Crate BV-120HR with idle noise issue - looking for some assistance

[sinewave]

Hi, I recently acquired a Crate BV-120HR amp head. It powered on but noticed it was missing the reverb tank and two of the 12AX7A preamp tubes. I put in two 12AX7A's I had laying around but it did not resolve.

Opening it up I found one fuse was blown, plus one wire internally had been squashed between the bottom cover that screws on and the frame which might have caused the fuse to blow. I wrapped that wire, replaced the fuse and noticed the tubes were lighting up. Waited for it to warm up and was glad to hear it was working. I ordered a replacement 8BB2C1A reverb tank and installed that today and confirmed that it's working fine.

However there's some background noise out of my guitar cabinet speakers from this head when idle, with or without a guitar cable connected. I took a short video to illustrate how much idle noise there is:

https://forslip.wistia.com/medias/8nsqlppv6t

The noise is happening on either channel. From the sound of what's happening in the video, might this trigger any ideas of best things to check?

[g1]

I don't see a schematic anywhere for this particular HR version. So using other schematics is not going to work well unless you are a fairly experienced tech. What is your experience level?
Do you have a correct schematic you can post?

From first listen, the noise source is before the gain control, but also common to both channels.

[TomCarlos]

My guess was that the "HR" version was nothing more than a Red cabinet and a Sammy plaque on the back of the amp. The controls (front and back) look identical to the BV-120H.

[g1]

If so, I would look to the first tube stage (V1a), possibly it's plate resistor, shown as R4 on the HBb schematic.

But before even that, it's not clear if tube V1 has been replaced, if not, it is the prime suspect.

[sinewave]

Hey guys, thanks for the input. The advice was spot on, replacing V1 tube fixed channel 1 and there was no longer any noise. I was still hearing the noise on channel 2 though and replaced the other 3 12ax7's and now both channels are quiet. Apparently there were some other bad 12ax7 tubes, I swapped one but it didn't resolve, and then two but still could hear the noise on channel 2. Had to head out to guitar center to buy a new 12ax7 to replace that last one in order for the channel 2 issue to get resolved. It had a set of old groove tubes in there when I bought it (the 6L6GT's are also groove tubes). As far as I know I don't have to replace the four 6L6GT/5881 since it's quiet now. I'm not the most versed on what to listen for in regards to those tubes so will probably need to read up on it to understand more on how they are affecting the tone, and on which channel etc.

Once again, I appreciate the input!