S-meter not working on SS3900

[magotony]

Hi everybody,

Last time I used the transmitter the s-meter was not working when tried to check SWR or transmit power (does with received RF), neither works the CAL pot. Today I've checked the final transistors and one of them looked as shorted (Emisor-Base conection marked as 022 on my multimeter). Also checked the diode of the transistor and had the same mesure inverted and also direct polarization, so I thought it was a short. After change both I checked again and...got the same mesures (haven't checked the smeter yet 'cause only have mobile setup).

So...

Anyone knows...

a) Why is happening this? Is normal?
b) What is going on with the s-meter?

Any idea is wellcome

PD: I have no external SWR or power meter...


Thanks for your support.

 

[Eldorado828]

My friend, looks like you really need some kind of external meter to know what you're really getting from the output of the radio. A dummy load would be great but not absolutely necessary in your case until you need to be more precise.

Can you verify that it receives?

 

[magotony]

My friend, looks like you really need some kind of external meter to know what you're really getting from the output of the radio. A dummy load would be great but not absolutely necessary in your case until you need to be more precise.

Can you verify that it receives?

Yes, you're right. I should but I'm saving for get the exam and the license. I don't want at the moment pay more money in CB27. Maybe I can borrow it from some friend.

Anyway I just posted the problem just in case someone else, with more skills than me in electronics, could have any idea.

Thanks for your reply!

 

[Handy Andy]

No S-meter - or you have no SWR and S-RF meter action?

No SWR may mean a broken trace in the riser card - no contact, no connection.

No S/RF meter means the circuit to the S/RF meter needs to be checked.

Bigger clues to this would be No receive, cannot be heard thru another radio - let alone see any indication on the other radio thru it's own S/RF meter.

If you can see meter action on another radio - like full scale reading - then you have a signal going out - just not registering on the radios' own internal - solves or reduces the problem to be a internal fix than an serious rework.

 

[magotony]

I can give more clues about the problem...

1) Needle works OK on RF receiving.

2) I made 2 QSO, the first one on 15 km distance. The second one with Germany (more than 1.300 Km), but this last one couldn't be finished due to my weak signal (I was on mobile). The first QSO can't remember my Santiago.

3) Needle moves a little bit (just to the number '1') when TX. On RX it moves OK.

4) CURIOUSLY, when I drop PTT the needle moves up to the end limit very strong and falls into 0-1 level again (¿Roger beep?).

 

[Handy Andy]

QSO's from the radio means it's working.

But I digress, might need to reheat some solder joints along the riser card that kinda looks likes this...

If this is your radio...
EPT360011Z board...

​

Check on the foil side - that riser card can break foil traces - vibration, age, stuff like that.

Try reflowing - CAREFULLY - and reheating solder to hopefully re-establish the connection.

Otherwise if you are aware of it's age, and it's older than ten years - or if you can no longer remember when or where you got it - is another clue - you might want to think about recapping it.

The board was made in factories long since mothballed that used parts from the lowest bidder - a.k.a. - CHEAP - so they may have started to go dry, when that happens they act more like resistors than capacitors.

 

[magotony]

Handy Andy your reply sounds really good. When I get some minutes will check that!
I really appreciate your reply.

The board...maybe is that or similar, as I've seen on Google. When I opened it saw jpmxx0236c impressed on it.

Yes, you're right. Is a rig comming from Asia (Phillipines) but it's price has been not a bargain and costed me the same than my first SS3900 at store. BTW, you're also right and is older than 10 years (bought it 15 years ago -or a little more-).

In any case, I will reply this post once know something else.

 

[Handy Andy]

When I opened it saw jpmxx0236c impressed on it.

This usually indicates a "homemade" board, meaning that the board was assembled pieces by piece in a factory this is work that is done by many, So that may simply be an Initials and identifier, the real board number is located below on the foil side.

​

Locate the Audio Chip and Power Regulator Q (or) TR41 - runs the same side as the AM Regulator.

On the foil side, between TR41 and Audio Amp - is the board number for mine - "Z" references an amortized board - only so many were made then stopped.