overvoltage to a circuit board lamp

[Cornboats]

Re: overvoltage to a circuit board lamp

I've changed 2 resistors so far.
So I've just copied and pasted an earlier post but then clarified;
"There was a resistor in the feed line of the lamp that wasn't measuring its coloured banding. green-purple-silver....gold. Removed it measures 17.29K so I put in a wp5s 10R 5W. Powered on , light was over bright and wp5s started smoking within a couple of secs."
This is the one in the pic with 1 leg pulled. It measured 17.29K
I thought I was playing safe by putting a 10r in its place. I've never had a resistor that measures so out of spec-have you?
The above is the 2nd resistor I changed.
The 1st one I changed was this one
The resistor I replaced was a 470R I put in a 3 watt ceramic 470R. It is situated directly in front of the lamp holder.
On the pic its the white ceramic.

[budm]

Re: overvoltage to a circuit board lamp

OK, so the 0.47 Ohm went bad.
I have a hard time tracing out the connection of that resistor, I can see one leg is connected to one pin of the 3-PIN device, but I cannot trace out to see when the other leg is connected to. I have a feeling that the lamp is being switch on through that 3-pin device. Are you 100% sure that the 0.47 Ohm resistor has direct connection to on of the lamp pin? How about the other pin of the lamp, what is it connected to?
How about the bad 470R? What resistance did it come out to be on the old resistor?
This board will be hard to trace due to board is double sided.

[eccerr0r]

Re: overvoltage to a circuit board lamp

The bulb appears to be driven by DC at least that's the guess because it seems to share a connection to one of the filter capacitors. I suspect a transistor and not a relay is turning it on.

What is that lamp for, is it a solely illumination or also an indication light? Did it used to click when turning on (indicating relay) or silent (indicating transistor)? Was it dimmable?

I'm suspecting a shorted transistor if it was meant to be dimmable (via PWM). Agreed, yes, this double sided board is tough to track. That via pack appears to jump to the top side underneath some component and I'm lost now...

[R_J]

Re: overvoltage to a circuit board lamp

I found some info on a Rusian site, one side of the lamp connects to C5 (+) 2200/50v the return line goes to mos2 (irf540n) Drain, its source is connected to R3 0r47/3w to ground. the gate is driven through R5 100 ohm from pin2 of ic (MC14504b?)

[eccerr0r]

Re: overvoltage to a circuit board lamp

That would add to the suspicion that it is either PWM controlled or at least transistor controlled. Definitely check the IRF540 MOSFET if it melted and shorted. Backtracing from that will be annoying as most of it is low power stuff that likely is software controlled...

[Cornboats]

Re: overvoltage to a circuit board lamp

Could you give me a link to the Russian site? I'd like to read any info available.

In answer to your queries. I've traced out the lines using a multimeter, as you say its difficult as the tracks hop from one side to another and then some just lead to a dead end- unless there's a 3rd track sandwiched in the middle of the pcb perhaps!
The 470R resistor I changed was reading 470r, I changed because it had discoloured and although either side is only slightly discoloured when you hold it up to an inspection lamp the inside of the pcb looks badly scorched. I asked Nice technical for details- no drawings available but measuring a spare they confirmed that it was 470r ditto the other resistor 1r.
The trace from the 1r goes to mosfet irf 2807 source & the - side of capacitor 2200 mf 50v and and the earth no 1 connector pin.
The other side of the 1 r goes to 2 mosfets irf 540n-source legs.

The lamp trace positive goes to +2200mf 50v and to .5watt r br,bl,or,gold next to 24v relay
the lamp trace negative goes to drain (middle leg)of mosfet . The source of the same fet goes to earth -pin 1 of the connector and also pin 6 blue line going to transformer and pin 8 green line going to motor.

The 540r trace. 1 side goes to + 2200mf 35v and also a.5watt resistor grey,red,red,gold
The other side of the resistor goes to a chip acf 40109 zfw 604
and the cathode of a signal diode and the + of 47mg 35v.

The lamp is designed to come on with motor operation and then stay on for a set time afterwards-usually 5 mins.
I hope I've answered your questions and it helps you understand the circuit- because I don't have a clue.

[R_J]

Re: overvoltage to a circuit board lamp

The Rusian site is: https://www.vorotaforum.ru/threads/2545/ this will take you to the thread.

[eccerr0r]

Re: overvoltage to a circuit board lamp

LOL feeding that site through google translate is hilarious. Must be a lot of colloquialisms used...

Someone actually did seem to post a schematic of some sort and/or placement guide on that forum. Alas, not signing up for yet another account...

Is that MOSFET shorted? With the lamp out, is drain shorted to source? Though that Russian thread implies that the MOSFET is not a common failure...

