Why not change out the tubes you have on hand, and swap the el34's side to side, noting any/all changes---
Don

Don,

You can watch the meters as the tubes warm up and begin to pass current.  Once the meters start to climb it's a matter of seeing where they stop.   If a left channel tube typically draws 40 mills and now draws 20 mills the right channel tube may begin to read higher.  Certainly if the left channel tube was removed completely, the current on the right channel tube will double.

It really doesn't matter what the meters say for the first few minutes as long as one or the other isn't pegged all the way over.  Any longer can cause damage to some amps depending on the amp and what part of the tube is shorted, or how shorted it is.  This would peg the meter pretty quickly in which case you could turn the amplifier off and remove the bad tube avoiding any damage.

Since both output tubes share the same cathode resistor, you will always need both tubes to be in good working order for the meters to read accurately.

The tubes need to match, so they should be replaced as a matched pair.  Within a couple mills is considered an acceptable match (within 10%).  

A yes, turning the amp for that 15 seconds isn't going to hurt anything so long as you're watching the meters.

Do you have (2) Rachel amps?

I'm considering adding another and bridging to mono. How does this sound? Is it perfect? Subtle degradation to the signal? Safe?

Thanks,
hifitubes

Hifitubes, I have had a pair of `Rachaels` bridged as `monos`, for stereo, about a month now. Around 50 hrs playtime.
Still undergoing the `Decware improving with time` period, which, as members are allways reiterating will be a long time.
But, tube selection notwithstanding, ( mid price nos &`dun rolling for a breather` ) the amps are as good as the material being fed in. No surprise there. They go very wide, give excellent sense of depth, and back to front is all there, 3D. Even top to botttom. If the drummer sits above the band thats where he`ll be. Bass, well, I think all bands should give the recording engineer a drink (tip) to record it well, `cos there are times it goes loud`n low,...and extended. Not often they let the kick drum try and pop the cones but listening to some JJ. Cale they did and it was very nice. In fact JJ albums `do` dbl & guitar bass and these amps love it. Treble. You can definately get lost in fluid guitar tone here. S.E.T. mid range heaven. Something that really surpised me was the hitting of metallic objects. Bells, cymballs, rims. Stark, airy, snappy, and they ring with a natural decay new to my ears. I`ve heard a small amount of piano, not solo, and just as the whole deal they sound effortless.
I cant talk about emotional airy fairy stuff but it`s the kind of sound where you just enjoy, and want to play more. And yes I can hear more info into the grooves.
lol, you knew I was going to say that didn`t you, after all I do have  Decware amps. You must get the same sound from your Rachael.

I got my new matched pair of JJ E34L's yesterday. Just installed them, exact same problem is still there. I then switched out the input tubes, turned the amp back on and the problem was there for a few seconds then disappeared, which of course made no sense to me. But I test the attenuator, everything looks fine now both meters reading around 42 mills with the higher gain input tubes, start playing one of my perfect condition 78's, sounds beautiful with pre-amp and Rachel almost at full volume like I'm used to, then half-way through the song I hear what sounds like laser beams shooting out of my speaker. Scared the s*&! out of me, never heard anything like it. I turned the amp off immediately after that. I truly hope this didn't destroy my relatively new speaker.  :'(

Steve,

Any ideas what's going on here? The only tube I haven't switched is the rectifier. It's dark and cloudy here today so I turned the room light off for the two minutes Rachel was doing ok to see the tubes glow. The rectifier tube only had glow at the top, can't remember but is there no glow in the middle or lower part of the tube?

Wow, crazy Decware lasers. Def switch out the rectifier imo.

I think he just meant HDR on your 78s, High Dynamic Range which I'm sure lend a lot of realism to the recordings.

I have one Rachel and considering going Open Baffle. Midrange is creamy but ACCURATE (e.g. John Prine's voice sounds incredibly there).

I would like to consider adding a 2nd Rachel someday.

Well I finally switched out the rectifier tube with a Philips 5R4GYS and the problem is still there. When the attenuator's turned all the way down the meters are at 40 mills, when I turn it up over half way the meters start pinging wild and my speaker sounds like it wants to shoot laser beams at me again.

I was about to call Decware before posting but realized their customer support's closed today.

I wish I had a back up amp to use while I send Rachel back for service.  :-/

'Luckily' my 10 year old VPI HW-17 is coming back from VPI Industries this week so I'll be able to catch up on about 30 hours of cleaning and archiving I need to do. There was nothing wrong with it electronically or mechanically but a design flaw leak had created a black mold farm inside the chassis unbeknownst to me all these years.

I forgot to mention I still have an audible amp hum seven feet away from the speaker when the attenuator's between 11 and 4 o'clock. And the amp still has a speaker busting pop while switching the input selector.

DPC,

My Rachel is also dead quiet two feet away no music playing when the attenuator is at 5 o'clock, wide open full volume. It's only when I turn the volume down does the hum begin. Please tell me how something else in the chain could be responsible for this?

Regarding the input selector speaker busting pop, so far it 'only' happens when I'm switching between my two McIntosh C8's which are on my 2nd and 3rd inputs. I haven't used the 1st and 4th inputs yet but when I switch to them, with nothing connected to them, there is no pop.

Also if you follow my thread in the FAQ forum you'll notice I've also said this is the best amp, regarding sound quality, I've ever owned as well. That doesn't mean that it's not responsible or free from responsibility for the damage and problems I've had/am having.

I mean a speaker not being driven by an amp doesn't blow itself right? I bought the Philips 5R4G tube from Upscale Audio, who tests all tubes with the best equipment before shipping them, and Decware said it found a "noise problem with the tube." Do you think it's fair if I were to return the now bad tube back to Upscale Audio?

I'm using Ortofon's highest end moving coil cartridge for standard groove. It only outputs 1.5mV and as I'm not using a SUT I have it directly connected to my C8 then to Rachel. With both the C8 and Rachel at max volume, it provides a nice full sound to fill my living room. Meaning I can't blow my speaker accidentally by turning my amps up to high. A normal listening level is Rachel full volume, C8 one notch below full volume.

I'm serious, if you think something else in my chain could be responsible then what? and why?

First, let me admit that I am the last person that should be asked for audio equipment advise.  That said, you say that the pop only comes when you switch to/from the McIntosh components.  Can you try putting another component in one of those places and take the Mac out.  My impression is that the Mac's could be sending some unwanted voltage/signal.

I also use the Phillips 5R4GYS rectifier from UpscaleAudio.  Seems to work fine for me.  I also replaced the EL34's with a pair of cyro treated Mullard's.  The jury is still out on that move.  The first set of Mullards I received gave off a horrific flash when I turned on the amp.  Shut it off immediately.  Vendor sent me a replacement set.  I'm not ready to report that the Mullard's are better than the original JJ's.

If Steve has checked over your amp and you replace any bad tubes then I'd cast an eye on the the up line components.

Just don't give up!  My experience is that when I finally find my problem I feel pretty good about it.