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Old 07-22-2020, 06:31 PM   #1
Skunch
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Question YDD Light Saber repair

hello everyone, I am attempting to replace a battery on a toy light saber for a friend. I finally found two batteries that actually fit in the hilt.

The original battery is a 3.7v 700mah lithium ion cell charged through a barrel plug in the hilt, via cable into any 5V usb type A slot.

the only replacement batteries I could find are 3.7v 750mah batteries and when they are connected, a small component on the edge of the board and a screw post (to secure the board inside the hilt), get very hot. I figured that the board could must be using the hilt as a heatsink since it's milled aluminum, but the components make a lot of heat while OFF! the battery doesn't seem to get hot, but I haven't left it connected for more that 10 or 15 minutes out of fear of burning out a component.

Could the 50mah bump on these batteries be causing this issue? does the thickness of the wires from the batteries matter? they are slightly different from each other.

I'll add some photos if necessary

Last edited by Skunch; 07-22-2020 at 06:33 PM..
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Old 07-23-2020, 03:15 AM   #2
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Default Re: YDD Light Saber repair

neither - you have a fault
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Old 07-23-2020, 03:35 AM   #3
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Default Re: YDD Light Saber repair

Show us good clear pictures.
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Old 07-24-2020, 02:22 PM   #4
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Default Re: YDD Light Saber repair

Okay, here's some pics to help this make more sense.

First pic is the original battery; The website leads to a dead domain, I've tried contacting them on facebook and ebay, but they will not sell replacement batteries.

Second pic a close of up the IC that gets hot

Third pic shows the board in relation to the hilt. You can see two screw posts that mount the board to the hilt, only the post on the right gets hot.

fourth pic is a close up of the board at full length

I hope this helps.

The device functions completely when I close the circuit with the battery, but the component gets hot, and I don't want to fix something just to have it break.
Attached Images
File Type: jpg 20200724_125547.jpg (459.8 KB, 16 views)
File Type: jpg 20200724_125624.jpg (546.9 KB, 25 views)
File Type: jpg 20200724_125535.jpg (550.6 KB, 16 views)
File Type: jpg 20200724_125651.jpg (629.3 KB, 23 views)
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Old 07-24-2020, 02:37 PM   #5
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Default Re: YDD Light Saber repair

602060 is the battery size.

why does R12 look damaged?
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Old 07-24-2020, 02:39 PM   #6
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Default Re: YDD Light Saber repair

Can you read what is printed on IC U5? It looks to be some kind of Voltage regulator.
Is there an insulator washer for that metal post so the post will not short out the copper traces under it?
https://www.aliexpress.com/item/4000088922874.html

Last edited by budm; 07-24-2020 at 02:44 PM..
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Old 07-24-2020, 04:01 PM   #7
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Default Re: YDD Light Saber repair

Quote:
Originally Posted by stj View Post
602060 is the battery size.

why does R12 look damaged?
I'm not sure, but I'll take a closer look when I get home from work.

Quote:
Originally Posted by budm View Post
Can you read what is printed on IC U5? It looks to be some kind of Voltage regulator.
Is there an insulator washer for that metal post so the post will not short out the copper traces under it?
https://www.aliexpress.com/item/4000088922874.html
I'll take a closer look in about 7 hours, but it when I looked closely, it appeared to be unlabeled.

Last edited by Skunch; 07-24-2020 at 04:03 PM..
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Old 07-25-2020, 02:30 PM   #8
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Default Re: YDD Light Saber repair

Quote:
Originally Posted by stj View Post
602060 is the battery size.

why does R12 look damaged?
that's because it is! Good eye, friend!

Quote:
Originally Posted by budm View Post
Can you read what is printed on IC U5? It looks to be some kind of Voltage regulator.
Is there an insulator washer for that metal post so the post will not short out the copper traces under it?
https://www.aliexpress.com/item/4000088922874.html
it appears to be unmarked, but take a closer look if you'd like
Attached Images
File Type: jpg 20200725_132207.jpg (357.6 KB, 16 views)
File Type: jpg 20200725_132320.jpg (336.5 KB, 19 views)
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Old 07-25-2020, 05:30 PM   #9
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Default Re: YDD Light Saber repair

https://www.badcaps.net/forum/attach...9&d=1595621882

Did you try removing that metal screw post and inspect the copper traces under that metal screw post? it looks to me that the metal screw post can make contact with many traces of the board if no insulator washer is installed under the post.
Remove the post and see if the IC still get hot or not.
Also check the RESISTANCE of C5 and C6.
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Old 07-27-2020, 06:32 PM   #10
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Default Re: YDD Light Saber repair

Quote:
Originally Posted by budm View Post
https://www.badcaps.net/forum/attach...9&d=1595621882

Did you try removing that metal screw post and inspect the copper traces under that metal screw post? it looks to me that the metal screw post can make contact with many traces of the board if no insulator washer is installed under the post.
Remove the post and see if the IC still get hot or not.
Also check the RESISTANCE of C5 and C6.
I removed the post, and the IC still gets burning hot, in a matter of 10-15 seconds. I'm not super skilled with a multimeter, and mine is german for some reason (I'm in canada). If the info I provide is wrong, let me know and I'll try again. I moved the dial over to the ohm section and chose the smallest increment; 200.

