First build, shruthi smr mkII filter with negative voltage issue (-5.8v). Sorted

G’day, thanks in advance for any assistance from people who’ve ‘been there, done that’.
my power supply is 7.5v, 500mA centre positive (7.73v out). the voltage regulators are in the correct place. Capacitor polarities are correct including the optional tantalum 100uF at C1. The 1054 chip is correctly oriented (even though the carrier isn’t, oops).
My positive voltages are bang on 5.0v but my negative results are -5.8v.
I did refresh a bunch of joints around the components involved which brought my negative voltage down from -6.3v
I did read the board to roughly 30 pages back but nobody had the same issue.
any constructive comments would be much appreciated :slight_smile:

No offence taken, I’m new at this stuff and I’m trying to be as clear as I can.
I’m honestly appreciating the help. :slight_smile:
I’ve switched to 9v which is giving me 9.25v pre-diode and 8.5v post diode.
Still getting + 5.0 v on red markers but now its - 7.75v on the green.

Have you checked with another multimeter?

Have you soldered the optional Tantalum Cap?

thanks for the input :slight_smile:
2nd multimeter (with new 9v battery) gives me 5.0v everywhere on the positive side and -6.30v on the negative side including the output leg of the 7905 voltage regulator.
The optional tantalum 100uF capacitor IS in place and soldered.
I apologize for my delayed responses, I’m in Australia.

so you want to tell us you aussies are slow? :wink:

What do you measure in the 7905 Input???
Id say you somehow managed to damage the 7905…. maybe you accidentally have reversed it?

I didn’t reverse the 7905, the instructions were quite clear about which direction it should face :slight_smile:
the terminal marked ‘0’ has -6.5v now as does the middle terminal. The terminal near the small dot and IC5 marking on the pcb registers 0.0v now. The plates on both voltage regulators (I’m assuming it’s a heat sink) are both located over the thick marked line.
This Aussie is definitely slower than your average Aussie :^D

Try temporarily adding a 1k resistor between one of the 5V points and one of the ground points (you can stick it through the holes and bend the legs a bit to have contact) when doing the test. This will load the regulator a bit but this is strange. I fear it might be a faulty regulator…

No offense taken by asking if you reversed anything. See here for my excerpts on reversing Parts…

It might be that the drop from the LT1054 is so high, the 7905 simply doesn’t get enough headroom to operate. Can you try with a 9V Supply?

fcd72 is right - I did not notice that 6.5V is what you also got in the input terminal. The 7905 would need -7V at least to operate. Which voltage do you get on each pin of the diode?

Looks like the 7905 is not doing its job at all. Is there a short between its input and output pins?

no excess solder on either the back or the front. I’ll buy another one but it’ll take me a few days to get to my local electronics supplier :slight_smile:
Thanks for your help, no doubt I’ll be back :^D
have a great day.

replaced voltage regulator 7905. All good now :slight_smile: