Liberty Plus MM

Starting a new topic to cover the Liberty Plus. This model has a coaxial power connector, an internal battery, and a TEG. It is meant to be able to run stand alone, not plugged in. The power connection is for charging the battery, supposedly only required once at the start of the season. The TEG is intended to power the unit during normal operation.

Below is a picture of the main board and a schematic.



*Updated schematic 7/29/20



Edited 2 time(s). Last edit at 07/29/2020 04:00PM by Ziggy.

Hah, the Liberty Plus schematic and board layout is essentially identical to the Independence, other than the connector used on the upper left. The independence has soldered wires for the battery and TEG connection. It also has the components for the external power supply, but they are not populated. It looks like the Liberty Plus should operate identically to the Independence, so my controller board and software should run in it. That's good to know so I can pick up a crapped out Liberty Plus and know it will work....

I own this massine.
One remark: it can very easily burn out! It is absolutely wrong board plan. The plus and minus is just next to each other. Some mousture between them and the full board is in flames. It happened to me, and I needed to exchange even the relay as it was completely burned.
I advise to seal the board with conformal coating like in robot mowers in front.

On the Independence topic, you wrote that you ordered the 330°C rated TGPR-5W-5V-40S modules. Have you installed and tested them? Are there any results yet?

I have received them and the TEC1-12710. As mentioned on the other thread, I've been swamped at work so I have not had a chance to work with either of them. I wish I could have got the 30mm modules - I don't think I'll get three 40mm modules to fit. (They were not in stock so I ordered what I could - and TBH I didn't measure first :|

The 12710 modules are supposed to be good to 200C, so I might try them in the MM1000 (it was running at ~150C albeit a bit cool) and the 'real' TEGs in the Liberty Plus - but I don't know if it takes 30mm or 40mm modules.

> and the 'real' TEGs in the Liberty Plus - but I don't know if it takes 30mm or 40mm modules.

Odds are the Liberty Plus is the same as the Independence, i.e. two 40x40mm TEGs in series...

From a blog reader August 10, 2020 at 8:52 pm:

I recently acquired a used non working Liberty Plus battery operated MM. Been at it to get it working. I have replaced nozzle, cleaned inside of combustion chamber and a bunch of other maintenance – including thermistor resistance check. The problem I am having now is that everything in startup cycle seems running as it should – except the gas solenoid valve is not activating. I manually activated the valve using a 12 volt power supply and it works and I was able to light off the nozzle flame.

I have traced the problem to the controller PCB. The surface mount transistor labeled Q1 is shorted (see Q1 in your schematic.

I am a retired EE – and although not expert in today’s digital tech do have a pretty good set of diagnostic and DIY skills to replace this SMT. My question is – do you have any info on the specs of this transistor – and where I can source a replacement? From your schematic it seems to be an NPN type (?) and just being used as a solid state switch to apply power to the solenoid coil. If you are open to discussing this let me know via an email and I will send you my cell phone number

Reply to blog reader August 10, 2020 at 11:08 pm:

No problem. Also check the forum, on the mosquito magnet section, where it is much easier to ask questions.
I believe any garden variety NPN small signal transistor (e.g., 2N3904) will do. It may take some doing to solder it in place of the smt device. To be sure, measure the solenoid dc resistance and calculate the current at 12vdc – it shouldn’t be much. Hard to understand how this could have failed. Plus if it fails shorted, the solenoid would always be on, and gas would come out, and the trap would work. Also check the diode, is it open (which would explain the dead NPN)? Of course, you need that to snub the inductive load.

From the blog reader August 16, 2020 at 11:12 am:

Thanks for reply – I was able to source the exact surface mount replacement transistor and R&R it on control board. Solenoid is now working again. I think maybe I may have caused the shorted transistor probing around when I was replacing nozzle and doing other maintenance. I am now having start up problems -an suspecting it might be related to bad propane ? The start up sequence seems to run ok – including the spark ignitor. I can hear the sparking occur – and visually see it occurring in the cat converter assembly when I have disassembled the unit for cleaning and bench testing. I know that the propane is being feed by new nozzle into the converter – but the spark will not ignite it and keep it burning. When I take a propane cigarette lighter flame to the output end of the converter it ignites the propane and the propane continues to burn after spark ignitor pulsing stops. When unit is fully assembled and i start it up it works as it should – but when it gets to the sequence of starting the spark ignitor pulsing – followed by the solenoid activation to feed propane I can hear a “pop” but it isn’t igniting propane to establish a continuous flame? Unit runs thru this start up process 3times – then shuts down with a slow flashing red error signal which indicated fuel problem? I have verified that thermistor is functioning OK, solenoid operation ok, (I have manually operated solenoid nozzle assembly to test nozzle flame pattern and it was ok) .

My next step is to try another 20LB propane tank to see if this makes any difference as I have exhausted all other possible problems ….

