Maybe U2 was damaged by the heat, or maybe U3 was not connected correctly. Anyway, good progress.

Replace with new working component also the same, scratching my head lol.

 

tracecom any other model of Q3 I can use other than BS250 or FDS9435A?

I have BS170, can I use that to replace?

 

First choice would be FDS9435A, which you have, or P-ch MOSFET with Rds of 1Ω or less, 1A. In TO 220 package there is IRF9640, NTE equiv. NTE2373; IRF9540 = NTE2371; NTE2382 or NTE2383. If the leads of TO 220 are twisted 90 deg, they will fit into breadboard.

 

tracecom any other model of Q3 I can use other than BS250 or FDS9435A?

I have BS170, can I use that to replace?

I was wrong when I told you to get BS170; it is an N-channel MOSFET and will not work for high side switching. But it is good to have for other projects, and should not be very expensive.

 

I see, I will keep them for other purpose then. Not time to test out today, I will try tomorrow and update my results.

 

RE post 318, R sub- no problem. jenovauh, what is measured V at U3-2?
Use battery to sub. for SP, connecting B1 + to TB2-1, B/B input.
Turn R23-2 down to 0 V, to disable charging, & turn R28-2 up to max V.
Lift one end of D2 & adjust BBR1 to 10 V, are LEDs on? Replace D2, lift D1 & adjust BR1 to 9.5 V, are LEDs on? reconnect D1.
Low battery adj: Use RSP, 10k pot as an adjustable V supply. Lift R27-2 & connect it to RSP-2.
Adjust RSP-2 to 11.5V, or to battery spec. for minimum discharge V. D-7 should be low.
Lower R28-2 slowley untill D-7 goes high. Battery is now disconnected from BR1 & Q4 & will remain disconnected untill battery is charged to about 12.6V. Note that D-5 V is set by V divider R29, R30, & D4. Divider current is about 10 μA, so V drop across R29 is .2V, subtracted from V ref, of 2.5 V gives a temp. ref V of 2.3 V at D5. When D-7 goes high, low battery, R20 is removed by rev. biased D4, changing D-5 back to 2.5 V ref. The V divider R28 & R 27 is about 5:1, so 5 X .2V differance represents a 1 V change in battery V, 11.5 + 1 [ 1.1 with R29 @ 22k ]= 12.5 [ 12.6 ] for battery reconnect.

 

I am free now tracecom and have about 2 hour to work on the U4. Assembling the component and will update in awhile.

RE post 318, R sub- no problem. jenovauh, what is measured V at U3-2?

Hi Bernard, I just measure and it is about 2.65 to 2.72V. I will try the rest of the instruction you have given after I finish the assemble again.

 

I am free now tracecom and have about 2 hour to work on the U4. Assembling the component and will update in awhile.


Hi Bernard, I just measure and it is about 2.65 to 2.72V. I will try the rest of the instruction you have given after I finish the assemble again.

U3 should be much closer to 2.5V.

 

U3 should be much closer to 2.5V.

Maybe because my +12V is actually +12.17V, I am using a battery, dont have regulated +12V power supply.

 

Maybe because my +12V is actually +12.17V, I am using a battery, dont have regulated +12V power supply.

No, U3 is actually a regulator; its job is to constantly output 2.5V even if the input fluctuates. If its output is not between 2.475V and 2.525V, either your meter is wrong or U3 isn't doing its job.

 

tracecom is right, U3 should be close to 2.5V, mine read 2.49V. Several V differance in battery should have little effect U3. It should be a single reading not a range of Vs.

 

I am not sure why I couldnt get 2.5V range. I even replace all new components and still the same. it is always at 2.65-2.72V. And then my U2 pin 1 is always around 11.47 to 11.52V.

 

Try moving U3 to another location with just 4.7k. Pin 1 no connection, pin 2, cathode, connect to 4.7k, other snd of 4.7k to + 12V. & pin 3 anode, connect to ground, batt -. Measure between ground & cathode.

 

Okay I manage to get 2.5V exactly already before you post the reply. I remove my wires and replace new one too and re adjust some component and it got 2.5V now. Maybe was loose or something. I check U2 pin is still 11.47V but I am able to adjust R20 and voltage drop to 0.1V

 

Which component can affect U2 pin 1 to have only 11.47V, so maybe I can change it to see if it helps to get 12V.

 

Which component can affect U2 pin 1 to have only 11.47V, so maybe I can change it to see if it helps to get 12V.

U2, pin 1 is an output; 11.47V is okay. With the 10k pot set to 4V reference, my output at U2 pin 1 switches from a high of 11.52V to a low of .072V.

 

U2, pin 1 is an output; 11.47V is okay.

I see, I thought it have to be 12V. Anyway I went to replace 2 FDS9435A and U2 pin 1 got 11.55V now lol. Also I found out that R23 when I adjust, it is affect the voltage up and down.

 

It is getting late again, always not enough time to spend on electronic learning. Time pass so fast when I am working with them. Guess I have to wait till tomorrow to digest what Bernard had instructed. Hope I can understand and not too difficult for me.

 

RE post 318, R sub- no problem. jenovauh, what is measured V at U3-2?
Use battery to sub. for SP, connecting B1 + to TB2-1, B/B input.
Turn R23-2 down to 0 V, to disable charging, & turn R28-2 up to max V.
Lift one end of D2 & adjust BBR1 to 10 V, are LEDs on? Replace D2, lift D1 & adjust BR1 to 9.5 V, are LEDs on? reconnect D1.
Low battery adj: Use RSP, 10k pot as an adjustable V supply. Lift R27-2 & connect it to RSP-2.
Adjust RSP-2 to 11.5V, or to battery spec. for minimum discharge V. D-7 should be low.
Lower R28-2 slowley untill D-7 goes high. Battery is now disconnected from BR1 & Q4 & will remain disconnected untill battery is charged to about 12.6V. Note that D-5 V is set by V divider R29, R30, & D4. Divider current is about 10 μA, so V drop across R29 is .2V, subtracted from V ref, of 2.5 V gives a temp. ref V of 2.3 V at D5. When D-7 goes high, low battery, R20 is removed by rev. biased D4, changing D-5 back to 2.5 V ref. The V divider R28 & R 27 is about 5:1, so 5 X .2V differance represents a 1 V change in battery V, 11.5 + 1 [ 1.1 with R29 @ 22k ]= 12.5 [ 12.6 ] for battery reconnect.

Hi Bernard, can I know this adjustment is for?

 

D = Low battery disconnect; C is charge control.