Sunday, August 30, 2020

Notes on the JBL Cheetah 11101 (truck) and 21101 (buggy)

These are hobby / basher grade 4WD cars.  They are a step up from toy-grade cars like the WLToys lineup, built and priced accordingly.  

They are not the toughest cars ever but are (reportedly) pretty decent.  Crashing any car from great heights onto concrete is likely to break it - these are no exception.

Do note these cars - and especially the 120A models - are rather beyond mere toys, and use extremely powerful motors.  The young, unwary or careless could easily hurt themselves, lose a finger, etc.  Use caution!

Basic specs:

  • 1/10 scale, 4WD
  • 515mm long
  • 3S, 4000 mAh battery, T-connector (a.k.a Deans), 15min
  • 3670-2500 kv motor.
  • 80A (80 km/h) or 120A Hobbywing ESC (100 km/h)
  • All-metal gears.
  • Part-metal chassis.
  • Oil-filled dual-rate (progressive) shocks.
  • 17mm wheel hex
  • 135 / 145mm diameter / 75mm wide tires w/foam
  • LED lights 

 Note: This car is NOT a rebadged Vikar Bison or DHK Zombie.

User manual:  RCGroups 1, RCGroups 2

Transmitter:  120A versions: KTH-91900G [Manual:  RCGroups]


Model differences:

Car (21101):  This model is technically the "21101", though most refer to it as a "Cheetah".  Has rear wing and different wheelie bar.  Most find the wing/bar break off easily on bad landings.  Dirt/pavement combo tires.  Car is sometimes available in a package with two batteries.

Truck / truggy (11101):  No wing, "inverted" wheelie bar that tends to not break (as easily).  Sand tires that reportedly don't do quite as well on pavement.  Old models had substandard wheel nuts that could come off, but newer ones (since mid-2017) don't.  Review, review 2.

Changing from car-> truck (or vice versa) involves changing not only the shell, but the mounts for the shell, as well as the rear wheelie bar. 

Model similarities:

-  All models are available in with 80A or 120A ESC.  The 80A is often called "original" or "version 1".  The 120A is sometimes called the "upgrade" version, "version 2" or "Extreme".

-  Most parts are common between the "old" 21101 car, the "new" 21101 car, and the 11101 truck.

Related models:

-  J3SPEED : Street / on-road tires, new controller, metal slipper mount.  Also 120A with 3670-3200kv (36*70mm) motor, so faster.  Drive axles may be thinner. (Review, Discussion thread)


Year-on-year differences:

  • 80A models had Flysky controller (4xAA) with throttle limiting.  120A models have different controller without throttle limiting.  It may be possible to bind a Flysky GT3C (with limiting) to the later models.
  • Original 11101 trucks had different wheel nuts that tended to spin off.  These were changed to the same 10mm hex nuts as used on the 21101 car.
  • Drive shafts (CVDs) were thin / weak, were upgraded around Q1 2018.

Known issues:

  • 80A ESC and steering servo are NOT waterproof. (experiences in snow are mixed)
  • 120A might be waterproof, but might also be just "splash-proof".
  • Check all screws BEFORE running for first time.
  • 21101 wing / wheelie bar breaks easily.
  • Tires may become unglued due to high available torque.
  • Drive shafts (dogbones) tend to bend.  Easy to upgrade. 
  • Some screws are threaded into metal parts and will back out over time.  Use Loctite.
  • Wheels are difficult to remove, especially the first time.  Heating with a hair dryer seems to help.
  • All screws METRIC, most screws are hex head (i.e. allen keys)
  • Differential output cups weak.

 Known non-issues:

  • "Crackling" sound from rear at low speeds - this is normal behavior for the brushless motor.
  • Transmitter range sometimes isn't the best.  Video to help fix
  • It is definitely possible to destroy the car in stock form.


Parts and upgrade info

Many upgrade parts are available (JLB, Aliexpress, Aliexpress 2, Banggood, MonkeyHobby).


  • It is possible to upgrade to 4S batteries, but beware of exploding tires.  
  • You also risk damaging your transmissions, especially the front gearbox.
  • Most people say the surest way to break parts is to run 4S.


  • Stock: JLB 3670-2500kv (Banggood)
  • Upgrade: Racerstar 4068 brushless motor 2650 kv
  • Motor heatsinks: Heat sinks for 530 or 540 motor size appear to work
  • Motor fan: Banggood (picture), Video


  • 80A (upgrade to original 80A, downgrade from original 120A): Gearbest , Banggood
  • 120A:
  • Note: people have tried spraying CorrosionX into the receiver and ESC to add a bit of waterproofing.  The effectiveness is unclear.


