ENG: 90-93 TCU Fix / Preventative Maintenance

[bhksk8r]

Love it.

This is a Very very old post but I have copied and put it in my bookmarks and passed it along. To say how fantastic this is..I soldered once in an Junior high electronics class and I"m 58 years old and that was 40+ years ago and I understand this post. Goes to show how well explained it is. Bravo!

I had recently been told that my transmission was the problem at that it was going to take 1-2k to fix it. I didn't think that was really the issue at only 160k on my 92 CB7 LX, so I kept researching.

Found this thread (haven't been on CB7 Forum for a long time) and immediately the light bulb went off in my head.

I ordered all the capacitors on eBay and waited anxiously until they came. It was freakin' embarrassing to drive people around stuck in high RPM's! I was stuck in 2nd and 4th and occasionally 1st and third gear...

Anyways, my grandfather and I pulled out the TCM and bingo, the 330uf capacitor was blown and it had leaked everywhere.

We cleaned up the board this morning, put the new capacitor in, soldered it, and put everything back together.

The D4 light was gone and my wife and I drove around all day with my 100% perfect shifting and working car again!

We tested the other capacitors and resisters and they showed up fine, so we only replaced the one.

I love this forum.

[SilverShadow]

This is a Very very old post but I have copied and put it in my bookmarks and passed it along. To say how fantastic this is..I soldered once in an Junior high electronics class and I"m 58 years old and that was 40+ years ago and I understand this post. Goes to show how well explained it is. Bravo!

[WagonLX]

I know this is an ooold thread but, THANK YOU Cloud. I did'nt even remove the old solder. Just heated it enough to get old capacitors out, and then reheated to get new capacitors in.

[cloudasc]

Back in December I started asking questions about the problem with my 1991 Honda Accord not having 1st & 4th gears. With the help from "cloudasc" and the pictures in "Preventative Maintenance" I was able to learn where the transmission computer was and how to remove it, how to test for failure codes, and to tell which parts to order for my transmission board. After ordering the resistors and capacitors I was finally able to get ahold of my retired TV repairman who replaced all 5 capacitors today. Two of the capacitors were definitely leaking which was better seen after removing them from the board. The two resistors checked out fine.

Took a 20 mile drive this evening and everything seems to be working great, just like it's supposed to.

Just thought I would contribute another story of someone who's issue was resolved by this thread.

[Bad_dude]

I've done this and I believe the vibrations from the bass is knocking the solder lose unless I'm not doing it good enough.You think I should add some hot glue to help?

Maybe you need to solder it differently. Take the new capacitors, cut the legs in half, they usually come too long. What I do is use a needle and heat the solder point up and push the needle through. Once it cools down, I pull the needle out. I do it both for the 2 points of the capacitor. Then put the capacitor in and pull it lightly but as close as possible to the circuit board. Bend the legs 45 degrees on the opposite side of the circuit board to keep the capacitor from moving before you solder. Make sure you use one hand to gently push the capacitor on the other side when soldering the first point. Then solder the 2nd point. Make sure you use just enough solder to hold the 2 points on. Do not use too little or too much. Then cut the extra legs length off as close to the circuit board as possible. There should be no movement at all even with your bass pounding if you do it this way. I have solder smaller stuffs then this.

[blackoutt]

Ahh ok I just need to practice more on my soldering skills I'll get it working right!

[cloudasc]

I've done this and I believe the vibrations from the bass is knocking the solder lose unless I'm not doing it good enough.You think I should add some hot glue to help?

The only reason the hot glue was needed/used was due to the board getting coated in carbon from the old resistors burning off. The resistors in my example are not using the original solder points, the "traces" for those points have affectivly been bypassed, thats why the hot glue was used to hold everything in place. If you do not have a board covered with carbon, and are using the original mounting holes you really shouldn't be having any issues with vibrations if the proper solder and technique is used.

[blackoutt]

I've done this and I believe the vibrations from the bass is knocking the solder lose unless I'm not doing it good enough.You think I should add some hot glue to help?

[Bad_dude]

OK. All done. It took some time as I didn't have the pump nor the braid to remove the old solder. Never the less, it's done. I replaced the capacitors of higher specs:
-1uF 50V up to 4.7uF 50V, the ones I bought exact specs of 1uF 50V was physically smaller so I didn't want to take a chance.
-330uF 10V up to 330uF 16V.
-33uF 35V up to 33uF 50V.
-220uF 35V up to 220uF 50V.
-4.7uF 50V up to 33uF 50V.
I hope this will keep the TCU working without problems for a while. It's reinstalled and drives as normal.
Here's the pics of the finished work below.
The front
The back
I hope this helps some one.
Here's a link on how to choose replacement capacitors.

[bobbycos]

i got the "cold heat" soldering device and it works half the time, my dad has an old Weller that i should try and bum off him

other than that i have the radio shack specials

but i have a tcu that i should open up and look at

[Bad_dude]

Yeah, the car was made and assembled in Japan, but the parts are not all JDM, like the headlights and corners in one piece and others. The VIN number is JDM.
I replaced the 2 biggest capacitors. I didn't have solder braid or pump so the back of the circuit board is a little scratched up. However the paths are still in tact. Just fine scratches from the slip solder point. That cheap helping hand thing was useless, keep falling over.
I found a good link on Soldering.
Oh, the capacitors are of the same values.

[cloudasc]

28100-PX4-922
6111 Lot NO.0510
3LX denshigiken
Hondapartsnow

I found the following information about our tcu's:

Japan-built EX: P/N 28100-PX4-932 H/C 3523933
Japan-built LX & DX: P/N 28100-PX4-922 H/C 3520269
US-built EX: P/N 28100-PX0-932 H/C 3521796
US-built LX & DX: P/N 28100-PX0-922 H/C 3521788

I guess your car is MAD JDM YO!

So despite the different layout, are all the capacitors the same as in my guide? Otherwise if you can post any info/pictures of each capacitor that would be greatly appreciated!

[Bad_dude]

28100-PX4-922
6111 Lot NO.0510
3LX denshigiken
Hondapartsnow

[cloudasc]

Whats the part number on the outside of the tcu case, it should have a barcode on it, and say:

AT CONTROL UNIT
28100-PX0-822-M1

Or something along those lines. Old capacitors, are old capacitors, they will fail eventually, and as they age, the probability gets higher, it definately wouldn't hurt anything to replace them, but I am unsure of any failures with that tcu, as its totally foreign to me.

[Bad_dude]

Thats wierd, at how many miles did you aquire your car, and how many owners were there before you? I'm thinking maybe the tcu that came with your car died, and a previous owner put in a tcu from another car?

Maybe obd1 prelude? When you WOT, at what rpms does your car shift automatically?

I got the car at 122k miles. It now has 153k miles. Just one owner before me. The car shifting depends on how hard I push the pedal. But 1st to 2nd usually around 2900k, then the rest depends on how hard. Some times it goes up to 3600k if I push it. But you think it looks like a prelude TCU? It looks pretty new. The bolts I took off seems like it's OEM on tight. You know that glue sound crack when you turn it?
Now if it looks this good, should I even bother with replacing the capacitors?
Thanks.