Todd Engineering PC40B Power Supply, need to know the numbers on an IC

[Pioneer621]

Hello everyone!

I’ll get to the point as I tend to type a lot, but details are below under my quick main question here.

A while back I acquired a broken Todd Engineering, INC. model PC40B Power Source Battery Charger / Power Supply.

There is one part in here that is blown beyond recognition, the PC Board designation is U1.

Can anyone tell me what the numbers are off this IC chip? It is an 8-pin dip.

Detailed post below:

The chip was actually intact when I first got the supply; I already attempted to repair it & got ahead of myself & forgot to replace U3 which is an LM393. I was pretty sure the 393 was shorted or at least leaky, but it took a few weeks to get the parts in & I forgot where I was at with this thing & did not replace the 393. Needless to say it blew up again & this time took out U1 (which may have been faulty anyhow), & stupid me did not write down the numbers off the chip before hand, I know I looked for a datasheet for the chip originally, but could not find a supplier for it anyway, but I should have wrote it down.

I originally found U2 bad which I replaced with an LR645, the original one was blown apart and from searching the web that is what I found that may have been in there & the pin-out seemed correct, but if U2 is something else please inform me on that as well. I also replaced D13 which is a 15v 1w zener diode as it was shorted, & I was pretty sure U3 an LM393 was bad as well but forgot to replace. I wanted to replace the known bad parts so I could continue troubleshooting, but now I am stuck not knowing what U1 is. This time around it also took out the other U3 which is a CNY17-3 which is located on the vertical PC Board, but fortunately I ordered one of those incase I needed it.

At this point I already replaced everything that I know for sure is bad except U1.

I seen this thread: https://www.electronicspoint.com/rv-power-converter-todd-pc40-insulator-problem-t46674.html

And was hoping someone here could help with this & may be able to tell me what U1 is.

I am not sure if I should post in the other thread or not, I seen a notice that I should post here, so I don’t know. I guess if no one here has one to look inside for me I can always try that thread too?

I would really like to repair this thing if at all possible, if not I can use it for parts, but I really hate parting something out unless it’s really beyond repair.

Thank you all for reading this & for any help you can give!

Take care!

 

[Pioneer621]

Good News!

I was sweeping the floor in my work room & seen a little black piece of something laying on the floor, picked it up & it was the top half of the blown IC. I work on a lot of projects & had cut plastic similar in size, etc. so I figured it was plastic or something as I already found similar pieces of plastic laying about, but figured I’d see what it was before I swept it up, sure enough, it was part of the IC. I looked a few times before but could not find it, figured it was gone!

It is a CS3845B

It is the PWM IC which is what I suspected, but was not sure of the exact one, found a similar one in a schematic of a TODD PC30 or something which may work as well, but glad I found the numbers to the original.

Just thought I’d post an update!

Take it easy everyone!

 

[thomas.gerchak]

Good News!

I was sweeping the floor in my work room & seen a little black piece of something laying on the floor, picked it up & it was the top half of the blown IC. I work on a lot of projects & had cut plastic similar in size, etc. so I figured it was plastic or something as I already found similar pieces of plastic laying about, but figured I’d see what it was before I swept it up, sure enough, it was part of the IC. I looked a few times before but could not find it, figured it was gone!

It is a CS3845B

It is the PWM IC which is what I suspected, but was not sure of the exact one, found a similar one in a schematic of a TODD PC30 or something which may work as well, but glad I found the numbers to the original.

Just thought I’d post an update!

Take it easy everyone!

Pioneer,

Did replacement of U1 fix the unit? I have a PC30 B and am looking for a schematic. You mentioned that you possibly had one. Is there any way that I might be able to obtain a copy? Thanks, very much.

Respectfully,
thomas

 

[Pioneer621]

Pioneer,

Did replacement of U1 fix the unit? I have a PC30 B and am looking for a schematic. You mentioned that you possibly had one. Is there any way that I might be able to obtain a copy? Thanks, very much.

Respectfully,
thomas

Hi Thomas,

I have not replaced U1 as of yet. I am waiting until I place another parts order before I get the chip I need for this supply & I just have not been able to yet.

The schematic I came across just says TODD PC30 & looks like it was hand drawn by someone, not sure if it’s the same as the PC30B or not.

I will post the link here so you can see it (took me a while to re-find the link!). It is a PDF file. I hope I am allowed to post links, if not I apologize:

http://www.ciciora.com/EV/pc30.pdf

I hope this helps!

Take care!

