Galaxy DX-2547 voltage regulator

It is AM modulator transistor.
When carrier is high, plenty of audio it gets hot.
Is it hot on RX only? How hot?
Remove vertical silver board and check if it get hot too. If so,I would measure current flow to driver and final on RX with DMM.
Also it is very bad soldering on it's legs, fix it if you can.
Mike

If the TX Power Regulator transistor is getting hot after a few seconds of it being turned on and not in transmit, the most likely problem is a shorted final or driver. Try taking the "Mirror Board" out in front of the final and driver, turn the radio on, see if the Power Regulator transistor (indicated in your first pic) is still getting hot. This board disconnects the power feed from the regulator to the final and driver.

Let it cool down first, and as Mike (SP5IT) and I have both said, pull the vertical silver "Mirror Board" back by and in front of the final and driver, and turn it back on, see if it still gets hot.

Go here...

http://www.cbtricks.com/radios/galaxy/dx2547/index.htm

Can't see too much but it loosk like you have the Bipolar version - single final.

The board is not that much different between the 10 or 11 - so there is more documentation on the 10 side (Bipolar) that you can apply to this.

But, if you have the MOSFET version - go here...

http://www.cbtricks.com/radios/galaxy/dx2547_mosfet/index.htm

The schematic of the "11" board is the MOSFET - if that is what you have.

Now, in regards to your problem. You are getting sage advice from the others in this forum...

DISCONNECT that Mirror Board...

Why? You may have a shorted device in the line feeding the Final and Driver - THAT INCLUDES EITHER THE DRIVER OR THE FINAL - they may be going bad.

This board, if you're MOSFET - is a sign that they are "latching up" you gotta replace both, for if one begins to fail - the other will cause the same failure or worse quit later when you need it - best to replace them in pairs.

A tricks to this is to realize that the mirror board jumpers three points. One feeds two - the One closest to AM regulator feeds the other two is parallel. Same time...

AM Regulator - FEEDER to - FINAL is middle jumper tab, DRIVER is farthest tab.

So design a jumper - and FEEDER to Driver (farthest one) and see if AM Regulator gets hot?

No, then remove jumper and jumper FEEDER to Final - does it get hot?

Either way, one of these two is causing a lot of current to be drawn - so it heats up the AM regulator.- Lets us know if the above can help you decipher this...

The first picture in the first post shows a Meanwell switching power supply, rather than an older analog one. This inclines me to believe that it MIGHT be a MOSFET version radio. Pull the final, it is definitely bad if it is pulling 2.5 amps in receive mode. See if you can read the part number. If the main board is indeed the bipolar version of the radio, the final in the schematics say it is a 2SC1969, and the driver will be a 2SC2166. If it is the MOSFET version, the driver and final will both be IRF520.
The fact that in the first pic of your last post shows that R244 is a 1/2 watt 47k (next to VR10, from your pic) causes me to also believe it is the MOSFET version.

Ok, since - if everything else being equal, the 2.5 amps can be presumed the Final.

But that doesn't mean it's the only thing...

There is a "BIAS CONTROL" used to set the bias of the final...

If that has opened up, YOU WILL ENCOUNTER the same problem over and over again...

So, check the potentiometer - on the 8 Volt TX line - across to ground - if it shows nearly infinite - you have your answer... Photo attached.

Then you have to figure out why that pot opened up or why the Final is triggered...

So you can do the ohmic check across the GATE to Ground - it should be less than 100K but more than 1K.

These pots are plentiful but you also need to know why the pot failed. If it's open, then you'll seen full gate voltage and your toast - again.

But if you can figure out what spiked it, you can prevent it.

This may be from other sources, not the 8 volt line - it may be from the RECTIFIED RF the Final GETS from the Driver - which may be an upstream issue...When you have several watts from the Driver, that 1K will still send RF back thru itself into the Bias circuit where it adds current and power to that pot, which has to dissipate that power. IF you send too much wattage to the Final, or a bad tune up - spurries can add to the level of RF present and add power to the bias circuit in which the devices in it has to dissipate that power along with any RF leaking thru, and the 8 Volts the Bias feeder sends into it.

I've seen this happen too - so my fixes are in several directions...

You have a part located in C218 - this is an NFB - you may need to change it's value - LOWER - or another mod they do is to use a 1000pF (102 or 0.001uF) Disc cap and a 1K resistor - this instead of the single cap - for now you have a variable NFB that you can tailor to the drive level you need the Driver to be.



Part of the "DRIVE" problem is the preceding part is a Bipolar into a Gate MOSFET - which is fine except for if it's too much drive in dynamic headroom you run into clearance headroom issues with the Driver seeing too much power from the preceding stage - Back it (RF power) off!

You really should put something like this in...
The 102 Disc cap will take more RF into itself in the loop - the 1K helps determine the GAIN of the circuit.

With more power into the loop - the Dynamic Range is lowered to help with the SUBSEQUENT stage receive power with less dynamics' signal strength - SSB should be just fine. In fact, this mod is used in Radios like the Cobra 148GTL, HR2510 and even this chassis - only without the cap resistor combo - this helps you quit losing finals from overdriven Drivers from the Poorly designed Pre-driver section that offers too much headroom but not enough COMPRESSION to limit spiking the Final - the Driver simply passes it along.

You can "tune" your drive by adjusting the 1K to a larger value (More GAIN example 10K ) or if the Final gets too hot, less than 1K (680 ohms minimum)

That mod helps keep your transmitter cleaner too. You are using C218, but it needs help.

Well, if the Final is bad, and the pot is good, you'll need to somehow protect your investment while you're away...

I've known of people that go out of the road and leave the radio to the family.

Sometimes it's a good thing, the kids keep in touch, but then too, kids can also be the ones that divulge too many details and the family unit - screeches to a halt.

CB is what it is...

But if someone or something abused it, or spiked it - that is a problem. A99's are DC grounded but a stepped leader can absorb enough of the static to poke the radio with it. Strumming the radial with high winds can do this too.


Hence the Urban Myth of "Coax into a Glass Jar before I go to bed"

Yes, you need set bias for replaced driver/final. AM regulator transistor is cheap, I would replace it too.
Mike

Your readings are above 19K - but not above 100K or thereabout - so this is a good sign.

I have a graphic attached to help you decipher this reading - you're measuring across two resistors - the Variable and R241...so yes, it will be lower...

You need to replace the Final yes, but I see, in your ohmic readings because of how it shorted - the wiper arm is key here...you'll need to rotate the pot and verify it has full turn adjustment range

MARK the head of the pot to the board - score an alignment mark to reset the pot to original spot after this test...

When you measure again... turn the pot to see if the readings change- if not - the pot has to be replaced.

You should have shown a short from one side, to the center tab - that is ground that covers both a FIXED terminal, and the Wiper terminal. In your post I think you confirmed this...The other FIXED terminal should have showed a mid-ranged ohmic reading...19K so you're ok with the POT as far as that goes...but is it still adjustable?


Now that the Final has been removed, are you back to "open" leads again on the board where the Final goes or are they - the pads - still showing 34 ohms? OR any type of dead short? (Measured across - One - the Source - (GDS) - should be ground foil. But the other two should show open measured across...