One of those days....

[jhitesma]

So last night I texted my buddy with the warp quad about FGA's performance and we decided if the weather was nice this morning we'd try to do a bit of flying.

I hadn't re-assembled the hex since I got back from Flite Fest, and in fact hadn't flown it since a gentle crash into the soybeans took out two props (and I didn't feel like walking back to my tent for more since my wife and daughter were waiting for me to finish off my last batteries and head home.) So I put it back together. Did some basic bench testing and confirmed things seemed ready to go.

Then this morning while I was waiting for him to show up I decided to do a quick front yard test flight just to make sure it was working well. Uh oh. Suddenly the hex was doing the same thing my twitchity 230 has been doing. Suddenly glitching in the air and dropping an arm then falling out of the sky Crud.

Well, my emax 250 should be good to go. No RX on it right now so I grabbed the one off my knuckle and put it on since I had just taken it off the 250 to put on the knuckle for flite fest. At least it still flies as well as normal. Though with the 5" "indestructible" props it feels sluggish and I'm still not at all happy with the tune (Just can not get luxfloat tuned to my liking...or any other CF PID controllers, really getting frustrated with it.) But at least something can fly.

My friend showed up and we tried to debug the hex and the 230 since they've both doing the same thing with one or more motors suddenly loosing power for no obvious reason. The hex has logging enabled so that will help rule out FC/RX issues, but the quad only has 4 motors to deal with so it's easier to debug - we started with the quad.

Did a few test flights and confirmed that it always seems to be the right rear motor that was cutting out. That's one of the unprotected KISS so while it seemed questionable that the ESC could be the issue as it still lit up and appeared to work...we decided to swap it out with a spare I have as the first test. Whoops, forgot to solder the oneshot jumper. Ok, now it flies. Hey, feels pretty good...maybe it was a bad ESC after...oh wait...there it goes again

Well nuts.

So let's try swapping the two rear motors to see if the problem follows the motor. Solder solder solder....solder solder solder...ok, motors swapped. Test flight. Wow! Feels great! Oh wait...there it goes. And it followed the motor. Well, that seems to answer that. Will have to tear apart that motor and see what's up, I'm guessing I finally burned out a winding running those DYS 1806 on 6x4.5" props.

At least that finally explains the issues I've been having with that quad for a month. Hopefully. Don't think I'll replace just that motor. Think I may wait until I can afford some 2204's for it and replace them all since I've been so unhappy with the DYS. Then I can build some more FT mini planes with the other 3 motors (Just ordered a 5 pack of firewalls last night, what a happy coincidence!)


So the hex...what's going on there. It was a gentle crash at FF. I was surprised it even broke any props. Let's try flying it again to collect some logs and see if it's always the same arm that drops. Oh wait...it's flying great now! Really great, just like always! Did a few flips and rolls and laps around the front yard...seems great. Ok let's take the hex and the 250 up to the field!


Got to the field, put the 250 into the air for some FPV...and crashed almost immediately...something didn't feel right. No damage, put the pack back on and tried it LOS to see what was up...throttled up for a flip...and it stopped responding then a second later (as it should) started beeping and fell out of the sky. Seem to have lost RX. Grrr. Checked things out and all looked ok...but the RX power light was going on and off. Re-connected it, with fresh tape on the connection to keep it secure...seemed good. Test flight again. Lost control almost immediately and zoomed into a wood pole.

Good news, the "indestructible" props are looking like they can loose the quotes and deserve the name. Wonder if surveilzone will ever send the the rest of my order they said they shipped almost two months ago.

But something is definitely going funky with the RX on that setup. It's one of my homemade ones and has never given me any issues...at least not until the last flight of the knuckle in combat at FF. I had originally thought it was a battery sagging...but then started to think it may have been RX lockouts from so much RF in the air...now I'm thinking something may have happened to this one. Will have to tear it apart and see what's up. Oh well.

Let's fly the hex! Feel good, little flip action...maybe I'll land and put on the goggles. Oh wait. Arm suddenly drops and falls from the sky The gremlin is back

Did some ground tests and the right rear motor is making a bit of a clicking sound that comes and goes and it's ESC is running WAY hotter than the other 5. Something is definitely up with that arm. Not sure what yet...will have to take that motor apart and see what's what I guess.

