Help needed, urgently!

[Oddvar R]

Hi. I am about to give up my Hiwatt build. This is my build number 19 and I don't understand anything. I have gone over it multiple times. Changed transformers, the pc boards, and parts then again. Yesterday I finally got some sound out of it, weak, but still sound. Then the amp suddenly died, in a fade out kind of fashion. Today the amp functioned again, but the master volume made som extreme feedback noises when turned up. And suddenly the heater pin 2 just explodes in a white light, the socket itself went black and partley melted, and the wires was torn off the soldierpoint. As you can see on the pic.

The 470r 10w Ohmite resistor got very hot on one point, as has happened once before.

It would be very nice to have some inputs here, or this will be put in the locker as spares in the future?

[bepone]

this second pic looks like this poor tube after carbonising all below the socket, went to another world, pls zoom better

[bepone]

how i see, you are using shitty sockets? this created all the short circuits around? remove the socket and never use pcb sockets again? the worst invention in history of tube accesories? genious who ever created this with porous FR4 material and without any normal clearance between pins.

to be rebuilt all with normal belton sockets and finish the problem for good?

[bepone]

with this short circuit you need to recheck all components in the output stage.. output transformer primary resistances, rect. diodes, disconnect all wires from power transformer and retest all the voltages without the load ( high voltage windinga and heater disconnected from the PT) .all can be bourned

[xtian]

All of your issues may be caused by ultrasonic oscillation, which can draw high current and melt things. Did you ever try swapping the OT primaries on this build? Did you do all the basic "first time start up" things, like test the voltages and current draw first without power tubes?

[Oddvar R]

All of your issues may be caused by ultrasonic oscillation, which can draw high current and melt things. Did you ever try swapping the OT primaries on this build? Did you do all the basic "first time start up" things, like test the voltages and current draw first without power tubes?

Hi. I did all those things, the only things I didn't do was change the filter caps. Whatever I did, same kind of trouble seems to persist?

[Oddvar R]

All of your issues may be caused by ultrasonic oscillation, which can draw high current and melt things. Did you ever try swapping the OT primaries on this build? Did you do all the basic "first time start up" things, like test the voltages and current draw first without power tubes?

Hi. I did all those things, the only things I didn't do was change the filter caps. Whatever I did, same kind of trouble seems to persist?

Before this happened it seemed to be closer to a recovery, voltages was close to ok all the pklaces I measured.

[bepone]

remove all the output tube sockets and install these for the start, this is major problem, you have short circuit between pin 3 (high voltage) and pin 2 (heater)

[Oddvar R]

Ok. I will try yhat.

[Oddvar R]

So, I have changed the power tube sockets to Belton, there is now sound in the amp. Or at least when only thre power tubes ar mounted. When I put in the 4th, the amp has no sound, an in addition, the master volume makes a hi pitched soun above a certain level? I hat to bother you guys, but I don't get it, this has been a very difficult build for me.

The voltage is the same on all tubes, bias 38, after changing the 1k resistor with 8.5k resistor.

I have also swapped the ot wires, but that made it even worse.

I also change the whole small strip board.

This tube socket that is left out for the amp to work, is the same that litterally went up in flames.
The 470R 5w capacitor was at one point extremely hot, but that seems to have cooled down.

[bepone]

good for the sockets! but i understood you didnt replace all of the sockets= you need to ..all are problematic. install all new, belton.

all the components in output section must be remeasured. when no voltage, discharged electrolytics, measure all the voltages must be 0. if all 0 volts then measure resistances of all the resistors in output section (again no voltage in the amp, amp switched off from the wall, for at least half hour!)

after when all the output sockets are new, recheck again all

[Oddvar R]

HI. I changed all four power tube sockets.

[bepone]

can you post some pictures now of internal wiring?

[Oddvar R]

Hi again. I seems now that there are som issues with the wiring going from what I believe is the negative feedback from the impediance selector. When I disconnect it, the noise goes away. The noise is a very high pitched sound, and it gets louder as the master volume is increased. It also is affected by treble and presence. It seems a bit lik oscilation, but I am not understanding amps enough to say what it is. Apart from this, the amp seems to function as supposed to now.

[sluckey]

Sounds like you simply need to swap the OT primary plate leads.