The problem not that he turned off or left on the system. :)

It could actually have been any number of things, but my suspicion is that the Placid voltage was inadvertently set a bit too high. Th 5.5V max is strict. :)

Not encouraging. New transistors do produce an output but it is 2.18v, with the reference voltage being 1.2 v.

Frank

Thanks for checking Russ,

Yes, this is the 1.2v reg.

Both LEDs are lit.

The opamp was replaced as well as the two transistors. I do have extra new transistors, if needed... Too much heat is a possibility!

Voltage between QP2 base pin and ground is 5.48v. (Between QP1 base pin and ground is 3.57v.)

What are the voltages at pins 2 and 3 of the opamp?

All of your fine help is much appreciated, Russ.

Two new transistors again gave 2.19v output. So I'm declaring this patient to be dead.

I'll find one of the ferrites and put it back. When Brian gets around to another batch of Tridents I will order one.

...besides, this board is ugly because somebody ground off one of it's corners!

Also, since we're on page two of this conversation, I will edit the first post with a mini-summary and lessons learned.

Cheers,

Frank

Good point. But rather than continue messing with the Placid and critical B2, I'll set up a less crucial pre-reg for testing and then report back on those Q's.

Re: the transistors, remember that at least one was bad before yesterday's swap because we went from no output to >2v.

With the VDD trident removed, the system sounds detailed but distinctly less outstanding! Clearly, the 1.2v board seems necessary to fully extract every drop of B2 'hi-fi juice'.

Frank

Edited by user Tuesday, April 19, 2011 8:43:48 AM(UTC)  | Reason: Not specified

Greetings Russ and friendly readers,

After a work-imposed break from soldering, great news - the 1.2 v Trident is repaired.

Making the measurements that Russ suggested there was some obviously weird behavior. LED1 was out due to over-voltage. When I measured opamp pin two vs. ground, the LED would come on! Measuring the other pins, Vout was almost equal to V+. I had 1 more new exact replacement op amp, so I decided to try using it. After clipping the 8 leads to remove the op amp I had installed, I found only 7 feet soldered in place and needing removal! Pin two had been poorly connected, explaining how pressure on the pin changed the output of the circuit.

With the repaired Trident the amazing sound quality of Buffalo II was instantly restored.

The bottom line on this experience is that both voltage and heat should be considered. The lessons I learned are several:

1) The 5.5v supply limit on the Trident op-amps should be strictly respected. They can take a bit more for a limited time, but there is no sonic benefit whatsoever.
2) If installing Tridents above a Legato, it is advisable to orient the boards vertically. When rotated 'sideways', they can still clear C15 on the Legato (ver. 2) and rise only a tiny bit above the AVCC board on B2.
3) The 1.2 volt VDD Trident, in particular, is key to maximizing the Buffalo II experience.
4) Thermal drift of the Placid requires attention.

At the moment I am letting everything reach temperature equilibrium and re-checking all voltages. I have 4 power supplies plus numerous other heat producers all positioned close together and not much air volume in the chassis, so I decided to use external exhaust fans. I would prefer to avoid them if I had more open space for convective cooling. Attached is a photo of my external chassis ventilation. Fortunately it is hidden in the top of an equipment rack because it is ugly! A ventilated 1U front panel atop the preamp/DAC gives the 800 rpm 12v fans about 15mm overhead space. The fan motors are shielded from the DAC and Tridents by grounded corrugated screens and are powered by an external 'wall wart' power supply. Speed control and a 47uF bypass capacitor help with physical and electromagnetic noise. They seem to be silent. An external power relay that is actuated by 5v from the preamp JT power supply prevents fan power supply lines from polluting the interior of the chassis. Again, the fans are not ideal but necessary with the space constraints I have chosen.

So, another really successful support case Russ! Thank you so very much!

Frank

Edited by user Monday, April 25, 2011 8:28:52 AM(UTC)  | Reason: Not specified

Hi,

I've just installed new set of Tridents in my B2, Placid regulated to handle new situation, everything seems to work ok - LEDs ok, voltages ok, BUT I discovered that QP1 transistor on 1.2V Trident is very hot. Should I worry about?

Thanks
Marek

Can you check temeprature of transistors in your 1.2V Trident - just with finger. Mine QP1 transistor is so hot that I can't hold it with finger more then few seconds.
I'm worried that QP1 will burn and it can effectively burny my B2..

Edited by user Monday, April 25, 2011 5:50:51 AM(UTC)  | Reason: Not specified

I'm glad to hear this is normal behavior. Thanks.

Edited by user Monday, April 25, 2011 1:21:20 PM(UTC)  | Reason: Not specified