new build: 18 watt lite IIb

[Phil_S]

Are you using a 120V pilot lamp with three lugs? One on each side and one in the middle? If so, the one in the middle is the tip of the lamp socket and the side lugs both connect to the sleeve. Use one side lug and the middle lug, not both side lugs. This is hard to see, so I'm guessing. You may have blown the lamp, too. Omit the pilot completely, temporarily.

[xtian]

No center lug on lamp.

[xtian]

I lifted the PT leads and started testing. Works fine with heater pair and HT CT attached, but not with HT pair attached. When HT pair is attached as shown in photo, AND standby switch is open, meaning no voltage is traveling to the filter caps, it still blows fuses.

I checked my diodes; they seem to be oriented properly and have not burnt up--my VOM still shows about half volt drop across each.

What am I doing wrong? Any reason I should have to lift the HT center tap, which is currently grounded to the chassis?

[Aleksi]

Hi xtian,

if you have a center tap on your PT's HT winding (and it's grounded), then you only need two diodes (one from each HT line to B+) and should remove those two bottom diodes (connected to GND).

So instead of
/\
\/

only

/\

BR,
Aleksi

[xtian]

First post, awesome post! Thanks, brother!

[xtian]

Got-r-done. Quietest (in the good way) amp I've built to date. Nice, smooth distortion. May tweak for less brightness and better overhead. OTOH, I did opt for Marshall stylee!

[xtian]

Finished and looking swee-eeet.

[tele caster]

Looking good. Nice wood work too.

[Phil_S]

I notice you have the power switches upside down. but clearly marked. You can do cab work and face plates for me any time. Very nice, indeed.

[xtian]

Thanks, guys. Not my cab; bought on the bay for $100!

Switches left upside down for family resemblance to big bro JCM 800.

[xtian]

Just wanted to report on this amp. It has become my favorite for many reasons; it's super quiet in terms of hiss and hum, and it just sounds wonderful with my Tele. I'm playing it thru a 1x12 solid pine cab with a blue Celestion AlNiCo. Our gig last night outside on the patio at La Salles in Chico, CA, was one of my favorite performances, ever. Tone! I love this rig. (And the rest of the band…yeah, they're bril, too.)

http://youtu.be/ZDOckwT0d5g

http://youtu.be/DCwg2S5Vn_U

[Reeltarded]

Second song. The places your guitar pops out sounds like "Believe in Miracles" by Jefferson Starship. Too cool!

I got a grin out of that!

[Phil_S]

Impressive! Really. You deserve to get signed. Then I can say I knew you when...

[cbass]

Sounds great.I like your bands logo

[rock_mumbles]

A friend built a 10 watt Wreck like amp and used a 125E OT, overall the amp sounded good and worked as expected, but there was a harshness in the highs that I didn't like.

I found a thread on AX84 about an EL84 4-4-0, Tilly Dog (the poster) experimented and ended using a Zobel filter with a 56 ohm 10 watt resistor and a 2uf cap across terminals 1 and 6 on his 125E to kill the harshness (he saw a spiking in the output with a speaker load).

I didn't have a 56 ohm resistor so I used a 47 ohm and 2uf film cap on Mark's amp, the high end was a lot smoother, the harshness wasn't predominant like it was ... it did cut the highs just a bit but overall it was a good fix.