Biomass Boiler not driving cleaner motor relay. ENERTRES BIOMASA BI-650

[sam_sam_sam]

Yes I would agree with you for the most part except that when you have reached the point of “no return” and it not going to be practical to charger the customer you can walk away or if you told the customer that there is a minimum charge weather or not I can fix or not I still should get the minimum charge that the customer agreed to now weather or not you can collect on that or is another thing now is it worth pushing the issue that is a hard call

I have a minimum charge that I charge customer when I am pretty sure I know what the issue is and I can fix it but there have been times that I have spent several hours when the customer problem is more than just the obvious problem because it more than one problem a device can have just like the example that you gave the one thing that you can take away from this experience to look the hole job more throughly but let just say for the sake of this example that after many hours you do get the device working because the customer gave you the device so now the question what do you do now do you give the device and charge them for what the gob should have cost if you had all of the knowledge from the beginning or you do not say anything at all and learn from the experience and call a day not a good place to be in because I have been there before

[edugimeno]

Yes, I find that in electronics repair its more difficult than in other jobs to provide an accurate quote and to charge for the real time you have spent. I guess mechanic car repair is kind of alike. You have an impression of what could be broken, given your own experience in similar products you have repaired (TV shows no image, but has sound, you EXPECT to replace the backlight strips), or just after a quick examination (SMPS chopper transistor shows a burnt spot, you EXPECT to replace the Q and call it good) but there there are many times that you end up spending a long time you could not have expected, sometimes because you overlooked something on your first examination (DC converter IC in the back side was burnt too) and if you sum up all the invested hours there's no way a client would pay that amount, probably closer of higher than purchasing a new product. Yes some of that can you can call it "invested into learning" but sometimes that goes way beyond that....

[sam_sam_sam]

I NEED to prove myself that I can repair it, and I feel SO proud when I fix it! And then if I can even get some money for the repair, wow, double prize I guess Im not the only like in this situation around here

One thing that I have learned about what to charge for a repair is how much time does it take to replace the parts that are needed plus a couple of hours of continuous research but the time to find all the information needed to do the repair this might not be the right way to do this but it the gain in knowledge is priceless because the next time you will make your money back when you first research the issue or issues with a given device for repair

I also repair devices for customers but I do not most of the time I do not give a quote because I really do not know what it going to take to repair a device but I will tell customers that there is a minimum of 4 hours that I will charge you if I have spent many more than 4 hours to repair there device

[edugimeno]

Yes Sam, thanks for your comment. Definitely I can't count as an experimented repairman, I have been "into" electronics for the last 35 years but always in the amateur side. I've always been an IT specialist and only recently with a morecomfortable job with more spare time, I've started offering my services sporadically to some known people and some of them have spreaded the voice so now there's like 10-15 people who call me from time to time to bring a TV, amplifier, car stereo, power supply or other weird piece of electronics that I have to repair and only very recently I have started charging them for the repair.
I see that I can't really charge them for the REAL time invested in the repair ,by far. Like you said, as soon as I find out the brand and model number, I start searching for information, schematics, common issues, badcaps entries, etc about that model and read as much documentation as I can. I may have repaired like 50-100 devices in the last 4-5 years and most of the times I've charged like 50-100€ for many of them. That's like 1 or 2h work depending on salaries, for repairs that usually have taken up to 8h in total...PRE-study, open, remove probably damaged IC's, Q, D's, order them, solder new ones, close, test, etc...
Most of the time I do this because every repair turns into a challenge for me and I NEED to prove myself that I can repair it, and I feel SO proud when I fix it! And then if I can even get some money for the repair, wow, double prize

I guess Im not the only like in this situation around here

[sam_sam_sam]

Ok final update on this with conclussions.

He tried it yesterday on the boiler and called me to state....: IT ALL WORKS PERFECTLY NOW!!

So somehow I may have damaged these transistors but they were already damaged because just by replacing them the board came back to life...

Despite being my fault or not my conclussion is that I still don't master the abilities to repair an electronics board as some of my testing techniques are dangerous...That's why even when I believe I can go ahead with some repair, I always come to this forum to get some assistance. In this case I tested the relays before...

Thanks everyone!!