[Cornboats]

Re: overvoltage to a circuit board lamp

Thanks for the link and the replies. I've pulled all the mosfets but they're testing good I'm afraid. Theres also a tip122 -voltage regulator transistor & a U1520 switch mode power rectifier-I haven't pulled them but they test good with a multimeter.
I don't know what else to do-

[R_J]

Re: overvoltage to a circuit board lamp

Happy Easter, You may be looking for problems you don't really have. The regulator is just a LM78L05. Is the only problem, that the lamp burnt out and the rest of the opener operates?

[Cornboats]

Re: overvoltage to a circuit board lamp

RJ Not quite sure what you mean. Do you think it could be the tip 122 not working properly?

I did some more tracing . The black and blue from transformer go to a bridge rectifier. The + out of this this reads 45v with motor running.
The purple from the transformer goes to a large rectifier diode, then through the 470R which gets hot then to the brown motor feed. This also reads 45V with the motor running.
Why design a circuit to come of different transformer tappings when the voltage is the same at 45v??

The transformer tra 121-1025 has a label next to the output legs which reads;
sec 0/22v, 5/32v

[R_J]

Re: overvoltage to a circuit board lamp

where is the tip122 on the schematic? what are you using for ground when you measure this 45 volts?

I could be wrong on the transformer but I believe it reads (in a/c) 0 - 22.5vac - 32vac (0 being the common)
so if you measure the voltage across C5 it will be 45 volts dc, I suspect the voltage across c13 would be around 31 volts dc, it should the drop across R8 (470ohm2w) down to 13 volts.
The output of the (Aout) controls the MOS2 which likely limits the currrent through the lamp and thats why you measure 45 volts across the lamp to ground but with the proper lamp in the socket I suspect it will work properly.
The LCOR is likely a pulse signal from the microprocessor which controls the lamp
This would also explain why the led lamp went up in smoke, it was not designed to be in this type of circuit.

The motor is likely 24volts and you don't see it going up in smoke.
It is likely a similar control circuit that controls the motor. Bout (pin4) to U6 which controls mos3 which is likely a slow startup circuit for the motor.

[eccerr0r]

Re: overvoltage to a circuit board lamp

Thanks for downloading the schematic.

This is a nutty design... The lamp is CURRENT regulated by the microcontroller. WTF. So basically the microcontroller needs to be working and not 100% duty cycle to prevent the lamp from burning out. Do you have a 'scope and what's the voltage of the gate of that IRF540 (MOS2)? If it's 13V and not PWM then your lamp will burn out.

Agreed, does this thing work regardless of the lamp?

BTW the tip122 is on the left middle, connected to the output of an ULN2004 inverting amp pointing leftwards.

[R_J]

Re: overvoltage to a circuit board lamp

It is a NICE design I see the tip122 now, I just did'nt really look too hard for it. whatever the design I suspect it must have worked fine before and if the mosfet is not shorted, installing a new lamp should fix it.

[CapLeaker]

Re: overvoltage to a circuit board lamp

Why not modifying the circuit to LED?

[budm]

Re: overvoltage to a circuit board lamp

I wonder why they have to make it so complicate to drive the lamp, it is just a courtesy lamp.

[Cornboats]

Re: overvoltage to a circuit board lamp

Thanks very much for all your replies. RJ -where did you get schematic from?- thats brilliant, now I feel I'm going to get somewhere.
I have got a scope and I'll come back with answers to all your queries later today.

[Cornboats]

Re: overvoltage to a circuit board lamp

Done some more work on it today- what a great help having a drawing.
Yes the motor works regardless of the lamp.
voltages across C5 are 43V and c13 32v , before R540 33v, after 13.5v, -all rdgs done with motor running.
There are 2 540N mosfets, 1 for the lamp, 1 for a remote flashing light -if required.
the flashing light gate voltage varies 0-1.6v. The gate for the lamp fet was all over the place max 10v then down to 3v then up again and it didn't go off with the motor. I tested out the resistor r5 r100. Markings had gone and as I pushed on the end with my test point it just came off the landing. Took it off the board but couldn't get any reading so I hard wired a .125w 100r straight from the processor leg to the fet gate leg.
Now the voltage is 1.4V going down to 1.13V with the motor on and 0 with it off.
I'll scope the gates and update later.

[Cornboats]

Re: overvoltage to a circuit board lamp

If I can change the lamp to an led it would be better. I have the 2nd of the 2 the customer bought here. lux0475-ba15s-ww. Its a 3Wac/dc 10-20V.

Could you advise mods needed to the board to make it work so its doesn't blow up an damage the board?

[Cornboats]

Re: overvoltage to a circuit board lamp

Both fets give similar traces but the trace for the flashing fets trace disappears for a split second equally.
Both are on about 10 times longer than they are off.