Daytek F19AH

**retiredcaps** · 09-01-2010, 04:19 PM

Re: Daytek F19AH

Originally posted by UserName666

I'm not sure what it is but it is labeled L102. D108 is what I just took out.

This boards also has an L107,L105 and L108 surrounding the Filter cap. Not that has anything to do with anything. Just not sure what the "L" is.

L indicates an inductor. They will measure 0.3 ohms on the multimeter. L102 is in parallel with D108 pins 1-3 (look at the back of the PCB). This explains why D108 was reading 0.3 ohms suggesting it is shorted.

This is why sometimes, "in circuit" testing, is not reliable. We know D108 is good out of circuit.

PS. Good job on the pics. It helps a lot.

**UserName666** · 09-01-2010, 04:20 PM

Re: Daytek F19AH

So if D108 is good it can be put back in?

**retiredcaps** · 09-01-2010, 04:31 PM

Re: Daytek F19AH

Originally posted by UserName666

So if D108 is good it can be put back in?

jetadm123 asked for these readings so wait to see if jetadm123 is satisifed first.

**jetadm123** · 09-01-2010, 06:23 PM

Re: Daytek F19AH

Yes, go ahead and put D108 back. Can you supply a photo of the logic board (board that that plugs in the 6 prong connector on the power board)?

Man, at this point I'm hoping that PlainBill may have a trick up his sleeve.

**UserName666** · 09-01-2010, 06:50 PM

Re: Daytek F19AH

A few different views.

Attached Files

**PlainBill** · 09-01-2010, 06:51 PM

Re: Daytek F19AH

Originally posted by jetadm123

Yes, go ahead and put D108 back. Can you supply a photo of the logic board (board that that plugs in the 6 prong connector on the power board)?

Man, at this point I'm hoping that PlainBill may have a trick up his sleeve.

At this point PlainBill is trying to find a rational explanation for the behavior of the output. Why is voltage detected at the input side of the opto-isolator, but not at the output? And what is the expected output voltage? Where did teh 'magic smoke' come from (or is that another monitor)?

PlainBill

**UserName666** · 09-01-2010, 06:55 PM

Re: Daytek F19AH

There was no smoke just a faint burn smell at the time it went out/died.

**retiredcaps** · 09-01-2010, 07:11 PM

Re: Daytek F19AH

Originally posted by UserName666

A few different views.

Holy. The very first monitor I repaired was coated in that dust like yours. It took more than 30 minutes just to clean up the insides to a respectable point.

I didn't think Winnipeg was that dusty!

**alexanna** · 09-01-2010, 07:53 PM

Re: Daytek F19AH

Originally posted by PlainBill

At this point PlainBill is trying to find a rational explanation for the behavior of the output. Why is voltage detected at the input side of the opto-isolator, but not at the output? And what is the expected output voltage? Where did teh 'magic smoke' come from (or is that another monitor)?

PlainBill

Try the poke and prod approach on the opto,Or just reflow the solder?
Al.

**PlainBill** · 09-01-2010, 08:27 PM

Re: Daytek F19AH

Originally posted by alexanna

Try the poke and prod approach on the opto,Or just reflow the solder?
Al.

I don't see the point of that. The design of the SG6841 is that the opto-isolator pulls the feedback input down to regulate the output voltage. A bad solder joint or open opto-isolator would allow the output voltage to rise. UserName666 has observed voltage pulses on both the input and output of the opto-isolator

Still, you bring up a valid point. Most of the parts check out. We're down to the point where only a few parts remain untested. The TL431 shunt regulator, the opto-isolator, the SMPS controller, and the power FET.

But by nature I abhor 'shotgunning' instead of logical troubleshooting.

PlainBill

**alexanna** · 09-01-2010, 08:38 PM

Re: Daytek F19AH

My idea of poke and prod was to move and flex things ,see if some thing will change.
If i understand things correctly isnt the opto pin 1 and 2 one the hot side and 3 and 4 on the cold side could chosing the wrong ground have made a difference in the readings?
Al.

**UserName666** · 09-01-2010, 08:53 PM

Re: Daytek F19AH

So I put D108 back in, plugged it in and the transformer is not clicking anymore. Hooked everything up thinking it might be fixed. Did not work...Started taking it back apart again and realized after I put on the screw & nut that I forgot to solder it. Soldered it and plugged it in again. The transformer still is not clicking. I think Im now further behind then when I started. Is it time to give up yet? Would forgetting to solder that in have blown something else????????????

