getting ~4.39 instead of 5.333... help!

[diplowave]

Of course R5 is 2,4k. Maybe i can replace R4 with a lower value resistor. I should try with a 5,1K. I think it would rectify TM6 voltage's.

[diplowave]

Not it's the opposite to increase the voltage to TM6, gotta put a stronger R4. I tried but it's not a good idea.

[diplowave]

I did further testing, if I replace R3 with a 12K resistor. I can get 5.30 volts at the tm6 trimpot. But I still have the voltage too low at junctions d44/d45, d45/r5, r5/tm6, tm6/r4. I do not understand the problem.

[mmm]

I soldered IC 23 and i have always tm6 around 4,60v and 4,90v.

Where exactly are you measuring?

[diplowave]

I changed a few components and I always odd measures. Now the trimmer is adjustable from 5.31 V to 5.36 V, at the pin5 of an6562 WTF



d44/45 juncture: 0,451v
d45/r5 juncture: 0,898v
r5/TM6 " : 0,986v
TM6/r4 " : 5,47v
r4/d46 " : 5,48v
d46/47 " : 5,70v
d47/r3 " : 5,37v
r3/r2 " : 25,2v
r2/r1 " :28v

[mmm]

As I've written before: You need to measure at pin 7 and make the adjustments according to this value. The voltage readings on pin 5 are not reliable.

Your sketch shows the voltage at pin 7 at 5.96V which is too much. Try to adjust so that this value is the proper 5.33V.

[diplowave]

I pulled a pin trying to change the trimmer. Because it was impossible to calibrate. For now I will continue assembling this x0xb0x, with the I / O board another x0xb0x.

[diplowave]

It was LM336Z was defective, I bought another supplier now I have 5,333 V. I wasn't lucky because I had two times defective LM336Z.

[diplowave]

I noticed with LM336Z5.0 voltage is OK but with LM336Z5 it's bad.
Does anyone know the difference between LM336Z5.0 and LM336Z5?

[robertsp]

I've got the same problem, a maximum of 5.32 volts possible.
I compared the datasheet of the component which was supplied with my kit (Fairchild LM336Z5 (http://www.fairchildsemi.com/pf/LM/LM336Z5.html)) and one from National/TI (http://www.ti.com/product/lm336-5.0 (The Z is just the type of package)).

Most features are the same:

• Low Temperature Coefficient
• Fast Turn On
• Easily Trimmed for Minimum Temperature Drift
• Adjustable 4V to 6V
• etc..

But then one difference jumps out:
The Fairchild: "Wide Operating Range Current: 10 mA to 400 mA"
National/TI: "Wide Operating Range Current of 600 µA to 10 mA"

Then I would think.. Just increase the current so it operates in the zener region.
But when I read further, BOTH datasheets state:
Absolute Maximum Ratings
Ir (Reverse Current) 15 mA
If (Forward Current) 10 mA

If one then reads forward to the Electrical Characteristics, also the Fairchild datasheet uses conditions of 600 µA <= Ir <= 10 mA. With all the same specs.
Just like almost all graphs. Look at the Forward Characteristics chart.
If you look at lets say 10mA, the Fairchailds forward voltage is 0.8 V, the one from National/TI is 1.0 V.
Is that maybe the problem? If we are using the LM336 as an adjustable shunt regulator, we're working in the forward region instead of zener or am I wrong?
Well at least that's the only difference I could find between the types.

[diplowave]

I tried with several lm336Z5 on the same board I/O -> Not good.
The first lm336Z5.0 -> 5,333 V in the center of the trimmer.

[robertsp]

It is quite weird. But as I don't have a LM336Z5.0 in my stock I wanted to 'fix' it with the Fairchild LM336Z5.
According to the datasheet the absolute resistance of the network can be anything from 2k Ohm to 20k Ohm.
I changed both R4 and R5.
R4 = 6k19 1%
R5 = 1k78 1%
The total resistance of R4 and R5 is almost the same.
But now I can regulate from <5.20V to 5.45V
Which I would think is enough. Anyway 5.333V is in that range
Maybe for others with the same type of LM335Z5 problem to try it.