Weird preamp/reverb issue Rectoverb 50 (resolved)

[spawnofthesith]

Last week I got a rectoverb 50 combo used from GC. Was shipped great, tubes removed individually wrapped etc. Fired everything up when I got it and instantly fell in love, worked for several days with no issue. Today on my lunch break I wanted to just hear that glorious tone for a moment, but was met with disappointment. Almost no noise and weird cavernous reverb. Lose almost all signal when I turn the reverb off with the footswitch. I ruled out chord/pedalboard issues by disconnecting and running straight in. If I turn the master/output/solo knob channel 2 in modern mode was just giving a clean tone. on channel 1, again extremely quiet even with everything cranked and just that weird thin reverb tone, kinda grainy. I haven't tried plugging directly into the fx return yet, but considering the output and solo knobs seem to be having the most impact I'm guessing the issue lies in the preamp.

I'm thinking/hoping that this is only a preamp tube problem but was wondering if anyone here had any further insight. I have plenty of pre and power amp tubes so I am going to mess around with that further this evening. Which tube position drives the reverb? I checked the manual but it didn't appear to say. I'm no amp expert but I would imagine the likely culprit is either that one, or the tube in the position before it?

Thanks for any tips

 

[TubesNStuff]

If this is the model from the late 90's/2000's, then the reverb is driven with an op-amp.

Running into the FX loop return is a good test. This will test 1/2 of V4, V5 phase splitter, and the power tubes. I guess if you have another power amp, you could see if anything's coming out of the FX send.

 

[spawnofthesith]

If this is the model from the late 90's/2000's, then the reverb is driven with an op-amp.

Running into the FX loop return is a good test. This will test 1/2 of V4, V5 phase splitter, and the power tubes. I guess if you have another power amp, you could see if anything's coming out of the FX send.

It's a Series II rectoverb 50 combo production years were early 2000s-2011

My only other amp is a twin reverb so no fx loop on that, would it be safe to run into the input of the twin from the fx send?

I figured I would start by just swap out preamp tubes one by one to see if that solved anything

 

[spawnofthesith]

Problem solved, V4 was cracked. Quite possibly my own fault. Pilfered a tube from my twin and will be picking up more