No the transformer is used to provide a cascade of different speeds, each winding is switched by each relay
I checked continuity between N and L and there is no shortcut
Maybe the wire was damaged
The guy is now scared to test it again as it caught fire last time....
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Yes that's exactly the method I was thinking of doing next time I can go there, measure current with direct 230v drive, and then thru the board and see if the board add extra current maybe due to a internal shortcut I haven't seen
But I'm still surprised that the current was able to burn my jumper copper wire and not able to trip the 3.12A fuse... Is it right to use a motor winding copper wire for this os does it have any drawback that I didn't realize? I can't figure out how such a diameter (I believe it was 0.95mm) didn't stand a current flowing in series with a 3A fuse...
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Fancoil.controller with current issues
Hi there! One friend called to say his fancoill (used for a main access cold Air courtain) controller caught fire, and asking if I could recover the half burnt board
He said the design was too bad as this thing was probably designed for hot water only, as the board was places right underneath the condenser radiators
I found some burnt traces and after a quick Google search for the board name (Pwr-05v-w) I could see an image of the original I was able to find where the original traces were going
The scheme seems simple, from what I understand mains gets into the while 3 lead...
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Grundig 39 WCP 2014 BRS. Bad BL, hack or fix?
Hi! I was given this TV. It would turn on fine but then after a while the BL would shut off while rest of functions would stay working. I assume this 99% means a shortcut in the BL so the PS detects the overcurrent and shuts off the BL pwr.
I managed to keep it up for the time enough to enter into settings and turn down the backlight to 50% which seemed to help. I was able to watch it for some hours several days
But the other day, I went to try it and the BL didn't even start at boot up. I want to repair it but: This is a spare TV that I want to keep at a house that I seldom...
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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...
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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...
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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...Last edited by edugimeno; 05-15-2024, 12:25 PM.
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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 [B]GND [/B]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...
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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...
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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!
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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...
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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
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Last update, I spent some time last weekend on this TV and found a position where the tape would allow the TV to turn on. BUT there was a small (like 4cm) bar at the bottom where the image was a little degraded, like greyed out. I moved the tape patch everywhere right and left, tried shorted pieces of tape, and nothing, I had to give up and leave it as is, this is a summer house where I spend only a couple months a year so I will probably be able to live with this.
Thanks everyone
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Final update on this. I replaced the mosfet by the correct model, and took it to be tested before I tried with the the resistor. It failed, "shorcut in bus" message right away.
Took it back home, put a 0,1 ohm resistor in the bus sense R and this tested perfectly now, with no errors and controlling heating correctly.
So this board had basically fallen into the wrong hands when it was sent to the shop to be repaired in the first instance. Thanks everyone who replied here!
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Ok, last one (hopefully) update on this.
I released some of the water pressure out, tested the heater for a while and seems to be running ok, continously with the new alternate "digital" board, so everything fine for now.
Thanks everyone!
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