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PostPosted: Sat Nov 16, 2013 1:00 pm 
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Hi Everyone,

I just finished putting together the tweed kit. This is my first amp build, I had planned on building it slowly over a couple of weeks but found that if I was home I couldn't leave it alone. Unable to concentrate on anything else I went for it and finished it last night. Everything went relatively smoothly and it worked right off the bat but there are a few issues. It was way too much fun! And it sounds great.


The 2 obvious problems that I have found are
1- it's a bit noisy, (hum) which gets louder as I turn up the volume.

-The amp isn't in a cabinet yet and from what I understand they are quieter when mounted in the cabinet so that could be it.
also, I didn't shorten the coaxial cable and I ran it under the board to the volume control is that OK. It would be easy to shorten it. where is the best place to run it?

2- the heater voltages are 3VAC from the tube pins to ground.

The other voltages are: with a JJ5Y3
AC mains 116V
B+ 356

V1, 12AY7
Pin 1, 125V
Pin 3, 1.8V
Pin 6, 117V
Pin 8, 1.8V

V2, 12AX7
Pin 1, 149V
Pin 3, 1.2V
Pin 6, 182V
Pin 7, 15.6V
Pin 8, 44V

V3, 6V6
Pin 3, 343
Pin 4, 307
Pin 8, 18.8

V4, 6V6
Pin 3, 341V
Pin 4, 310V
Pin 8, 19V

The rectifier voltages are
Pin 4, 337V
Pin 6, 337V

On the board from left to right the voltages are:
voltages listed on the layout in brackets

19V (22V)
310V (348V)
228V (255V)
44V (50V)
15.8V (18V)
183V (204V)
150V (158V)
1.2V (1.4V)
126V (130V)
118V (130V)
1.8V (2.0V)

Any comments/suggestions are really appreciated

Thanks Stephen for a great kit!
Jim


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PostPosted: Sat Nov 16, 2013 10:48 pm 
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Location: Qualicum Beach, BC
Congratulations on getting your first tube amp project working!

Your voltages look OK. They are all within 10% of the expected values which is normal for tube amps. The high voltage AC coming out of your power transformer is a bit low which accounts for all the other voltages being low. Check the AC at the wall outlet. That might be lower than usual.

For the hum issue, check all your ground connections and make sure all your jacks and ground lugs are tightly fastened to the chassis. I would keep the coax cable as short as possible and run it under the board directly from the pot to the tube socket. Of course, you only connect the coax cable's shield at the pot. Make sure the shield at the other end can't contact the chassis.

Make sure the cables running to your guitar and speaker are good, too.

I don't think that putting the amp into a cabinet would have much effect on the hum. Unless right now it's sitting near something that generates a big electromagnetic field.


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PostPosted: Mon Nov 18, 2013 6:10 pm 
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Thanks for the reply,

The AC from my wall outlet is around 114V so is a bit low/

I shortened the coax cable and that got rid of some of the noise.
I also found out that the heaters need to be measured to one another not to ground. When measured together they are 6V.

The last problem is that when plugged into the bright channel I get pops when I touch the guitar strings. I'm guessing this is a grounding problem.
I checked the impedance of all the points that connect to ground. Everyone was below 1ohm except for where the .00047 cap connects to the tone control. On the Bright volume side of the cap lead I get a reading but nothing off the lead on the tone side. I guess I broke the cap somehow. Based on my limited electronics knowledge it seems the tone pot is grounded through that cap, and because it's broken the tone pot is not grounded. Could this account for the pops and some of the noise?

Thanks
Jim


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PostPosted: Sun Dec 01, 2013 12:30 pm 
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Everything seems to be sorted out now. The amp is running very quietly and sounds great.
In the end the two issues I had were: I didn't shorten the coax cable and/or it wasn't properly connected. Shortening it and redoing the connections reduced the noise quite a bit.

The other problem was a noisy 12ay7 tube, I replaced it and now the amp is very quiet.

Many thanks to Stephen for answering my many emails!
This was my first amp build, one of the reasons I chose Trinity (aside from the quality) was that I was told the instructions were clear and the customer support was very good. I couldn't agree more.

I'll post some pictures and clips once the cab and speaker arrive.


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PostPosted: Mon Dec 02, 2013 9:46 am 
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Great news. We've have a few noisy EH tubes so we should find out what tube type you put in there?

