Mobile Radio - Lessons Learned

[lazypengu1n]

Preface
Purchased an ICOM ID-5100A and was testing and figuring out the wiring. I have an 12V AC to DC convertor 19.3AMPs Max 12V. I had this connected via 10G wires to a Anderson Powerpole 8 way splitter then to Power Filter then to the Radio. I have a dummy load antenna from my HT that I decided to use since I heard NOT to transmit without an antenna. Programmed by Callsign (D-Star), set the frequency to my Hotspot at home, clicked to connect and then BAM! Lights out, power supply is making a charging/discharging whine. I smell what I know is some component must have burnt out. That's strange, I've used this Power Supply for over a decade without any issues. Tested with a meter and it looks good. Has to be the radio. Opening the shell, I smell that distinct smell of burnt electronics, definitely burnt something.... hoping it didn't damage anything major and that I didn't just turn my brand new radio into a desk brick. Searching and found the bad component, turns out the Reverse Polarity / Over Power diode blew (closed instead of open cause it would have allowed power into the unit and caused greater damage). I assume the dummy load antenna wasn't enough and the RF when back to ground and over powered the circuit and caused the diode to fail.

Mistakes (Accidents always an accumulation of smaller mistakes)
1 - Not using a fuse before the radio.
2 - Assuming a HT dummy load antenna would handle the power on a mobile unit

Lessons Learned
1- I know now how P6KA18 (P6KA18AHE3/54) diodes work (they fail fused instead of blowing open)
2 - Where to find such diode - Mouser - Replaced by newer version P6KE18AHE3/54.
3 - That most mobile radios / CBs that are blowing fuses all the time are doing this due to a failed diode. (Easy .50 cent fix)

So now I am waiting for Mouser to ship out the parts, I ordered 10 since shipping was $7.99 no matter what. If anyone makes the same mistake, it should be an easy fix. Other people have snipped the diode and radio comes back to life but no longer protected. I could do that to make sure I'm not waiting for nothing, but at this point it will either work or won't. At least now I know how to troubleshoot a failed diode.

I will post more on this as parts come in and I do the repair so if anyone else ever happens to have the same problem.

 

[appraiser]

in my day they were called Zener diodes.... not transient voltage suppressor devices....

And yes, you could take the diode out and the radio would power up.

When the Zener's junction broke down, it is no longer a diode ( voltage will now flow both ways, think of it as a check valve) and lets power short to ground blowing the fused power or just letting the power take the path of least resistance to ground.

Take the damaged diode out by cutting it or unsoldering it from the board the power supply section of the device should work

 

[UJay]

Something is strange here. The radio was powered up allowing the ability to program the rig? What is your 12V AC-DC Converter/power supply?
If it is 12V, That voltage could be too low for a mobile rig (Increasing current through components whilst letting the smoke out... etc...) & Increasing the load by transmitting...

Good luck, things like these are discouraging, learning opportunities. The D-Star equipment is a big investment.

 

[drgrant]

Something else is in play there, having a bad load on the antenna jack doesn't immediately let smoke out....

I'd double check your wiring.... and then some. Power filter? WTF you need that for? it's an FM rig...

-Mike

 

[lazypengu1n]

Something is strange here. The radio was powered up allowing the ability to program the rig? What is your 12V AC-DC Converter/power supply?
If it is 12V, That voltage could be too low for a mobile rig (Increasing current through components whilst letting the smoke out... etc...) & Increasing the load by transmitting...

Good luck, things like these are discouraging, learning opportunities. The D-Star equipment is a big investment.

Power Supply - Radio Shack 19.3A max 13.8V. I keyed up once, heard some weird interference on my computer speakers and it shut off. No smoke but can smell something in the radio unit. The power supply tested good after with a Voltmeter. Only when it was connected to the 5100 did the power supply sound like it was cutting in and out, pulsating. Doing this I could smell something more so I decided to stop and open up the radio. Pics coming soone.

Something else is in play there, having a bad load on the antenna jack doesn't immediately let smoke out....

