Hot Air Station - Air Pump Failing

[redwire]

Re: Hot Air Station - Air Pump Failing

Those potentiometers are weird chinese stuff because it is a dual-potentiometer housing, right angle, PCB mount, but only the one top wafer is used. The WH148 family is a pretty generic chinese ripoff of Alps.

I haven't seen the exact same part for sale, ever. You could ask vendors if they can supply one.

What could be done is take out the pot, take it apart (bend up 4 tangs) and swap out just the phenolic wafer/shaft from a new potentiometer. Just keep the old housing and transplant the wafer/shaft portion. It's really no fun and I use a hammer/screwdriver to bend the tangs back down flat putting it together. Note hazardous live mains on its 3 pins, so the pins should not touch other stuff.

If you stay with 500k, I would change the cap from 0.1uF to 0.047uF for better control. Or go 250k and keep the original 0.1uF part. 20k is too low

I had the same pot failure in a 4000W ebay "SCR" controller, exact same circuit but bigger triac. I took it apart and there was a defect/crack in the carbon track, just a cheap build.

[caphair]

Re: Hot Air Station - Air Pump Failing

Out of circuit at the lowest setting on the meter it reads .830MOhm so 830kohm and doesn't gradually decrease to 370k and then to 0 ohms with a hair turn after that.

Only pot I have is a B20k could that be used?

Would these from Amazon work? Pretty similar size specs expect for the leads and the back mounting piece the original has

[stj]

Re: Hot Air Station - Air Pump Failing

that's an american value, in europe the closest would be 470k
frankly, anything is better than what you have!

[caphair]

Re: Hot Air Station - Air Pump Failing

If it's low or full-blast only, then I think most likely the pot has failed, or its soldering connections. It could be a low quality lazy BT137 triac, I did see that once.

I would check the (hot air) potentiometer with an ohmmeter and see if the wiper might be going open or it's noisy. Halfway should be around half value etc. but in-circuit it will read lower and non-linear and I would lift one end pin of the pot to take readings.

Part of the problem is the crappy design - a (hot air) 500k pot is best for 220VAC, and 250k for 120VAC, to give a good range of control (with 0.1uF gate cap). So a 500k pot on 120VAC has a huge dead zone, nothing really happens until you are past 3/4 rotation. The minimum-air trimpot is to help cover that up but it just keeps things at a minimum until the pot is way past that.
I'm not sure if you are running 120V or 220V.

It is a 500k pot B500k and they have the first two pins tied together. Finally took the front off. So looks like a bad pot as it reads 120k till the very end of its travel which is then 10 ohms.

Should I replace it with a 250k or would that require messing with the trim pot? How do I make sure I'm getting equivalent replacement? Are they all the same size for the value? There's a ton on eBay makes it hard to know which one to get

[sam_sam_sam]

Re: Hot Air Station - Air Pump Failing

I’m on 120v. I can’t tell which pins are being used as it’s soldered from the front so would need to remove from the housing. But measuring 1st and 3rd pins it reads 120k as well as pins 2 and 3, and no change really until it’s on the max air setting then it jumps to 10 ohms.

Comparing to the other two pots they read 2.2k and gradually change as expected. But about half way on them reads 3k then it drops down as you continue. Maybe in circuit it’s giving those readings. But the one for air speed doesn’t have a smooth change

This tell me that the trim pot is bad and that more than likely your biggest problem with it

But did you pin one to pin two because pins two and three might be tied together

[caphair]

Re: Hot Air Station - Air Pump Failing

If it's low or full-blast only, then I think most likely the pot has failed, or its soldering connections. It could be a low quality lazy BT137 triac, I did see that once.

I would check the (hot air) potentiometer with an ohmmeter and see if the wiper might be going open or it's noisy. Halfway should be around half value etc. but in-circuit it will read lower and non-linear and I would lift one end pin of the pot to take readings.

Part of the problem is the crappy design - a (hot air) 500k pot is best for 220VAC, and 250k for 120VAC, to give a good range of control (with 0.1uF gate cap). So a 500k pot on 120VAC has a huge dead zone, nothing really happens until you are past 3/4 rotation. The minimum-air trimpot is to help cover that up but it just keeps things at a minimum until the pot is way past that.
I'm not sure if you are running 120V or 220V.

I’m on 120v. I can’t tell which pins are being used as it’s soldered from the front so would need to remove from the housing. But measuring 1st and 3rd pins it reads 120k as well as pins 2 and 3, and no change really until it’s on the max air setting then it jumps to 10 ohms.

Comparing to the other two pots they read 2.2k and gradually change as expected. But about half way on them reads 3k then it drops down as you continue. Maybe in circuit it’s giving those readings. But the one for air speed doesn’t have a smooth change

[redwire]

Re: Hot Air Station - Air Pump Failing

If it's low or full-blast only, then I think most likely the pot has failed, or its soldering connections. It could be a low quality lazy BT137 triac, I did see that once.

I would check the (hot air) potentiometer with an ohmmeter and see if the wiper might be going open or it's noisy. Halfway should be around half value etc. but in-circuit it will read lower and non-linear and I would lift one end pin of the pot to take readings.

Part of the problem is the crappy design - a (hot air) 500k pot is best for 220VAC, and 250k for 120VAC, to give a good range of control (with 0.1uF gate cap). So a 500k pot on 120VAC has a huge dead zone, nothing really happens until you are past 3/4 rotation. The minimum-air trimpot is to help cover that up but it just keeps things at a minimum until the pot is way past that.
I'm not sure if you are running 120V or 220V.

