Building a symmetrical PSU B1 buffer

[sonidos]

I texted him. He said real life has him busy today.

 

[Salas]

 

[udailey]

And the long gnd jumper is soldered in both sides? The way the inwards NPN goes up is OK, there is continuity to the relay and 180R is its spec coil Ohmic, then a dead BC546 speculation remains. Do you have any cbe npn to substitute? Just any. Can you read V also in the mid leg of the lower npn?

HI Salas,
Heard you missed me
I have been getting my wheels bent back to where they should be and polished. They have been letting the tires leak because the seal is no good. I have been fighting for good pricing and also had to take my daughter to the zoo today. So busy til now.

Okay I have 178.2 across the relay. It seems to be okay and if I use a 9V battery to the diode the relay clicks.
The jumer is soldered on both sides.
Voltage on mid leg of lower NPN is .73
I have other NPN. I do have more BC546, BC550CG, and some 2N2905A which I am betting are not the best for this. I am not sure if you would like me to try the same or different one.
Uriah

 

[Salas]

BC550. The other transistor does not open, your reports lead me to believe.

 

[udailey]

So the top of the two BC546 needs to go and sub in a BC550? Is this what you want?
Uriah

 

[Salas]

Both as a pair. Also be sure that the 10k resistor is 10k indeed. I wonder also why your power led wasnt giving light. Was it with cathode towards the near pcb edge, or not?

 

[udailey]

I did check before soldering it in, the LED I mean. But that doesnt mean I couldnt make a mistake although I can tell the difference between A and K.
Okay so replace both BC546 with BC550?
10k resistor says 1002 on it. Its a Dale RN55. It measures about 7.1k after 1 minute but its in the circuit so I dont expect to be able to get 10k from it if it happens to be parallel to something else.
Uriah

 

[udailey]

Both as a pair. Also be sure that the 10k resistor is 10k indeed. I wonder also why your power led wasnt giving light. Was it with cathode towards the near pcb edge, or not?

I could use alligator clips to 2.2k and GND and see if another lights up or not.
Uriah

 

[Salas]

Sure.

 

[udailey]

LED works with Alligator clips.
Uriah

 

[Salas]

That led is supposed to go to the front panel. So for those putting it there on the pcb, just leave it standing proud enough, until the system goes in a box. Then chop off mid leg height, and use the remaining pins for attaching thin twisted wire to the front panel moved power on led. That way you wil not have to work the pads hot again.

Lets see with the new npns. All else looks correct till now.

 

[udailey]

Dang I only have one of each. I have a few more BC546 but I also have a lot of 2sk170. Can I use 2sk170 here instead of BC550? Sorry about this, I just checked bag label, not quantity in the bag.

 

[Salas]

Just change the one that looks towards the 2 parallel resistors face down to edge of board. No NJFET. BC550.

 

[Salas]

I will be offline for an hour or so, hope it works with that new npn.

In any case:


BOM MASTER CALL:

Upper NPN that looks towards B1 audio part = BC550B or C

Lower NPN that looks towards the two resistors = BC517 Darlington

For sure very high current gain.

If CRT is making any last minute stuff, better print it on the PCB too.

 

[udailey]

Have to pick up wifey at work. So will do this quickly and test after I get her.
Uriah

 

[udailey]

Salas is a genius.
Uriah

 

[udailey]

Okay I have to go now but had to hook it up first.
One channel pops at turn on. Every time I turn it on and a little pop on turn off.
The other channel works fine when the relay clicks over but the one that pops has no music just a hiss.
Have done no testing yet for DC but did not see the cone go into excursion.
Uriah

 

[Tea-Bag]

I will be offline for an hour or so, hope it works with that new npn.

In any case:


BOM MASTER CALL:

Upper NPN that looks towards B1 audio part = BC550B or C

Lower NPN that looks towards the two resistors = BC517 Darlington

For sure very high current gain.

If CRT is making any last minute stuff, better print it on the PCB too.

CRT may be making last minute stuff, I think.
Salas, would ZTX450's work as well here?

 

[Salas]

BC517 for the pull, some CBE NPN pin order for the drive. Better be one more 550, since they will buy for the regs part. ZTX 450 looks reverse pin order and low hfe.

 

[Salas]

Okay I have to go now but had to hook it up first.
One channel pops at turn on. Every time I turn it on and a little pop on turn off.
The other channel works fine when the relay clicks over but the one that pops has no music just a hiss.
Have done no testing yet for DC but did not see the cone go into excursion.
Uriah

That particular relay proves a pig. For one it needs much current gain to be pulled. Its unlikely you have an audio side problem, it may still be the relay not contacting well on one side. But measure before the relay. Maybe there is something before input or some audio side njfet has given up the ghost like that inadequate or dead 546. You can look for DC offset and signal on the 220Rs. If you don't have a generator, a steady tone cd or a PC tone wav can let any dvm measure AC RMS. Or even some repetitive busy music. Then you will know if you have to bin that relay or look elsewhere. Is your soldering iron more than 25W BTW? I wonder about erratic relay occurences or thermal stress.