I can hear a “pop” but it isn’t igniting propane to establish a continuous flame

Perhaps there is something wrong with the air/fuel mixture. I am having a similar problem with my Patriot (not plus), about which you might have read on the blog, but the Patriot is marginally working. Your pop is from some fuel and air igniting, however, perhaps there is not enough air and fuel mixture to keep the combustion going.

• Check the regulator - a full tank has slightly higher pressure, might work with a failing regulator for a while. I believe the output should be ~11 inWC.
• Is there an obstruction? With trap off, attach an electric pump to the Schrader valve and check the pressure. Perhaps an obstruction is inside the metal case constricting the exhaust or fuel/air flow.
  !!! Don't back-feed the regulator - valve must be closed. !!!
• (Dangerous: Light the propane coming out of the nozzle with the solenoid on.)
• While starting, does the thermistor assembly get hot (100°C or so) at the thermistor?

What was the replacement solenoid driver transistor?

Again, please register for this forum so you can respond here.



Edited 2 time(s). Last edit at 08/16/2020 04:23PM by dev.

> but when it gets to the sequence of starting the spark ignitor pulsing – followed by the solenoid activation to
> feed propane I can hear a “pop” but it isn’t igniting propane to establish a continuous flame?

If you hear a 'poof' or 'pop' shortly after the solenoid engages, that usually means the propane has ignited in the cat chamber. If it doesn't keep burning, it could be one of several things:

- Spark is not strong enough to fully ignite, due to low voltage or arcing elsewhere
- Bad propane or bad regulator
- Blocked/bad air flow in carburetor
- Blocked or incorrect nozzle
- Too much air flow in carburetor. I have found that the gas will not ignite if the fan is running at full speed. This is unlikely since OP is running standard controller.

It looks like you've covered most of them, but it's worth checking...



Edited 1 time(s). Last edit at 08/16/2020 04:26PM by Independence.

> I believe any garden variety NPN small signal transistor (e.g., 2N3904) will do.

I have temporarily replaced the solenoid transistor with a TO-92 2N2222 transistor before, and it's worked fine

>You wrote - I believe any garden variety NPN small signal transistor (e.g., 2N3904) will do.

I have temporarily replaced the solenoid transistor with a TO-92 2N2222 transistor before, and it's worked fine<


I was able to source some SOT-23 2N2222A transistors and managed to replace the defective Q1 solenoid switch.

I also discovered the probable cause of ignitor not lighting off fuel mixture. The root problem was caused by several senior moments related to my taking apart the cat converter in my Liberty Plus to clean it. I took it apart about a week before some surgery I had scheduled and set the parts aside figuring I would reassemble it during the weeks recouping from the surgery. I mistakenly reassembled it wrong. I put the small circular white ceramic honeycomb back into the carburetor cap - when it should have been inserted into the input side of the converter casting itself. I discovered this after seeing your pictures you posted of the cat convertor you took apart.

I fixed this - but now I am having problems with the ignitor. Before I R&R'd the solenoid transistor on my Liberty Plus it went thru its correct start up sequence. Now it does not. The ignitor now works erratically on start up. Instead of hearing a long series of sparks - I only hear about 2 to six of them and then they stop. This pattern tends to repeat itself several times before the startup sequence stops, The transistor Q2 on the controller is located right behind the one (Q1) I replaced and Q2 is the switch that controls the ignitor. I am thinking maybe I disturbed something on the controller board when I replaced Q1? It seems Q2 gets it's base drive to activate the ignitor from the PIC on the control board.

I am a retired engineer - Graduated in 1967 and the curriculum only taught vacuum tubes - no solid state. I am no expert when it comes to today's tech - and know enough to get myself in trouble ....

Any ideas or suggestions on what I should look for??

Bigwalt Wrote:
> Now it does not. The ignitor now works erratically on start up. Instead of hearing a
> long series of sparks - I only hear about 2 to six of them and then they stop. This pattern tends to
> repeat itself several times before the startup sequence stops,

First thing to check is that you're getting the base drive from the PIC to Q2. The PIC output to the base drive resistor should be at 5V when the igniter is turned on. Next thing to check is that the collector of Q2 is pulled down. If both those things are happening, then it could be something on the igniter board. Unfortunately, I never traced that schematic out as I never had any trouble with it. As far as I can tell, once Q2 is turned on, it activates a high voltage charge/discharge circuit that just keeps cycling as long as Q2 is on. The input voltage to that circuit is taken from the battery, so you can actually tell the state of the battery from the frequency of the clicks. A higher voltage results in faster clicks, while a low voltage results is slower clicks.

One last thought is to make sure the return lead for the igniter is screwed down tight on the cat converter. The spark return is via the case of the cat and if you don't have good contact to it, it's not going to work reliably. You could also remove both the igniter and return lead and let them spark on the bench and see if there is any difference.

< I am a retired engineer - Graduated in 1967 and the curriculum only taught vacuum tubes - no solid state. I am no
> expert when it comes to today's tech - and know enough to get myself in trouble ....

Today's environment is wonderful for the tinkerer. IMHO, the Arduino platform has done wonders to introduce micro-controllers to the everyday person. In the old days, it would take a lot of reading and figuring out register settings, etc just to get a controller running, but today, any kid with a computer and an Arduino board can start programming instantly.