C5 reads a resistance of 13.0, and C6 sits at about 142.9-142.2

R10 won't register until the I select the 20k range, it's measurement is: R10: 2.01
R12 won't register reliably until I move to 2000k, my result moves around a lot, from a negative value of -400 to a positive value of 318.

R12 seems busted, and I don't have the means to replace it. This toy was dropped off to me because the battery no longer charged or worked at all. Could a bad resistor kill the battery? I know a small shop in town that should be able to fix this for me if they have the replacement part.

I've attached some pics of the board with the post removed. I don't see any traces or contact points, but those could be sandwiched between the fiberglass.

*edit*

I forgot to mention that the toy does not work 100% as it should; pressing the power button turns it on, and pressing again makes star wars noises... if you wait for the current sound to finish. pressing the button again before the current sound has finished results in a non-stop loop of distorted sounds.
Attached Images
File Type: jpg 20200727_170237.jpg (406.8 KB, 8 views)
File Type: jpg 20200727_170254.jpg (372.4 KB, 6 views)

Last edited by Skunch; 07-27-2020 at 06:48 PM..
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Old 07-27-2020, 09:11 PM   #11
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Default Re: YDD Light Saber repair

Quote:
Originally Posted by Skunch View Post
I removed the post, and the IC still gets burning hot, in a matter of 10-15 seconds. I'm not super skilled with a multimeter, and mine is german for some reason (I'm in canada). If the info I provide is wrong, let me know and I'll try again. I moved the dial over to the ohm section and chose the smallest increment; 200.

C5 reads a resistance of 13.0, and C6 sits at about 142.9-142.2

R10 won't register until the I select the 20k range, it's measurement is: R10: 2.01
R12 won't register reliably until I move to 2000k, my result moves around a lot, from a negative value of -400 to a positive value of 318.

R12 seems busted, and I don't have the means to replace it. This toy was dropped off to me because the battery no longer charged or worked at all. Could a bad resistor kill the battery? I know a small shop in town that should be able to fix this for me if they have the replacement part.

I've attached some pics of the board with the post removed. I don't see any traces or contact points, but those could be sandwiched between the fiberglass.

*edit*

I forgot to mention that the toy does not work 100% as it should; pressing the power button turns it on, and pressing again makes star wars noises... if you wait for the current sound to finish. pressing the button again before the current sound has finished results in a non-stop loop of distorted sounds.
C5 and C6 resistance readings are made using 200-Ohm scale, correct?
If that is the case, then C5 is bad or pin 3 of U5 is bad, same for C6 and pin 4 of the IC.
Did you try rubbing the top of the IC U5 with Alcohol to see if you can read anything on top of the IC?
Can you read the P/N of U4?

Last edited by budm; 07-27-2020 at 09:14 PM..
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Old 07-28-2020, 03:44 PM   #12
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Default Re: YDD Light Saber repair

Quote:
Originally Posted by budm View Post
C5 and C6 resistance readings are made using 200-Ohm scale, correct?
If that is the case, then C5 is bad or pin 3 of U5 is bad, same for C6 and pin 4 of the IC.
Did you try rubbing the top of the IC U5 with Alcohol to see if you can read anything on top of the IC?
Can you read the P/N of U4?
Yes, C5 and C6 are on the 200-Ohm scale

I've attached a pic of U5 and U4, it's hard to read, but some characters are stamped into the top. it appears to read "LTH7"

U4 reads "8002B" and "CJCJ1V 1"
Attached Images
File Type: jpg 20200728_143533.jpg (472.1 KB, 10 views)
File Type: jpg 20200728_143646.jpg (505.7 KB, 8 views)
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Old 07-28-2020, 09:06 PM   #13
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Default Re: YDD Light Saber repair

Quote:
Originally Posted by Skunch View Post
Yes, C5 and C6 are on the 200-Ohm scale

I've attached a pic of U5 and U4, it's hard to read, but some characters are stamped into the top. it appears to read "LTH7"

U4 reads "8002B" and "CJCJ1V 1"
8002b is the amplifier IC, pin 6 is Vcc, pin 7 is GND.
LTH7 (LTC4054) is the Li-ION charger control IC.
https://www.sunrom.com/p/ltc4054-lth7-sot23

C5 (13 Ohms reading) is connected to BATT pin 3 of LTH7.
C6 (142 Ohms reading) is connected to Vcc pin 4 of LTH7.

