Power on right channel not quite right. Need suggestions

[last lemming]

So the first set of tests, tested fine, but when I did the voltage checked the right channel was off:

IA = 216V
IB = 210V
OA = 213V
OB = 158V
OC = 75V
OD = 95V
OKA = 72V
OKB = 97V
OKC = 2.54V
OKD = 1.63V

I’ll check over my connections, but is there something I should hone in on?

 

[Paul Birkeland]

The middle leg of Q2A likely needs a lot more heat to be well soldered.

 

[last lemming]

I just noticed the 2 leds next to OC are not lit.

I’ll look into the middle leg

 

[last lemming]

Ok, the middle legs are all well and soldered. Now the OA and OC LEDS come on but flicker.

 

[Paul Birkeland]

Flickering tends to mean something is loose, which still points to a flaky solder joint.  DC voltages are still most important, did those change?

 

[last lemming]

So I cleaned the board, and retested and the values are good now, but now, but the LEDs on OC don’t light up at all now

New numbers

IA = 216V
IB = 214V
OA = 167V
OB = 162V
OC = 97V
OD = 96V
OKA = 98V
OKB = 978V
OKC = 1.87V
OKD = 1.46V

 

[Paul Birkeland]

That is a working set of voltages.  Do the LEDs glow in a dark room?

 

[last lemming]

No. Not at all.  I even reflowed them.  They flickered earlier, now they just don’t work. Where does the power on the fed the from?

When I cleaned the board from flux I used rubbing alcohol, could plugging in the unit before alcohol is 100% dry blow out the LEDs?

Would a bad tube do this?

 

[Paul Birkeland]

I would definitely not reflow the LEDs.  When they are not illuminating, it's rarely ever the LED connections themselves, but rather other parts of the amp that aren't working properly that are unrelated to the LEDs themselves.  If you apply too much heat to the LEDs, they can be damaged as they are not particularly hefty and they get pretty warm from soldering.

You don't have a bad tube.  Your voltages are perfect, as far as the tubes know your Eros is working perfectly (assuming OKB is 97.8V, not 978V)

Can you post some photos of the top and bottom of your center C4S board that's mounted up front?

 

[last lemming]

I’ll try to get some photos. I tried plugging in the unit to my stereo and I started getting a kind of rumbling with a hiss type noise from the right channel. Left channel was quiet at first, then after about a minute I started getting a similar but not quite the same noise from the left channel. This is with the unit plugged on and connected to the amp, but no record spinning.

 

[Paul Birkeland]

Did you have a turntable hooked into the Eros when you hooked it up to your stereo?  With an open pair of inputs, you could run into some issues. 

Without a DC voltage problem to chase, you could certainly try just replacing the LEDs on their own. 

 

[last lemming]

I did have all the interconnects connected.

Btw, this the bottom photo was taken prior to the center leg being resoldered.  The top is current.

Do the LEDs contribute to the sound?

 

[Paul Birkeland]

It looks like possibly you may be using lead free solder, or perhaps an iron that's not hot enough (maybe both).

The LEDs bias the current source loads.  They have to be HLMP-6000 diodes, other choices may simply not work properly.

 

[last lemming]

I’m using Kester Sn60Pb40 with rosin and my temp is 681F

I guess I’ll order more LEDs and give it another shot there.

 

[Paul Birkeland]

If you can turn the temp up over 800F, that will help.  Despite the hotter temperature, the solder will flow out far more quickly and result in your parts heating up less.

 

[last lemming]

Well, I ordered most the parts to replace the board (just in case), because I pulled the two LEDs that wouldn’t light and bench tested them. Guess what, they both worked.

 

[last lemming]

in retesting my outputs and inputs I couldn’t get a stable reading on the output center pin, it kept going into the negative readings.

Also which side is conductive on a PCB. In trying to remove QC2 I nicked the eyelet on the top side pulling away a piece of the eye so it wasn’t a complete circle anymore. The bottom of the eye is fine and the trace on top going to the eye is still intact. Is this still serviceable?

 

[last lemming]

Ok. I’m about to give up. I’m about to give up!!!

I replaced many of the components on the audio board out of frustration and I double checked EVERY connection solder and where they are supposed to run to and from and I see NOTHING wrong. Yet no none of the LEDs in the audio board on the right channel light at all.

I’m stumped. My last readings on the audio board are:

IA = 216V
IB = 210V
OA = 214V
OB = 158V
OC = 7V
OD = 95V
OKA = 15V
OKB = 97V
OKC = .6V
OKD = 1.63V

 

[Paul Birkeland]

The 0.6V at OKC would have me wonder if there's a solder bridge on the 2N2222 pins that have turned it into a diode.

 

[last lemming]

No solder bridge. Looked under a 10x loop.

I ran a resistance check on all the component