SSR01 questions

[MacMiniHiFi]

Hi P-A,
I have started populating the SSR01 board that I bought from you and I have some questions that I think you can answer in a second (I know that it would take me hours to figure it out myself.......).

1) On the silkscreen there are two different indications (thin and fat line) for the position of the Vref and I assume they are there because of the different pinnings of the LM431 and LM329. Which go where?

2) Which are the resistors corresponding to R8, R9 and R7 on the JSR03/05? (question taken from our e-mail communication).
Your reply:
R7 -> R12
R8 -> R7, R8, P1
R9 -> R10, R11
The best thing you can do is to print out both of the schematic and compare.

3) From the BOM for the 5V supply I understand that the voltage is set by R8 and R11 (both 1k). R7 is shorted and P1 and R10 open.
If I want to fine tune the output voltage using a pot at P1 I should/could:
a) Leave R7 and R8 open and mount a pot at P1.
b) Leave R8 open and use a a fixed resistor (R7) and a pot (P1) in parallel to set the desired voltage.
c) as in a and b, but shorting R8 in stead of leaving it open?

Did I get something right here or am I entirely off?

Thanks for a very nice layout,

Nic

[peranders]

1 the figure is the LM431 of the VR1.

2, 3) I have both schematic and BOM's for 12 variants but not published yet. You can get these working copies for the time being.

a) R8 must be shorted!
b) R8 must be shorted!
c) ...

The feedback is a voltage divider and you must make sure current can flow from output of the regulator via the feedback network down to ground. The net FB (see the schematic) MUST have a resistance to ground AND to the regulator output. R8 may never be omitted.

If you want to trim the voltage:

1) R7 + P1, R8(wire)
2) R7 + P1, R8(resistor)
3) P1, R8(resistor)

I'll recommend you to avoid having R8 = wire since the gain then can be near 1 which is not good. The gain should be 1.5 or more but max 10.

[MacMiniHiFi]

Finally I found the time to build the SSR01 supply. To avoid problems I followed precisely the BOM for a 5V supply (BOM-ssr01r0(5V, LM431)).
However, in stead of the expected 5V I get 3.02V....
I have checked and double-checked all component values and placing. All in full accordance with the BOM.
The red LED's lit up (DZ1 somewhat brighter than H1).

Any help would be appreciated.

Thanks,
Nic

[peranders]

What is your input voltage?

What is the voltage across the LM431?

Do you have the J1, J2, the sense connections shorted?

[peranders]

Any results?

[MacMiniHiFi]

Sorry for the late reply. I did not solve the problem but got a JSR03 to do the work :)

The sense connections are shorted.
9-18V input voltage (tried various, but it makes no difference).
1.23V over LM431.

Thanks,

Nic

[peranders]

Voltage at:
pin 7, 6?
pin 2, 3?

I have now a very detailed picture over the board in various output voltages and 5 V is one of them. I will publish them next week.

[MacMiniHiFi]

pin 7, 6 = 4.19V
pin 2, 3 = 0.26V

I hope it means more to you than to me  :?
Thanks,
Nic

[peranders]

Measure these voltages with repect to ground. I want also to know the voltage across collector emitter of D44H11. Should be 2.5 V if the LM317 is working properly. You are sure the both the sense shorted to output and ground?

[MacMiniHiFi]

Pin2 = 1.51V
Pin 3 = 1.23V
Pin 7 = 5.33V
Pin 6 = 1.13V
col/emi = 2.52V
Both sense pads on PCB shorted with solder blob.

Any idea?

Nic

[peranders]

Pin 2 voltage should be less than pin 3, otherwise the regulator won't start. Do you have the LM431 mounted in the right position, the fat outline? How have you connected the REF pin to the CATHODE?

[MacMiniHiFi]

The LM is mounted correctly.
Having a look it seems that the ref connects to R15 under the underside of the PCB (in accordance with the BOM). The cathode connects to R14 (47R). The other end of R14 connects to R15, R16 and R17, but none of these are present (again in accordance with the BOM). In fact, it looks a little bit unconnected.........

Nic

[peranders]

Is the REF really connected via 47 ohms the cathode? What is the voltage at REF and the cathode?

[MacMiniHiFi]

The voltage vs. GND is the same at REF and cathode (1.23V if I recall). I measure 75R between REF and cathode so it would appear they are connected like that. Are you suggesting that I may have a short somewhere?

[MacMiniHiFi]

The reference is a LMV431IZ (Farnell code 9486259).