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i was excited to put together my Ubitx today after finally getting a roll of .5 mm solder yesterday. I’m not an expert by any means in electronics assembly - I’d say that my proficiency is probably 33 on a scale from 0-100. Anyway, I assembled the components and put the radio together. However, I mistakenly switched two of the three wire cables. The one that I used for the power was supposed to be for the volume control. Normally there would not likely be an issue but for the fact that the way the connector attached to the board, the polarity was actually reversed (I should have double checked this but I didn’t since I was excited to power it up). Of course, when I switched on the power, an acrid odor was produced. I immediately switched off the power and noticed the issue and swapped the wires. Powered up the radio after the correction and the display flashed green with all black boxes and then powered off (note I have a push button power switch installed). If I hold the toggle switch in, the display stays on but had the black boxes across the display. I suspect the switch could be bad, but I’m also worried that the reverse power fried something. There is no visible damage but that doesn’t mean there is no damage. Any thoughts would be appreciated.

Gus
W9SSN

Hi Gus,

Well, if you smelled something then likely something got a bit too hot!

A couple notes:

The black squares on the display is normal if you haven't adjusted the contrast for the diplay yet (small smt pot on the board).

Looking at the schematic I notice two places where reversed power will end up with a circuit with electrolytic capacitors hooked up backwards.? Check the schematic for these (one is the power line to the lm386 audio chip -- the other is nearby).? Electrolytic capacitors don't like being hooked up backwards and are likely permanently damaged.? I would replace them with similar value parts.

You should get a good magnifier out and a strong light and examine both boards well for burnt traces.?? If you find any, note any parts connected to the traces as they may need to be investigated for damage.

Make sure you have the CW key resistor in place -- the board will stay in transmit and never go to receiver unless this is installed.

Finally, see recent posts about reverse polarity protection :-0

73,


Mark.

Thank you, Mark. I do have the 4.7k ohm resistor installed and I will try to adjust the contrast as well. Perhaps that will fix the issue, save for my switch, which is not functioning and needs to be replaced. If not, I will try to swap out the caps, but hopefully the very short application of reverse polarity didn’t totally damage them. I appreciate your response.

-Gus
W9SSN

Gus,

This is not very clear to me:

>? However, I mistakenly switched two of the three wire cables.
>? The one that I used for the power was supposed to be for the volume control.
>? Normally there would not likely be an issue but for the fact that the way
>? the connector attached to the board, the polarity was actually reversed?

The volume control on the uBitx is wired up to an 8 pin connector,
the power supply goes into a 3 pin connector.? Would be hard to swap them.
Exactly what pin did you connect the +12v wire from your power supply into?
Exactly what pin did you connect the ground wire from your power supply into?

It is possible for those caps to be damaged by reverse polarity.
But if?you see no apparent damage, they are probably in good enough shape.

Reverse polarity on the main +12v rail will pretty much destroy the Raduino?
and also blow a bunch of parts on the main board.? That would be difficult to repair.

I think I would first try to get that Raduino working.
You can unplug it from the radio, feed it between 8 and 12 volts, and see if you can?
get the display to work.? If the display works, see if you can hear the BFO by tuning in
a nearby shortwave receiver to 11.059mhz, listen for a clear CW tone with a piece of
wire for an antenna from the receiver coming within a couple inches of the Raduino.
If the display works and you can hear that tone, the Raduino is fine.

If what you did was wire your power supply into VOL-M and/or VOL-H and/or Ground
(the three volume control wires), I'd think the damage would be limited to the LM386 at U1.
Do you see obvious cracks or craters in the case of U1?
Q74 might have been hurt, but I doubt it.? There is a possibility that a negative supply on VOL-M
could have gotten through the LM386 into the +12v rail, but the 100 ohms at R74 would
somewhat limit the current available for wrecking havoc.
?
Jerry, KE7ER

Gus,

As a potential way of isolating the fault, you can unplug the Raduino from the main board and run the Raduino from a USB port on your computer, or other 5 volt supply.? That would let you know if the display and Nano are OK.? If you do this, you do not need the controls connected to the 8 pin connector on the Raduino.? plug a microUSB cable into the Nano on the RAduino and into a PC or other USB 5 volt source.? The display should light up, and you should see the normal startup screen.? If I interpreted your description, you put the 12 v power to the volume control connections on the uBITX board.? That could have taken out the Nano on the Raduino, as there is a connection to the Nano for CW side tone.? The Nano does not like anything over 5v or under 0v relative to the common on the Nano.? Nano's are cheap, so no big deal if you need to replace it.? Just make sure that you get one WITHOUT the headers already soldered, as they need to go on the other side of the board to work in the uBITX.

If that does work, then the Raduino is Probably OK.

Going beyond that will depend on the test equipment that you have.

By the way, did you do the test in step two of the wire up instructions from HF Signals?


I would do that test to verify that the board is still operational.? Note that the Raduino is NOT installed when measuring the current.

73
Evan
AC9TU

Hi Jerry,
i am using the amateurradiokits.in enclosure, which comes with some extra items to wire up connections, one of which is a three pin connector for volume. What happened was that the red and black wires on the 12v power supply to the board were reversed, maybe 15 seconds of power supplied before I cut it.

i adjusted the contrast and the display is working and shows the frequency, although the encoder doesn’t seem to change the frequency. I am going to disassembly, check all of the solder joints and see if I can see any obvious visible damage to any components. Right now, I don’t see any, other than my on/off switch, which needs to be replaced since I need to hold it in to maintain the power on to the unit.

