C4S board problem, bad voltages [resolved]

[kip.duff]

Finished my R monoblock and played in mono while I finished L monoblock.  R amp checked out OK except resistance at B2 was 10.2k (both amps actually- specs call for 8.2k)- I don't think this is a problem.  R amp Kreg A: 3.5V, Kreg B: 7.2- too far off?  (specs call for 4.1V and 6.3V)  I have Psvane 300Bs TII and GE JAN W5670s.

Anyway my main problem is wrong C4S board voltages on left monoblock.  OA: 192V, moves around depending on trim pot position.  OB: won't go lower than 185V with trim pot and I think was at 240V when I first fired up.  Actually, OA and OB voltages rise and fall together with trim pot adjustment.  Also, B side LEDs aren't lit up.

I was worried when soldering the C4S boards because it's hard to see solder flow like on the larger pads- since I wasn't sure about getting proper joint, I think I overheated transistors, LEDs, small resistors, regulators causing failure(s).  Also, I think I should have changed to my 600F soldering tip. I'm getting ready to order parts right now- can't wait to hear them in stereo!  Part kits available for C4S board?  Or I can just order the suspect parts.  Advice appreciated.  Thanks, Kip.......... 

 

[Paul Birkeland]

Anyway my main problem is wrong C4S board voltages on left monoblock.  OA: 192V, moves around depending on trim pot position.  OB: won't go lower than 185V with trim pot and I think was at 240V when I first fired up.  Actually, OA and OB voltages rise and fall together with trim pot adjustment.  Also, B side LEDs aren't lit up.

You need to triple check your jumpers.  OA shouldn't move with trim pot position.

-PB

I was worried when soldering the C4S boards because it's hard to see solder flow like on the larger pads- since I wasn't sure about getting proper joint, I think I overheated transistors, LEDs, small resistors, regulators causing failure(s).

At Bottleheadquarters, we solder at 900F.

 

[kip.duff]

Damn! Your'e good.  B+reg jumped to OB instead of IB.  Thanks so much, Kip..............

 

[kip.duff]

All voltages checked OK- amps sounding great- breaking them in now.

So- I'll leave my soldering tip at 700- works a lot faster.  I guess those tiny electronic parts are tougher than I thought.

Thanks, Kip....................

 

[Paul Joppa]

The solder and wire and terminal/PC board need a certain quantity of heat to flow properly. The higher the iron temperature, the faster that happens and the less time there is for the heat to go up the wire to the silicon parts. So, if the soldering is done optimally, a hotter iron actually heats the component less. But the time available for heat application is less, so you have to have a good "feel" for the operation and some dexterity to get away with the higher temperatures. I am somewhat clumsy, so I run mine at about 750F. It's a good idea, if you have an adjustable temperature, to keep it at a fixed point so you learn to know your iron.

 

[kip.duff]

Paul:

Excellent point- thanks for getting me on the right path.  Based on what you're saying and my experiences that I remember now, the 600F tips are kinda useless.

Slowly getting to know these new amps- anxious to hear them with proper speakers- that's next on list of stuff to get.............