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PostPosted: Mon Dec 02, 2013 9:59 am 
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I replaced it with another EH 12ay7 this one is very quiet. I also tried a couple of 12ax7's I had laying around, they're quet too but I like the amp more with the 12ay7.


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PostPosted: Mon Dec 02, 2013 11:44 pm 
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Glad you got your amp working.

There's quite a difference in gain between a 12AY7 and a 12AX7. It's over double with the AX. You'll get more volume and more crunch. The 12AY7 is what gives the amp its warm, bluesy sound.

Here's a link to a good video on thetubestore.com website comparing the gain of various tubes in the 12AX7 family.
http://www.thetubestore.com/Resources/G ... ain-Factor.


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PostPosted: Tue Dec 03, 2013 9:33 am 
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Thanks for the info and the link. The amp sounded great with both the ax7 and ay7 but the ay7 works better for the sound I'm after.

I have an idea for a mod and was wondering if it was possible. I find that with humbuckers the normal channel is too dark and the bright channel sounds great but is a little bit too boomy. With single coils the normal channel is still too dark for my taste but I like the sound of the bright channel. So my plan if it's possible would be to:

Modify the Normal channel so that it's exactly the same as stock bright channel (keep the .1 uf coupling cap). Then change the coupling cap on the Bright channel to .022uf as suggested in the manual.
This way I'd have two versions of the bright channel one for humbuckers and one for single coils.
Is this possible?
It looks like it could be as simple as adding another 500pf cap between C2 and the lug 3 on the tone pot. (But maybe not!)

Thanks
Jim


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PostPosted: Sat Dec 14, 2013 2:04 am 
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If you look at the schematic you'll see that the tone control hangs off the bright volume pot wiper. Cant recall how much effect the tone control effects the dark one hardly ever use. But they end up mixing back through there respective volume pots into the next stage On most amps the output of a tube goes into the top of the volume pot and you take off what you need from the wiper. In the case of this amp it feeds into the wipers and the volume pots are looped together back to ground. Its what makes a 5e3 well a 5e3. Never could completely under stand that portion . The channel interaction is where its at for me (if you plug into one side and start moving the other volume it changes things.) You could also plug into both (jumper) and see what tones you can come up with there. I suppose you could also wire it up the other way your thinking . think you might have to add another tone pot but then you would no longer have a 5e3

Im just rambling now. Think there was some previous post on breaking the channels into something like a brown face


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PostPosted: Sat Dec 14, 2013 12:20 pm 
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Just realized that the tops of the pots are tied together

And if that made any sense

People assume that time is a strict progression of cause to effect. But actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly-wobbly timey-wimey... stuff.


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PostPosted: Mon Dec 16, 2013 5:50 pm 
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The cabinet (trinity) arrived last week. The speaker hasn't arrived yet so a friend lent me one so I could get the amp up and running. Here are some pictures:

The cabinet is beautiful and the amp sounds great! I can't wait until the speaker arrives. I'm going to play it stock for a while before doing any mods.


Attachments:
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photo 1.JPG
photo 1.JPG [ 153.19 KiB | Viewed 7248 times ]
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PostPosted: Sat Feb 07, 2015 11:55 am 
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just thought of a switch mod that might get what your after. split cathode (not new mod) with a dpdt switch. one side ties both cathodes through the stock cathode resistor and cap. flick the switch and the bright channel goes through 1.5k and 25uf and the normal channel goes through (i ll pick some what marshal values 820r .68uf. The other option is to have a bright cap on the vol pot for the normal channel. (just dont know how it would effect the rest of the circuit). but could also be put on a pot switch (pull bright) This would make it all defetable back to a 5e3. probably stick with the first stage coupling caps to .022uf


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PostPosted: Sat Feb 07, 2015 4:00 pm 
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If you really want to brighten and tighten up the Bright chnnel, reduce the coupling cap to .022 and increase the treble bypass capacitor (500pF) that circumvents the Bright Volume potentiometer.
you can also tighten it all up by running it through a 1.5K shared cathode resistor instead of the 820.
A DPDT option is good too. Put it on a Volume pull pot.

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PostPosted: Tue Apr 16, 2019 1:45 am 
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This is great information, Many thanks for sharing.


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PostPosted: Tue Apr 16, 2019 2:30 pm 
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Location: Shawnee, OK
Here's a source of good tweed info and other fender vintage amps. https://robrobinette.com/How_Amps_Work.htm

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