So not a very good day for flying for me Didn't even bring the mobius figuring that would be asking for trouble

Guess I've got some motors to take apart and see what's going on with them.

 

[Snarls]

Bummer, well at least you found the issue with the 230, are narrowing in on the hex, and have a mysterious RX that you know the construction behind. Unfortunate when all your available flying machines have some issue :l Sounds like you did not have any serious damage from crashing besides broken props though so that is to be thankful for. Hopefully you'll be up and flying soon and your props show up!

 

[jhitesma]

Yep, glad to finally know what's up with the 230 for sure, that's been bugging me for weeks. I really wanted to bring it to FF since it would have easily fit in my carry-on without having to take it apart...and I can fly that thing acro like nothing else But it had to stay home since it was misbehaving

I could actually take the motor off my FT Scout and put it on there and get it back in the air now that I know it's a motor...but I love flying that little scout around and hate to take bits off of it....

Just took apart the suspicious motor on the hex. Nothing obvious jumping out at me. Did a quick resistance check on the windings and they all show 0.2ohm...but that's not always enough to say for sure:

I've been wanting to pick up one of the LC meter for years since they're quite useful testing a number of things I encounter in my radio hacking. Just debating whether to be patient and get one for $16 off ebay on the slow boat or pay double that to get one from amazon and have it here tuesday....probably going to be patient, I have more time than money for this right now...could get a new DYS motor for the 230 for the price difference

No serious damage, just 2 props. Though I'm about out of HQ props now...so time to restock on those as well.

And my knuckle is still in flying shape other than a broken boom. And I have wood on hand for that so about 15 minutes of work (an hour or two if I paint it) and I can have that back in the air at least.

The RX issue is probably just from the sloppy construction on that one. I should be able to fix it easily enough.

However I did want to share something I noticed today that could easily be causing issues.

This is the ESC I first suspected was causing issues on the 230. This I suspect is why a lot of people running KISS on carbon frames are burning them up so easily:





That was mounted with the "usual" 3M outdoor double sided tape. Thankfully I had standard electrical tape under the DST foam tape as the combination of pressure from the wrap around the ESC combined with the heat from the ESC has caused 8 caps and the voltage regulator to push completely through the foam tape. If the electrical tape wasn't there those caps would be in direct contact with the carbon fiber. And while the outside surface of CF is usually not extremely conductive due to the final gelcoat of epoxy...there's still a very good risk of a short. It also means the foam tape isn't providing any protection against vibration/impact between the ESC and the arm. This is why I usually use a double layer of foam tape now or a layer of craft foam in addition to a layer of the foam DST.

Since I built the hex later I kept that in mind right...right? Well...here's the ESC on the arm that's having issues on the hex:



Do as I say not as I do boys and girls! I do these things and share it so you don't have to repeat my mistakes This could explain a few things for sure. Looks like I didn't use electrical tape on any of the hex arms and only used one layer of foam...I must have been in a rush. Going to take them all apart and do them right this weekend. The big black voltage regulator poking through isn't a big deal, that's just the silicone case - non-conductive. But those caps poking through...those shiny bits on the ends are their terminals.

Just touching the probes from my ohm meter to the arm I get no resistance reading. But moving them around a bit I do get continuity. So add in some vibrations and with those terminals poking through the foam rubbing against the arm they may be shorting out which could easily cause intermittent issues like I've been seeing.

 

[jhitesma]

Two other thoughts to share at this point....

1) This is probably another downside to my use of self fusing silicone instead of heat shrink. I've already been warned that it's worse thermally (holds in heat more than heat shrink) but it also puts more pressure on the ESC's. I considered that a positive since it kept them from coming loose. But now I'm thinking it's more of a liability since it compresses the foam more. I need to replenish my clear heat shrink...anyone remember what size is best for warp/twitchity sized arms like this? Cranial?

2) I've been doing a lot of research on carbon fiber fabrication the past few weeks. Have an idea brewing I'm not quite ready to share yet. The CF Twitchity used is a 2x2 twill weave. The CF on my emax is a "1x1 plain weave". I don't have a warp here to compare but photos online look like a 1x1 on the plates and 2x2 on the arms, same for blackout. Though again I can't say for sure since I don't have actual parts here to compare with. (and of course this is just the outer visible layer - what's inside could vary.) What I've learned in my research is that 1x1 and 2x2 are the most common weaves. 1x1 looks more like a checkerboard while 2x2 looks more like a herringbone. It may seem counter-intuitive but 2x2 is actually stronger than 1x2 because the fibers don't overlap each other as much which gives them more strength. There are also 3x3 and 4x4 weaves which have a more exaggerated herringbone look and are even stronger. The twill weaves are also easier to do layups with as they drape to various shapes better (not an issue for the flat plate used in these quad designs) which tends to make them more popular even if they look a bit "funkier" at first glance.

