Rocket issue

[DocJames]

Hi everyone. Need a little help sleuthing this problem out. I retrofited a VVR into my rocket build and on start up, I started to hear a increasing hum, until the fuse popped. I re-checked all the connections, as well as solder joints, and they looked fine. so I installed a new fuse and tried again. Same thing, but this time I started to see arcing in the rectifier tube. So I figured, I had a bad rectifier tube. Switched it out with a new one, and same thing happened (arcing). I wasn't able to get any B+ values as this all happened within 10 seconds of startup.

At this point, I pulled the VVR and reconnected everything up normally to see, if the issue went away. Now I don't get any arcing in the rectifier, but my B+'s are non-existent. Heater AC on V1 looks fine, and everything is glowing nicely. There's a slight bit more hum coming from the transformer, then there was before. MY rectifier values on the plates are close to normal (258AC), but my heater values are null.

So at this point, I'm wondering if I fried the PT. Anyone have any words of wisdom?

[M Fowler]

DocJames,

We will need to see full chassis shot of the amp guts to see how you wired the power supply and rectifier circuit to help out.

Mark

[guitarsnguns04]

I agree with mark...post up some pics

[DocJames]

here's a few pics. Let me know if you need different angles.

[M Fowler]

Hmm, I'm not seeing anything out of the ordinary.

MY rectifier values on the plates are close to normal (258AC), but my heater values are null.

No 6.3vac filament supply voltage at all? How about the 5vac? What is the rectified DC voltage?

Mark

[Colossal]

Doc,

Did you install the VVR according to the usual spec? The VVR should have a reservoir/B+ cap in front of it, so in other words, you would have say a 40uF cap right after the rectifier tube, then the B+ going from that cap into the VVR board, then to the cap stack. Not sure if that's the way you were doing it and still having problems. The popped fuse suggests a big current draw on startup so something seems amiss with the VVR installation.

[passfan]

What kind of power tranny did you use. Typically the 5 volt winding is yellow and the 6.3 volt is green. Could you have burnt the filament out of your rectifier?

[M Fowler]

That looks to be the typical Heyboer transformer wires.

[DocJames]

Yeah my Install of the VVR must have been off. I'll post pics tonight trying to show the path that I took. I'm getting 6.3 AC on all the heaters, on the EL84's and 12ax7's. What I'm not getting is any DC voltage on the filter caps, and my B+ are not reading at all. I may have just burnt out my gz34 again. Maybe that was what I was noticing with the arcing, is my filament going. Unfortunately I have no other ones handy (I'm quite the slow hobbyist with this, life busy, etc.). So I'll order up a few maybe this time .

Cheers.

[Lonely Raven]

Is your VVR transistor isolated from the chassis?

[DocJames]

It had the mica sheet between it and the chassis. However, I also placed heat transfer compount on it. Maybe that allowed some flow to chassis.