How to go about checking this PCB

[david74]

Hi, I have this ignition PCB, it opens a valve but does not ignite. I bought a primitive tester for £7.99 and what I checked was the fuse and the output terminals.

The fuse is ok and output terminals show 0.05 (My Ohm meter goes from 1 to 0 and says 200kO on the selector knob dial). But I can't read anything on the input of the grey little box the output terminals are.

I went to the local phone shop and the person there poked around with the meter and spotted a blown capacitor.

He said he would be happy to swap out any faulty part but also said that he had no means of finding which one was which.

Can I find anything conclusive with a multimeter on the board?

I understand that capacitor appears as an open circuit to the 3V multimeter.

If I wanted to order the capacitor, how would I figure out its specs?

Please could anybody check out the photo?

There is a primitive diagram on the box.

 

[Spoon]

Ok, correct me if I'm wrong, but the component that you have circled is a resistor. (The one with the 4 coloured stripes)
To get the value of the resistor, you use the coloured stripes.
The stripes to me look like brown, black, brown. and the end one looks Gold. That will give you a value of 100 ohms and a tolerance of plus/minus 5%
The wattage of the resistor, you may find out by measuring the length and comparing it with the catalogue lengths.
Also the value of the resistor may be printed on the PCB when you take the damaged on off.

 

[david74]

Ok, correct me if I'm wrong, but the component that you have circled is a resistor. (The one with the 4 coloured stripes)
To get the value of the resistor, you use the coloured stripes.
The stripes to me look like brown, black, brown. and the end one looks Gold. That will give you a value of 100 ohms and a tolerance of plus/minus 5%
The wattage of the resistor, you may find out by measuring the length and comparing it with the catalogue lengths.
Also the value of the resistor may be printed on the PCB when you take the damaged on off.

Oh, thank you, it just says R42 on the board probably referring to a parts list on some schematics.

What about my other question. Should that grey box read anything on inputs? Actually!!! I pressed harder and it shows 0.01!!!

Do you think swapping that resistor out would sort the PCB? What potential other, bigger problem it could indicate to check first?

BTW, I checked the 24V power supply, and it does show 25V. I did not check it under load.

I also checked the 100 Ohm resistors on eBay but they also specify wattage e.g. 1/4 or 1.8. And the look small, mine is at least half an inch wide.

How do I check other resistors. My tester has diode continuity knob position. When I check a nearby component that looks like a diode, it gives reading jumping around upper 19 hundreds. And it does it both ways.

The other blue large resistor (R4) shows 0.05 but the yellow (R21) says 36 which means that my tester not just goes from 1 to 0 but also gives larger numbers than one.

 

[westward10]

I believe the terminals on the grey box are the 20kv output for the ignitor.

 

[david74]

I believe the terminals on the grey box are the 20kv output for the ignitor.

Yes, they are and I consulted AI and it says that the 0.5 reading on output and fluctuating reading between 0.0 and 0.1 on input is really low. Does it mean they have melted and then fried the resistor?

I ordered a pair of 3W 150 Ohm resistors on eBay because the black line Spoon took for black is actually blue.

There is a little bit of soot on the inside of the box around the 20kV terminals.

 

[mainline]

Oh, thank you, it just says R42 on the board probably referring to a parts list on some schematics.

What about my other question. Should that grey box read anything on inputs? Actually!!! I pressed harder and it shows 0.01!!!

Do you think swapping that resistor out would sort the PCB? What potential other, bigger problem it could indicate to check first?

BTW, I checked the 24V power supply, and it does show 25V. I did not check it under load.

I also checked the 100 Ohm resistors on eBay but they also specify wattage e.g. 1/4 or 1.8. And the look small, mine is at least half an inch wide.

How do I check other resistors. My tester has diode continuity knob position. When I check a nearby component that looks like a diode, it gives reading jumping around upper 19 hundreds. And it does it both ways.

The other blue large resistor (R4) shows 0.05 but the yellow (R21) says 36 which means that my tester not just goes from 1 to 0 but also gives larger numbers than one.

To be able to check most components properly you would need to take them off the pcb or at least one leg or more.

 

[david74]

I checked the other resistors and compared the readings with the stripes and they were all a match except one where AI said it should be 33K Ohm but my tester just shows that it was 32.7 without specifying that it was in K.

The problem was that the protective coating the PCB and parts are covered in are difficult to scrape through.

I could not get any readings from the relay but the board was opening the valve so if that was what relay was supposed to do, then that is ok.

 

[mainline]

I checked the other resistors and compared the readings with the stripes and they were all a match except one where AI said it should be 33K Ohm but my tester just shows that it was 32.7 without specifying that it was in K.

The problem was that the protective coating the PCB and parts are covered in are difficult to scrape through.