What's the point of #2? Not much. Just something interesting I've learned about various types of CF that I thought was worth sharing. If my plans go as I hope I'll be sharing a lot more about CF in a few months. As many of you probably know I've said for a long time that I'm not a big fan of flat plate CF for quads. I don't dislike it. But I still believe that for most people G10 has a minimal weight penalty, for an equal thickness survives crashes better and is cheaper. But that doesn't mean I don't like CF. I love it. I just believe that using flat plate of CF doesn't give enough benefit to really be worth it and is mainly for looks and because CF sells. But doing engineered formed CF is more involved and expensive so we don't see it very often.

And that's what I've been researching Making your own CF plate apparently isn't all that hard it turns out. And doing engineered forms isn't much harder than that. In fact in some arms of our hobby (competition gliders/slopers) it's quite common. I just haven't seen much of it in multis other the occasional custom canopy or other decorative bits. I have a few ideas I want to try that could make for very light very strong frames...possibly even addressing some of cyberdactyls thoughs on thrust column obstruction.

I'm still very much in the research stage of this. I have to pay myself back for what I spent at FF and get my fleet back in the air before I can go spending money on fabrics and resins or get too involved in building forms Heck I need to finish my balsa RV-4 too (which is getting some composite work which will be good practice/warm-up though with fiberglass instead of CF.) This is something I've been thinking about this since before I built my first quad but have kept mostly quiet about. I'm reaching the point of diminishing returns on research vs. experimentation though and figure sharing some of my thoughts may help force my hand into finally putting some of what I've been trying to learn into practice.

 

[cranialrectosis]

Two other thoughts to share at this point....

1) This is probably another downside to my use of self fusing silicone instead of heat shrink. I've already been warned that it's worse thermally (holds in heat more than heat shrink) but it also puts more pressure on the ESC's. I considered that a positive since it kept them from coming loose. But now I'm thinking it's more of a liability since it compresses the foam more. I need to replenish my clear heat shrink...anyone remember what size is best for warp/twitchity sized arms like this? Cranial?

I use 3/4" over those booms with small ESCs like the KISS.

I also put 1/2" over the CF boom where the ESC will sit to further isolate the ESC in case of tape melt through.

 

[cranialrectosis]

I am tinkering with my hex today as well. I love this PDB. It makes powering things a snap.

 

[jhitesma]

Re-mounted the ESC's...and did a test flight. Did well for a few minutes...then the right center motor cut out.

It's way hotter than the rest. I think the issue I'm having is the KISS are cutting out due to thermal overload. But not sure what exactly is causing that. Yes, it's hot out today but I flew in hotter temps last summer. Though that was with BS12's with no thermal cut-out so maybe I was able to abuse them harder.

The motor that was cutting out earlier seems fine. Guess I'll tear this one down and clean it next to see if that helps.

The motor cutting out on the 230 definitely seems to have an issue. Found a difference in resistance between two of the leads so there's probably a burned winding somewhere.

At least the hex made it through FF before this started happening.

 

[PHugger]

Thanks for the KISS advice. I'm at that stage on my BO Hex.
You are using -

• Insulating tape on the arm
• 2 layers of DS foam tape
• And then shrink vinyl over the whole shebang (around the arm)

Is this correct?


Best regards,
PCH

 

[C0d3M0nk3y]

I am tinkering with my hex today as well. I love this PDB. It makes powering things a snap.

This is what you'd be looking at without the PDB:

 

[Burly]

At least the hex made it through FF before this started happening.

Could the reason be that the weather was cool at FliteFest?

How about this...
Could it be that your 12-5 volt regulator on the ESC that drives the ESC's Atmel Chip be dropping out due to overheating?
I looked at the pictures on the Flyduino site, to see if I could identify the regulator...and look up the datasheet.
I thought the number was M39100...but couldn't find any datasheet.
Embedding the regulator in foam certainly is not helping.
If your receiver was dropping out...wouldn't all four motors display the same symptoms at the same time?