  • 10kg (or more) servo recommended
  • Upgrade: 
  • Some users report the Futaba S3003 works fine, even though it is "weak"
  • Some people report the TowerPro MG995 works fine (video)
  • Note: some report all-metal steering improves the turning angle over the stock plastic parts.


  • Metal upgrade (Banggood, Aliexpress)
  •  Note: some report all-metal steering improves the turning angle over the stock plastic parts.


  • Pro-Line Badlands 3.8 wheels/tires do fit. (Pro-Line)
  • Can use 1/8 tires with 17mm hex (i.e. GoolRC)
  • BSR Berserker 1/8 wheels fit.   (Hobbyking)
  • ZD Racing 1/8 wheels with 17mm hex should fit (unconfirmed).  (Banggood
  • Wheel nuts are M10.

Wheel bearings:

  • Wheel hub bearings 10x15x4mm. 


  • 3S 4000 mAh
  • Length: with spacer foam 138mm, without 148mm.
  • Tray is 49mm wide (some say 51mm)
  • Height limited by body shell.
  • 260g


  • Pinion must be 32 pitch!
  • Stock: 15T: Aliexpress
  • 13T: Aliexpress (13T, 14T, 15T)
  • 17T fits.
  • 18T is reportedly too large, it interferes with one of the motor mount screws.  Can be made to fit with appropriate grinding.

Spur gear:

  • Stock: 52T
  • No known upgrades


  • Stock oil is likely 400 wt
  • People report good success with 800 wt
  • Note: weights in the range of 15-70 are "non-standard" USA weights.  Weights in the 200-800 range are the same oils rated using "standard" weight ratings.


  • Reported as:
    • Original: 8mm
    • Second: 6mm
    • "Upgrade": 10mm 
  • "New", "upgraded" version (reportedly): Banggood
    • Note: these were upgraded back in 2018, photos may not be correct.  
  • There is reportedly a "hardened" version (as of 2019), but this is unconfirmed.

Slipper clutch:

  • Metal upgrade: Banggood
  • Note: it is not typically necessary to adjust the slipper. 

Tuesday, August 25, 2020

Private Internet Access (PIA) Next-Gen servers break apps and smart home devices

 Problem:  After restoring your PIA connection from after it broke using router-based VPN, you do not have full connectivity.  

Specifically, none of your smartphone apps or smart home devices work properly.

  • Your router IS connected to the VPN
  • You ARE using the correct encryption, port, and ca.crt combination
  • They DO have a working internet connection
  • They CAN see the internet
  • They DO work outside the VPN

But they can't log in to, or access, their respective servers through the VPN:

  • Gmail: Useless "View more" link that does nothing
  • Banking apps: Can't log in
  • Starbucks: Endless "Finding stores"
  • Ecobee:  "Trouble connecting to your device"
  • Honeywell Home: Endless startup
  • Ratuken Kobo: Endless accessing "My Books"
  • Smart Life: Endless startup
  • Lastpass: Password vault is empty
  • Roblox: Endless loading
  • Minecraft: Can't join multiplayer servers
  • Terraria: Can't join other players 
  • Pixel Guns 3D:  No multiplayer available
  • Ecobee thermostat: Pings "", but "unable to connect to web servers".
  • Lyriq water leak detectors: Permanently offline 

etc, etc, etc.

Oddly, Windows PCs work.  Chrome, Maps, and Play Store work.  Some other apps work.  Many don't.

PIA confirmed the cause was "resolvers for [the] legacy network" - i.e. on their end.

Solution (for router-based VPN only, this example is DD-WRT):  

0.  Follow this guide exactly.

1.  If your OpenVPN does not even try to connect, try removing this line from Additional Config:

 pull-filter ignore "auth-token"

It should at least connect now, but you will still have app/device issues as noted above. 

Note: This bug appears to affect only very old versions of DD-WRT.  If you can upgrade your firmware, you likely should.

2.  Set your router DNS to:


3.  Change to a "Next-Gen" server.  These all end in "".



4.  You have to try different encryption / port combinations, to see what works.

For example, I used AES-128-CBC SHA1 on port 1198, using "ca.rsa.2048.crt".  It did not work, resulting in the app/smart device issues.

I then changed to AES-256-CBC SHA256 on port 1197, using "ca.rsa.4096.crt".  That worked fine.

 You don't need to reboot your DD-WRT router (but you do need to hit "Save", then "Apply Settings"), and resolution will be more-or-less instant.  When you hit a "good" setup, you will know it.

 The above did work on OpenVPN 2.3.  Newer DD-WRT builds have 2.4, hopefully it works for that too.

 Similar steps should fix Tomato, ASUSWRT, Merlin, pfsense, whatever.  (I hope.)