[stj]

Re: Hot Air Station - Air Pump Failing

check the soldering and do a recap.
my old one, they hadnt even stuffed the parts into the board properly before soldering them!!

[caphair]

Re: Hot Air Station - Air Pump Failing

I think this YH852D+V2 pump is mains AC powered, with other 852D+ variants instead using the 24VDC wand blower fan. Here I see three triacs, two opto-couplers, one DIAC.

The AC triac controls are 24VAC to the soldering iron, the other for switching mains to the hot air heater, and last one Q7 for phase-control switching (what I think is) AC mains to the pump. I might be wrong but I think it's a fish-tank kind of pump so it needs AC.

There is a 1MEG trimpot U3... for the pump speed control (minimum?). Careful the TRIAC heatsink is hazardous live, if you go in there with a screwdriver to twirl it.
Trimpot U1, U2 by LM358's are for temperature cal.

I have found bad potentiometer that made it "all or none", and once I had a TRIAC become very insensitive and same result. I would expect the light bulb test to have some part-way brightness?

If bumping the station changes things, it might be bumping the pump to start it or there is a bad solder joint or wonky potentiometer.

Bumping doesn't change anything. When I had the lightbulb connected it seemed the same brightness (dim) up to the highest air setting then it goes full brightness. I also noticed some hiccups in the light when changing settings. Some quick instances of the light going off then back on.

Should I attempt to play with the trimpot for pump speed?

How could I test the pot and triac? I was wondering if cleaning the pot would do any good but it seems different than I'm used to seeing. Almost looks like there's silicone grease inside the enclosure

[redwire]

Re: Hot Air Station - Air Pump Failing

I think this YH852D+V2 pump is mains AC powered, with other 852D+ variants instead using the 24VDC wand blower fan. Here I see three triacs, two opto-couplers, one DIAC.

The AC triac controls are 24VAC to the soldering iron, the other for switching mains to the hot air heater, and last one Q7 for phase-control switching (what I think is) AC mains to the pump. I might be wrong but I think it's a fish-tank kind of pump so it needs AC.

There is a 1MEG trimpot U3... for the pump speed control (minimum?). Careful the TRIAC heatsink is hazardous live, if you go in there with a screwdriver to twirl it.
Trimpot U1, U2 by LM358's are for temperature cal.

I have found bad potentiometer that made it "all or none", and once I had a TRIAC become very insensitive and same result. I would expect the light bulb test to have some part-way brightness?

If bumping the station changes things, it might be bumping the pump to start it or there is a bad solder joint or wonky potentiometer.

[caphair]

Re: Hot Air Station - Air Pump Failing

I connected a 40w bulb (lowest wattage I had) across the motor terminals and it lights but dimly and doesn’t increase in brightness with increasing air speed knob, only when on full air speed does it get brighter.

So seems like a controller issue. How would I go about figuring out the problem? Weird that sometimes it works. I tried gently tapping on components when it’s acting up hoping maybe a bad solder joint but it had to affect

[caphair]

Re: Hot Air Station - Air Pump Failing

Do these diaphragms look bad?

[caphair]

Re: Hot Air Station - Air Pump Failing

are you sure it's a phase-angle dimmer?
my old station had a 555 timer driving the triac.

I’m honestly not too familiar with the two types or the operation of these units. What should I look for to determine? Here’s a pic of the unit.

Does the hot air heater run straight off the mains and the soldering iron off the 24vac tap?

[stj]

Re: Hot Air Station - Air Pump Failing

are you sure it's a phase-angle dimmer?
my old station had a 555 timer driving the triac.

[redwire]

Re: Hot Air Station - Air Pump Failing

A stalled pump rotor would draw more current and give lower voltage for a given control setting. Once it's spinning, the voltage reading would go up. It's just an AC light dimmer/TRIAC doing the speed control, no regulation. A multimeter with true-RMS will read the voltage more accurately.

So I'm thinking the pump is getting stuck and it's not the electronics at fault.

But if you suspect the pump speed control TRIAC circuit, you could put a 25W light bulb in place of the motor and see how it works as a light dimmer.

[caphair]

Re: Hot Air Station - Air Pump Failing

I think it's mechanical stiction in the pump, high friction that needs it set high to get it moving, rotating.

Would that explain the voltage readings when it cuts out?

[redwire]

Re: Hot Air Station - Air Pump Failing

I think it's mechanical stiction in the pump, high friction that needs it set high to get it moving, rotating.

[caphair]

Re: Hot Air Station - Air Pump Failing

Today the air flow started acting up and cuts out unless on the highest setting.

Sometimes after going to the highest setting and back down it’ll work but not consistent.

I measured the ac voltage at the connector going to the pump and when it’s working it steadily rises from 38vac on lowest setting to 118vac on highest.

When it cuts out it measures from 28-34vac on any setting except the highest which kicks the pump back on at 118vac

Would this be an issue with the pump itself?

[stj]

Re: Hot Air Station - Air Pump Failing

get a pair of thick rubber gloves and cut them up??

[madan1]

Re: Hot Air Station - Air Pump Failing

I did not use any glue for the hoses. Just zip tied them to the nozzles.
The rubber sheet I got from a local shop.. it's just a generic 1mm rubber sheet. It's not really the best solution, because it is too stiff, but works for me. I use the air usually for small smd components and do not really need high air volumes.
I think silicone rubber sheets will be better.