It may be that all of your ECSs are on the verge of overheating their regulators...and it just happens to be this specific regulator that is a little more sensitive than the others...and pops first.

I know if a capacitor pops...it's gone.
I don't know if FET's will shut down with overheating?
If so, they may be the culprit and shutting down.
But if they're passive like capacitors...they will blow like capacitors.

When I look at these small KISS ESCs, the first thing I ask myself is...where are the heatsinks?
I know most ECS have a heatsink of some sort.
Of course, the idea is to keep these ESC's small and light.
It's too bad they weren't about a 3/8 of a inch longer at either end, so then they could put 4 mounting holes in the corners that you could attach 4mm Nylon standoffs using nylon screws.
You would just heat shrink the ESC on the arms as normal...with the standoffs providing 4mm of relief.
And if you mounted the Board with the FETS facing down, you'd actually have some room in the airgap to glue on some small heatsinks on the top of each fet...or a single heatsink to cover all 6.

If you needed more room, increase the nylon standoff height from 4mm to 5mm.
Additionally you could cut some side windows in the heat shrink to further promote ventilation, as well as a window over the 5-12 volt regulator.

But with the current KISS PCB layout...I see no way to get any standoff type ventilation in these small ESC's.

 

[Cyberdactyl]

I agree the use of CF for most people is overkill that just want to fly and are on a budget. CF is amazing stuff, but if you're willing to drop to G10, a budget MR can be reasonably priced, somewhat light, and durable. That's why I did the posts about buying plate CF and cutting it yourself IF someone insists on using it, vs expensive (and IMHO overpriced) frames.

One of the negative aspects of multirotor marketing and forums, that can be argued, is that there is this almost fanatic push for someone to purchase a CF frame as their first MR, when a MUCH cheaper solution would be more than fine.

Buying CF cloth, for me anyway, doesn't appear to be worth it for the effort, IF I am not going to shape it more than merely make a plane/flat surface. CF cloth is close to the same price since 4-8 layers of a 'fine' weight are going to be required. Of course, I totally agree, if the decision is made to form it, it changes the whole ballgame, in that a world of options open up. Not only does formed CF look sexy, but intelligently shaping it for structural strength vastly improves it over fastening plates together for an approximate desired shape.

But I understand the draw of carbon fiber, even to this day, it still amazes me.

 

[cranialrectosis]

This is what you'd be looking at without the PDB:

Every time I see that copter...

Damn that's a nice build codemonkey.

 

[C0d3M0nk3y]

Every time I see that copter...

Damn that's a nice build codemonkey.

Thanks! It's been way too long since it's been in the air. I'm trying to correct that.

 

[PHugger]

Cranial what is that called, a White Out?
Eerily similar to my BO Hex.



Best regards,
PCH

 

[C0d3M0nk3y]

Cranial what is that called, a White Out?
Eerily similar to my BO Hex.

Ha! I did think about calling it that for while.

The build thread is over here if you haven't seen it.

 

[jhitesma]

Thanks for the KISS advice. I'm at that stage on my BO Hex.
You are using -

• Insulating tape on the arm
• 2 layers of DS foam tape
• And then shrink vinyl over the whole shebang (around the arm)

Is this correct?

Mostly. I'm just lacking the shrink since I have to wait a few days for it to arrive But that is the eventual plan

With shrink instead of silicone tape you can probably get away with just one layer of DST since the shrink doesn't put as much pressure against the ESC. But it's cheap insurance to use two layers as long as you have clearance for the extra height which isn't much.

 

[jhitesma]

Could the reason be that the weather was cool at FliteFest?

Actually despite being in the desert the weather here today is pretty close to Saturday at FliteFest. Upper 80's with 50% humidity. Which is what makes this all the more perplexing. Oh and bleah, I moved here to get away from this kind of weather

Though the more I think about it the more I realize that I haven't really flown the KISS in high heat yet. I didn't start using them until cranial sent me his back in...November. So this is the first real heat I've flown them in. Then again before FF doing test flights in the yard even when the 230 was falling out of the sky the hex was still flying great and it was 114 out that week.

So I'm really thinking something has happened somewhere that's causing a motor/ESC combo to run hot at times.

