Ray Jefferson Model 155 Marine Battery Charger

[johnbkobb]

RBL testsset on meter black - lead on pin 1 under cup off corner


B R
1 - 2 .538
1 - 3 .557
1 - 4 1.009
4 - 3 .554
4 - 2 .539

R B

1 - 2 open (display flashing just as if leads were not connected)
1 - 3 open
1 - 4 open

R3 is measured at 18.1K Ohms it does look like it is burnt but it measures in the circuit good the bands are brown, burnt looking part appears to be grey, orange and gold

 

[(*steve*)]

B R
1 - 2 .538
1 - 3 .557
1 - 4 1.009

That's expected

4 - 3 .554
4 - 2 .539

Can you double check that you had the black probe on pin 4, not the red one?

R B

1 - 2 open (display flashing just as if leads were not connected)
1 - 3 open
1 - 4 open

As expected.

It looks like the bridge rectifier is OK.

R3 is measured at 18.1K Ohms it does look like it is burnt but it measures in the circuit good the bands are brown, burnt looking part appears to be grey, orange and gold

Yep, those bands make sense. I'll have to review the PCB because that resistor is clearly not doing what I think it is.

The most important measurement now will be the voltage across the capacitors, but I expect that will be OK.

After that, the problem looks like it's due to the TL494 not switching the mosfets. The AC voltage measurements across the purple circled transformer pins will confirm that.

We'll have to figure out why...

 

[johnbkobb]

Had a setback. The PCB board fell over on to the metal enclosure case and shorted in these 3 places.

Black - PCB board trace from PBL405 pin 4 to 470uF 200V negative side

Red - PCB board trace from the other 470uF 200V positive side to Q1 (IRF830 center pin) pin 2

Yellow - PCB board trace 470uF 200V negative side to Q2 (IRF830) pin 3

I heard a loud pop when the board fell over onto the metal enclosure case and shorted out so I immediately unplugged it then after it was unplugged there was another pop before I finally got the board off the side of the enclosure case. I looked at the component side of the board and saw no apparent damage. When I checked the solder side I found these 3 traces damaged and took a picture and circled in yellow, red and black. Should I reflow some solder on the trace damage?

PBL405 rectifier now has nothing between any of its 4 pins no matter how I connect the test leads.

 

[(*steve*)]

If you're lucky you may have only taken out the bridge rectifier. I'm surprised it didn't fail short circuit and then blow the fuse -- that's pretty typical.

The mosfets may also be damaged. It's also possible that there were other points that were shorted and other components may be damaged.

The good news is that you have a series of measurements from a number of components on the board. You should repeat all of these measurements (resistance/diode check ones first) and note any significant differences.

What you really need to do is to ensure that your workspace is suitable for this work. It is entirely possible that you could have done damage to yourself if this had fallen on you, or if you had instinctively reached down to catch it.

I recommend that your workplace is clear and has an insulating surface. An open newspaper will do. Make sure that your cables (mains cables especially) do not hang off the edge of the bench.

edit: it sounds like you'll need a new bridge rectifier at a minimum, but probably best to see what else is damaged so as not to waste a trip.

 

[johnbkobb]

I don't have a place nearby where I can buy parts for this so I'll have to order online. My guess is that I won't have the parts for at least a week though. Only part I have available is 1 IRF830. Had 3 but used 2 to get it so the fuse wouldn't blow by putting 2 of my new ones in. I've started a cart at Mouser but only have a few items in it right now. The PBL405 is one of the items in it I think I think.
Do you have a land line I could call? If so PM it to me.
Thanks

John

 

[(*steve*)]

It may be worth putting a TL494 on the cart if they're not too expensive. I can't rule out this being faulty. Order a socket at the same time. It will save you pulling out hair if you ever need to replace it again.

I'm not sure what mouser charges for freight, but here I'd be better off buying more than I need (or at least buying everything I need at once) because freight would be a large proportion of the total cost.

You shouldn't need to flow the solder over those points. I don't think the tracks were damaged, it's just where the capacitors got discharged (that would have made a pop) and then where current from the mains flowed long enough to destroy the bridge rectifier (potentially a larger pop).