When you test C5, is the battery still connected to the board?
If not, I would remove LTH7 and see if the 13 Ohms reading gets higher resistance.
BTW, you did not accidentally connected the battery in wrong polarity at any time, correct? That can damage the IC.
You can see how the LT7H connected compared to the application circuit, it is connected just about the same a shown in the spec sheets.
Attached Files
File Type: pdf LTH7S.PDF (338.6 KB, 2 views)
File Type: pdf LTH7R.PDF (341.1 KB, 2 views)
File Type: pdf LTC4054.pdf (192.4 KB, 2 views)

Last edited by budm; 07-28-2020 at 09:12 PM..
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Old 08-04-2020, 06:38 PM   #14
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Default Re: YDD Light Saber repair

So I took it to my local electronics repair guys, and they treated me really well. he looked over the whole board and probed everything on it, fluxed and reflowed all the components and he replaced the resistor an equivalent part. you can see the finished work in the photo attached.

He also deduced that the repeating button static noise is due to low battery, when he hooked it up to his power supply and provided 3.7 volts, it would never glitch out. he lowered the voltage and it started making the noises again.

The U5 component no longer gets hot, even while charging. I can press my finger on it and feel some warmth, but it's not uncomfortable.
I need to fix their cable, it's very cheap and fraying at the connector joints. I don't see any broken wire fragments yet, so I'm gonna slide some shrink tube over them, and then hot glue them separately and cook the shrink tube over it.

I'll update if it's working properly!
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Old 08-04-2020, 09:30 PM   #15
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Default Re: YDD Light Saber repair

So did you recheck the resistance of C5, C6?
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Old 08-05-2020, 11:37 AM   #16
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Default Re: YDD Light Saber repair

Quote:
Originally Posted by budm View Post
So did you recheck the resistance of C5, C6?
C5 now consistantly reads 15 and then drops 14.5, and C6 is always 60, and then drops down to 59.5, both are measured on the 200 ohm scale

I plugged it in to charge over night, but it still doesn't work, no excessive heat or anything. I had all the parts in a box with foam I'd be surprised if I damaged anything, so this is likely something I did wrong? or maybe the cable is finally broken? it still reads 5V at the barrel plug, which is wierd, but I can't get a read on amps. I'm gonna try and patch the cable and see if I can get a better reading.

***EDIT***

After I patched the cable, I was measuring less about 4.2 volts and no measurable amps, so I ditched the old samsung travel adapter they've been using and plugged it into my bench PC. 5V and some fluctuating amp numbers are now being read. I assume that because this is a front panel usb port, the amps will increase with demand up to 1 amp. If I'm wrong let me know

Last edited by Skunch; 08-05-2020 at 12:05 PM..
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Old 08-05-2020, 03:46 PM   #17
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Default Re: YDD Light Saber repair

Quote:
Originally Posted by Skunch View Post
C5 now consistantly reads 15 and then drops 14.5, and C6 is always 60, and then drops down to 59.5, both are measured on the 200 ohm scale

I plugged it in to charge over night, but it still doesn't work, no excessive heat or anything. I had all the parts in a box with foam I'd be surprised if I damaged anything, so this is likely something I did wrong? or maybe the cable is finally broken? it still reads 5V at the barrel plug, which is wierd, but I can't get a read on amps. I'm gonna try and patch the cable and see if I can get a better reading.

***EDIT***

After I patched the cable, I was measuring less about 4.2 volts and no measurable amps, so I ditched the old samsung travel adapter they've been using and plugged it into my bench PC. 5V and some fluctuating amp numbers are now being read. I assume that because this is a front panel usb port, the amps will increase with demand up to 1 amp. If I'm wrong let me know
So the resistance reading of C5 and C6 were done with the battery still connected? If the battery is still connected, the readings are invalid.
The charger IC takes the 5V input and drop the Voltage down to 4.2V for charging the battery, it starts with constant current first then switches to constant Voltage mode in final stage.
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Old 08-06-2020, 02:32 AM   #18
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Default Re: YDD Light Saber repair

most desktop computers can supply a lot more than 1A - they just link the usb ports to the psu.
sometimes they use a polyfuse, but often it's for multiple ports so you can pull 3A or more.

laptops are different and can shut you down.
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