How about this...
Could it be that your 12-5 volt regulator on the ESC that drives the ESC's Atmel Chip be dropping out due to overheating?
I looked at the pictures on the Flyduino site, to see if I could identify the regulator...and look up the datasheet.
I thought the number was M39100...but couldn't find any datasheet.
Embedding the regulator in foam certainly is not helping.
If your receiver was dropping out...wouldn't all four motors display the same symptoms at the same time?

I don't believe the receiver is dropping out - I still have signal. The regulators weren't embedded when I first assembled it...they've just sunk in over time due to the pressure from the silicone tape. Big part of why I've ordered new heat shrink instead. The silicone tape is nice for a lot of things and is ok as a temporary measure...but I'm done with it for ESC protection.

I also don't think it's the regulators overheating as the motor ESC combo that's dropping out are both hot. If it was just the ESC I could see it being the regulator.

When it shut down I took a temp reading and the ESC was reading 115f. Hot...but not so hot that it should be damaging components.

It may be that all of your ECSs are on the verge of overheating their regulators...and it just happens to be this specific regulator that is a little more sensitive than the others...and pops first.

I know if a capacitor pops...it's gone.
I don't know if FET's will shut down with overheating?
If so, they may be the culprit and shutting down.
But if they're passive like capacitors...they will blow like capacitors.

I would suspect the FET's before I'd suspect the regulators. I haven't noticed the LED's dimming or blinking when it happens which I would expect if it was the regulators.

I don't see anything that looks like it could provide thermal monitoring on the board...so I'm assuming something is overheating and shutting down. But I'm only assuming it's thermal since the arm that's dropping seems to be running about 10-20 degrees hotter than the others when it happens. But it doesn't always happen.

One thought is that I'm not running signal grounds. I haven't noticed any issues without them so I haven't bothered to run any. But maybe something is now more borderline and one or more ESC's aren't getting a clean signal and are freaking out. Could explain the heat somewhat....

When I look at these small KISS ESCs, the first thing I ask myself is...where are the heatsinks?
I know most ECS have a heatsink of some sort.
Of course, the idea is to keep these ESC's small and light.

Flyduino has said that when pushing them hard you can add a heatsink if you find it necessary but when used within their ratings it shouldn't be necessary. And the temps I'm seeing while high aren't so high that a heatshrink should be necessary. Plus the amps I'm pulling should be well within limits based on the tests I did after initial assembly.

I'm not 100% convinced that the heat is the cause of the issue I'm seeing. It could just be a symptom. I need to check the logs from the brain board this evening...haven't had time to yet.

What's really odd to me is how it moved from one arm to another. Unless I was just wrong about which arm was dropping before...it's harder to tell on a hex than a quad Plus having the same issue one two frames weeks apart is odd. Admittedly the KISS are about the only thing in common - the quad is running DYS 1806 motors with a nanowii while the hex is running Cobra 2204's with a Brain FPV board. They've both running oneshot which is one thing in common, and they both aren't running signal grounds. (but the 3.3v Brain board is more likely to have an issue with that than the 5v nanowii...except the nanowii developed issues first.)

And on the quad it does appear to be motor related as the issue followed the motor when I moved it from one arm to another, and a resistance check of the windings on that motor did show one being almost twice as high as the other two.

Not saying it can't be the regulators overheating...I'm not not convinced it's the most likely issue at this juncture. I'm still thinking it's the FET's over heating due to whatever is causing the motor/ESC to run hot. I'm really hoping the logs will give me some hints...assuming I had enough room in memory to capture the last few test flights

 

[jhitesma]

I agree the use of CF for most people is overkill that just want to fly and are on a budget. CF is amazing stuff, but if you're willing to drop to G10, a budget MR can be reasonably priced, somewhat light, and durable. That's why I did the posts about buying plate CF and cutting it yourself IF someone insists on using it, vs expensive (and IMHO overpriced) frames.

Yep. G10 really is underrated. I had a great conversation with the owner of Detroit Multirotor at flite fest who had a number of nice G10 frames and agrees that unless you're racing competitively G10 is a better choice for most people. I've done more damage to my twitchity 230 since the CF upgrade than I did to the G10 version. The G10 version tended to just bend and bounce back. The CF version I've really torn up the ends of the arms since the CF is so much harder.

