Mark V issue: Tube rectifier isn't working

vo.van · Jan 12, 2013

Channel 1 while switched on Tube/ Diode rectifier switch on "Tube" is not working on 10 and 45 W. It does work on 90W.
Channel 2 is similar. All modes on Channels 1, 2 while switched to Diode seems to work.

It looks like one of triode preamp tubes is gone. How to check it? I don't want to bother to waste time to take it to service despite I do have a warranty, Just the gas would cost more and a down time.

Cheers

fr0sty · Jan 12, 2013

tube rectifier doesn't engage on 90 watt modes. There is only one rectifier tube on the mark v. Replace that one. It's in the manual which tube it is.

vo.van · Jan 12, 2013

Thanks. Which is a rectifier tube? Enclosed manual description. Could it be V7?

V1A-- Input Stage
V1B-- 2nd Gain stage CH1/CH3,
3rd Gain Stage CH2
V2A-- 2nd Gain Stage CH2
V2B-- n/a
V3A-- 3rd Gain Stage CH1/CH3,
4th Gain Stage CH2
V3B-- 4th Gain Stage CH1
V4A-- Reverb Send
V4B-- 2nd Drive stage CH3
V5A-- 1st Drive stage CH3
V5B-- Reverb return
V6A-- 4th Gain stage CH3
V6B-- Effects return stage
V7A&B-- Driver/Phase inverter

miqueas92 · Jan 12, 2013

Could it be "the" rectifier tube¿

looking at the back of your amp it will be the one farthest to the left, right next to a 6L6 power tube. Turn your amp on, have on standby, turn standby off and see what happens to this tube, it should light up if good, if not... well, you may have found the culprit.

Mick

thunda1216 · Jan 12, 2013

all of those are preamp tubes. the rectifier will be a larger tube closer to the rear of the amp like the power tubes

vo.van · Jan 12, 2013

thunda1216 said:
the rectifier will be a larger tube closer to the rear of the amp like the power tubes

the one next to transformer? That might be V7.

thunda1216 · Jan 12, 2013

the phase inverter/driver tube is a 12AX7 preamp tube. The 5U4G is the rectifier tube. Looking at the back of the amp it will be the large bottle tube farthest to the left. The next four to the right are the power tubes. V1 through V7 are the small tubes closer to the front of the amp.