Not enough voltage at IC22 and IC23 - power part

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kevofromspace
 
Posts: 4
Joined: Fri Sep 27, 2013 9:55 am

Not enough voltage at IC22 and IC23 - power part

Post by kevofromspace »

Hi everyone,

First I've read all the topics about the wrong voltage at IC22 and IC23, but I did'nt find a solution about my problem.
I checked all the components before soldering them. I rechecked all the values after soldering with the color code and the multimeter. The voltage values of the previous tests are the right ones too. I tested the diodes 44, 45, 46, 47 too, the voltage is 0.4v for each one (is that normal ? )

By turning the Trimpot, here are the values I measured :

IC22 Input: 1,7 to 2,2 v
IC22 Output: 4,6 to 5,1 v

First I througt that the LM336Z5 was defect so I replaced it with another one but the values are the same.
I read in another topic that the impedance of the multimeter could distort the value, so I soldered the IC23 part with capacitors and resistors to measure the voltage at J4. The voltage ranges between 4,8 and 5,1 volts. Far from the 5,33 volts...

Can somone help me to find the cause of the problem ? Thanks in advance !

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substyler
 
Posts: 428
Joined: Tue Dec 02, 2008 6:29 pm

Re: Not enough voltage at IC22 and IC23 - power part

Post by substyler »

hi,

it seems that some faulty (or just wrong) LM336Z-5.0 reference diodes floating around.
look on the 5V diode and read exactly this: LM336Z-5.0 (not only LM336Z 5)
if you not see exactly LM336Z-5.0 on your part, it could be wrong.

I had some LM336Z 5 and saw the same problems with voltages!
after getting some LM336Z-5.0 everything went good.

partnumber at DigiKey: LM336Z-5.0/NOPB-ND

cheers,
Sub

kevofromspace
 
Posts: 4
Joined: Fri Sep 27, 2013 9:55 am

Re: Not enough voltage at IC22 and IC23 - power part

Post by kevofromspace »

Are you sure those components are different ? I purchased some LM336Z5.0 on ebay, and it is writen "LM336Z5". I compared the datasheets and I saw no differences :?

kevofromspace
 
Posts: 4
Joined: Fri Sep 27, 2013 9:55 am

Re: Not enough voltage at IC22 and IC23 - power part

Post by kevofromspace »

It was indeed the voltage regulator.. I replaced it with the LM336Z5.0 and now it works.

Great, but why ???

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