The one thing that is very important to understand is how the circuit works one rule that I have is when I see mechanical relays to test them I remove them from the circuit board because 95%of the time there is some type of protection circuit that keeps the circuit from being damaged by emf or electrical spikes

When checking optics sensors is a little tricky sometimes to in that you have to have the positive and negative correct when checking the LED side of the device with a meter in diode mode

One thing that is very helpful is to look up ic chips for what the pin outs are and what they are and how they are supposed to function

Google is your friend and also You Tube is also your friend as well this how I have learned a lot about electronics and how to repair stuff like this

One note do not be so hard on yourself because you are learning something that you do not have very much experience with as you do more research and repairs you will learn more about how different circuits and how different components work

I can not count how many times things have gone wrong when trying to fix something that I did not do the research that was required to have some kind-a understanding of how the circuit works and this is how you can get in trouble but remember that this is also a learning process and that this is part of it

When I first started repairing electronics devices like lcd monitors and switching power supply I came across this forum and hung out here for a long while before I found a couple of monitors that did not work and I wanted to repair them I got help from some people on this forum that took the time to point out how to research different devices and how to understand how and what functions the device does and how to check ic chips

As far as repairing switching power supplies I learned a lot from hanging out around here and YouTube videos and watching videos very closely and playing them over several times until I understand what and how they were doing it

Congratulations on the success of your repair on this device I have been following your progress on this repair because I also have learned something from it as well

One more item that did not end up in the landfill

[edugimeno]

Ok final update on this with conclussions. Summarizing: Client states that one of the functionalities of the board (pellet ash cleaning motor) is not starting, neither during normal operation, nor during tests screen,

There is one relay in a row of several, that clearly drives the 230V ac voltage to the cleaning motor. Before any other test, I try to apply 24v dc to all relays directly and they all click on-off but this-supposedly-faulty -one goes like slow and weak. I measure all driver transistors and all give the same readings but the ones driving this relay. It seems that 2 transistors drive each relay in aparallel like and OR gate.,

I replace these 2 transistors and turn the board back to the client.

He tried it yesterday on the boiler and called me to state....: IT ALL WORKS PERFECTLY NOW!!

So somehow I may have damaged these transistors but they were already damaged because just by replacing them the board came back to life...

Despite being my fault or not my conclussion is that I still don't master the abilities to repair an electronics board as some of my testing techniques are dangerous...That's why even when I believe I can go ahead with some repair, I always come to this forum to get some assistance. In this case I tested the relays before...

Thanks everyone!!

[petehall347]

can always short relay driver c to e with board powered . or get real technical and monitor voltage on it base

[redwire]

It's your fault. You blew it up lol. This is how I look at it...

A BJT consists of two diode junctions inside. For a transistor to work, the C-B junction must be reverse-biased, and the E-B junction is forward-biased.
But when you apply 24V across the coil, current flows backwards through the transistor's two diode junctions - the C-B junction is forward-biased on, and the E-B junction avalanches as a zener because they are around -7V only.
Then current flow is from the GND, as the board also draws power. You end up supplying the board with 24V power flowing backwards through the transistor(s) and if the current is too high, it will damage them. Note the transistor base will appear negative V and the resistor protects the MCU output pin hopefully.

If it was a 5V relay/power the transistor(s) E-B junction would not avalanche and conduct, so maybe this is why it can work then.
I just remove relays that I suspect are bad and bench test them.

[edugimeno]

Im realizing... when I applied 24V across the protecting diode, all I did was applying +24v to the upper rail (already common +24v for all relays) and 24v GND to the other side of the coil, which is directly fed by both transistors, and driven to gnd by one of them when their source signals becomes high. Is putting their collectors to GND a source to backcurrent? I don't see how this can damage them. Not trying to argue, just not able to see it.
And like I said, when one transistor switches on, the other, in parallel like an OR gate, would be "suffering" this backcurrent too, like when I manually applied this voltage to the whole pair, right?
See attached reduced schematic...
Thanks!

[redwire]

What schematic? Current flow normally is from emitter(s) to GND, leaving the coil(-). But it goes backwards when putting only 24V power on the coil, it is trying to power up the entire board! Flows into the emitter(s).

For functional safety, sometimes a relay driver needs consensus from two microcontrollers or supervisor systems. As a redundant "AND" gate. So it will have two inputs- even though one is all you need and see on other control boards.
But you seem to have an "OR" gate with the two transistors.

