missing leds on one c4s board

[jagmeetbatth]

hello
i am building amplifier using your kit and i am not getting leds on one of c4s board
the other board have leds light up
OB voltage with working c4s =around 220
OB voltage no leds c4s= 300 plus

 

[Paul Birkeland]

i am building amplifier using your kit and i am not getting leds on one of c4s board

Is this one of our kits? If so, which one?

If not, you'll have to describe what you're building to get an idea of what might be going on.  Based on the limited information available in this post, the center joint of Q2 isn't always easily soldered, and this can create the issue you describe.  Whatever you do, do not apply a ton of extra heat and solder to the LED solder pads themselves, as this can damage the LEDs. 

 

[jagmeetbatth]

its one of your kit .someone gave it to me to build for them
in photo the one on left side c4 board doesnt light up led and voltage at OB is diffent(higher) than other board.
there is sound output but very quiet in headphones.
the right side c4 board two led light up

 

[Paul Birkeland]

OK, this is a Mainline kit, so I have moved your thread to that section of the forum.

Can you describe what's going on under the R4 resistors on the center C4S board? 

On the center board, what are the Kreg and +reg voltages on each side?

 

[jagmeetbatth]

i just marked red r4 resister with marker as they were missing but later found and soldered.

voltrage A side +reg=306v
kREG 1.2v
B side +reg 218v
Kreg 4.18v
DC

 

[Paul Birkeland]

It would help to see the bottom of the high current C4S board on the problematic side. 

 

[jagmeetbatth]

attached

 

[Paul Birkeland]

Pin 1 on the center 9 pin socket should have a connection.

 

[jagmeetbatth]

thank you done b1 to 16L
both boards light up on a side led and sound output is very very quiet

 

[Paul Birkeland]

thank you done b1 to 16L
both boards light up on a side led and sound output is very very quiet

You need to measure the voltages before using the amplifier.

You also need to set the bias before using the amplifier.

Failure to do this is using an amplifier that may not be working properly, and there can be some unfortunate consequences...

 

[jagmeetbatth]

adjusting the bias .
voltage is stuck at 215v on 30 and 20 pin
doesnt change anything when i adjust potentio

 

[Paul Birkeland]

The center C4S board has OA and OB pads, could you provide DC voltage measurements on each of them?

 

[jagmeetbatth]

ob 7.5v
oa 5.6v

 

[Paul Birkeland]

On the side where you were missing the red wire, a new 431 regulator will likely be required to get the regulated voltage to drop down.

Can you post a picture of the bottom of the center PC board up front?

 

[jagmeetbatth]

here?

 

[Paul Birkeland]

Can you let me know what soldering products were used on this?  There seems to be a ton of flux all over everything and that's rather unusual.  Also there appears to be two wires going to pin 1 of the 12AU7 socket, and I'm not sure why that is either.

 

[jagmeetbatth]

they wer both going to 19L i removed one now .too muct flux shouldnt be an issue.
any more areas i need to check .
still stuck at 215v on 20 and 30

 

[Paul Birkeland]

Does the voltage at the "O" terminals on the center board change if you attempt to adjust the trim pots either way?

Depending on the flux used, flux can indeed cause some substantial issues.

 

[jagmeetbatth]

yes it does change at oa and ob when i adjust trims

LM431? faulty

 

[Paul Birkeland]

If the LM431 is faulty, your Breg voltages would be incorrect, are those incorrect?

What voltage ranges are you able to get on the OA/OB terminals on the center board while rotating the trim pots?