CrackSB worked fine for one year till now. Need help troubleshooting [resolved]

[Paul Birkeland]

That's not zero, that's "OL", which stands for "over limit", which is many millions of ohms.

[deltaray]

I see, what should I check next?

[Paul Birkeland]

Put it all back together, paying special attention to how the TIP50s are mounted so that the metal tabs don't touch the heatsinks, then recheck the resistances on terminals 1-10.  We may have been chasing absolutely nothing this whole time.

[deltaray]

Alright, have put it back together.

Find below the resistance measurements (from 12U):
1: 14 MΩ
2: 8 MΩ
3: Zero
4: 15 MΩ
5: 15 MΩ

6: 2.5 KΩ
7: OL
8: Zero
9: OL
10: 2.5 KΩ

[Paul Birkeland]

OK, those are OK resistances, so now we are back to repeating the voltage checks, being careful to turn the amp off if B+/2/4 dip down below 100V.

[deltaray]

Sorry for the late response.

After measuring it for a while I noticed that led will light up now. Albeit delayed from the others.

This are the measurements with the led up:

OA 117V
OB 112.7V
G 1.9mV
B+ 200V

After trying the audio now. It seems the amp and tube would need a 1 min warm up. In between that time, there would still be loud popping in the left channel. But it seems fine afterwards.

[Paul Birkeland]

Flip the big PC board over and reheat every solder joint that isn't an LED. 

[deltaray]

Done just that.

Looks fine now, that LED light now lights up within 5 seconds.

There's a slight slight imbalance to the right side, but other than that it sounds fine

Thank you!

[deltaray]

After letting it rest to run again. I notice that LED light will light up first, follow with the rest all lighted up. However after some while, will hear a loud pop on the left channel and the LED light goes off.

If I switch it off and try again, the exact same thing repeats.

[adydula]

I had issues like this a long time ago, and it was the LED itself. I replaced it and its solid now for 2+ years...if the solder joints are well done and this is still happening it may be the LED is mechanically
stressed and broken, making a poor contact...

You can poke around "CAREFULLY" with the chopstick method on the pins the LED is solder to, or gently move the LED to see if it comes back on..indicating still a poor solder connection OR the LED is damaged
mechanically.

These leds when installed in the confined space IMO needs some strain relief do they are not moved around when you insert and change out tubes...if they are soldered very tight with no extra leads bent upwards abit to help with this movement they can get damaged from the movement.

Hope this helps..
Alex

[deltaray]

thanks for that advice! if i were to consider replacing, is there a specific model for the LED to get? or would it be the case where i have to totally replace all leds

[Paul Birkeland]

The LEDs are HLMP6000s.  Any other LED may lead to some unpredictable performance issues.

[Doc B.]

https://bottlehead.com/product/hlmp-6000-leds/

[deltaray]

thank you!