This was the result of several days back and forth with PIA tech support.  Only their eventual fix has kept me with them, as I was just about to pull the trigger on NordVPN.

However, I can't help but say their NextGen rollout is a bit of a dumpster fire:

  • These problems should not be occurring.
  • They certainly should not be dumping people off perfectly good connections that have been flawless for years for reasons unknown. 
  • Their router setup guide was not updated in advance of NextGen rollout, which is dumb.
  • Their support staff seems unable to readily support the NextGen rollout, which is even dumber.
  • Tech support actually told me I had to figure out the NextGen settings by interpreting the '.ovpn' file for my preferred PIA server, which is dumbest of all, as that is not support.

 It's almost like they never saw the NextGen transition coming. Which is just shoddy business.

Yes, I know there was a merger.  So either they had to changeover with little to no warning, or they forgot about their massive upcoming server changeover because of new business cards.  Either way, it's crap for the customer.

Tuesday, August 18, 2020

Private Internet Access (PIA) suddenly stops working

Problem: PIA stops connecting.  No changes on your side.  DD-WRT.

Error: N VERIFY ERROR: depth=1 error=certificate has expired: C=US ST=OH L=Columbus O=Private Internet Access CN=Private Internet Access CA
20200818 14:33:13 N TLS_ERROR: BIO read tls_read_plaintext error: error:14090086:lib(20):func(144):reason(134)


1.  Your router time setting is wrong.  Try re-setting or selecting another NTP server, just to be sure.

2.  PIA changed something.  Seems they did so recently (August 18, 2020).

If (2), your only real solution is to completely re-set up your DD-WRT router using the latest settings.  Instructions are here.


-  Specific protocols now need specific ports.  Be sure to get the right port/.crt combination.

-  PIA added a line to "Additional Config":

pull-filter ignore "auth-token"

This line completely borked my ability to connect - DD-WRT wouldn't even try.  Taking it out fixed it, I don't know why.  It may be because my DD-WRT is old.

I was also unable to connect using Blowfish, although I suspect that was the new config line above.

Saturday, August 15, 2020

Cleaning white landscape rock to like-new condition

 Problem:  I want to re-do my landscaping, but want to re-use the existing rock.  The old rock has gotten brown and yellow stains on the bottom - can I clean it?

TL;DR:  No, you can't.

As far as I can tell, the rock is called "Crystal White".  Mine looks to be about 1" / 25mm size.

Over time, it develops brown and/or yellow "staining" on the bottom.  This is likely due to oxidation.  

This means taking up and re-laying down the same rock doesn't work, since half the rock will be discolored instead of nice and white.  As this rock is hard to find and potentially expensive, I wanted to re-use the same rock instead of throwing it away.

It may seem obvious that you can - or can't.  Some people report success in "cleaning" their rock.

I tried the following materials to eliminate the discolorations:

  • Barkeepers Friend (oxalic acid)
  • Stainless Steel cleaner
  • TSP (premixed / ready-to-use)
  • CLR (straight)
  • Palmolive dish detergent
  • Glass cleaner (ammonia)
  • Muriatic acid
  • 70% alcohol
  • 20% chlorine bleach
  • 50% chlorine bleach
  •  Toilet cleaner (hydrochloric acid)

All were soaked for at least 24 hours.

 None of these had any cleaning effect.  CLR made the rock stink and turned the veins yellow, and muriatic acid dissolved the rock:


None of the other cleaners had any meaningful effect.

So, if you have this type of rock, don't bother trying to clean it for re-use.

Saturday, August 1, 2020

Vantec NBA-200U external USB sound adapter unable to output 7.1 ANALOG audio from Nvidia Shield via Kodi

TL;DR: As title.  The Vantec will NOT output 7.1 ANALOG audio from an Nvidia Shield TV / TV Pro using Kodi.

It will output 5.1 audio via optical S/PDIF (Toslink).  And it will play most 6.1 and 7.1 video files through that interface. 

You will probably even hear sound through your rear surrounds while playing those files, so you may think that you are actually getting 7.1 sound. 

But you're NOT, because optical S/PDIF is NOT capable of sending 7.1 audio due to bandwidth limitations on that interface (as everybody should know by now).  Most likely your receiver is doing some smart sound processing without you even realizing it.

My receiver is old, and does NOT handle sound via HDMI.  And I figured if I'm upgrading, why not move from 5.1 optical to 7.1?  So I needed 7.1 ANALOG sound. 

The Vantec is supposed to do that by outputting 7.1 sound via four 3.5mm audio jacks.  You use 3.5mm-to-RCA cables to connect these to the analog inputs on your audio-video receiver (AVR).