If the mosfets were turned off (and it seems they are) then they may not have been damaged, but this sort of thing can cause large spikes and if you managed to short out to other parts of the circuit then you may have damaged other things -- as you note, invisibly.

 

[73's de Edd]

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Sirs . . . . .

I'm just now tuning in on this thead, and thought that I had seen it started on another thread . . .but with it not having evolved into this higher state of analysis.

I had used the other info and was tracing circuit action in my mind and was step in step with what has now already been said here so I'll only inquire for info that I don't think that I have seen up to this point.

What is the high voltage rating on he main B+ supply caps? Those two big black 'uns.

I am seeing the secondary LVPS paltry requirements being derived from the AC line transformers right terminals over to the C7 filter cap and its diode to feed LV DC to the TL494 Switch Mode regulator IC and 4 bipolar drive xstrs.
Having the output of the 494 feeding into the 2 X 2 totem pole arranged bipolar 1015's and 1815's will give HARD full drive to the driver transformer located just above them.

ASIDE . . . .in looking back for the board layout . . . .

HEY . . . . there DOES seem to be another Ray Jefferson 155 post under Eduard, but his has the R7-R6 gate voltage divider resistors all flamed out.
I can clearly make out their color coding as being blackened-blackened-blackened.

So . . . . HE must, for sure, have at least a bad Q2 FET.

Between the use of both photos one can see the factory original cheap carbon film resistors that were used for the R7 (R572?) 1 K ohm and R6 (R472?) 75 ohm gate divider circuitry of Q1 and Q2.

Steve sez . . . . .
The purple circled resistor looks like it has gotten too hot (I don't know what it's purpose is).

Now back to that driver transformer, its isolated secondary is going to be needing a B+ drive level to the gates so I believe that overheated resistor is being the series source of that voltage.
With Gate to Drain and Source inter crashing, expect some collateral component damages.

John, you mentioned the AC across it (indicating a moderate AC ripple), but what DC B+ level do you have on either side of it ?
I consider its B+ source to be tied to the output of the second BIG BLACK main filter.

Far right bottom corner I am seeing the derivation of the heavy duty output source of the supply and I was ALSO querying the heat /discoloration in the past times across the vertical mounted BLUE film resistor (R20?)
It looks like Eduard's has fared better than yours..

I can account for the two secondary battery supplies, with them coming from the heavy Full Wave Bridge metal cases, down just below the heavy power fuse.
But I see no third source , but, look at the top right corner and see if that plastic heat sinked device might be just a 3 leaded full wave rectifier would then possibly be giving the third supply.
( Probably symbolized with diode polarity directions on its case.) Or, at the least, a part identifier number.

All for now . . .


ADDENDA: .

BUT I do see in the interim, while I was poking this up, that the thing go BOOM on its FWB rectified side to the FETS foil lines .
And I do see a 200V DClevel being mentioned now.
Did you test the FWB in the DVM's diode test function instead of its ohms range. Accounting for an open reading if using the ohms function
I feel that the foil paths opened up as fuse links.
But any DEAD short would be a definite failure.


My procedure for that NOW needed PCB foil repairpath is the fact that Hobby shops offer small sheets of copper foil for copper tooling .projects.
The thickness is even slightly thicker in gauge than the PCB foil . . .thats velly good !
I clean up the mess on the PCB and leave a clean gap and rosin up and scrape to tin the opposing ends and use solder wick to leave a final tinned smooth surface.
Then press a piece of clear scotch tape on top of the damaged area and trace over the foil and opened path outline with a fine blue Sharpie or 0 .5 mm drafting pencil.
Pull up the tape and stick over the foil and cut out the "patch" about 1/16 longer than the PCB foil gap.
Rosin up and tin both sides of the copper patch and move over to bridge the gap and reflow solder the
unions between the connections.
Pull out acid brush and MEK-Acetone-Xylene or alcohol and final clean the area of rosin, dry and burnish with a q-tip to a silvery shine..
The completed repair them impinges upon meeting Mil spec or NASA rework standards.
MUCH neater and original than an ole hunk of wire bridging the gap.


73's de Edd

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