5F1 New Build Very Low Volume

[bob78h]

Hi guys,
I just finished building a tweed Champ using a Triode kit. The problem is that the amp is very quiet. I need to have the volume up at 12 and also my guitar volume at 10 to even hear anything. Not sure where to start troubleshooting, any ideas? I checked B+ and voltages on the tube sockets per advice in other threads and they seem normal...

Thanks.

[Jazz P Bass]

You are not supplying any relevant information.
How about posting the B+ value.
Also what is the 6V6 cathode voltage measurement at idle?
Next item would be the 6V6 grid voltage.
What is the Vac signal measurement, everything full on & banging a chord?
On to, what is the Vac voltage on the speaker connections when doing the above?
Any or all of these facts could provide a clue.

[loudthud]

If the guitar sounds distorted, that could be a short at the speaker jack. Since the speaker winding on the output transformer is a very low resistance, you should disconnect (unsolder) one of the wires between the jack and transformer, then measure the ohms between the jack's terminals. It should be about 3 ohms if you have a 4 ohm speaker or 6 ohms if you have an 8 ohm speaker. If you measure less than 1 ohm, look for some kind of short at the jack or in the speaker cable.

If the guitar sounds kind of normal, that could be a short or wiring error at the input jacks. Unplug the cord at the guitar and measure the reisitance between tip and sleeve. It should be about 1 Megohm or 136K ohms depending on which jack you are plugged into.

[bob78h]

Sorry, I'm new to this stuff. What is the 6V6 cathode and grid? Like which pins?

So what just happened plugged in the amp and I must have shaken something. It got really really loud (like cranked at 12 loud). Then there was some staticy noises (like a loose connection) and it went back to being quiet. I actually hit the cabinet a few times and got it to where it is now a reasonable volume. But I still basically have to have it cranked at 12 to get a normal volume. It gets pretty quiet below 7 unless I have my guitar volume wide open. Does this sound like poor soldering? Speaker jack or maybe volume pot or input jack? Or something else entirely?

[bob78h]

If the guitar sounds distorted, that could be a short at the speaker jack. Since the speaker winding on the output transformer is a very low resistance, you should disconnect (unsolder) one of the wires between the jack and transformer, then measure the ohms between the jack's terminals. It should be about 3 ohms if you have a 4 ohm speaker or 6 ohms if you have an 8 ohm speaker. If you measure less than 1 ohm, look for some kind of short at the jack or in the speaker cable.

If the guitar sounds kind of normal, that could be a short or wiring error at the input jacks. Unplug the cord at the guitar and measure the reisitance between tip and sleeve. It should be about 1 Megohm or 136K ohms depending on which jack you are plugged into.

The guitar sounds normal. I get 1.48M for the high input and 141K for the low input...

[Jazz P Bass]

Sorry, I'm new to this stuff. What is the 6V6 cathode and grid? Like which pins?

So what just happened plugged in the amp and I must have shaken something. It got really really loud (like cranked at 12 loud). Then there was some staticy noises (like a loose connection) and it went back to being quiet. I actually hit the cabinet a few times and got it to where it is now a reasonable volume. But I still basically have to have it cranked at 12 to get a normal volume. It gets pretty quiet below 7 unless I have my guitar volume wide open. Does this sound like poor soldering? Speaker jack or maybe volume pot or input jack? Or something else entirely?

I would take five and then come back at it.
Recheck all of your work.
The symptoms describe something goofy.

[loudthud]

Look at post 14 in this thread: http://music-electronics-forum.com/t12667/

[bob78h]

Post 14 says something is wrong with my layout?

Is there a resource that lists what voltages I should be getting for various parts of the circuit?

I spent a little more time just playing through the amp and the thing is it sounds great. The problem is that I have to have it wide open at 12, and the volume I'm getting is more of what I'd expect to get at maybe 7? A very comfortable bedroom volume and what I think is much too quiet for a cranked Champ.

I checked the input jacks and they seem to wired correctly... The resistances that I posted above seem fairly close to the values you provided.

[Enzo]

Look really close anywhere wires are connected, see if two adjacent wires are touching, or if maybe two pins on a tube socket are touching, or perhaps a blob of solder sits between two solder lugs on the speaker jack, etc etc.

[bob78h]

I believe I may have found the culprit. I took a chopstick and while the amp was on, strummed and poked around at the wires. This probably unsafe but low and behold, I poked one of the filament wires at pin 7 of the power tube and the amp got really loud. Looks like a bad solder joint there. Gonna redo it and hopefully that fixes things.

EDIT:
Actually, wrong again. It seems to be the wire from the output transformer to the speaker RCA jack was shorting on the bolt that mounted the jack. Seems to have fixed the volume issue. Whats interesting is I actually got a nice creamy sound at the lower volume. Now its pretty clean even all the way up. Any idea why this is the case?

[g1]

the wire from the output transformer to the speaker RCA jack was shorting on the bolt that mounted the jack. Seems to have fixed the volume issue. Whats interesting is I actually got a nice creamy sound at the lower volume. Now its pretty clean even all the way up. Any idea why this is the case?

That was with the volume cranked, so the amp was distorting heavily. It just wasn't as loud because of the short at the bolt. The short was diverting power away from the speaker, but what was getting to the speaker was still as distorted as what you now get with the amp cranked.
It's similar to what you would get if you were using a power attenuator between the amp and speaker, with the volume of the amp cranked wide open.

[Chuck H]

+1
If you got that "creamy" tone with the "volume up at 12 and also my guitar volume at 10" then you need to duplicate the same conditions. If your cranking the amp and turning the guitar down, that isn't the same conditions. If you ARE cranking the guitar also and the amp is almost clean there may be another problem.

What sort of pickups and pickup selections are you using when the amp is cranked but almost clean?