Blown PT?

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

Moderators: CurtissRobin, Daviedawg, Graydon, zaphod_phil, rock_mumbles

User avatar
crgfrench
Occasional poster
Occasional poster
Posts: 290
Joined: Fri 04/27/18 3:02 am

Re: Blown PT?

Postby crgfrench » Sun 06/23/19 4:50 pm

0 x

Riffmonster
Newbie
Newbie
Posts: 36
Joined: Tue 02/09/16 12:38 pm

Re: Blown PT?

Postby Riffmonster » Sun 06/23/19 5:36 pm

crgfrench wrote: Paul Ruby has a good startup guide:
https://paulrubyamps.com/info.html#FirstPowerUp

Rob Robinette too:
https://robrobinette.com/Tube_Amp_Startup.htm
These are great resources, thanks. Chopsticking the cap does not alter the noise at all though...
0 x

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1390
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Blown PT?

Postby JMPGuitars » Mon 06/24/19 9:21 am

Riffmonster wrote:
Sun 06/23/19 5:36 pm
Chopsticking the cap does not alter the noise at all though...
No, tap the caps with the chopstick. It won't alter the noise, but it may give you a clue as to whether or not any are defective.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
Amp Tools & Test Equipment
(anti)Social: Facebook · Instagram

Riffmonster
Newbie
Newbie
Posts: 36
Joined: Tue 02/09/16 12:38 pm

Re: Blown PT?

Postby Riffmonster » Tue 06/25/19 5:32 am

JMPGuitars wrote: No, tap the caps with the chopstick. It won't alter the noise, but it may give you a clue as to whether or not any are defective.
Yes, that’s what I did but I couldn’t detect anything. I am starting to think, that it is the power supply in my room. I borrowed two other amps and they both make a lot of noise in my room. The room is super small too.

As a side note, the lite2b seems to be louder than a 50watt JMP haha...
1 x

Daviedawg
Superior Amp Tech
Superior Amp Tech
Posts: 521
Joined: Fri 01/08/10 2:00 am
Location: Scotland

Re: Blown PT?

Postby Daviedawg » Wed 06/26/19 12:56 am

Going back to listen to your video it may be that you are suffering from external electrical interference. My soldering station causes noise similar to that. More common sources used to be fluorescence lights. But they are less common now. You could try a simple test of switching everything else off including adjacent room. But my feeling is that you would hear it all the time not just with the guitar.

Dd
1 x

Riffmonster
Newbie
Newbie
Posts: 36
Joined: Tue 02/09/16 12:38 pm

Re: Blown PT?

Postby Riffmonster » Thu 07/04/19 8:15 am

Thanks Dd for the input! The noise is a bit less with the lights and soldering station turned off.
Since I got tired of troubleshooting, I decided to order new parts (resistors, caps and filter caps) and try building it up again. I will use the same chassis, turret board, tubes and transformers so the costs are manageable. I will keep you updated!
0 x

User avatar
colossal
Occasional poster
Occasional poster
Posts: 190
Joined: Thu 05/10/07 2:00 am
Location: In and around the lake

Re: Blown PT?

Postby colossal » Thu 07/04/19 10:30 am

Are you using a shield plate to cover the chassis while testing?
0 x

Riffmonster
Newbie
Newbie
Posts: 36
Joined: Tue 02/09/16 12:38 pm

Re: Blown PT?

Postby Riffmonster » Thu 07/04/19 10:33 am

No I don't. I actually do not have one available here at the moment.
0 x

User avatar
colossal
Occasional poster
Occasional poster
Posts: 190
Joined: Thu 05/10/07 2:00 am
Location: In and around the lake

Re: Blown PT?

Postby colossal » Thu 07/04/19 12:15 pm

Riffmonster wrote:
Thu 07/04/19 10:33 am
No I don't. I actually do not have one available here at the moment.
It's very possible your amp is just picking up the room noise, as has been previously mentioned. Usually, a test of any amp is to be able to dime the controls and have no oscillation, even without a shield plate. However, if the environment is dirty, this can easily couple to the amp, inducing noise. A shield plate can be very effective. It must couple to the chassis to create a faraday cage.

If you have some metal foil tape, such as what is used for furnace ducting, you could place some strips on a piece of light plywood or masonite (or whatever you might have...cereal box would be a good candidate) and use that as a temporary shield plate. It might be tempting to use a piece of aluminum foil but you can kill yourself if collapses into the live amp. Use something rigid. You could use some spray adhesive on a piece of foam core or cereal box cardboard and lay out a piece of aluminum foil on it and smooth with a pencil.

If you've already gutted the amp, great. No need to test anything, but you probably need a plate the next time you are up and running in that room. But, to hedge against radio or line noise in the first place, nothing beats a good layout, good lead dress, and a solid ground scheme.
1 x

Riffmonster
Newbie
Newbie
Posts: 36
Joined: Tue 02/09/16 12:38 pm

Re: Blown PT?

Postby Riffmonster » Thu 08/01/19 10:11 am

Hey guys,

sorry for the long silence, I have been quite busy!
I have rebuilt the amp and the noise is very acceptable now and it sounds awesome!
However, when I tried to record some samples with my two notes captor, i noticed that at full drive the sound includes something like a phaser sound if I let a chord ring. I attach a file for you to listen. I am unsure if it is from the captor or some kind of blocking distortion. What do you think?
Cheers!
Lite2bPhase.mp3
You do not have the required permissions to view the files attached to this post.
0 x

Daviedawg
Superior Amp Tech
Superior Amp Tech
Posts: 521
Joined: Fri 01/08/10 2:00 am
Location: Scotland

Re: Blown PT?

Postby Daviedawg » Fri 08/02/19 2:20 am

Always hard to be totally definitive on recordings, but that sounds like "fizz" to me. It is not too hard to rectify. A search will find a number of references to fizz and what to do about it.

There is a specific fix called the Paul Ruby fix. But I cannot remember how it went.

Dd

Edit. There is a whole sticky on the topic up at the top of this section.
Edit 2. storage/18-watter_buzz_info_311.pdf. This includes a diagram of the fix Paul adopted which has been used successfully by others.
0 x

Riffmonster
Newbie
Newbie
Posts: 36
Joined: Tue 02/09/16 12:38 pm

Re: Blown PT?

Postby Riffmonster » Fri 08/02/19 6:45 am

Thanks man, that looks like an easy (to try) fix! I will order some diodes and tell you about the results.
Cheers!
0 x


Return to “18watt Technical Discussion”

Who is online

Users browsing this forum: No registered users and 11 guests