Dead DX2517

[Robb]

The rectifier does not appear to be wired up wrong.

The 2 yellow wires coming from the transformer go into the 2 terminals marked "ac"

The red wire comes out of the terminal marked +

The white wire comes out the terminal marked -

With my meter on the 20 ACV setting, I get 12.24 out of one yellow AC wire, I get 11.94 out of the other.

Switch it back to DC volts,

I get nothing out of the red wire marked +

First off, it sounds like you are measuring the AC to ground. We are talking about AC here; not DC. You have to check AC across both output leads of the xformer. Then test the output voltage across both DC outputs of the rectifier.

Usually, these xformers put out about 18-22vac. It then goes thru the rectifier and there is a couple of volts dropped down - max. Then the 10,000uf cap smooths whatever AC ripple is left on that line. Then the voltage reg circuit will bring it to 14.3vdc when VR601 is adjusted properly.

Use the schematic.

 

[Ranch55]

Yes, as Robb posted above. See my previous again.......

 

[TruckerKevin]

Okay that makes more sense now. lol

Across the transformer leads I get 19.60 on the ac setting

But where I am getting confused Robb, is I only have 1 dc output from the rectifier, the other is ground.

What I am saying is, you said measure the dc voltages across the 2 dc terminals coming out of the rectifier, but they consist of a positive and a negative

 

[TruckerKevin]

If you mean put the volt meter to dc volts, the neg. lead to the - terminal and the + lead to the positive terminal, I get 0 volts

 

[Ranch55]

Okay that makes more sense now. lol

Across the transformer leads I get 19.60 on the ac setting

But where I am getting confused Robb, is I only have 1 dc output from the rectifier, the other is ground

That is correct, that is your two dc voltage measurement points. The positive dc voltage coming from the rectifier is one VOM dc probe, the other negative (ground) coming from the recifier is the other VOM dc probe.

 

[Robb]

If you mean put the volt meter to dc volts, the neg. lead to the - terminal and the + lead to the positive terminal, I get 0 volts

If you are certain that you have the AC into the rectifier correct; then the rectifier has gone short. But I'd be real sure of that first.

You can also test the rectifier out of circuit - or the old one for starters. You will need to use the diode function of your meter and look at the schematic to see each diode in that rectifier pack and test each one in both directions of the diode. Simple: a diode should only conduct in one direction ONLY.

 

[Ranch55]

If you mean put the volt meter to dc volts, the neg. lead to the - terminal and the + lead to the positive terminal, I get 0 volts

Okay, do this.
Connect the rectifier to the transformer leads. DO NOT connect the rectifier dc positive and dc negative terminals to anything.
Measure the ac voltage going into the rectifier across the two yellow wires with your VOM in ac volts.
Next, put your VOM on dc volts and read the dc voltage coming out of the positive and negative terminals of the rectifier. You should see in the neighborhood of maybe 16vdc to 24 vdc.

 

[TruckerKevin]

I just did exactly as you said, to the letter.

I unsoldered the 2 dc lines so they are not connected at all, and puugged the unit in.

I get 19.48 on the AC setting across the 2 AC leads.

I flip back to DC volts.

With negative lead on - terminal and positive lead to + terminal, I get no volts at all.

I move neg. lead to chassis ground and recheck to be sure, still nothing.

 

[Ranch55]

The rectifier is dead .........

 

[TruckerKevin]

So at this point, I should (should) be able to take an external power supply and hook it to the positive and negative leads once I find the value required and turn this radio on, since that is the bridge rectifiers job is to convert it to dc volts, right?

 

[Ranch55]

So at this point, I should (should) be able to take an external power supply and hook it to the positive and negative leads once I find the value required and turn this radio on, since that is the bridge rectifiers job is to convert it to dc volts, right?

Hold on, let me check the schematic again. I did exactly that also on a radio and you need to do that "after" the internal voltage regulator, as you want to bypass that also.

 

[Ranch55]

Positive lead of power supply to the "ON/OFF" switch point where it comes out of the voltage regulator circuitry and negative side of power supply to ground.
Get a new rectifier ......

 

[Ranch55]

Are you connecting the power supply to the leads that would connect to the rectifier dc terminals ?
DO NOT connect that way.

 

[TruckerKevin]

No

So far I have tried running the positive wire to the power switch but still got nothing as far as powering on the radio goes.

I DID get power to the fuse block and power supply board now by doing that, but the radio still does not power on. I have it disconnected right now, I want to study the schematics and make sure I am not over volting anything first.

But, just a question. Why would I not be able to connect it to the rc dc terminals? Isn't that what the rectifier does, supply voltage to the power board?

 

[Robb]

So at this point, I should (should) be able to take an external power supply and hook it to the positive and negative leads once I find the value required and turn this radio on, since that is the bridge rectifiers job is to convert it to dc volts, right?

Permit me to say this about that . . .

If you cannot troubleshoot a relatively simple power supply circuit using your meter to determine simple things like testing each diode inside a bridge rectifier; then what chance do you have fixing the radio - which is far more complicated? I don't know if you know how to test diodes; but it seems like now would be a good time to start. It is actually a lot easier than you might think.

Pardon my saying that; but if it were me working on this thing, I would see to it that the power supply circuit was right, tight, and out of sight - lol. Determination counts here. Don't let this thing beat you; that is the whole point here. Get that meter fired up and test those diode packs. If they are both fried - probably - then build one from scratch with loose diodes; or buy another diode bridge. They aren't expensive. A 10A bridge should be sufficient; less than ~$2

Let's say that the radio has a dead short in it. Which is possible from I'm seeing so far. You will find out soon enough if you use an external supply to test.

I would mark and remove the output of the regulator circuit from the board and then test and repair each part of the rectifier and regulator circuits one at a time before hooking it all back up together.