DONNA ROCKET FIRED UP...Uh Oh!

[Greg]

Well I fired up the DONNA ROCKET.

I used a 4x12 Carvin Legacy cab with new speakers. Speakers still new

The Cab is 16 ohm. Facing the rear I turned the selector all the way right. This is 16 correct? From Rt to Lt 16-8-4???

Sound was a bit noisy at full volume and changed when I touched the strings like a single coil does.

Everything seemed fine for about 5 minutes then the sound went very low. It came back up and I played another few minutes then went very low again. I turned it off.

What should be my next step?

I guess I should have followed the Express start up procedure

Should I do that now?

Time to check voltages?

[Blind Lemon]

Sounds like maybe a loose connection or bad solder joint....start there. On startup of my last Rocket build the tone stack was not working, I had soldered the ground wire to one of the pots but not the bus bar. Took about 10 minutes to find. I have had quite a few startups now and I "ALWAYS" expect to find something wrong no matter how systematic I go though the build. Only you know how you wired your impedance selector switch, double check it to make sure. Go though the startup, and write down your voltages. If the voltages are good, save them to compare with your next Rocket build.

BL

[M Fowler]

Take the time right now to mark your impedance on the back of the amp in black marker or tape/pen.

Carefully go over the entire amp from power supply to input and use a magnifing glass to check for wires that need to be trimmed back on all pins whether tube or pots. Take a small needle nose plier and gently tug on each wire see if the solder joints are good. You would be surprized how it looks good from one angle and another you see the bad solder connection right away.

Mark

[fishy]

Fading in and out..... almost sounds like a filament related issue.

[Richie]

Fading in and out..... almost sounds like a filament related issue

Yes.. also check the ground of the 220k of the PI resistors,if its loose the amp will also fade or drop out.

[rawnster]

I agree with Fishy. Embarrassed to say, but when first firing up my rocket build, I experienced somewhat similar symptoms. A magnifying glass helped locate an inadequate solder joint on a filament wire on one of the powertube sockets.

[angelodp]

Rawnster. thats interesting, on my Rocket build I occasionally have V4 fail to light up. I jiggle the tube and it does finally come on. I better get in there and check my solder points on that socket.

ange

[mcinku]

My friend had similar issue with his amp...

...at the end it was a faulty standby switch. It looks like it was loosing connection somehow.

[M Fowler]

As I said earlier go over all the solder points and the problem will be solved.

Mark

[Greg]

As I said earlier go over all the solder points and the problem will be solved.

Mark

That is the task for this evening...then a voltage chart.

I read the Express build and saw that there was a color callout for the trannies but I cannot find one for the Rocket using Heyboers from Allyn.
I need to know what impedance is associated with what colors, etc...

[gahult]

Greg,

The output transformer wiring is at the bottom of this page.

https://tubeamparchive.com/viewtopic.ph ... a470#67612

Gary

[fishy]

Greg,
Small steps, and follow the guidance as best you can. Most startup issues are generally simple to correct once you find them
Consider these as great opportunities to learn so make the most of them. If amps fired up first time every time, our knowledge would be worse for it.

The voltage chart cannot be under estimated. It can point out areas of concern when you start an amp up and help fix an amp that has gone South.