I turned it on this afternoon and this time it failed to start. In about two or three minutes and before I had time to measure voltages as suggested by Mooly, both boards powered up,one a few seconds after the other. I suspect this behaviour has always been present, although I would usually ´jump-start´them before it happened.
no, betting is not what you should be doing. It is not down to chance, it is design.
You need to be able to design the regulator to suit the operating conditions for which it is expected to perform.
If you cannot do this, you should NOT be altering anything from an existing proven design. You need to satisfy yourself that this is a reliable proven design and copy it exactly.
You should also be taking steps to increase your knowledge base.
AndrewT: You are right, it is a proven design. And both boards behave the same. I finally got a bigger 15v transformer today, 1A rating. Will try it this weekend.
I will measure voltages if it fails again (and remains faulty for as long as I need to complete the checklist)
I will measure voltages if it fails again (and remains faulty for as long as I need to complete the checklist)
Have you had any luck with this ?
I got hold of a copy of Doug Selfs new book yesterday (Small signal design) and this problem was mentioned.
If there is a large capacitance (100uf or more) between the rails ie between +15 and -15 it can in some cases cause the regulators not to "start".
Also mentioned was the problem of rails that rise unequally and this can cause latch up particularly in NE5532 I/C's causing large currents to flow.
All credit to Doug for the above.
I got hold of a copy of Doug Selfs new book yesterday (Small signal design) and this problem was mentioned.
If there is a large capacitance (100uf or more) between the rails ie between +15 and -15 it can in some cases cause the regulators not to "start".
Also mentioned was the problem of rails that rise unequally and this can cause latch up particularly in NE5532 I/C's causing large currents to flow.
All credit to Doug for the above.
Mooly, thanks for the input. It has been consistently powering up faultlessly for quite some time now, especially since I tapped the supply to feed a small two op-amp circuit as well as the equalizers. Hence I´ve had no chance to take voltage measures so far.
Doug Self´s observation seems to fit this case. I´m quite convinced there are no bad solder joints and the components are as specified.
By the way, the change to a beefier transformer did not improve things so I reverted to the original.
Doug Self´s observation seems to fit this case. I´m quite convinced there are no bad solder joints and the components are as specified.
By the way, the change to a beefier transformer did not improve things so I reverted to the original.
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It does seem a possibility then... perhaps adding the two opamp circuit in some way has altered the balance of things.
Must admit it's a problem I had never heard of before, or indeed ever come across on any of my builds.
Perhaps even a different brand of regulator may solve the issue.
Must admit it's a problem I had never heard of before, or indeed ever come across on any of my builds.
Perhaps even a different brand of regulator may solve the issue.
The fault still occurs but it´s rare. Over time I´ll try to complete the voltage readings you suggested. I hope we can find an answer then.
This is just a thought . . . it almost sounds like you aren't drawing enough current from each regulator to "get it going", so to speak. I've seen this happen before, but usually with switching supplies. They require a certain current draw to kick-on. The fact that you initially shorted the outputs, (big current draw), to get them going supports this. Also, adding more load, (the new op-amps), also supports this theory.
Try connecting a 150-ohm resistor across the pos and neg outputs. This will pull around 100ma's, and should help to determine if that might be the problem.
Try connecting a 150-ohm resistor across the pos and neg outputs. This will pull around 100ma's, and should help to determine if that might be the problem.
Artie, Thanks,I´ll try that. I´m also thinking that the cable gauge I´m using between the transformer and power supply circuit is very thin and 1meter long. Just read somewhere this could also cause problems.
So I´ll switch to thicker wire and see what happens. If it still fails I´ll add the resistors. If I did both at once we would never know what fixed it!
So I´ll switch to thicker wire and see what happens. If it still fails I´ll add the resistors. If I did both at once we would never know what fixed it!
kamal
Hi friends i need crystal clear sound in my amplifier. so i want any audio circuits using transistors or op amps. tone control circuits also i need.
Hi friends i need crystal clear sound in my amplifier. so i want any audio circuits using transistors or op amps. tone control circuits also i need.
Just wondering if the 150ohm resistor worked. I have a duel 15v thats having trouble powering the positive side. It works but sum times it has to be switched on off on to get it working.
I could never make the on-board regulation behave so I finally bypassed it and tapped a regulated power supply that was powering other circuits in the box. Working perfectly.
I work in the business and the earlier suggested idea of a diode connected across each of the regulator outputs will stop the problem. Use 1N4004 or similar:
Diode 1 - cathode (-) to +15V reg output. Anode (+) to 0V
Diode 2 - cathode (-) to 0V. Anode (+) to -15V reg output.
You will note that as such they are each "reverse connected" across the regulated supplies.
This prevents one of the regulators intermittently finding it's output dragged past 0V and consequentially winds up "latched", and from what I've seen does not occur if you pull more than approx 0.1A continuous at switch-on. I have not tried the resistor trick (150 ohms is pulling 0.1A @ 15V which requires 1.5W resistors or preferably much greater and would dissipate quite some unnecessary heat) - so cannot vouch for that working.
Best regards,
Diode 1 - cathode (-) to +15V reg output. Anode (+) to 0V
Diode 2 - cathode (-) to 0V. Anode (+) to -15V reg output.
You will note that as such they are each "reverse connected" across the regulated supplies.
This prevents one of the regulators intermittently finding it's output dragged past 0V and consequentially winds up "latched", and from what I've seen does not occur if you pull more than approx 0.1A continuous at switch-on. I have not tried the resistor trick (150 ohms is pulling 0.1A @ 15V which requires 1.5W resistors or preferably much greater and would dissipate quite some unnecessary heat) - so cannot vouch for that working.
Best regards,
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Thanks, blue_glo . Since everything runs fine now I no longer have a reason to make the on-board regulation work. Realize that this is an old thread already. I initially thought that sharing a transformer for the various supplies and boards might affect the performance, hence my insistence on making this supply work, but I have not heard any deleterious effect whatsoever.
Thanks again for sharing your experience and knowledge. It may came in handy in the future.
Cheers
Thanks again for sharing your experience and knowledge. It may came in handy in the future.
Cheers
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