Problems with DONNA ROCKET

[Greg]

Hey fellas,

I finally got the nerve to do a voltage chart. It is attached. Nothing seems outside the range of those compiled by Gary.

These are my observations during power up and voltage reading:

A. Power on 2 minutes then switched standby on and heard a scratchy pop sound in speaker.

B. Played great at mid volume on amp but cuts out abruptly to very low volume...maybe 5-10% of normal volume level. Intermittent cut out then I had to turn on standby for a minute then it would go back to normal volume.

C. At very loud amp volume setting it cut out sooner than it did for mid volume.

QUESTIONS:

1. Where do we measure mains at? I used the black lead that attaches to PWR SW2...Is this it?

2. Where do we measure the secondaries at?

3. Why are mu heater voltages all zero? Are these AC?

I know these may be stupid questions but I have to ask if I don't know.

Tonight I will take several more close up photos and post.

[fishy]

Greg,
You can measure the power at the switch.

The filament voltage is ac. Something around 6.3Vac although these might vary a little depending on incoming power, tubes and wiring.

You measure the secondaries across 4 and 6 on the tube rectifier. You have already done this. (green / yellow wires from the PT to the rectfier)

Tubes are usually top of the list. Do you have known good tubes?

Post some pics when you get the chance and maybe someone can spot something. Going over the build again closely is always a good idea.

[Allynmey]

Greg, recheck your ground connections. Reheat and flow solder on all your ground connections. It only takes a few minutes. Then check tubes.

[mumford]

Sounds like a loose wire to me--the louder the amp gets, the more likely it is to shake loose a little bit.

[Greg]

Well I found I had missed the solder joint for the grounding connection between the 40uf capacitors C14a and C14b. I soldered these together and thought it would fix the problem...nope. Now when I fire up the amp it plays at very low volume only...I am going back in and rechecking all other joints, but I wanted to post this in case I damaged something by playing the amp without C14a and C14b.

[Greg]

I rebuilt the cap stack, moved the safety bleeder resistors, un-soldered, twisted and re-soldered wires from PT, re-flowed all solder joints, removed an unused ground wire and walla....SHE ROCKS!

I want to thank everyone for the help:
Allyn, Fishy, Gary H, etc.

Now on to the attenuator with bedroom level included, then maybe a modded TS9,

Who would like to sell me the attenuator kit?

[MooreCowbelle]

install a VVR - look it up here. Rockets like them!