Rocket Build

[ampbldr2]

I am making progress on building my first Rocket. Here are some build pics so far.

One question I do have is about the Cap Stack. Do I need to run both ground wires of the cap stack directly to the screw post of the Rectifier socket or can I just drill a hole and use the ground mounting slugs or whatever you call them?

-Todd

[xtian]

Using the screw post of the recto socket as a ground point is not best practice. Better to drill a hole and create a ground point with proper hardware.

[ampbldr2]

Using the screw post of the recto socket as a ground point is not best practice. Better to drill a hole and create a ground point with proper hardware.

Will do. An update to the layout drawing to show a ground lug on the chasis would be helpful instead of at the socket.

[xtian]

The drawings are records of Ken's work, not necessarily best practices. (Heresy!)

[sunnydaze]

It's better to separate the grounds for the pre-amp filters from the power amp & PI filter. I usually try to match the preamp and PI filter grounds to the spot those tubes are grounded and the power filters near or at the same spot at the PT ground. I know when I built my first rocket, I initially grounded all in one spot as per the layout. Had a little bit of hum, separating the grounds eliminated.

Hope this helps.
mike

[RJ Guitars]

I am in total agreement with Sunnydaze on separating the grounds and xtian as well... including the heresy.

[ampbldr2]

I did separate the pre and power grounds. My issues are far worse. V2 preamp tube is not conducting and I am seeing 9.4 mv in pin 3. My voltages on the amp seem to be very low as well. I am not sure I used the correct primaries. I attached my voltage chart as well as a latest pic. I have been trying to figure this one out all day with no luck.

I tried reflowing solder and even as far as replacing V2 socket. I also disconnected the circuit at V2 pin 3 and inserted a 68k to ground yet V2 still will not conduct as the voltage at pin3 of V2 is reading millivolts. Not a successful day.

[ampbldr2]

Also, I have been using a bulb current limiter the whole time. My heater measurements are pin to ground. Also in that last pic is old showing the 22uf cap in backwards. I corrected the polarity but made no difference. Still seeing 0v at V2a pin 3. I am expecting to see 2.9 v ac for the heaters. Not sure why they're so low.

[xtian]

You will not see correct voltages until you remove the bulb limiter from your circuit. The limiter is only needed during first-time start up, to make sure nothing is going to run away from you and smoke.

If you power up normally (no limiter, and all tubes installed and heaters working), you should see 150-200 volts on the anode (pin 1) of V2a, zero volts on the grid (pin 2) and about 1.5 volts at the cathode (pin 3).

Let's say everything looks good, except still no voltage at pin 3. That can only be a bad tube, the wrong value cathode resistor, or cathode resistor not connected to ground.

Let me know what you find.

[ampbldr2]

You will not see correct voltages until you remove the bulb limiter from your circuit. The limiter is only needed during first-time start up, to make sure nothing is going to run away from you and smoke.

If you power up normally (no limiter, and all tubes installed and heaters working), you should see 150-200 volts on the anode (pin 1) of V2a, zero volts on the grid (pin 2) and about 1.5 volts at the cathode (pin 3).

Let's say everything looks good, except still no voltage at pin 3. That can only be a bad tube, the wrong value cathode resistor, or cathode resistor not connected to ground.

Let me know what you find.

I had no idea. With not that many builds under my belt this was the first time I used a current limiter and it stumped me I took out the eliminator and all the voltages seem normal. Amp is working. Ill take measurements again tomorrow. Thanks xtian