New two holer rocket reverb --> need help!

[rootz]

Hi, I'm Bas (pronounced as Buzz in English). Not a newbie on amp building, but no expert on Trainwreck amps too.

I recently finished a 2xel84 rocket reverb based on the layout of Normster and have got a couple of issues with it:

1) The reverb hums a lot when turning up the reverb return pot (the one connected to the PI entrance). Isolated the connectors to the reverb pan and shielded the wires to the pots;
2) The screens of the output tubes are glowing. Currently using 100r screen grid resistors. Is that normal for AC30 like amps? I'm using a 400 or so Ohm choke, but of course the amp is drawing less current as it is a two holer. What would upping to 470r do? Change in sound?
3) Crackling/static noises when plugged in to the guitar input jack. The crackling goes away when unplugging or holding the input against the chassis and making contact (grounding). The input is isolated from ground.
4) Voltages down the line are to low. V1b is getting 60 volts on the plates, which should be 90-100 volts. The 18k dropping resistor is almost dropping 100 V, way more than expected. So V1 or V2 is drawing massive current. This problem occurred after isolating the reverb connectors from ground. Before voltages were higher and about right.
5) There seems to ride a strange sizzle on top of the notes.

I'm using a star grounding technique, but not really sure if I implemented it in the right way. I couldn't use the ground scheme in the layout because I'm using cap cans with combined grounds. So I thought making a star ground would be a good idea. All pots are on a buss bar. All grounds of the board are connected underneath it. The buss bar and input jack ground are connected to the board and the board is connected to the common tab of one cap can. The cans are connected to the star ground. Maybe I made a mistake here and made a huge ground loop.

Hopefully the pictures will provide any other info that is needed to tackle the problems. The sound of this thing is phenomenal and it fully deserves it to work flawlessly. I hope you can help me.

Kind regards,

Bas.

[rootz]

More pics.

[rootz]

Almost there

[rootz]

The last ones.

[martin manning]

Given the noise when a guitar is plugged into the input and the high current draw on V1, I suspect that the grid of the input stage does not have a good ground reference; i.e. the 1M grid leak resistor does not have a good ground, or the input jack is not wired correctly. The reverb hum is something else... is one side of the reverb loop grounded? Get some voltages on the power tubes to see where the screen is vs. the plate. Nice looking build!

[hans-jörg]

Hello,
I would remove these small blue coupling caps. They give you a very hissy sound. Jm2c.

Hans-Jörg

[rootz]

Given the noise when a guitar is plugged into the input and the high current draw on V1, I suspect that the grid of the input stage does not have a good ground reference; i.e. the 1M grid leak resistor does not have a good ground, or the input jack is not wired correctly. The reverb hum is something else... is one side of the reverb loop grounded? Get some voltages on the power tubes to see where the screen is vs. the plate. Nice looking build!

Will check on the ground reference of the V1b grid. I'm mostly working with Marshall type inputs, the one used is new to me. Maybe I just made a wiring mistake.

Both sides of the reverb are grounded at the star ground. Aren't they normally grounded at the chassis when not insulated??

The screens are running a tiny bit higher than the plates. That explains the glowing! I'll swap the 100r's for 470r's.

Thanks for the compliment! The paint job is kinda suffering from all the howling around. Will fix that later.

[rootz]

Hello,
I would remove these small blue coupling caps. They give you a very hissy sound. Jm2c.

Hans-Jörg

Those are 500 pF ceramics. Albeit they give very little hiss, I might swap them. What would you suggest in these spots? Silver mica?

[rootz]

I tackled a few problems:

The input is quiet now. No more strange sounds when I plug in a guitar. The grid of the first tube is getting its ground reference and measured 1M from grid to ground which is good.

The screens stopped glowing after replacing the 100r resistors for 470r's. The difference in voltage between the plates and the screens is still just 1 volt, so I might give 1k's a try to be perfectly safe.

The low voltages in the pre amp are solved. It appeared to be the tubes in V1 and V2 were the problem. My NOS Philips Ecc83's are not as good as I thought they were. I'm getting 93 V on the plate of V1b now, which is just fine IMHO. This is with a SS recto (plug in) and 275 V secondaries on the PT. I might adjust the 18k dropping resistor to get the right voltages when using a tube recto.

The hum on the reverb is still present. It's always there, but gets louder when turning up the reverb control. The hum level is not dependent of reverb tank placement and is also still present when the cables to the reverb tank are unplugged. I'm using shielded wire on the reverb; moving the wires around with a chop stick didn't really help.

So I'm still in need of some help guys...