Everything working great, then...

My [Latino kit] ST70 is about a year old; my [Ebay] PAT-4 about two years.  Everything was great until a few days ago.  Power on.  All "on" indicator lights are lit; all of the ST70 tubes lit and glowing properly.  Absolutely no sound, not even the very very faint signal from the Heresy IIs.  No changes from the days and weeks before - system cart not moved, and no one has messed with the system.  All connections from/to components and speakers checked, and all fuses intact.  No lightning storms nor recent neighborhood power disruptions.  Two months ago I added a Marantz 6005 CD/DAC player, but, again, all working fine up until recently.

Some help from other members would be greatly appreciated.  I have a Bottlehead Foreplay preamp that I could substitute for the PAT4.  Other than that, I don't know where else to start looking for the solution.

Many thanks in advance.

My firs thought is check your rectifier.  Just  because the heaters are working does not mean that you have high voltage.
Swap out for a new rectifier. I know this can happen because about two months ago I was listening to vinyl and suddenly the amp went quiet just like someone had shut if off, however the heaters were still glowing bright red but no sound.  Chaned for a new rectifier and "Viola" back in business.

You could try swapping the pre, but I'd think no hiss from the speakers would indicate an amp problem. Rectifier is also first place I'd look as that's common to both channels.

DO post back if that helps or doesn't. Always nice to be able to see solutions as well as the problems.

(Bonus points if you have a spare rectifier on hand.)

"Dead" giveaway that there is no B+: tubes that aren't hot!

I think you hit it on the head - no bias. And, me being me, no spare rectifier on hand. I'll be buying at least two.

The first lasted only a year. Is this typical? I believe I have correctly biased the amp, checking it when moved to our new home and every 45-60 days. Amp gets a lot of use - not happy with the headphones and iPad.

The kit came with the Sovtek rectifier. Other brands recommended?

Thank you for your replies. The forum is very worthwhile.

Hearing good things about the new production TungSol 5AR4 ... Genelex is also getting good reviews.

Have you checked the bias?

New Sovtek rectifier, and a backup, arrived today, and I am back in business.

At initial startup, bias range was down slightly to .380-.385. I assume I should let it run for a few hours, then check and adjust the bias to .400?

Very quiet the last few days around here - a slight amount of withdrawal. I have a set of Grado cans and iTunes, but it just is not the same as the great ST-70.

Thanks again all, for your help.

Every tube will bias up a little differently ... With a new tube, I set it to spec once it's warm, then again after playing it for a bit, then let it idle a while and check it again. You may see some small variation, but it should stabilize after a few hours at most. After that, the occasional spot check is always a good thing.