Pearl 3 Burning Amp 2023

[wanders]

OK, got 17.3 vdc all around. Do you want me to continue to bring the project along using the 12v transformer? Or secure a 15v transformer. Thanks for help.

 

[rhthatcher]

Great news! No smoke and 2.3v in front of regs. Do you have 15v after regs?

Have you measured the bias current in the circuit yet?

 

[wanders]

No work beyond no smoke and PSU/Phono voltage checks. I'll proceed with the current trans and see what gives.

 

[rhthatcher]

I'm curious what you get when you measure voltage on R27. If you are high on current and end up changing R27, I'm curious to see if that impacts the pre-reg 17.3V much. You need 2V+ before the regs, and and you have 2.3V now. So once you check out R27 I think you're ready for rock'n'roll. Or jazz, classical, etc.

 

[wanders]

With R27 at 220R getting 2.3 & 2.4, Got 470R, 510R, 680R, thought I'd try 510R.

 

[wanders]

With 510R in R27, showing 2.5-2.7V. Readings are pretty jumpy; and both D-1 LEDs are flashing.

 

[rhthatcher]

Do readings settle down? I get a couple blinks on power up.

 

[wanders]

The blinking is steady. (It was blinking steadily before the resistor change.) The voltage reading at R27 is very unsteady, but it was steady before the resistor change.

 

[rhthatcher]

Try a board solo and see what happens

 

[wanders]

Tried both boards solo (one at a time). Both behaved the same: LED flashed steadily, voltage readings were jumpy, but in a small range between 17 and 18 volts.

 

[rhthatcher]

What are you seeing for voltage where the schematic shows +/-15? Just after regs?

 

[GKTAUDIO]

The only time I noticed non-stop blinking was when I was underpowering mine with a bipolar bench supply. Randy's query about post-reg voltage sounds spot-on to me.

 

[wanders]

right side, jumping around between 14-15

 

[wanders]

both sides on, same behavior except a little less voltage - 12-14

 

[GKTAUDIO]

I think you will need a 15V transformer. Smaller transformers tend to have poor regulation, so unloaded they will read quite a bit higher than loaded.

 

[wanders]

That's where I suspect this is heading. But, I'm not in a rush, happy to see it through.

 

[rhthatcher]

I think you’re going to need a 15+15V transformer. Send me a private message with your shipping info.