dynovalve":18gvnmvs said:
posted this on the forum but thought I'd see what you had to say....
Sometimes (on 3 & 4th channel only) My amp will "stutter" in & out. I am
99% sure it is the noise gate doing it. Usually the noise gate functions
fine but sometimes it seems to turn on & off when it shouldn't like it is
confused. It is set pretty low and the slightest touch will normally make
it come on at this setting. When "stuck" I can strum a hard chord and it
stutters a bit then eventually straightens out and works fine. It doesn't
do it that often and only channel 3 & 4 do it so I am thinking that noise
gate "freaks out" sometimes.I emailed ENGL about this and they didn't name
the the noisegate as a possible suspect. ??? and implied a tube and a
couple other related things.
I have brand new tubes & changing them out did changed nothing.
. It did this once at a show for a second and has me worried about trusting
it not to "stick" at a time when the spotlight is on me. It would be hard
for a tech to diagnose maybe because it does it so infrequently like once
every third night. I will try again but the first time it ever did it I
think I turned the noisegate off and it still did it!!! I really believe it
is the noisegate flaking. No pops,crackles etc. It goes to silence just
like when the gate comes on/off. I love this amazing amp so much and for it
to have this rain cloud aggravates me.
Question #2. When pulling out tube V5 (preamp) the socket seems to move a
little before the tube does and makes a low pitched "squeek". I know the
sockets are PC mounted so this worries me. I don't know what the sockets
ENGL use look like so I can't tell if it may just be the ceramic/inner
moving in an outer ring or something in which case may be considered
normal.
Thank you so much.
I also believe from reading the description that your issue is NOT related to the noise gate itself. Especially since the issue occured at least once when the noise gate was off.
The most likely cause is a preamp tube or the socket. Preamp tubes in Invaders are numbered V7-V9 and V10 being the Phase Inverter which is considered power amp section. So whatever preamp tube socket is squeeking or moving most like is due to loose pin retainers in the socket which can give the appearance that the socket itself is moving (but it can't move as it is soldered into PCB).
When I get tube amps for service (any brand for that matter) I ALWAYS take out all tubes, test them in a tube tester (even when new as quite a few new tubes come bad quality), clean and scrub all socket pin retainers, the manually tighten the retainers until the tube has the least amount of slack when inserted. This insures proper contact of tube pins with the sockets and therefore with the PCB of amp.
Especially when amps are a few years old they need to be cleaned of corrosion and all sockets adjusted REGULARLY, once a year is best or at least every time you change tubes which should be at least every 2 years or more often if you play a lot. The tubes are always the weak link in the chain and players must ensure they buy tested tubes from a good source and get them tested, checked and power tubes re-biased on a regular basis to avoid problems.
Some NOS preamp tubes last very long, many many years, but those tubes' pins themselves need to be cleaned and brushed off corrosion to ensure proper contact. I can not emphasize enough how important this is. Think of it like the spark plugs in your car. When they are dirty and old they don't work properly and the engine does not run well.
I have seen it all what tubes can cause, up to burning 2 inch holes into PCB and blackening half the board. That particular PCB was totaled and had to be replaced. The player did not change power tubes in 4-5 years with regular play and never got the amp serviced.
So what you should do is take out all tubes incl. power tubes, get a contact spray and soak the retainers. Then scrub the retainers using a tube, by going in an out of the sockets 5-10 times. Do not use a tool do to do this as there might be lethal voltages lurking on the plate pins !
Then try the amp again. If the problem persists the retainers need to be tightened. You can only do this with a tool and MUST DISCHARGE THE FILTER CAPS first. This procedure should be left to a tech.
I solved so many problems by just thoroughly cleaning the amp inside out, testing the tubes, scrubbing the tube pins clean etc etc. When it's done right the amp will run like a clock work again.
If you have any more questions please feel free to ask.
Sincerely,
Jens Kruse