I could not get any readings from the relay but the board was opening the valve so if that was what relay was supposed to do, then that is ok.

You maybe lucky and it’s just that resistor gone open.

If not it could be a number of things.

 

[david74]

You maybe lucky and it’s just that resistor gone open.

If not it could be a number of things.

Well, before I cash out £83 on a new board, it is worth trying a resistor for £2.25.

 

[mainline]

Well, before I cash out £83 on a new board, it is worth trying a resistor for £2.25.

If the resistor gets hot very quickly I would unsolder the transformer and see if it does the same.
If it doesn’t then it’s more than likely the transformer is duff.
If it still gets hot then it will more than likely be the switching or both.

Because of your limited experience and lack of test gear that’s probably the easiest steps to take.

 

[david74]

If the resistor gets hot very quickly I would unsolder the transformer and see if it does the same.
If it doesn’t then it’s more than likely the transformer is duff.
If it still gets hot then it will more than likely be the switching or both.

Because of your limited experience and lack of test gear that’s probably the easiest steps to take.

If the resistor gets hot very quickly I would unsolder the transformer and see if it does the same.
If it doesn’t then it’s more than likely the transformer is duff.
If it still gets hot then it will more than likely be the switching or both.

Because of your limited experience and lack of test gear that’s probably the easiest steps to take.

Do you mean the ignition coils or the 24V one because that was hot. It was first thing I noticed when it stopped working.
The 24V one is quite massive. I can hook up to it easily and see if there is voltage drop on ignition.
Hooking up to the little ignition one is complicated.
I'm off to shops on Town street to resolve the resistor. They just arrived.

 

[david74]

The moment of truth. The guy at phone shop was off today so I bought a soldering gun for £9.99 and swapped it myself.

 

[david74]

I have a video with the resistor catching fire. If you have trouble with watching flashing videos, take migroleave in advance. The fireworks start after my phone switches to selfie mode for the second time.

 

[david74]

The aftermath. Now not only the resistor is blown but the capacitor next to it has spilled its guts.

 

[mainline]

The aftermath. Now not only the resistor is blown but the capacitor next to it has spilled its guts.

Well at least you got some ignition, pity it was from the wrong place.
The capacitor may have been the source of the short so you could change it along with the resistor again.

 

[mainline]

Do you mean the ignition coils or the 24V one because that was hot. It was first thing I noticed when it stopped working.
The 24V one is quite massive. I can hook up to it easily and see if there is voltage drop on ignition.
Hooking up to the little ignition one is complicated.
I'm off to shops on Town street to resolve the resistor. They just arrived.

The LZL-24H is a relay.

Yes I meant the ignition one.

 

[david74]

Well at least you got some ignition, pity it was from the wrong place.
The capacitor may have been the source of the short so you could change it along with the resistor again.

What I will do when I get the replacement board, first I will try it in the machine to see if that works.

If it does, then I will replace the resistor and capacitors and compare readings with working board.

Once it does match, I will try it in device again and if works, put it on eBay half price perhaps to recover some money. Or perhaps I could do something more sinister and send the new one back under 14 days return policy.

Also I will maybe develop understanding how certain electric components work together apart from one being blown out when the other is short.

 

[Avo Mk8]

What I will do when I get the replacement board, first I will try it in the machine to see if that works.

If it does, then I will replace the resistor and capacitors and compare readings with working board.

Once it does match, I will try it in device again and if works, put it on eBay half price perhaps to recover some money. Or perhaps I could do something more sinister and send the new one back under 14 days return policy.

Also I will maybe develop understanding how certain electric components work together apart from one being blown out when the other is short.

Realistically, unless you can get hold of the circuit diagram, the board is "beyond economic repair".
R41 is now a gonner. Things burning up are quite likely symptoms of a fault elsewhere, not the actual faults. You may have to detach components to individually measure them, and doing lots of that could end up damaging the pcb or components.

Some of us like dabbling with electronic repairs, and it can often be successful with simple faults like droppers in power circuits, but I suggest a reality check here, and it would be more worthwhile checking there's nothing wrong in the boiler that's going to blow up the next PCB.️

 

[david74]

Realistically, unless you can get hold of the circuit diagram, the board is "beyond economic repair".
R41 is now a gonner. Things burning up are quite likely symptoms of a fault elsewhere, not the actual faults. You may have to detach components to individually measure them, and doing lots of that could end up damaging the pcb or components.

Some of us like dabbling with electronic repairs, and it can often be successful with simple faults like droppers in power circuits, but I suggest a reality check here, and it would be more worthwhile checking there's nothing wrong in the boiler that's going to blow up the next PCB.️

That is a valid concern. But I checked the spark plugs, they are open. And the PSU did not drop the voltage on the fire if you noticed.

