Rogue Audio. Reliability issues? Anyone?

Another vote for Rogue's reliability. I've owned (and still do) two of their preamps RP-7 and RP9 as well as their power amp Stereo 100 for years and have zero issues with them.  Build and sound quality is excellent.  I did have the RP7 upgraded to the RP9, sent it to Rogue for the upgrade with ~2 week TAT.  Rogue is a quality company in my experience.

So a post above says they have manual bias.  turn the bias down by 10 mA and that should help a lot.  If it is a KT88 then maxx plate dissipation is 40 watts.  I'd run it at 30 watts and if having problems, I'd use  25 for a while.

You need to know your plate voltage.  It is pin 3.  Either measure it or find a reference for your amp (this is amplifier specific, not tube specific, don't use plate voltage max off the tube data sheet).  

Then calculate your bias:  25= Voltage x current so bias current  = 25/voltage. 

Jerry

The amp uses KT120s

Per the amp’s manual:

Using the bias tool, slowly turn the screw on the potentiometer that is adjacent
to the switch until the bias meter reads ~ 35 miliamps (mA). Turn the screw
clockwise to lower the bias and counterclockwise to raise the bias. Note that
there are two ends on the bias tool. Using the end with the recessed
screwdriver will greatly facilitate this operation.
9) Flip the switch back into the “run” position thus disengaging the tube from the
meter circuit.
10) Repeat the above steps for each of the tubes in both channels.
As it is a quick operation, the tube bias should be checked on a regular basis. Note
that the bias will change slightly on a day to day basis as the wall voltage
fluctuates. Constant biasing will wear out the bias potentiometers prematurely so
do not adjust the bias unless it is more than 4-5 mA from the correct setting.

The Op didn’t state how many approximate hours he has on the tubes, but unless they are all nearing end of "expected life" , there’s no reason to replace all since each is individually biased. That said, the bigger immediate issue for the Op based upon a google search is that new KT120’s appear to be out of stock at a number of vendors.

They might have got somewhat of a bad rep for their cathode-bias amps of 20+ years ago. That would be the 88 and M120 models. These amps threw out a whole lot more heat, which can cause problems.

Their current tube amp models are manually biased via trimpots & built-in meter, and these have proven quite reliable. With any tube amp, there’s no 100% perfect fail-safe for a sudden catastrophic tube short. I had this happen with an Electro Harmonix KT90 in my Rogue Apollo monoblocks, circa 2010. It dusted a metal oxide resistor and singed ~ 1cm of circuit board trace. Trace was still working but the solder mask got burned off so Rogue replaced the whole board under warranty. So yes, a bad tube can cause collateral damage that requires service. I switched to KT120 tubes after that incident, and they’ve been exceptionally reliable. Never had another problem in the next 12 years of Apollo ownership.

Tube amps with advanced auto-bias & protection circuitry might have a slightly lower risk, and P2P wired amps have no PCB board to damage. Never had the slightest issue with my VAC auto-bias tube amps so far, though I’m only 4 years in with these amps.

In your case, I would definitely send the Atlas in. Bit of a bummer, but better to get this sorted now. It's a great little amp, and Rogue customer support is fantastic.

Power tubes are matched for Gm and Ip.

Bias controls static Ip [plate current].

Gm is how much the tube responds to drive change.

Mismatched tubes have more 2nd harmonic, i.e. fat tube sound coloration.

I match drivers, triode halves and power tubes. The difference is clearly audible.

See ieLogical Valve Tester.

@nickrobotron Tube gear is pricy to own. I had a GL KT88 eat its cookies at about 1k hours. [It’s silly to run w/o hour meters.] So now I have GL KT88 spare quad, spare pair and spare.

Most tube gear is pretty simple and easily repairable with a bit of knowledge and a schematic. Of course, if you’re careless it can kill you. $175 seems cheap enough.