Buying CF cloth, for me anyway, doesn't appear to be worth it for the effort, IF I am not going to shape it more than merely make a plane/flat surface. CF cloth is close to the same price since 4-8 layers of a 'fine' weight are going to be required. Of course, I totally agree, if the decision is made to form it, it changes the whole ballgame, in that a world of options open up. Not only does formed CF look sexy, but intelligently shaping it for structural strength vastly improves it over fastening plates together for an approximate desired shape.

But I understand the draw of carbon fiber, even to this day, it still amazes me.

Yeah, if you're just going to make plate there's not much benefit to buying cloth and doing your own layups. I only plan on making a few small flat plates as tests and samples when I start experimenting.

I also have to admit that a professionally made engineered frame will almost certainly cost more than it's worth to produce. It doesn't make much sense from a business stand point. Then again there are people who would say the same about CF slopers or DLG's not being worth what they cost, so I guess it's a matter of perspective. With things like the drone nationals giving more cred to quad racing maybe there will be a market for absurdly expensive hand laid custom frames in the near future.

I should mention I'm also interested in alternative composites. Just like I think G10 plate is underrated a formed fiberglass frame could be lighter and stiffer than a plate built CF frame and still handle crashes as well or better. But what about a scrap built composite....I've found a number of people who advocate corrugated cardboard between CF layers for a light stiff and strong material. On my ultra budget mini quad experiment I had good success with gift cards laminated to light ply as a very strong composite material. Maybe an almost free frame made from cardboard from my recycle bin laminated with denim from old worn out jeans?! Maybe it's just that I'm tired of CF frames that all look like CF...but it seems there's lots of possibilities for experimentation and creative ideas

 

[Burly]

Yes, I'd definitely connect up the Signal Grounds wires and see if that doesn't improve things.
Your instincts are correct in that the current will flow fine through the circuit without the Signal Grounds.
But the issue may not be the flow of current, but may be the increased susceptibility of the square waves generated by the FCB to electrical noise.
And with these FETS switching large currents...there will be noise.

Signal Ground won't eliminate noise, but without Signal Gound, the effect of the noise could be much much more pronounced.
The added noise could push the square waves below threshold or above threshold.
This could cause the motor to loose sync and probably cause it along with the FETS on the ESC to over heat.
Also, if a motor is acting up on its own (ie. coil shorts) it could cause additional noise...affecting square waves...yada yada.

It may be that as you fly in warmer environments the electrical noise increases...until it starts creating these threshold issues.
Whereas flying in winter may not produce enough added noise to matter.

The only time you may be able to get away with not having a signal ground is when you have differential communications with devices on the same circuit. If you have different power circuits you may need a ground.

Back in the old days, I was working in large warehouse that had a lot of conveyers and process controls.
Any wires carrying data could conceivably run in close proximity to large motors and noisy fluorescent bulbs with bad ballasts.
The computers that that talked to all the conveyor motors used RS232 Async communications.
Async signals through a cable were only good for up to 50 feet, and this warehouse needed cable runs of up to 1000feet.

The solution was to buy RS422 line-drivers that would immediately take the ASYNC TX/RX signals and make them differential signals running over 4 wires. TX+ and TX- transmitted one direction....and RX+ and RX- went the other way.

Any noise hitting the cable effects the voltage on all 4 wires equally.
As a result, the net(differential) voltage carried in either direction stays the same.
It is the net differential voltage that is important, and not the absolute measured voltage in any one wire.

See if adding the Signal Grounds will help at all.
I'd be interested in the results.

 

[jhitesma]

There is one other bit of data I've forgotten to share. And that is that at FF I had my VTX disconnected since I wasn't flying FPV. This morning I re-connected it since I was hoping to do some FPV.

One of the first things we did when debugging was to disconnect the FPV transmitter again - but the problem persisted. Then a little later the problem mysteriously vanished again. Since the problem had vanished we went ahead and re-connected the FPV transmitter and re-tested and everything still seemed good...at least until we got to the park

The RC RX and VTX are much closer together than I usually run them right now as well since I was in a rush to put the RX back on this morning. The RX is practically under the VTX - which is why I was suspecting the VTX at first.

So that's one more bit of potential interference that could be causing signal issues.

Just got my daughter in bed and will be seeing if I can pull some logs shortly. Then I'll fire up the iron and add some grounds just to try and eliminate that as a possibility.