First build problem

[bkguitar]

So I pulled the trigger today on my tweed deluxe clone. I had it on a limiter and without tubes it was fine, flip on the standby switch and it's still ok, bulb glowing but very very dimly. When I put in the rectifier same, then preamp tubes, same, and when i finally put in the power tubes the same for the power switch, but when i flip the standby the limiter isn't glowing brightly, but it definitely glows and the pilot light dims in the amp. The speaker kind of hisses the whole time. I'm new to this, so just trying to figure out what is wrong, but I would guess it has to do with the power tube wiring, so I double checked it and couldn't find anything wrong. Any help would be great. Thanks.

[vavlehead]

Limiter??
Time to bust out the meter when its pugged into 120VAC.
flip the power switch ( leave amp on stand by ) and measure the rec and tube heaters voltages. Do you know how???
Also make sure you are aware of the safety concepts of working with amps!!!!!!

[Jazz P Bass]

If, as you say, the voltages all check out, ditch the limiter.
As a rule I do not use a lamp limiter on tube amps.
Strictly solid state.
You do not indicate which build you are working on.
A (2) 6L6 push/pull amplifier will "pull" 80 watts at idle.
So the limiter in this case is hurting you.
For power up checks I install a 1 amp fuse.

[bkguitar]

The amp is a 5e3. I know how to check voltages, I've done some minor amp work like recapping and stuff, but never a whole build from scratch. I guess at this point I know everything is wired, but since I haven't actually gotten an amp working on my own am not entirely certain of my work. In this case, I'm afraid that there may be a short and I would fry something. That's why I'm using the limiter, especially because the first time I fired it up, I accidentally shorted the filament leads and burnt up the transformer. But I've already read into all the danger and I'll update soon with voltages off the limiter.

[Jazz P Bass]

Your voltages with the limiter installed will be lower than without it.
Ditch the limiter.
Put in a 1 amp fuse.
If the fuse holds & all the main voltages look good, put in the proper fuse & play it.
Ideally you would want to measure the current that the amp is drawing from the mains.
And a variac to ramp up the voltage.
And two meters to monitor the B+ & the heater voltage.

[vavlehead]

this is a good read...

Paul Ruby Amplifiers

[Chuck H]

From one side of the winding to the other. It's AC so theres no chassis reference for voltage readings.

[bkguitar]

So the voltages for the filament were right. I got 6.8 VAC over the entirety of the filament. There was a cold joint on one of the pins but I was able to fix it. When I moved onto the rectifier I got 5.2 volts on the yellow leads, pins 2 and 8, and 690 over the red which checks out with the transformer schematics. The B+ voltage was 480 VDC at the switch and pin 3 of both power tubes.

Everything was working ok from the start i guess except for the cold joint in the 12ay7... Turns out that limiter was just throwing me off... So anything else I should do now? Maybe check biases and filter caps? Or is there really not a huge need? There's a little hum, but it sounds pretty damn good. Thanks a lot for everyone's help! I couldn't have done it without your advice and knowledge!

[bkguitar]

So I thought the build was done, but didn't really have a problem until I started really playing with it. I ended up modding the volume circuit a bit to make it so I don't have to fine tune the volume around 1 to play it at home, but I noticed a hiss after a while. I started playing and after playing for a while (at pretty much any volume (1 before the mod, 4 now)) the amp starts to fizzle or crackle. I don't want to say hiss, because hiss makes me think more of like when an old tv goes to static, but if I shut off the standby and flip it back on it's gone. It normally just starts randomly. I'm not entirely sure what it could be. Maybe a cap of some sort is bad?

[Chuck H]

There are a couple of things it could be. Bad preamp tube, dirty preamp tube pins, failing plate load resistor or possibly a preamp cathode resistor.

Try a preamp tube swap, you only need one known good preamp tube to do it. If that doesn't fix it try to get the problem going and then twist knobs to see if it affects the problem in any way (ie: the volume knob does turn it down or the tone knob does change the EQ of the unwanted noise as well, etc.). This could help narrow the search. Otherwise I would guess that it's not something critical to other amp parts and since trouble shooting this kind of thing can be difficult I might just try to get the problem going and keep it going until something fails. That would narrow down the problem.

Just a note... If the amp is exposed to moisture (even just high humidity) carbon comp resistors, black fiber boards, cloth brade wire and paper bobbin transformers can absorb moisture and cause similar symptoms. None of the listed items should be used in a modern amp IMHO since equally good sounding parts are available that don't suffer this malady. A good rule of thumb is: never store your amp in a place where you wouldn't sleep.

[bkguitar]

Well my amp is in my bedroom, so I think it's ok on the moisture thing. But the preamp tube is fine, same problem with another tube which is new (the one in originally was new anyway). I'm thinking it may just be a bad solder joint because it just randomly starts. When I just had it happen, I ended up turning down the volume knobs and when i turned down the normal channel volume it went away, so I'm guessing bad solder joint somewhere in circuit before the volume pot.

[Jazz P Bass]

"when i turned down the normal channel volume it went away"
That should place the problem before this control.

I see a lot of "bent pins" on preamp tubes.
Which spreads the socket contacts.
Which makes the amp ..........(insert weird whatever)
Something that you might want to check.