I only hear about 2 to six of them and then they stop

Use a clip lead, or a wire, and carefully try connecting Q2's collector to its emitter, which will bypass the PIC and Q2 and directly power the igniter. It should keep clicking until you remove the connection. If this works, there is a problem with the transistor or the PIC. Otherwise, there is a problem with the power supply, or the igniter. If so, measure the voltage going into the igniter.

Both output leads from the igniter (I hope there are 2 leads!) need to be connected, but I suspect they are because you are getting initial sparks.

Another possibility is that after a few normal sparks, the igniter output is doing a much smaller arc or resistive connection via a path (carbon build-up?) somewhere, and preventing the spark. You can troubleshoot this with the bypass, but be careful: ⚡High Voltage⚡

Thanks so much for taking the time to figure out and do the schematic on the Liberty Plus spark discharge ignitor. I am still at work trying to get my Liberty Plus running. I have solved all the previous problems and am 100% sure that all the critical components are now functioning as they should but it still refuses to light off. It runs through its start up sequence - and I can hear the spark ignitor functioning and smell the propane odor coming from casting output opening - but the propane will not ignite. If I put my hand over the output opening of the casting for a few seconds while the ignitor is sparking I can hear a faint pop - but the propane does not light and continuously burn. I am thinking that either the ignitor spark does not have enough energy to properly ignite the fuel mixture - or the fuel mixture is too lean to support continuous burning? I have bench tested the ignitor board and it produces a blue arc that will discharge across about a 1" gap. I have checked the ignitor ground lead connection to the casting and inspected the actual ignitor that is mounted inside the cat convertor casting and can't see any problems.

The one thing I have done that I am beginning to suspect is the regulator. The original regulator that was on the Liberty Plus was really in bad shape - so I replaced it with a new one that was a non adjustable type set for 11" water pressure I actually tested it using a manometer I made and showed 10 to 11" of pressure. I am thinking that perhaps this is not enough pressure to deliver the needed amount of propane into the cat converter casting which results in a fuel mixture that is too lean to support combustion.

Any ideas or comments would be appreciated. If you want to discuss with me send me a PM and I will respond with my cell phone # I am located in ME - EDST

I can only go over a couple of things to look at, some of which you may already have done, but just for completeness and for the benefits of others who may come by later:

- I assume you have the right replacement nozzle? Delavan 1.75 GPH 45 degree A cone?

- 11" WC seems to be the right pressure for the regulator, though I haven't actually measured mine.

- Is the carburetor air intake/shroud in line with the fins of the heatsink to force air into the chamber? Too little or too much air can cause lack of ignition. The fan should be running at a slow speed when the igniter and gas are turned on.

- Check the igniter in place, at night, when it is activated, and see if there is any spark leakage anywhere else. On my board, they can actually spark across the HV transformer pads on the board if the igniter is not connected. There is insulation applied on those areas to prevent that. Check yours. Also check to see it is not sparking from the outside of the igniter to the metal foil on the cat converter.

That's all I can think of right now. On my units, after the igniter turns on, a few seconds later, the solenoid turns on, and within a few seconds, I can hear a 'poof' and then the temperature starts to rise. Like they say for car engines, if you give it spark, fuel, and oxygen, it will fire....

produces a blue arc that will discharge across about a 1" gap.

That is quite an arc. I received a cheap gas grill spark igniter mentioned in another thread, and it produced a sort of weak arc across about 1/4" gap. It would not ignite the fast moving propane from a blow torch, but did ignite the slow moving natural gas stove. But yours evidently produces much more voltage and energy, so it should be OK.

I am assuming that the thermistor does not warm up at all, right?

Did you test the gas coming out of the nozzle? The flame should be about 1-2" or so. The 11 inWC regulator sounds OK, I think that's what all the home traps all use. But the propane has to exit the nozzle sufficiently. And I tested a regulator that produced 11 in WC, but had some irregularity that would not matter to a gas stove, but that, after a period of time, caused my Defender to enter what I called "abnormal combustion." Read the blog. In that case, replacing the regulator helped.

Does the fan slow down during the ignition sequence? I believe the slow down makes for a richer, slower fuel/air mixture, like a choke would do.

If I put my hand over the output opening of the casting for a few seconds while the igniter is sparking I can hear a faint pop - but the propane does not light and continuously burn.

You are obstructing the exhaust, which perhaps makes a richer mixture, or at least, a slower moving mixture. The pop is the propane/air lighting suddenly. But then the combustion goes out (when you let go?). What happens if you keep the obstruction in place for a minute or so? Does the case or thermistor assembly start to warm? If so, wait a few minutes for the catalyst to warm up, then let go and see if the combustion continues.

The next level is to check for obstructions inside the metal case, and the catalytic converter, which could cause problems. A metal brush to clean the insides, and MAF (Mass Air Flow Sensor) cleaner to clean the CC. These measures have helped others in the past.