2.it won't provide polarity protection.
Some techs prefer to put the diode before the fuse as a practice to keep positive voltage off the ground plane.

Now the diode installed after the fuse will do the same but if you miswire anything after the fuse,then you will be holding a really neat looking paper weight. The diode only conducts one way and I personally have used this method to protect some of my equipment. A fuse is a fuse. Only protects from current. I prefer to protect my equipment from reverse polarity before it gets into the ground side. I do this because I have repaired many rigs with fuse first, and the owner hooked up the pwr source wrong. You can also wire it in series with ur power cord externally .some chips will fry before u get the display to glow. - 5 or - 12 is a whole lot of hurt to a static sensitive chip. Just my two cents worth.

Everyone has their own way.

73s
Have fun
David
ka9koj

ajparent1/KB1GMX
 

My prefered way uses a diode and relay.  Relay has zero voltage drop.
IF the diode does not conduct,
    then power to the relay does not happen and power to the board never happens.
When the diode/relay combo I add an "idiot led" bicolor before the relay depending
on polarity red not good, green good, none means fuse or no power.  
Why go that far? Never loan gear, and bad stuff happens in a hurry.

But I still include a fuses (each lead) before the reverse polarity diode.  Why?
If the negative side is case and I hook the positive to the case we get sparks
and fried wires in most mobile environments.  Lets protect the source.


Allison

Jerry Gaffke
 

The relay trick is good, especially if running a kW.
At 10W, semiconductors are fine.

At a minimum, I'd just make it series schottky diode into the main uBitx rail with a 0.5A fuse there.
I have a lot more faith in the $0.10 diode than I would in a $1 ebay relay.
Still have a good spot for that idiot light.

PA-PWR fused separately at 3A, with beefy enough traces and coils that the fuse blows first
when the IRF510's intrinsic diodes see reverse voltage.
 
If fuses are deemed too expensive, perhaps just a skinny trace on the PCB where
power enters and goes to the series schottky. 
Have a big feedthrough on each end to mount a replacement fuse.
The 3A PA-PWR fuse could be a thicker trace, or perhaps just a skinny wire to the power connector.


A fuse on the ground lead is not something I've ever worried about,
but you give a good argument.  Again, maybe just a skinny wire (such as the 26 gauge
hookup wire provided with the uBitx) from power connector ground lug 
to chassis and PCB grounds is a sufficient fuse there.

Jerry, KE7ER


On Tue, May 22, 2018 at 12:58 pm, ajparent1/KB1GMX wrote:
My prefered way uses a diode and relay.  Relay has zero voltage drop.
IF the diode does not conduct,
    then power to the relay does not happen and power to the board never happens.
When the diode/relay combo I add an "idiot led" bicolor before the relay depending
on polarity red not good, green good, none means fuse or no power.  
Why go that far? Never loan gear, and bad stuff happens in a hurry.

But I still include a fuses (each lead) before the reverse polarity diode.  Why?
If the negative side is case and I hook the positive to the case we get sparks
and fried wires in most mobile environments.  Lets protect the source.

Jack Purdum
 

I had a skinny trace fuse on a CRK-10A QRP transceiver which did burn through, but not before it fried virtually everything else on the board. I wouldn't trust a skinny trace fuse in a circuit at all...period. That's sad, too, because it's a really nice rig with an outstanding receiver.

Jack, W8TEE

On Tuesday, May 22, 2018, 4:28:17 PM EDT, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:


The relay trick is good, especially if running a kW.
At 10W, semiconductors are fine.

At a minimum, I'd just make it series schottky diode into the main uBitx rail with a 0.5A fuse there.
I have a lot more faith in the $0.10 diode than I would in a $1 ebay relay.
Still have a good spot for that idiot light.

PA-PWR fused separately at 3A, with beefy enough traces and coils that the fuse blows first
when the IRF510's intrinsic diodes see reverse voltage.
 
