Help with H117S LDO

[killian6pk]

H117S is a 1.2amp Low Drop Out Voltage Regulator
Below the H117S is printed ADJ 221
Not sure if that means that this is an adjustable LDO or not.
My question is: If I am getting an AC reading on my DMM of 5.4v on each leg does this mean that the LDO is probably bad? Below is the DataSheet for this part. I could not find one with the S on the end. Reading the datasheet the S could just stand for the SOT 223 package.

http://pdf1.alldatasheet.com/datashe...SMC/H1117.html

[selldoor]

Re: Help with H117S LDO

Why are you testing in vAC?
It will be adjustable another clue is there will be small resistors in circuit connected to the legs. The test is that the voltage difference between leg 1 ( Adj/gnd) and leg 2 will be 1.25vdc higher if it is good

[killian6pk]

Re: Help with H117S LDO

Thanks, I have the flu I think, so my mind is not working very good. I meant dc not ac. I will look for the resistor. and check the voltage between the first two legs.

[redwire]

Re: Help with H1117S LDO

It's a chinese clone (H1117, AMS1117 etc.) of the venerable LM317, with some hype and overspecs...

It's adjustable (S version) but there are also fixed voltage versions. If the ADJ pin is grounded, it's fixed O/P.

Make sure there is 1.25VDC difference between the output and adjust pins. If not, the IC could be driving a shorted load (gets hot), or it could have bad input voltage (ripple), or the IC itself might be bad.

Oddly the datasheet says Vout max. is 4V for the adjustable version, surely a typo.

[mariushm]

Re: Help with H117S LDO

It's not a chinese clone of LM317, it's a clone of 1117, which is made by pretty much everyone ams1117, nxp1117 etc: http://www.digikey.com/product-searc...2556290?k=1117

1117 can do 0.8-1.2A with 1.2v max dropout , lm317 does 1.5-2a with 2-2.5v dropout etc etc the designs are different enough.

Pinout should be adjust/ground , Vout, Vin, tab should be Vout.

Use this datasheet if you want:

Check resistors between adjust and out and between adjust and ground, that's basically the voltage divider giving feedback to the regulator. See page 2 on datasheet above.

Replace with a generic adjustable 1117 from the digikey link above if the regulator is blown.

[killian6pk]

Re: Help with H117S LDO

It's not a chinese clone of LM317, it's a clone of 1117, which is made by pretty much everyone ams1117, nxp1117 etc: http://www.digikey.com/product-searc...2556290?k=1117

1117 can do 0.8-1.2A with 1.2v max dropout , lm317 does 1.5-2a with 2-2.5v dropout etc etc the designs are different enough.

Pinout should be adjust/ground , Vout, Vin, tab should be Vout.

Use this datasheet if you want:

Check resistors between adjust and out and between adjust and ground, that's basically the voltage divider giving feedback to the regulator. See page 2 on datasheet above.

Replace with a generic adjustable 1117 from the digikey link above if the regulator is blown.

The number on the part does not suggest the output voltage (if adjustable). How do you determine that output?

[budm]

Re: Help with H117S LDO

Calculator:

[mariushm]

Re: Help with H117S LDO

Page 2 of the AP1117 datasheet I linked above.



Vout = Vreference x ( 1 + R2/R1)

Vreference is 1.25v on 1117 linear regulators.

R2 is resistor between adjust pin and ground.
R1 is resistor between adjust pin and output.

Example in picture above is for 2.5v out : Vout = 1.25 x (1 + 121/121) = 1.25 x 2 = 2.5v

Measure the resistances by the two leads and do the math.

[killian6pk]

Re: Help with H117S LDO

On the first LDO there is one resistor below leg #1 printed on it is 221 it measures on DMM as 216ohms I do not see a second resistor connecting leg 1 and leg 2.

On the second LDO there is one resistor parallel to pin 1. Printed on that resistor is 331, it measures 298ohms. Again I do not see a second resistor between leg 1 and leg 2

The attachments are my attempt to show the location of the resistors in relation to the LDO.

[budm]

Re: Help with H117S LDO

Can we see the actual pictures of the board, LDOs?

[killian6pk]

Re: Help with H117S LDO

Yes I will get a picture for you.
Will be tommorrow I am still not in good shape from this flu attack.

[killian6pk]

Re: Help with H117S LDO

Can we see the actual pictures of the board, LDOs?

Bud here are the pictures you wanted. However, I retested these LDO's and this time they all checked. I sometimes wonder how I can test something one time and get really screwy readings like all 3 legs of these LDO's testing at 5v and then come back a day or so later run the exact same readings and get totally different results. Anyway I checked the first LDO (middle of picture one) and the first leg read 3.84v, second leg was 5.08v and third leg was 6.7v. Second LDO at top of picture one: First leg 2.085v, second leg 3.34v and third leg 4.87v. The third LDO is in picture two at the bottom right. First leg on it was 0.586v, leg 2 was 1.84v and leg 3 was 4.83v. It appears to me that all 3 are good based on the second testing. Does that sound correct to you?

[budm]

Re: Help with H117S LDO

"I checked the first LDO (middle of picture one) and the first leg read 3.84v, second leg was 5.08v and third leg was 6.7v" This is how you figure out if it is good or bad as far as the output voltage should be, you will add 1.25Vref to the pin 1 reading to get the expected output voltage. So 1.25V + 3.84V (PIN 1), then the output pin should be = 5.09V (+/-2%), Good.
"Second LDO at top of picture one: First leg 2.085v, second leg 3.34v" OK.

"Third LDO: First leg on it was 0.586v, leg 2 was 1.84v " OK.

What bother me is the odd voltage input like 6.7V and 4.83V, they do not sound right.

[killian6pk]

Re: Help with H117S LDO

"I checked the first LDO (middle of picture one) and the first leg read 3.84v, second leg was 5.08v and third leg was 6.7v" This is how you figure out if it is good or bad as far as the output voltage should be, you will add 1.25Vref to the pin 1 reading to get the expected output voltage. So 1.25V + 3.84V (PIN 1), then the output pin should be = 5.09V (+/-2%), Good.
"Second LDO at top of picture one: First leg 2.085v, second leg 3.34v" OK.

"Third LDO: First leg on it was 0.586v, leg 2 was 1.84v " OK.

What bother me is the odd voltage input like 6.7V and 4.83V, they do not sound right.

The problem I am having is no 12v from the power board to the connector on the first pictured board. I was trying to run down the cause for this and was checking the LDO's to see if they were the cause. That is when I started this thread because of the strange reading of (5v on all pins).

So is it possible that one or both of these LDO's could be causing this odd input voltage? Also do you agree that they are fixed output as opposed to adjustable? Thanks for your help.

[budm]

Re: Help with H117S LDO

The output voltages of the LDO are OK, it is just that the input voltages are strange, especially the 5V is little low.
What kind of product are we working on here?

[redwire]

Re: Help with H117S LDO

Is this the same Sanyo DP32642 from your old post? The schematic/service manual link is still there. That helps ALOT.

IC6001 has 12Vin, looks like 5V power for the tuner A6102. IC1600 has 5Vin stdby, and 3.3V out stby.