There are no other inputs or outputs to check.

I did similar shuffle with an Abarth Spider SatNav SD card. I bought one with valid preburned identity code, used it to download and install the latest maps, then after two weeks (from the first insertion of the card), once it encrypted the contents to my particular VIN, it allows to create and use backup on any card which I did and then restored the original contents to the original card and sold the it on eBay with 10% off. If it makes sense.

What startles me, is that during fireworks, the fuse did not go.

 

[mainline]

That is a valid concern. But I checked the spark plugs, they are open. And the PSU did not drop the voltage on the fire if you noticed.

There are no other inputs or outputs to check.

I did similar shuffle with an Abarth Spider SatNav SD card. I bought one with valid preburned identity code, used it to download and install the latest maps, then after two weeks (from the first insertion of the card), once it encrypted the contents to my particular VIN, it allows to create and use backup on any card which I did and then restored the original contents to the original card and sold the it on eBay with 10% off. If it makes sense.

What startles me, is that during fireworks, the fuse did not go.

The only reason the voltage on the power supply didn’t alter was that the power supply is obviously well regulated and working as it should.
If you had been monitoring the current it would have been another story.

 

[david74]

The only reason the voltage on the power supply didn’t alter was that the power supply is obviously well regulated and working as it should.
If you had been monitoring the current it would have been another story.

The board supplier says they need two weeks to fulfil the order. In a meantime, I still have the second replacement resistor from the pack. How to determine the capacitor specs to order? How to thwart potential overload to avoid the fireworks if I plug it in which did not require an arm and a leg in sophistication?

 

[mainline]

The board supplier says they need two weeks to fulfil the order. In a meantime, I still have the second replacement resistor from the pack. How to determine the capacitor specs to order? How to thwart potential overload to avoid the fireworks if I plug it in which did not require an arm and a leg in sophistication?

Really speaking you could do with a current limiting power supply.
a decent soldering /desolderer station.
A capacitor tester
Diode/transistor tester
A ring meter.
A circuit diagram
and knowledge and experience.
I would remove the capacitor and the transformer, replace the resistor and try again.

 

[david74]

Really speaking you could do with a current limiting power supply.
a decent soldering /desolderer station.
A capacitor tester
Diode/transistor tester
A ring meter.
A circuit diagram
and knowledge and experience.
I would remove the capacitor and the transformer, replace the resistor and try again.

Thank you, I will try that. But what do you mean by transformer? Forgive my ignorance but is not it called an ignition coil. Well it is a transformer. I hear you. I will try it without resistor first (and without transformer) to see if it opens the valve and come back to you.

Is there an AI that could be supplied with photos and come back with a diagram?

 

[david74]

The LZL-24H is a relay.

Yes I meant the ignition one.

Great. Thank you! BTW, there is a 24V 50A transformer too.

What I did now was to snip a leg of that resistor and without unsoldering the ignition one (but without connecting the spark plugs), I launched it and funny enough it not only opened a valve but it also went into intensive venting mode that it did not start before.

Should I add a video? Anyway here it is.

I did hear a clear click of the valve opening.

And I also understand that relay can potentially be used as a transformer. Or at least as an amplifier. Forgive my ignorance. If I sound daft.

I will hear for your answer before I do anything else because I have hair raised at the moment and need a 12h cooldown in any case.

 

[mainline]

Great. Thank you! BTW, there is a 24V 50A transformer too.

What I did now was to snip a leg of that resistor and without unsoldering the ignition one (but without connecting the spark plugs), I launched it and funny enough it not only opened a valve but it also went into intensive venting mode that it did not start before.

Should I add a video? Anyway here it is.
View attachment 118665

I did hear a clear click of the valve opening.

And I also understand that relay can potentially be used as a transformer. Or at least as an amplifier. Forgive my ignorance. If I sound daft.

I will hear for your answer before I do anything else because I have hair raised at the moment and need a 12h cooldown in any case.

The fault is probably going to be in the igniter circuit.
A relay is used to switch a higher current/voltage from a smaller one in this case it maybe switching the fan/valve or other circuits.
The igniter circuit will be delayed until the fan has cleared any gas and then switch gas to the pilot /ignitor until the sensor knows that the pilot is ignited.

 

[david74]

The fault is probably going to be in the igniter circuit.
A relay is used to switch a higher current/voltage from a smaller one in this case it maybe switching the fan/valve or other circuits.
The igniter circuit will be delayed until the fan has cleared any gas and then switch gas to the pilot /ignitor until the sensor knows that the pilot is ignited.

I have a plan, I will remove the transformer. Remove the igniter. See if igniter does spark. In the process, I'll have the multimeter connected to 24V to see how it behaves.

