Problems with Rocket

[mobisimo]

Hey folks,

I recently finished a rocket build - on a platform that has seen numerous other forms - and ran into an apparent volume problem. At first switch-flick, the gain was maybe half of what it should have been (read: quiet and no distortion at all) and over a few minutes of playing and fiddling around the level diminished so it was almost inaudible. The transformers seemed quite cool although the power tubes, after roughly a minute, were hotter than hell. The power supply voltages are all about where they should be and I hesitate to fire it up again to check output tube bias until I hear from you all. (Changed preamp tubes [...thinking PI...] and encountered same problem.)
I would very much appreciate any advice as to how to proceed.

Mobisimo

[billyz]

Post a picture. Double check the Power tube connections especially the cathode to resistor/ parallel cap to ground. If all measures good, then use a variac to power up at low voltage and check the bias. Also, might want to test the power tubes.

[Allynmey]

better yet, post a voltage chart.

[mobisimo]

Thanks a lot for your attention. Will post pictures as soon as I am able. Voltages are as follows:
B+1 - 342v
B+2 - 333v
B+3 - 260v
B+4 - 332v
B+5 - 232v
Voltage measured at the positive end of the cathode cap/resistor was 10.64v.
I had forgotten to ground the 220k post-PI resistors. Fixed that problem, though the power tubes still get really hot and the volume slowly fades out. I remember B+5 being around 185v before the fix. Could I have smoked the power tubes?

[billyz]

Did you reverse B3 and B4 ? what are the pin out voltages?

[mobisimo]

Nah, that was a typo. I'm apparently an amateur at typing also. Should be 232v. This means B+4 and B+5 are equal, which should not happen.

[billyz]

even if it was would not cause the problem you described.

[billyz]

BTW, the power tubes could have been hotter than hell anyway. More importantly, were they glowing cherry red! I would double check all your solder joints and recheck your wiring , particularly in the front end.

If you don't have a variac use the light bulb limiter to start it up. Then you'll know if you have a short.

Picture worth a thousand words.

[mobisimo]

Pics. No red plating as far as I can tell.

[mobisimo]

Swapped out the first stage coupling cap. Still no sound. How red is cherry red? ...

[Allynmey]

Voltages are way high!

290-295V Plates is about right.
V1A is about 95V
About 9.5V on the power cathode is just about right.

[mobisimo]

I'm using a GDS 36watt PT and have used this same power supply before but with a 1k/25w wirewound as a choke. Rectifier's plates look bright too - what happens when a recto dies?

[billyz]

My eyes are not so good but. I see a lot of bad solder joints, check the 220k resistor off the PI for one. And I would double check your entire Power supply layout and wiring. Some of the resistors look damaged and the layout looks wrong, ie from the Choke to the screens on the el84's. but I am not familiar with the power supply board you are using. Make sure the 40uf cap is connected to the Choke /screens.

I think you should, download the Rocket Schematic and the layout and recheck your work step by step. and resolder everything. did you use the higher voltage secondary of a Toneslut power tranny? there are two different sets of B+ secondaries.

I would not lay the Control grid resistors down like that either. Stand them straight up.

just saw your post on the PT.

[billyz]

A choke looses less Voltage than a Big Resistor/inductor.

[pureoldsound]

you have the Hi-Cut .0047 cap soldered to both 220K. It should be soldered to just one. Is that 33K input resistor doing ground with the chassis?