my 18 watt rocket-ish build

[milkyBK370]

Hi, I'd be interested to see the layout you used for this. How does it sound?

[hans-jörg]

Hi,
shouldn´t be the screens (329 VDC) lower than the plate (322 VDC)?
Probably 319 VDC or lower (the screens) or Pin 7 is 329 and Pin 9 is 322?

Otherwise ...

It should write: plates B+1 and screens B+2 (before and after the choke).

I´m shure it was a typo

Hans-Jörg

[wsaraceni]

i'll fire it up again and re-check the voltages. newborn taking all my time. i havent picked up the guitar in 2 months or so.

[wsaraceni]

sounds pretty good. havent gotten to play too much. but the layout is kinda trainwreck size board with z-wreck style layout.

[wsaraceni]

with a new baby i havent had a chance to check this out. havent fired any amps up in 6 months or so. hopefully fire it up this weekend to get a new voltage chart. wish me luck!!!

[wsaraceni]

Hi,
shouldn´t be the screens (329 VDC) lower than the plate (322 VDC)?
Probably 319 VDC or lower (the screens) or Pin 7 is 329 and Pin 9 is 322?

Otherwise ...

It should write: plates B+1 and screens B+2 (before and after the choke).

I´m shure it was a typo

Hans-Jörg

so i FINALLY got it back up to check the voltages. its been a while
all the voltages throughout the amp are lower than originally posted but im still getting 315vdc on pin 7 and 322vdc on pin 9 of the el84s. weird thing is now im popping fuses. and im out of fuses so i cant fire it up to see what the issue is until after i get some more. any reason why these voltages could be off?

[ampgeek]

Guessing that the lower voltages are due to high PT loading. That is further supported by the popping fuses.

Pull the power tubes, look for shorts in the B+ string, stick a light bulb limiter in the AC mains and give it another go.

Good luck,
Dave O.

[wsaraceni]

will do. also going to buy some cheaper el84s. you dont want to know what i've been using to test up until this point.

[wsaraceni]

i hope im wrong, but i think i just saw a picture where i had B+1 and B+2 both actually wired to B+1

[wsaraceni]

nevermind. they are wired correctly. i'll keep poking around

[ampgeek]

I think that I saw mention of a B+ line fuse in an earlier post.
Is that correct?
If so, which fuse has recently started popping?
And...yes..by ALL means! Do take care of those NOS Mullard EL84s!!!
Good luck mate,
Dave O.

[wsaraceni]

got the new tubes. a pair of jj el84s and a pair of EH - el84s. first fuse that popped was the main fuse. then i replaced it and the other fuse popped. the one coming off of the standby switch. so technically both fuses popped. I'll have to go back and look to see what fuses i should have in there. i believe the main fuse is 1a sloblow and the other fuse is 1/2 amp fast but i'll verify. when i fired up the amp a year or so ago i did use the light bulb limiter and had no issues. and the amp, at relatively low volumes, sounded pretty good.

[wsaraceni]

on a side note. anyone know where i can get a really cheap tolex headshell that would work for an trainwreck ceriatone chassis?

[wsaraceni]

so im having a little trouble with values for the fuses. since they both popped i seemed to have lost them and need to order new ones. what values should be in an amp like this for each fuse?

[ampgeek]

I looked at a couple of 18W schematics and it looks like a 2A Slo-Blo for the mains fuse is a good choice.

Not sure about the HT fuse though. I would think that a 1/4 to 1/3 A Slo-Blo wouldn't do any harm there.

Do you know what your PT HT current rating is? ~1.25X that should work fine as well.

Cheers,
Dave O.