 

[Pioneer621]

Well thought I would update this a little.

I got the part I needed for this & figured I’d toss it in & see if it worked. I put a small low wattage light bulb in series with the 120vAC line voltage before powering it up incase there was a big problem & it would help stop horrible damage in the event of a failure, probably would have still did some damage if something failed, but figured I try it as a precaution.

Once I got brave enough to plug it in, the red error light came on along with the power light. It took several seconds for the line voltage to reach an appropriate level to turn it on as the large filter capacitors were charging, but once the line voltage reached approximately 90vAC, measured after the limiter light I had in series, the red error light on the power supply shut off & it had 13.2vDC output which is what the sticker on the bottom says its output is with no load is, I tested the output with a small 12v car tail lamp light bulb and it lit it up fine & seemed to have ok output & stayed steady, the current limit light was limiting too much for testing & I had to plug in another one to keep it on while powering the small load.

I noticed U2 the LR645 seems to run a bit warm, but maybe that’s normal. After several minutes of testing driving the small taillight load all seemed to be ok, so I went ahead & removed the current limiting on the line voltage & it seems to be working. I loaded it with about 10 to 15 amps for some quick testing and it seemed to power it ok, the unit stayed cool & the output voltage did not drop too bad, but I only did quick testing. Hopefully this thing is fixed now & it hangs in there, if it blows up I would try to post back. If it does I may try to repair it one more time, but after that I’ll use it for parts as these switchers are difficult to work on!

Again, just wanted to update this thread.

Take care everybody!

 

[Resqueline]

Congratulations, and thanks for sharing!
Sorry we could not be of any help but relieved you managed perfectly anyhow.
You're welcome back with any issues.

 

[Pioneer621]

I appreciate that Resqueline! I understand how it goes when searching & asking for info on something like this, sometimes someone can help & sometimes they can’t, just depends on what it is & if anyone has any experience with what you’re inquiring about. I figure it can’t hurt to asking questions just incase someone may be able to help out a little.

I’m glad I found this forum as I find myself coming back to read topics often anyhow! So I enjoy coming here. I lot of knowledgeable people here & a lot of interesting stuff!

Thanks again!

 

[Jerry B]

PC 40 Power supply problems

I'm glad to find this site with so many helpful people. I also have a problem with a Todd Eng., PC 40 Power supply. Mine must be older because I do not see any indicator lights on it. The problem is no output. I have tested the input and the main diode does provide DC to the three boards mounted there but no output can be found on any of the boards. I am convinced like another member that the first board is a master board. I have had it out of the chassis and can see no obvious damage. Does any one have a suggeston as to where next to look. I read that someone has a electrical diagram for this. Could you post or email a copy please.

Thank you,

 

[Resqueline]

Pioneer621 posted the link to a PC30 schematic in the 4th post right here in this thread.
If your PC40 is similar you can start by checking for Vcc on pin 7 of U1. Pin 5 = "Gnd". Beware of this circuit being at mains potential however.
If no Vcc is present check S1, D3, R8 & R9. If Vcc is within spec's (9-30V) check if Vref is 5V on pin 8, and if R3 is ok.

 

[Jerry B]

Thank you Resqueline for the help. I have completed the investigation based on your suggestions. Here's what I found: I have 168 volts at D1 and 13.0 v at pin 7 and both sides of S1. I have 4.9 V at pin 8. R3 reads .3 ohms. I re-instslled the board into the chassis and powered it up. It now is producing 13.65 vdc and is running a RV style hair dryer. What the heck? Loose connections...

Thanks to all. I'll keep the diagram as it was very helpful

 

[linetrash75]

I have a PC-40 that has no output, When i was checking things with my multi-meter I found this little thing that just cumbled to dust when I touched it. i was on the little circuit board that plugs into the main big board. I know nothing about this stuff would somebody mind trying to fix it for me if i send it to you? If you can't fix it you can keep it , If you can we can work out some payment. If you are up to the challenge send my a pm Thanks Jed

 

[Jerry B]

Todd PC 40

Why don't you post some pictures of the burned area and perhaps someone can identify the parts for you. I'd be happy to try and repair it for you, but I would have to do the same thing (identify and locate the defective parts). Keep posting and we'll try to help out.

 

[Marlin]

todd eng pc40dc

can i get drawing for todd eng pc 40 dc unit? i have one in need of repair. thanks very much. marlin

 

[lascc61]

Anyone have the schematic from PC40b ? i can't find any information about this. Please i need as soon as possible. Thanks.