New to the hobby and plenty of questions (Heng Long)

[shumarkarknein]

Heys guys.
As I've mentioned in the title, I'm new to the hobby, but I'm also a big fan of modding anything I can get my hands on.
That said, I'm about to purchase a Heng Long T90 (3938), however I haven't made such purchase yet 'cause there are a few things I don't fully understand.
I've spent the past 6 weeks watching channels from veterans hobbyists to avoid having to bother you guys, but still these questions remain unanswered:

1. If I upgrade a tank with a TK7.0 to TK7.1, do I need to upgrade every single system in the tank, or are parts interchangeable? I know that 7.1 specific parts like the servo barrel won't fit a 7.0, but do 7.0 parts fit 7.1?
2. I read somewhere that a radio controller for a 7.0 is the same for 7.1, but didn't see any confirmation about this info. Is this true?
3. Thanks to my country's lovely tax system, I can only afford to buy parts from aliexpress without having up to 400% tax rate, and unfortunately there seem to have an abundance of parts for T90 that don't specify which main board they use (like barrel smoke and fpv parts). Do "extra parts" like these fit any main board after 6.0 or is there any website I can find out which board do they fit based on their model?
4. I've seen a few shtora (red eyes) available for purchase, but all of them are listed as specific for 6.0 boards, but since they're essentially leds, I wonder I can change the connectors to fit other boards. If so, please, what is the name of the connectors for 7.0 and 7.1?
5. Do I need a specific aft mkt cannon to fit a 7.1 servo barrel for the T90, or can the stock one be made to fit?
6. I've heard that the recoil system for the 7.0 is, for lack of a better word, awful because the sound is out of sync with the cannon, and the cannon itself fires slowly while recoiling rapidly. Is this standard, or is it a fixable bug?
7. Do I also need welding skills to add upgrades, or is it more like making sure you're fitting conectors into their appropriate slots?

(Note: I haven't added any links for parts I've mentioned as I don't wanna break any forum rules)
Thanks for taking the time to read my silly questions.
I hope you all have a great day!

[Rubicon99]

The 7.1 only gains you the option for servo recoil and servo elevation. Are you aware that to add servo recoil you will have to modify the barrel of the T90 so it can move in and out. As it comes from the factory the T90 barrel is molded to the mantle.

Servo elevation is not really needed on the T90 as the stock system works well with most aftermarket servo recoil systems.

The 6.0 system is actually in many respects better than the 7.0 and all but a few plugs are the same. So it is mostly a plug and play swap between the 6 and 7 systems.

[SoCalBobS]

Just to expand on Rubicon's post:

1. Apart from the servo recoil feature, 7.0 and 7.1 are functionally identical and interchangeable. 7.1 also has a servo operated elevation feature, for when you inevitably get into customizations. It's not used in stock HL tanks.
2. 7.0 Controllers work identically for 7.0 and 7.1 boards (excepting the recoil). However the 7 series is not compatible with the older HL 6.0 versions. There is a 7.1 controller available. It is compatible with both HL boards. It just has an extra channel, for additional capacities.
3. "Most" extra parts will work with both 6 and 7 systems, as they just use simple DC red/black wires. Connectors may be different. Voltages are the same. if you are concerned, there are diagrams online for both systems that list each channel's voltages.
4. I added red eyes on my T-90. They plug in to the same type slots on 6 or 7 boards. The connectors are JST's but there are a couple of places you could plug them in, with different plugs. Just buy the lights, you'll see the plugs. Pretty much all circuits except the motors are 5 or 6 volt.
5 & 6. Rubicon addressed this. You'll need an aftermarket recoil unit, which may require a 7.1 board if it is servo operated.
7. Welding, do you mean soldering wires? If so, yes you'll ultimately want to do that. Most JST connectors can be crimped if you have the right tool, and you can always twist wire ends to get them the right length, but soldering is better.

As R said, adding a recoil barrel would require some plastic surgery and a new barrel. Some HL tanks come with separate barrels for their abysmal recoil, so aftermarket recoil systems on them usually just bolt in.

[keilau]

Another option is to buy a metal recoil barrel that is compatible with TK-7.0 MFU. toucanhobby.com is in China and you should be able to avoid the import tax.

https://www.toucanhobby.com/products/hl-3938-3939-plastictracks-dzn1?variant=44624248307962&currency=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&srsltid=AfmBOop_FvLqnELghyJzce_1K9pDn6pLUaa1AGNckMGh1J5uSuJN-6UR8ac

[shumarkarknein]

Thank you all for so many in-depth replies. And yes, SoCalBobS, I did mean soldering, I got a bit confused with the appropriate word, thankfully you answered exactly what I needed.
Again, thank you all for taking your time to answer the questions of a newbie.

[RXMan]

Newbie here too. Hopefully I'll find someone in San Diego to pick their brains. I just got myself a few HL tanks and looking to start modifying and painting them.

[Rubicon99]

Newbie here too. Hopefully I'll find someone in San Diego to pick their brains. I just got myself a few HL tanks and looking to start modifying and painting them.

You are in luck. San Diego has a tank club that meets and battles almost every month. A number of us on here attend.

RichJohnson on this site is the head guy for the SD club. Send him a PM and he can give you more details.

Otherwise just ask your questions here on the forum there are a lot of knowledgeable members that can help you with questions you have.

[RichJohnson]

Hiya Rx man, there are a good handful of us in San Diego that have meeets almost monthly at mission bay near sea world and many from up north travel down for the meets. I run the Facebook group San Diego rc tank battles.
i will send you a pm. Good to have you here.

[dai phan]

Just to expand on Rubicon's post:

1. Apart from the servo recoil feature, 7.0 and 7.1 are functionally identical and interchangeable. 7.1 also has a servo operated elevation feature, for when you inevitably get into customizations. It's not used in stock HL tanks.
2. 7.0 Controllers work identically for 7.0 and 7.1 boards (excepting the recoil). However the 7 series is not compatible with the older HL 6.0 versions. There is a 7.1 controller available. It is compatible with both HL boards. It just has an extra channel, for additional capacities.
3. "Most" extra parts will work with both 6 and 7 systems, as they just use simple DC red/black wires. Connectors may be different. Voltages are the same. if you are concerned, there are diagrams online for both systems that list each channel's voltages.
4. I added red eyes on my T-90. They plug in to the same type slots on 6 or 7 boards. The connectors are JST's but there are a couple of places you could plug them in, with different plugs. Just buy the lights, you'll see the plugs. Pretty much all circuits except the motors are 5 or 6 volt.
5 & 6. Rubicon addressed this. You'll need an aftermarket recoil unit, which may require a 7.1 board if it is servo operated.
7. Welding, do you mean soldering wires? If so, yes you'll ultimately want to do that. Most JST connectors can be crimped if you have the right tool, and you can always twist wire ends to get them the right length, but soldering is better.

As R said, adding a recoil barrel would require some plastic surgery and a new barrel. Some HL tanks come with separate barrels for their abysmal recoil, so aftermarket recoil systems on them usually just bolt in.

I see that you added the red eyes to your T-90. Are they pretty easy to install? Dai