**PlainBill** · 09-01-2010, 08:59 PM

Re: Daytek F19AH

Originally posted by UserName666

There was no smoke just a faint burn smell at the time it went out/died.

I've got a few ideas running around my mind. I see two possible approaches. The first will require a fairly good soldering iron. The second will require a variable power supply, or you may be able to get by with several batteries.

The first thing to double (triple) check is the orientation of the caps you installed. I've marked what should be the + and - sides of the caps; please verify they are correct.

The second thing to try is I have marked two inductors in the upper left hand corner with a white L. If you have received your soldering iron, remove the lower one on the board and see if the power supply will work. This disables the inverter. (I'm not sure your 'cold soldering tool' will work on anything this heavy. That is heavy gauge copper wire).

Another approach will require a variable DC supply or several batteries. (Don't remove the inductor for this test). 'D' Flashlight batteries, a 6 volt lantern battery would be ideal. Even a 9V DC transistor radio battery might be sufficient. Assuming you are using a 6V battery, hook the - terminal of the battery to the - lead of any of the caps you replaced. Next, measure the voltage of the battery. It will probably be above the nominal output voltage for the battery. Hook the + terminal to one of the + leads of any of the caps you replaced. Now measure the voltage of the battery again, then disconnect the battery. No need to run the battery down. What voltage did you read with the battery hooked up?

PlainBill

**UserName666** · 09-01-2010, 09:10 PM

Re: Daytek F19AH

"I've marked what should be the + and - sides of the caps; please verify they are correct." - Did you upload a pic because its not showing on this end.

By 9v that just means a everyday 9v battery??

Could someone possibly address my concern in post 72 about having forgotten to solder D108?

**retiredcaps** · 09-01-2010, 09:13 PM

Re: Daytek F19AH

Originally posted by UserName666

Could someone possibly address my concern in post 72 about having forgotten to solder D108?

There is a good chance there is no more damage. With D108 out of circuit, the voltage stops right there. The circuit is "open".

**UserName666** · 09-01-2010, 09:15 PM

Re: Daytek F19AH

The resistance between pins 1 & 3 is back to 00.3ohms. Is there any reason the transformer may have stopped clicking? At a TOTAL loss now.

**jetadm123** · 09-01-2010, 10:04 PM

Re: Daytek F19AH

Originally posted by UserName666

The resistance between pins 1 & 3 is back to 00.3ohms. Is there any reason the transformer may have stopped clicking? At a TOTAL loss now.

Any chance the power supply has started? Remember, the clicking indicated the power supply was trying to start. Checked for 12V at the output? Power LED on? Have the voltages at pins 2,7 and 8 on IC101 changed?

**UserName666** · 09-01-2010, 10:07 PM

Re: Daytek F19AH

Originally posted by UserName666

The resistance between pins 1 & 3 is back to 00.3ohms. Is there any reason the transformer may have stopped clicking? At a TOTAL loss now.

To narrow things down a little more I tested a few more things.

-The 10uf 63v cap by the filter cap that was previously fluctuating between 11 and 17 volts is now sitting steady at 1.584 volts

-IC101 Between pins 1-3 the input voltage is 4.27 volts where it used to fluctuate from 15-19v

-No voltage coming to opto isolator anymore

I will say that when I put D108 back in it did take quite a while. If it was good out of board and I somehow heat damaged that part does that give cause for the previous symptoms? If now damage it would have been the same result as not soldering it in???

**UserName666** · 09-01-2010, 10:11 PM

Re: Daytek F19AH

Originally posted by jetadm123

Any chance the power supply has started? Remember, the clicking indicated the power supply was trying to start. Checked for 12V at the output? Power LED on? Have the voltages at pins 2,7 and 8 on IC101 changed?

No because when I noticed it first stopped clicking I hooked everything backup thinking it was fixed but didnt work.

There is 161 going into the transformer but nothing coming out. I'll have to find my previous post about pins 2,7,8 to find out what it was before.

**PlainBill** · 09-01-2010, 10:17 PM

Re: Daytek F19AH

Originally posted by UserName666

"I've marked what should be the + and - sides of the caps; please verify they are correct." - Did you upload a pic because its not showing on this end.

By 9v that just means a everyday 9v battery??

Could someone possibly address my concern in post 72 about having forgotten to solder D108?

Ahh, crud. Here it is.

PlainBill

Attached Files

Daytek F19AH

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