After I posted my replay, I read Jerry's recommendations.? I like the second receiver test for the BFO to verify that the Raduino RF section is working.? I will need to remember that for future references.? You can do that when powered by the USB connection as the Si5351a runs off of the 3.3v rail that comes from the Nano.

Another possibility for the source of the smell is it came from the volume control.? If you truly put 12v across it, and the wiper was close to one of the ends, you could have smoked it.? Since the resistor is behind a metal case, you may not see it without close inspection.? Run a resistance check on it as well.

73
Evan
AC9TU

Reversing the power supply into the board can blow a bunch of stuff,
and thus be hard to fix.
But the fact that the Raduino works at all is a very good sign.

The Raduino is usually dead in the water after an event like this.
It is still possible that it is partially damaged (blown IO cells into the Nano?).
If a friend also has a uBitx, maybe try your Raduino in his uBitx to see if it works.
But it might have to be a very good friend.

If the encoder is wired up properly and the encoder did not come defective,
it should cause the frequency shown in the display to change.
If that does not work, check your wiring closely.
You can verify that the encoder is working properly with an ohmmeter,
disconnect it and measure the resistance from terminal A of the encoder?
(as shown in the wireup diagram) to terminal C.? It alternate between
open (thousands of ohms) and shorted (near zero ohms) as you rotate the knob.
Then do the same for between terminal B and terminal C.

If PA-PWR (the +12v into the IRF510 finals) got a reversed supply, then
look hard at L9 and the traces from it to the IRF510's and the PA-PWR connector.
Either L9 or the traces will fry, but probably not the IRF510's.
That could well be the source of your smoke.

With any luck at all, anything on the TX rail did not see -12v, only the RX rail saw -12v.
Most of the stuff that the RX rail goes to is pretty well protected by resistors, limiting current flow.
The LM386 at U1 and/or R71 could have blown, the 100 ohms at R71 would have limited currents
into U1 to 120ma absolute max but that's quite a lot.
I suspect most of the transistors would survive due to the nearby resistors, maybe all.

Once you prove out the Raduino somehow and have U1 working to where there's
a hiss in the headphones, you might try Farhan's procedure outlined here for the Bitx40:
? ??
Farhan is using a piece of wire maybe a meter long as an antenna to pick up
local QRM (digital clocks, microwaves, atmospheric noise)
and inject that noise into various parts of the receiver.

This could be very challenging to get working again.
Or you could be lucky.

Jerry, KE7ER

Luckily I purchased everything on a card with purchase protection that covers damage to products within 120 days of purchase, so I may just submit a claim and repurchase the kit new. Kind of the unsophisticated way out, but I probably do not have the experience necessary to diagnose and repair the radio. I’ll check these items and see if I can’t get it working, but I may just chalk this up as a loss. Thank you for the educated insight on the issue - very much appreciated!

best,

Gus
W9SSN

That strikes me as unethical.
You received a kit product, and damaged it by not following the instructions.
Generally, when buying a kit from most any vendor that you put together,
you don't get a refund when you screw up.

At these prices hfsignals is not making much of a profit per unit.
They can't afford to go along with that sort of thing.
And I doubt they will.

Unless you agree to pay a $129 "shipping and handling fee".? ;-)
Which may not be a bad option if this thing really got trashed.

Jerry

Hmm, if your credit card company is willing to insure you when building a kit like this,
that's ok with me I suppose.? Seems unlikely.
I doubt anybody (you or the card company) will be getting a refund from hfsignals.

There are lots of SSB transceiver kits out there.
The uBitx has its warts, but it works well enough and packs a lot of features for the price.
If it was possible to stay in business at a significantly lower price, there would be a dozen
such products available on ebay/alibaba/...

It's a totally open design.
Anybody who thinks they can make money by kitting these up for less
can go ahead and give it a try.? Don't have to know anything about design,
just how to copy.? And how to deal with the occasional ornery customer.

Good luck with that!

Jerry, KE7ER

It’s totally ethical. If you understand the purchase benefit of certain credit cards, this is exactly the type of incident that purchase protection covers. It would be idiotic to not take advantage of the benefits available. That’s like saying it’s unethical to reject insurance coverage for an accident for which you are at fault. Insurance is EXACTLY intended and designed to cover precisely that scenario.?

Hi!

I think some credit cards offer protection for things like, "Oops I dropped my phone and it broke!" type accidents, and they don't seek money from the vendor, but just cover the cost with profit from their card fees.? So maybe something like Gus' accident would be covered too!

But don't toss it Gus as I'm sure someone in the group would offer you something for it!

73,


Mark.

Gus

I will join the chorus of those suggesting this is a different kind of transaction. A large portion of the kit is parts, some to ladies who wound the toroids, and others who guided automated assembly. They need this work to make ends meet. Meanwhile a worldwide crew can help if you have a DVM available.? Most of us have experienced build issues, just hang in there.

Or see if your insurance will buy another one.

Curt

I don’t understand, this is exactly what I was saying. If I can claim the loss under the purchase protection provisions of the credit card on which I made the purchase, which I can (not is it unethical to do so as this is exactly what the insurance is intended to cover), why would I not do that and buy another? From the supplier’s side, they only see two purchase transaction. This insurance benefit has no impact on the vendor other than doubling its sales to me. This is part of the reason I pay $450 per year for this particular credit card.

Hi Gus,

I think most people haven't had experience with this kind of purchase protection available from credit card companies.? I hope they cover it so you can start fresh on a new board!

Anyway, you're not an idiot -- no one but you ever makes that kind of mistake (Not!)

Cheers and 73,


Mark.