AC30 Build Help! I'll keep building, you keep helping!

[sluckey]

Click on the "switches" link at the bottom of this page for the best impedance selector switch.

[evancorylevine]

Click on the "switches" link at the bottom of this page for the best impedance selector switch.

thanks! I ordered it!

[evancorylevine]

Hey beauts! What are the specs on the fuse I need?! I just finished wiring everything and realized I have no rise!!!

Edit: autocorrect

[sluckey]

The fuse size is listed on the Weber layout and schematic.

[evancorylevine]

Got it!

The amp works as expected on the normal channel!

The vib-trem channel also works. In vibe mode, though, the speed knob doesn't do anything.

The brilliant channel makes hissy noises and a very low output signal.

Whatchy'all know?!

[sluckey]

The vib-trem channel also works. In vibe mode, though, the speed knob doesn't do anything.

If the speed works in trem mode it should also work in vibe mode. Switching modes is not related the speed.

[evancorylevine]

The vib-trem channel also works. In vibe mode, though, the speed knob doesn't do anything.

If the speed works in trem mode it should also work in vibe mode. Switching modes is not related the speed.

Right you are. I misheard it. Two out of three channels working, then!!!

Any idea about the brilliant channel?

[sluckey]

Probably a wiring error. Look around V1A and V2 circuits. Measure the voltages on those tubes.

[evancorylevine]

All my wiring seems alright. Where should I measure the voltage across?

[John]

Measure each pin's DC voltage. Red lead on pin, black lead to ground. Your filament pins of course are AC, skip those.

[evancorylevine]

V1:

1: 119
2: 0
3: 1.33
4:
5:
6: 91.3
7: 0
8: 1.3
9:

V2:
1: 267
2: 170
3: 170
4:
5:
6: 170
7: 0
8: 1.34
9:

Any ideas?

[sluckey]

Voltages look good. I still suspect a wiring error.

[evancorylevine]

I've checked all wiring with a continuity meter against the layout. I'll do it again I guess!

[sluckey]

Try this... This test will bypass the V2 "bright" circuit and make the bright channel sound much like the normal channel. If the hiss goes away and the volume of the bright channel sounds OK, then the problem lies within the V2 circuit.

Do this exactly as I say. No more, no less. Don't read between the lines.

1. Pull V2 tube and lay aside.

2. Disconnect the wire from the center lug of the Bright Volume pot and just let it dangle in the air without touching anything.

3. Disconnect the wire from the center lug of the Treble pot and connect this wire to the center lug of the Bright volume pot.

How does the bright channel sound now? If still hissy and low volume the problem is with V1A circuit. Likely suspects would be C5 (500pF) coupling cap or R12 (220K) plate resistor.

If the hiss and low volume is now OK the problem lies within the V2 circuit. Undo the changes in steps 1, 2, and 3 above. Recheck V2 circuit wiring and verify all component values are correct.

[evancorylevine]

I did all that, and the bright channel seemed to output nothing.  I put the wiring all back.

I checked C5 and R12 and they are the correct values, and they are wired correctly.

[evancorylevine]

Any ideas?

[evancorylevine]

DEVELOPMENTS!

I got the brilliant channel working. I went through and checked every connection and made sure that there were no shorts on adjacent connections. Now the brilliant channel seems to work as expected.

A couple things, though. The chassis seems to be pretty microphonic, even with all of the levels turned all the way down and nothing plugged in. It makes a sound if I tap hard on the chassis, or turn standby on or off or pull the vib/trem pot-switch.

When I'm plugged into brilliant, I can hear it at a low volume if I turn up the regular channel.

There is a very audible low in time with the trem when I turn it up.

Any ideas?

[evancorylevine]

Have I been forsaken? Have I committed a fatal faux pas?

I'mona do some google searches for microphonic tube amps. Wish me luck! I'll happily take your directives at your leisure!

[sluckey]

Any ideas?

Most people just don't say anything when they have no ideas.

[evancorylevine]

Any ideas?

Most people just don't say anything when they have no ideas.

That is a very elegant and reasonable policy. I'm just glad I didn't rub anybody the wrong way.

I moved some of the tubes around to put microphonic ones in less amplified places, as I understand it, and that seems to have done the trick with the microphonic chassis.

I'll be double checking everything tomorrow with fresh ears and eyes.

[evancorylevine]

Some developments!

I thought everything was working last night...

When I woke up today and gave it a run, the vib/trem channel just sounded like a normal channel. It wouldn't vib-trem.

Whaddaya know?

[evancorylevine]

i switched around some of the vib tubes and the vib/trem came back. honestly, did weber send me some bunk-ass tubes?

[evancorylevine]

now I played a chord into it, and it went away again. No more vib/trem.   

[EKDENTON]

doug sells the nice rotary impedance switches on this page. Works good i have used them before.

http://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=Switches

{EDIT- removed order ID from URL so it works for anybody - PRR}

[evancorylevine]

doug sells the nice rotary impedance switches on this page. Works good i have used them before.

http://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=Switches

{EDIT- removed order ID from URL so it works for anybody - PRR}

Already got it! It's up and running!

Can we close this thread? I got everything working, basically!

[sluckey]

I can lock this thread if you wish.

[evancorylevine]

I can lock this thread if you wish.

Yes please, thanks!