Help needed to Fix Inward connections Pre

[Tempestb]

 

[Tempestb]

7924 - (2) second one

 

[Tempestb]

Scope shows ripple

 

[Tempestb]

The rest regulators - fine 7818 , 7918 , but one 7915 shows strange wave

 

[Tempestb]

This one

 

[keefaz]

For the 7915, 5 mV ripple is within specs (from quick look at datasheet), no it's too high it should be maximum hundreds of uV instead, still it's low ripple

Sorry for the pin out error in my previous reply, you did well measuring from right pins on regulators (not left).
It appears 7824 reg has problem

 

[Tempestb]

Yeah - thanks ... I have 7915 ... 7824 not arrived yeat ... that 7915 ripple  half  ammount  as 7824 I think..... should I replace it too?

 

[keefaz]

I wouldn't replace the 7915 yet, surelly this regulator is for power opamps that have enough PSRR to attenuate 5-10 mV ripple

You make sure you tested 7824 output pin (right pin) not input (center pin)?

 

[rmburrow]

Looks like a bad electrolytic cap somewhere.... get out the clip leads and try a known good cap across each electrolytic in the power supply...cap may test OK but have high ESR..you still have trouble... FWIW
Ripple should be very low or nonexistent on the DC lines...

 

[Tempestb]

Thanks ... i’ve Checked twice the 7824 I’ll check one more time before swap ... from what I’ve seen in the data sheet 7824 1-Input 2-ground 3 output ........ 7924 1 and 2 swapped .... ill try to check what caps in his network

 

[keefaz]

Yes pins are correct, also did you double check the 7924 measurement that shows the flat wave on scope?

 

[metalb00b00]

Thanks ... i’ve Checked twice the 7824 I’ll check one more time before swap ... from what I’ve seen in the data sheet 7824 1-Input 2-ground 3 output ........ 7924 1 and 2 swapped .... ill try to check what caps in his network

High quality low impedance/low ESR electrolytic caps for you to consider (these are mostly radial and rated at 105C degrees):

Nippon Chemi-Con KZE/KZH/KY (brown sleeve, white print), LXY/LXZ (blue sleeve, white print)
Panasonic FC (blue sleeve, gold print) FM (black sleeve, gold print) FR (black sleeve, white print)
Nichicon UHD/UHE (black sleeve, white print), UPM/UPV (brown sleeve, white print)

Buy brand new, not NOS.

 

[Tempestb]

Yeah thanks - I’ve got some Nippon chemi, brown ... and couple of black ones                                                                    (Yes pins are correct, also did you double check the 7924 measurement that shows the flat wave on scope?)- yes - first turn to ground coupling - place at middle of screen then to DC coupling - to seee voltage readings - then to AC coupling - and it stais flat .... same as 7818 and 7918