If fuses are deemed too expensive, perhaps just a skinny trace on the PCB where
power enters and goes to the series schottky. 
Have a big feedthrough on each end to mount a replacement fuse.
The 3A PA-PWR fuse could be a thicker trace, or perhaps just a skinny wire to the power connector.


A fuse on the ground lead is not something I've ever worried about,
but you give a good argument.  Again, maybe just a skinny wire (such as the 26 gauge
hookup wire provided with the uBitx) from power connector ground lug 
to chassis and PCB grounds is a sufficient fuse there.

Jerry, KE7ER


On Tue, May 22, 2018 at 12:58 pm, ajparent1/KB1GMX wrote:
My prefered way uses a diode and relay.  Relay has zero voltage drop.
IF the diode does not conduct,
    then power to the relay does not happen and power to the board never happens.
When the diode/relay combo I add an "idiot led" bicolor before the relay depending
on polarity red not good, green good, none means fuse or no power.  
Why go that far? Never loan gear, and bad stuff happens in a hurry.

But I still include a fuses (each lead) before the reverse polarity diode.  Why?
If the negative side is case and I hook the positive to the case we get sparks
and fried wires in most mobile environments.  Lets protect the source.

Jerry Gaffke
 

Sounds like somebody just made a wild guess at how wide.
Or didn't have some of these other issues fully figured out.
Did anybody ever evaluate the failure?

A skinny trace with feedthroughs such that the owner can choose to cut the
trace and put in something better seems a fine compromise.

The scheme I presented is $0.10 for the schottky series diode, 
otherwise no additional burden to this $109 rig. 

Jerry


On Tue, May 22, 2018 at 01:36 pm, Jack Purdum wrote:
I had a skinny trace fuse on a CRK-10A QRP transceiver which did burn through, but not before it fried virtually everything else on the board. I wouldn't trust a skinny trace fuse in a circuit at all...period. That's sad, too, because it's a really nice rig with an outstanding receiver.
 

david todd <kg9rb@...>
 

 


Sent from Yahoo Mail. Get the appjerry,

you are right a gnd is a ground all the way around. yes the fuse will help on providing a path, but like i said , i would protect it before the fuse because I've worked in the consumer electronics field for 25 years and all the mis wired units I've worked on, was fried. yes a schottky diode is good, . I've seen zeners being used, triacs,optic isolators and other components. but why make it more complicated. some will put a fuse in and throw away the diode to their junk box for another project.some will just use an onboard inline fuse while others may opt for only a diode in series with the hot lead to the switch. and if I'm going to protect my equipment,i use one before the fuse. yes the diode will short out or burn open.ive seen both. and me personally , i wouldn't take the chance to have a positive voltage on my ground plane. a ground is a ground like u said and if any chips or gets on the board are sensitive to a very very brief surge of positive voltage where its supposed to be negative,well i don't want to replace all my equipment I've had for over 35 years since 1980. I've been doing it ever since.yes the diagram is representative of the on/off switch on the audio board. i didn't use that. i installed a toggle switch near the entry point where the source comes in. that way any noise that may be induced into other circuits by running the longer wires are eliminated.And I've seen diodes burn open and the fuse never blew and the fellow hooks it back up the same way and its toast.because the diode is now open and cannot prevent + voltage to ground .that is why i install polarity protection outside of my rigs before the fuse. i don't trust components.


anyway good discussion.
this my own preference of doing things jerry. your suggestions are valid and on the mark.
others will think I'm a crackpot. but if you ever seen ebay filled with $500 or higher rigs where the op hooked up the wrong polarity?
those units should protect from that but a lot are lacking due to the designs. no matter how much the rig is worth.

anyway  good info and hope to work you on the bands sometime.

73s,

david todd
ka9koj

i

david todd <kg9rb@...>
 

jack,
I've seen rigs like yours burn just like that and they were commercially built. don't feel so bad. it happens to us all eventually.

73s
david
ka9koj
 


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