Obviously, this means you need an AVR that has such inputs.  I have a Pioneer VSX-1016TXV, which has dedicated 7.1 analog inputs.

 (OK, laugh all you want, but it works great.  I'm NOT spending $500-$1,000 for a new HDMI-audio receiver when my existing stuff works perfectly well!)

Once I realized what I needed, I did my homework.  Nvidia recommends the Vantec

So, Vantec to the rescue.  I plugged it in, Android installed it silently.

Except, no matter what, it didn't work.

Here's what DID happen:

1.  At best, all I could get was stereo sound.  In many instances, I got ticking / buzzing only, or no sound at all.

2.  If I tried to play a file the Vantec didn't understand, it often locked up (activity LED stopped). 

It would then refuse to output anything - even stereo or 5.1 - until it was reset, or the Shield was rebooted.  This occurred on nearly all Dolby 7.1 and DTS 7.1 test videos, and (maybe) even a couple of 5.1 test videos.

3.  The Vantec would lock up even on files it should have handled, such as "U-571" in 'standard' DTS Digital Surround 5.1 (i.e. not DTS-HD 7.1 or DTS-HD MA 7.1).  This occurred when using either analog 7.1 out and optical S/PDIF out.

 For reference:

-  The problem is not with my AVR - I checked the multichannel 7.1 inputs, and they work perfectly.

-  The problem is not with my files.  I tried them on my old Minix box, and they work perfectly, including on 5.1 channel test videos.  On the Shield, the 7.1 analog outputs simply do not output anything to anything except for front left/right.

-  The problem is not with passthrough settings.  Using identical settings, optical S/PDIF works (including 5.1 surround), but analog 7.1 outputs do not.

-  The problem is not with the Shield USB.  I tried both, they were both set to always-on, and I even tried setting USB to max performance.  No dice.

There are a bunch of other devices like the Vantec on the market.  Most use the same C-Media chipset, so I don't think any of them will work any better.

I debated keeping the Shield TV Pro since it is faster, x265 capable, and will work as a Plex server.  But having the Vantec lock up on random files is a no-go for me, much less the family.

So, my advice to anyone with an old setup that does not handle HDMI audio is:

-  If you want S/PDIF, the Vantec basically works, and you should get the ability to play back 5.1, 6.1 and 7.1 files via Toslink optical (in 5.1 only).  But be prepared for it to malfunction / lock up if it 'sees' something it doesn't grok. 

-  If you want 7.1 analog out, do NOT buy a Shield TV.  There is no way to get analog surround sound out of it using commonly available USB sound card adapters - regardless of what a few Amazon commentators might say. 

Other devices based on the same chipset may or may not have the same issues.  I don't know, and I'm not spending the time to find out.

However, if S/PDIF / Toslink optical floats your boat - and you can get a USB adapter that doesn't tend to lock up - these are the settings that worked for me:

-  Dolby audio processing ON
-  Available formats to MANUAL
-  Set all available formats to ENABLED
-  Stereo upmix is ON

(Note that "Forced volume" can be set ON or OFF, but it won't work.  It only works for HDMI audio, not for USB audio. )

On Kodi:
-  Number of channels: should not matter, mine was 2.0
-  Output configuration: Optimized
-  Pass-through ENABLED
-  Dolby Digital AC3 capable receiver ENABLED
-  Dolby Digital AC3 transcoding DISABLED
-  [if shown] Dolby DTS capable receiver ENABLED

On receiver:
-  Sound source set to digital / optical

With these, I was able to play:
-    Dolby Digital 5.1
-    Dolby Digital Plus 7.1
-    Dolby TrueHD 7.1
-    Dolby TrueHD 7.1 Atmos
-    DTS Digital Surround 5.1
-    DTS HD MA (Master Audio) 7.1

(These were the reported formats - can't be 100% verified.)

However, channel-check videos showed that the surround channels of Dolby Digital Plus 7.1, Dolby TrueHD 7.1, DTS-HD MA 5.1 and DTS-HD MA 7.1 did not come through.  They were undoubtedly downmixed to 5.1 to get through the optical interface.

Other variations on this may also work.  For example, you could try setting the Shield audio formats to "Automatic", just to see what happens.

For that specific setting, I suspect the formats that will be output may be limited by whatever is hooked to your HDMI.  If you have a new TV that supports "everything", the Shield will likely output everything.  If you have a projector or other device that doesn't support certain audio formats, the Shield might detect this and prevent certain audio formats from playing.

Note the last paragraph above is 100% pure speculation on my part, based only on the fact that the "Automatic" setting didn't seem to work well for me.  (I have an Epson projector and old AVR, neither of which handles HDMI sound.)