I'd double check your wiring.... and then some. Power filter? WTF you need that for? it's an FM rig...

-Mike

I had amps in cars back in the day and thought that would be needed for the truck to filter the alternator noise. If not, anyone interested in a noise filter for cheap?

 

[lazypengu1n]

Testing the diode in either direction on the meter shows continuity.

The negative wire is a little singed.

 

[UJay]

It looks like it let the smoke out like a flair scorching the wire. Measuring diode's in-circuit = you could be measuring across the power supply's transformer (or any of the radio's innards).

What is your PS and the filter you referred to in the original post?

 

[lazypengu1n]

Power Supply




Filter



How it was hooked up. The fuses were the 40A since the max on the power supply was 20 anyways I didn’t think of it. I will be using a 20 fuse on both sides next time around.

 

[afeid]

The diode is not soldered in properly, not saying that is the cause of your issue but the solder should have flowed up the lead to the pads on both sides of the board. If you wanted to push the issue that could bea manufacturing defect.

 

[HorizontalHunter]

I agree with Appraiser.

The band is the negative side of the diode so it will only conduct if the polarity to the radio is reversed to protect the radio.

Desolder one end to remove it from the circuit electrically and retest to ensure that it is really shorted and that there isn’t another issue. If it is the only issue the radio should power up. Don’t leave it out. You should replace it. They are cheap insurance.

IME diodes usually open when they fail.

You should also visually inspect the other components paying special attention to the electrolytic filter caps. Look for bulging on the top of the can and also look for the rubber seal being pushed out on the lead side of the cap.

Bob

 

[lazypengu1n]

The diode is not soldered in properly, not saying that is the cause of your issue but the solder should have flowed up the lead to the pads on both sides of the board. If you wanted to push the issue that could bea manufacturing defect.

You think so? I suppose. Anyone else have a 5100A for reference? If it's as simple as replace the diode I can do that but having to deal with waiting for warranty to look and decide. I did just buy it from HRO less than 2 weeks ago.

 

[lazypengu1n]

I agree with Appraiser.

The band is the negative side of the diode so it will only conduct if the polarity to the radio is reversed to protect the radio.

Desolder one end to remove it from the circuit electrically and retest to ensure that it is really shorted and that there isn’t another issue. If it is the only issue the radio should power up. Don’t leave it out. You should replace it. They are cheap insurance.

IME diodes usually open when they fail.

You should also visually inspect the other components paying special attention to the electrolytic filter caps. Look for bulging on the top of the can and also look for the rubber seal being pushed out on the lead side of the cap.

Bob

Definitely agree that removing the diode and re-testing it. I have the new diode on order, 10 of them so hopefully they will show up this weekend. I think I will be safe cutting it out, putting the correct 20A wire from the factory and testing?

Like this?

 

[afeid]

You think so? I suppose. Anyone else have a 5100A for reference? If it's as simple as replace the diode I can do that but having to deal with waiting for warranty to look and decide. I did just buy it from HRO less than 2 weeks ago.

Worked in electronics manufacturing for many years, this would fail most inspections, does not meet IPC standards. if there are multiple layers to the circuit board the diode may not be connected to them all.

 

[HorizontalHunter]

You think so? I suppose. Anyone else have a 5100A for reference? If it's as simple as replace the diode I can do that but having to deal with waiting for warranty to look and decide. I did just buy it from HRO less than 2 weeks ago.

The pads on the component side should have solder present as well to avoid a cold solder joint. Critical on a multi-layered board probably not an issue here. It probably didn’t get hot enough when it was wave soldered.

Bob

 

[HorizontalHunter]

You should fix the black wire as well. You have no way to know how much the conductor was damaged when the diode blew. Cut, tin, and resolder.

Might as well do it right seeing as you are there.

Bob

 

[lazypengu1n]

You should fix the black wire as well. You have no way to know how much the conductor was damaged when the diode blew. Cut, tin, and resolder.