I will start with 2mm gap and go down to 0.5mm.

But that is all tomorrow if it is not busy as it should be as it has been quiet.

 

[david74]

I connected the igniter coil in reverse and it shows 1/100 reduction. It jumps between 3 and 2 volts. Which is plausible because the reverse would make it 20-30K. Which is the rated output.

Edit: I should have realised, it was 24V. I connected 240V to inputs and it blew.
Edit2: This looks pretty much like mine. ebay.co.uk/itm/156355372366

 

[Avo Mk8]

Edit2: This looks pretty much like mine. ebay.co.uk/itm/156355372366

If you look up the Anstoss ZIG2 igniters there are different versions, but either mains voltage, or 300V dc which produce 20kHz output, so I don't think they are a direct replacement.

 

[david74]

If you look up the Anstoss ZIG2 igniters there are different versions, but either mains voltage, or 300V dc which produce 20kHz output, so I don't think they are a direct replacement.

Ironically when order from HSP arrived it was a weird ZAG 1 igniter.
It has a sticker on it with the PCB part number but says Ignition generator.

I admire such elaborate scam.

Anyways, I went on eBay and bought a piezo igniter in order to be able to manually light it as long as the faulty PCB was able to open the valve.

A few moment later. Suddenly I started to recognise my PCB in Ravenheat igniter PCBs available on eBay. It has to do with my autistic brain.

I can swear I searched with the part number with no results, but here it was now for just £39.99 in Dewsbury, just 11 miles from me. So I got the lodger to take me there and here it is. It works!

I was not sure if anything in boiler itself blew the PCB so I connected the flue sensor through the Ohm meter. It jumped from 1 to 19 during ignition and it started.

And I have a warm house now. I have started a PayPal case as this HSP is not responding.

 

[picturevalve]

Ironically when order from HSP arrived it was a weird ZAG 1 igniter.
It has a sticker on it with the PCB part number but says Ignition generator.
View attachment 118762
I admire such elaborate scam.

Anyways, I went on eBay and bought a piezo igniter in order to be able to manually light it as long as the faulty PCB was able to open the valve.

A few moment later. Suddenly I started to recognise my PCB in Ravenheat igniter PCBs available on eBay. It has to do with my autistic brain.

I can swear I searched with the part number with no results, but here it was now for just £39.99 in Dewsbury, just 11 miles from me. So I got the lodger to take me there and here it is. It works!

I was not sure if anything in boiler itself blew the PCB so I connected the flue sensor through the Ohm meter. It jumped from 1 to 19 during ignition and it started.

And I have a warm house now. I have started a PayPal case as this HSP is not responding.

View attachment 118764

What was the value of the burnt resistor in the new unit?
Was it 1k or 1k5 perhaps?

 

[brianmoooore]

What startles me, is that during fireworks, the fuse did not go.

A word of caution when replacing burnt resistors in mains powered devices: Resistors that are likely to catch on fire under likely fault conditions are often special fusible resistors which are designed to combine the properties of a resistor and a fuse, and so not catch on fire (and burn your house down).
A fire caused by such a modification could possibly invalidate your insurance, if the insurance investigators managed to track down what had happened.

 

[picturevalve]

A word of caution when replacing burnt resistors in mains powered devices: Resistors that are likely to catch on fire under likely fault conditions are often special fusible resistors which are designed to combine the properties of a resistor and a fuse, and so not catch on fire (and burn your house down).
A fire caused by such a modification could possibly invalidate your insurance, if the insurance investigators managed to track down what had happened.

That’s why I queried the resistor value, the third band may originally have been red rather than brown - hard to tell the difference when it’s burnt up- but an order of magnitude difference in the resistance 1.5k instead of 150 ohm.
Unfortunately, when a design is “on-edge” these special resistors can give repeated faults, tempting some people to replace them with something “more robust”.
Having said that I don’t think this was a special, all the ones I’ve seen don’t burn up.

 

[picturevalve]

I checked the other resistors and compared the readings with the stripes and they were all a match except one where AI said it should be 33K Ohm but my tester just shows that it was 32.7 without specifying that it was in K.

The problem was that the protective coating the PCB and parts are covered in are difficult to scrape through.

I could not get any readings from the relay but the board was opening the valve so if that was what relay was supposed to do, then that is ok.

Your meter has a 3 1/2 digit display, so the max. reading on the 200k range is 199.9k, so 32.7 reading is 32.7k. You interpret the meter reading wrt the meter range selected.
On the 20k range, the max. reading is 19.99k. A reading of 0.32 on this range would mean 320 ohm so you would switch to the 2k range if you wanted more "resolution" on the reading - that 320 ohm would then turn out to be between 315 and 325 ohm, usually.
Read the manual that came with the meter.