Building a symmetrical PSU B1 buffer

[udailey]

Okay, no music. No relay click. The LED near the LM7805 is not on. I get 5V and 10V on BC556 and 2SK170 in the B1 circuit.
I get 5V from the LM7805 and 5V across the parallel resistors that feed the relay. I also get 5V on 2k2 feeding LED. Suppose I should replace LED.
Ri

 

[Salas]

npapp:

4 non matched Leds and 1k trimmers connected as rheostats instead of the fifth Led. Use pins in the 5th place and crocodile clips, so you will not unsolder anything and destroy the pads. After you set it, measure the trimmers and substitute resistors upright soldered on those pins. They will be different.

 

[udailey]

Used 9V battery and 100R resistor and tested relay. It works.
Uriah

 

[Salas]

Okay, no music. No relay click. The LED near the LM7805 is not on. I get 5V and 10V on BC556 and 2SK170 in the B1 circuit.
I get 5V from the LM7805 and 5V across the parallel resistors that feed the relay. I also get 5V on 2k2 feeding LED. Suppose I should replace LED.
Ri

7805?

7812 hello!

 

[billyk]

7805?

7812 hello!

Beat me to it!

 

[udailey]

Hey be gentle I thought if using 5V relay we are to use 7805, no?

 

[billyk]

Logical conclusion, but that is what the resistors are for. It is jumpered for 12v relay and the resistors are for the 5v relays.

 

[udailey]

Okay. I had read Jean Paul talking about 5V relays and 7805 so I just assumed. Well thats easy. Be right back

 

[Salas]

Don't go jumper the resistors and keep the 7805. Without 7812 the driving circuit won't open. Its 7812, jumper, 12V relay, or 7812, resistors, 5V relay. No 7805.

 

[npapp]

npapp:

4 non matched Leds and 1k trimmers connected as rheostats instead of the fifth Led. Use pins in the 5th place and crocodile clips, so you will not unsolder anything and destroy the pads. After you set it, measure the trimmers and substitute resistors upright soldered on those pins. They will be different.

Perfect, thanks I will report back soon.

 

[Salas]

What is it for? You will run 200mA CCS with those 16R in parallel. Sink accordingly. +/- 15V smells like op amps?

 

[npapp]

Yes Opamps, I/V stage from Buffalo24. current requirement 60-70ma. I have been listening to this DAC as is for several months now so hopefully I will be able hear any difference with the new psu.

 

[udailey]

7812 in place and there is still no relay clicking. LED still not turning on near 7812. After several seconds I start to hear this weird sound. Real low volume and it sounds like if you put your ear in a Conch shell. I dont think this is the sound I was looking for LOL
.5A fuse blew. I replaced it and it is not blowing again. However I got one of those Antek 50VA 15V toroids and wired it up, then turned it on and started hearing that sound for the first time. So I removed it and put back the CT transformer. Sound is still there.
Still worries me. Rails are different now. 10.2 and 11. R1 has 2.16 and 2.04.

 

[Salas]

Where do you hear that sound? Near the relay? Comes from it?

 

[udailey]

Is this that oscillation that everyone has mentioned?

 

[udailey]

sorry posted at same time, I didnt want to stick my head to close to it. I will now enter the mouth of the beast.
Uriah

 

[udailey]

Its hard to tell. I think I will go pick up my wife from work and then after dinner add that cap and see if I get rid of the noise.
Uriah

 

[Salas]

Kannan had a ''chatter'' and Tea bag. Kannan changed a 7812 and was gone. If it is that, put a 0.15u cap across C,B of the transistor that drives the relay (the one facing towards the 2 drop resistors). But first, tell me, what voltage you measure from those 2 resistors output to ground?

 

[kannan_s]

Its hard to tell. I think I will go pick up my wife from work and then after dinner add that cap and see if I get rid of the noise.
Uriah

When you power up - you will not hear the noise till few seconds later - you can hear the click of the realy coils and then you will hear the noise. If that is the case, then the noise is from the relay due to some sort of voltage spikes on relay coils. You can solder 150nF cap - across the transistor driving between C/B - you can read the thread - you can eevn see Salas' post with clear location of this cap. This should cure the chatter issue. Any value 0.1nF to .22NF cap will do.
kannan

 

[billyk]

sorry posted at same time, I didnt want to stick my head to close to it. I will now enter the mouth of the beast.
Uriah

Old car repair trick I used to use listening to the inside of an engine. I would place a long screwdriver on that part of the motor and my ear against the other end. The sound would then be transmitted to my ear. If you have something like a dowel rod, maybe a wooden ruler, you could place it on the relay and hear if it was from there??