5 pin converter killing a radio?

[KangMudDuck]

D-104 lollipop wired for 4 pin, using a 5 pin converter into the 148. I have been trying to set up the mic listening to a SDR about five miles away. Can do a few test keys to adjust the mic before the radio shuts off, have to unplug the power supply to get it working again. The other radios on the same power supply work with no problems after the 148 stops working.

The mobile D-104 works fine in the 148, and the lollipop sounds good going into a Stryker. Lollipop sounds very scratchy with the 148 before it shuts off the radio. I haven't had the time to put the lollipop on a 5 pin connector for the 148, just wondering if anyone has an idea why the radio shuts down. Is that something that may happen with a 5 pin converter?

 

[Handy Andy]

Er, no, but the MB3756 that is the power supply Regulator that delivers 8 volts can do this if the mic is not wired right. Thermal shutdown.

Only one pin needs to be grounded to make the radio TX - if you "ground" RX - DON'T - that is just the speaker return it USES ground at Pin 3 - because it will short thru to pin 4 - while Pin 4 - GROUNDS Pin 5 - and OPENS Pin 3 - so 4 is "common" to 3 and 5 - while 2 is exclusive to pin 1.

• Yes, Pin 2 is also Ground, but will interfere with Audio signal.
• Be flexible - Pin 4 is true Board Ground, Audio Ground is filtered - so that is handled on the 4-Pin DONGLE side - 2 and 4 from 5-Pin are tied TOGETHER - on the 4-Pin plug side..

So ... Pin 5 isn't grounded - only to Pin 4 when in TX - that is for the MB3756 to toggle two lines - RX to TX and back again when done

Then, Pin 3 - is your speaker, yes, you can go right in there and measure from that pin on the panel, to the speaker cone and see 8 ohms across those terminals at the speaker. Pin 3 is live for the Audio line.so you can ground it and yodel for instant talkback.

So make sure Pin 3 routes to speaker, pin 4 to board ground FOIL ground like Battery Negative ground. That is different from CHASSIS or case / panel sides ground.

Which brings up another condition - is the radio "Strapped"?

Being that Case rear panel and Battery Negative are tied as one ground?

• IF so, please remove this ASAP
• - can Damage the MB3756
• - which needs to run mounted thru an INSULATOR onto it's back and tab of it so it stays ISOLATED from panel and case ground and only ground it sees is thru it's Pin 4 on the main PCB.
• Pins 3 and 5 ON THE MB3756 - use caps to control ripple and steady the regulation within it. If these are shorted - Look out!

On the 5 pin to 4 pin "dongles', the wiring scheme is like a Cobra/Uniden 4 pin

4-Pin Dongle side...

Pin 1 - Ground - Shorts to Pin 4 in RX, Shorts to Pin 3 in TX
Pin 2 - AUDIO - Live in TX - some it is LIVE all the time.
Pin 3 - TX - Open in RX - Shorts to Pin 1 in TX
Pin 4 - RX (Speaker Return -Speaker is live on this line) Shorts to Pin 1 In RX


5-Pin "Plug" side...

Pin 1 Audio - Live in TX - in some radios they want this shorted to Ground in RX (Pin 2)
Pin 2 grounds - so ties the 5-pin mic's 4 and 2 together - Usually Shield
Pin 3 Speaker RX - Shorts to Pin 4 in RX, Opens in TX - breaks speaker connection.
Pin 4 Common SW - Shorts to Pin 3 in RX - SHORTS to Pin 5 In TX
Pin 5 TX Mode - Open in RX, Shorts to Pin 4 in TX

So when doing the Dongle Conversion...

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[KangMudDuck]

Thanks @Handy Andy I'm going to try the 5 pin connector first and see what happens, I'll be back to study your reply if the regulator continues to shut down.

I'll also investigate the battery negative, a local a couple miles away says he hears a hum and that it goes away when I put my finger on the case. I don't hear the hum on the SDR five miles away.

 

[Handy Andy]

I hope it helps you.

There are a lot of questions about 5-pin microphone plug to jack wiring.

And we haven't even touched on if a previous user of any radio having mic wiring problems - did they rewire the plug to suit another mike?

It's never an easy answer.

 

[KangMudDuck]

That D-104 had never been wired to a connector, nor has it ever been used until very recently. Came from the Astatic factory to my work nearly 30 years ago, they apparently forgot how to do brass plating for their limited edition Diamond Eagle run.

I figure the 4 pin soldering job I did is OK because it sounds good in the Stryker, I'll put it on a 5 pin connector and see what happens, if it works, the 4 to 5 pin converter is going back for a refund.

 

[Handy Andy]

Ok, just don't forget that the MB3756 needs mounting to side panel through one of those Mica insulators to allow it to drain off the heat from it's regulation and switching - but not short out to the case. If it did - it could go very bad...

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[nomadradio]

Really sounds as if someone sold you the wrong 5-pin converter. That plug was used on more than one kind of radio, and wired more than one way.

The usual trouble we see from those converters has to do with the extra pin. The 4-pin mike has only one ground connection, used for audio and transmit/receive switching, all together. Connected to pin 1.

The 5-pin socket on the 148 has two ground connection. Pin 2 carries only the audio current. Pin 4 carries only the transmit/receive switching-circuit currents.

Keeping them separate simplified the design for Uniden, the manufacturer.

But the one ground connection on the 4-pin mike will either connect only to pin 2. Or only to pin 4. Or to both. Those are the three possible choices.

One way tends to make the receiver audio feed back, especially in SSB modes. One will tend to cause feedback squeal noises on AM transmit.

The other method will frequently cause some of each.

But your problem just sounds like an adapter wired wrong for your radio.

73

 

[KangMudDuck]

@Handy Andy @nomadradio The converter was the culprit, works excellent on a 5 pin connector. Now to see what a 5 to 4 pin converter does...