[edugimeno]

Im a little confused on this. Per the schematic, it looks like these relays have 2 transistors that will drive the coils, mounted in parallel, like different sources will be able to independently drive them high.
If having fed 24V manually at the coil lead would damage the transistors, what if one transistor drives 24 to the coils? It would be also getting 24V in reverse to the other transistor in paralel right? So this leads me to think that if it's me who applies the 24V across the coils leads, the voltage seen by the transistors would be the same as if the other transistor would be providing it during normal circuit operation, and I wrong?

Thanks again!

[redwire]

Injecting 24V across the relay coils causes back-feed through the transistors and can damage them. It's not a good idea.
I think what happens is reverse current flow throught the (zener) E-B junction and forward C-B junction diodes.

[edugimeno]

Thanks. I directly injected 24V to the relay coils (across protetion diodes). I checked polarity, in this case the common point is the positive side, and then GND is switched by the driver transistors
I haven't checked all those parameters. All I have checked is the protetion diode and it tests OK
Yes the K1N transistor is an BT3904 NPN transistor which has Vce=40v (this board is powered at 24v), and has Ic=0.2 and P=350mW while the old one 1GW has Ic=0.1 and P=250mW, so it looks like it would work fine
Thanks!

[harp]

My 2nd question is, being that I only applied direct voltage to the coild of these 2 relays (correct voltage, correct polarity), and there are only shorted transistors in the relays I checked, is there any chance that I could hve burned these transistors just by having tested the coils in circuit? Once I felt smoke at the second relay, I stopped checking all the other relays, but I don't know if it was me who was burnng them and the original issue was other...

So on what points you are injecting voltage, 24v?
Have you inspect conections from positive rail through relay and transistor to negative rail? Are negative rail ground? Coil resistance, driving voltage?
It is general bad idea to inject voltage without limit the current, but if you inject directly on coil, that should be the smallest resistance in this circuit, so the most current should pass through coil, not transistor...

Use multimeter in continuity mode and traceback schematic of that part of circuit.

And... 1GW = BC847CW or BC847C is not 5x BC547C... I not check datasheet.
Make sure that transistor is same type, voltage and current capabilityes.

[edugimeno]

Im back, my local shop received the new SMD transistors. Instead of 1GW, I got K1M, do you believe they would fit?
Also I got one of the 2 transistors on another relay shorted too. My 2nd question is, being that I only applied direct voltage to the coild of these 2 relays (correct voltage, correct polarity), and there are only shorted transistors in the relays I checked, is there any chance that I could hve burned these transistors just by having tested the coils in circuit? Once I felt smoke at the second relay, I stopped checking all the other relays, but I don't know if it was me who was burnng them and the original issue was other...

Thanks

PS: I was able to remove the old transistors with no much effort just by using a normal solder iron, switching from one side to another quickly and pushing gently with tweezers. I removed the relay to make some room, which was way harder to remove than the Q's using a basic desoldering pump

[edugimeno]

i dont have trouble with components this size they are pretty big compared to the real small ones . thing is with an iron its difficult to hot up 3 legs at the same time . what i do is add new solder with my iron then hot air .

Suppossedly flux around would help getting the heat spread around the whole transistor, that's my hope...Will see when they come

[petehall347]

I will prpbaby get one of those magnifiers with a weight. I don't have hot air, only a gas powered soldering iron that has a point for hot air, but having some other tiny smd R's very close, I tend to belive that with hot air all the stuff around is going to get loose

i dont have trouble with components this size they are pretty big compared to the real small ones . thing is with an iron its difficult to hot up 3 legs at the same time . what i do is add new solder with my iron then hot air .

[edugimeno]

good magnifier with light. and hot air works a treat .

I will prpbaby get one of those magnifiers with a weight. I don't have hot air, only a gas powered soldering iron that has a point for hot air, but having some other tiny smd R's very close, I tend to belive that with hot air all the stuff around is going to get loose

[edugimeno]

And does it sound reasonable that feeding 24V to the relay coil pins (correct polarity) the transistor started to smoke? Is this a hint that the Q was already blown?

Also can I have damaged any other electronics before the transistor driver (like an IC) maybe getting these 24V to get back to the IC?

Thanks

[petehall347]

good magnifier with light. and hot air works a treat .