Might as well do it right seeing as you are there.

Bob

Will do.

I appreciate everyone’s input. I will definitely post up some more information and pictures to share as I work in fixing this. Time to find all the soldering equipment I’ve collected over the last 15 years.

 

[UJay]

May be worth it to check the power supply as possible suspect..

 

[lazypengu1n]

May be worth it to check the power supply as possible suspect..

The next time I’m hooking this up will be to the truck.

 

[AHM]

Something else is in play there, having a bad load on the antenna jack doesn't immediately let smoke out....

I'd double check your wiring.... and then some.

If it had pifted immediately upon power-up instead of first Push-to-Talk,
I would have suspected reverse polarity from the power supply.

But it didn't, so I can't.
Sigh.

 

[HorizontalHunter]

If it had pifted immediately upon power-up instead of first Push-to-Talk,
I would have suspected reverse polarity from the power supply.

But it didn't, so I can't.
Sigh.

I read the OP’s post differently. I read it as blowing when connected to power.

Bob

“Programmed by Callsign (D-Star), set the frequency to my Hotspot at home, clicked to connect and then BAM! Lights out, power supply is making a charging/discharging whine.”

 

[AHM]

I read the OP’s post differently. I read it as blowing when connected to power.

Bob

“Programmed by Callsign (D-Star), set the frequency to my Hotspot at home, clicked to connect and then BAM! Lights out, power supply is making a charging/discharging whine.”

Yahbut how'd OP program before first power-up?
Ah, I don't do D-Star but now I see the rig uses an SD card.

So did OP burn the SD on a computer, insert it,
and then blow up the rig upon first power-up after all?

Another way to pift a rig is for the chassis or coax braid to hit the B+.
But frankly that Radio Shack supply looks better insulated than my Alinco miracle switcher.

Now, if the goober who manufactured the 8-way PowerPole splitter crossed the wires internally,
*that* would blow things up nicely. And if only some outlets are miswired,
and OP reconnected to a random different outlet between initial configuration/programming,
and first dummy-load test,
that could do it.

Sigh.

 

[lazypengu1n]

Hello All,

Parts came in.



As it was before doing anything.





The TVS diode I believe they are called failed on. I took the diode out and confirmed with a meter that it was bowing continuity either way. Tested the new diode and did not get that behavior.

Desoldering the diode was a PITA since the entire board is stuck to a huge heat sink. Taking it apart seemed like too much work so I didn’t go that route. I had to turn my soldering station to the highest setting to get the pins unsoldered.



I cleared the holes for both legs, check for the correct orientation and soldered the new diode in. Wished the job was cleaner but hell its done.







Radio tested good. I know I wasn’t going to hook it up to my power supply again but what the heck. I made sure to use the factory 20A fuses this time.



Defintely NOT pressing PTT until it's in the truck and the correct antenna attached.

 

[AHM]

Parts came in.

It's nice that you:

1. Verified the component had failed, by comparison with the replacement.
2. Showed the rig booted up OK.

Only in retrospect it occurs to me that if you'd known it was going to suck to
cleanly replace the diode, you had an alternative:

1. Crush the old diode.
2. Bend the leads up.
3. Tack the new diode onto the old one's leads.

Because it's a power supply circuit, it's not like lead length matters much.

That hack is partially inspired by a method I've seen of replacing
a blown glass fuse with pigtail leads that is soldered to a circuit:
Back in the day, TV repairmen wouldn't bother unsoldering a blown pigtail fuse -
they'd just snap a a pair of back-to-back fuse clips onto the blown fuse,
and then snap a replacement fuse (no pigtails) into the matching clips.
The clips were riveted together on either side of gray cardboard wings
that shielded both fuses from their sides, and from each other.

(In high school I found one of these piggyback frobs
inside a curbside TV that I tore down for parts).
=====
ETA: found one, used for hacking pinball machines. Maybe the original I have only has one pair of wings like this one.

 

[HorizontalHunter]

Nicely done.

73,

Bob