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Has anyone had a problem getting their sIII cranked to 10. I am getting feedback out the wazoo. I can dime the volume but when I get past 7 on the master it starts feeding back as if you were holding the guitar in front of the speakers. I am using Duncan 59 pickups whick are not high gain. I can control it some if I roll off the tone control. It is worse in the neck position than it is in the bridge. I have tried different cables, tubes, and moving away from the amp. The channel sounds incredible but I just can't seem to get it to ten without the feedback. With the cable in and the guitar unplugged it does not do it. Is this just the way mine turned out or has anyone had this problem? I have had amps before that would do this but it seems eveyone is able to get there with no problem. This is a stock build. So far I havent felt a need to change anything cause it is so sweet just the way it is.

In my experience, it's pretty rare for an sIII to squeal.

What Output transformer are you using? s2? It should work with the blue wire on pin 7 of V5 and brown wire on pin 7 of V4 but if not, try this. Reverse the leads from the transformer to the output tubes. i.e. put the blue wire on pin 7 of V4 and brown on pin 7 of v5.

Did you use the shielded wire from Vol pot to V2?

Can you post a pic of the build??

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Ok, I think I found my stupid mistake. I ran the shielded wire for the volume control under the turret board and maybe it was too close to the OT. I moved it over the top and it is much better now.

Smokin',

All's well that ends well but can you dime it now?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hey Guy's,

I got busy and side tracked from my amp. Moving the shielded wire to v2 seemed to help at the time but it has gotten worse since. When I get the master up around 8 or 9 it squeals. I am using the S2 trannies. I went back in and shortened my leads to the TMB input. Checked my grounds and reheated all of the connections on the buss bar with a gun to make sure I got the bar hot enough. I have looked this thing over well and just cant see anything. I do have my OT leads twisted going to the EL84's. I'm not sure if the way I routed those is causing a problem. I also tried reversing the leads and it sounded worse so I think they are correct. Here is a link to some pics. http://home.insightbb.com/~jaggers/pics.htm

Thanks

Quite unusual. There should not be any squeal and your build looks good from what I can see. The routing of the OT wires is fine.

Did you solder the shielded cable grounds at the control/input jack end?

Since it doesn't happen when there is no guitar connected, it might just be the instrument. Do you have another guitar to try? Some guitars are prone squeal! What happens when you move away from the amp?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

"Did you solder the shielded cable grounds at the control/input jack end?"

Yes I did do that. You may be correct about it being instrument squeal. I just broke out a 20' Planet Waves cable after reading your post and moved about 15' from the amp and it is not as bad. It still squeals some but hardly at all in the bridge position and more so in with the neck pickup. I think I am probably over reacting. Thanks for looking over the build. By the way I am totaly satisfied with the tone of the stock build at this point. I have not even considered doing any of the mods. You guy's have this voiced nicely for my setup.

Let's see if there are any other comments on it. Glad you like the voicing. Let us know when you get a chance with another guitar.

BTW, what input were you using, Hi? Low? What happens when you change that?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hey Stephen,

I forgot to mention I did try with both of my guitars. Both are Hamers and have Seymour Duncans. One has nickel covers and one does not. It is about the same on both guitars. I was plugged into the high input. Even in the low input I still get some feedback. I did plug into my 4-12 cab that has some older (low effeciency) speakers in it and it almost went away. It was only squealing in the neck position with the guitar volume on 10. Roll it off to 9 and it stops. I am running very efficient speakers in my 2-12 cab (Private Jack and G12H-30). Maybe that has something to do with it.

Ok, so I'm posting a question to see if anyone else has a problem. I hope we can find out and help you sort this out. We could always drop the gain a tad in the TMB channel and that would probably do it, but lets not go there just yet.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

You know, the positioning of the shielded leads shouldn't be as much of an issue as you make it out to be...frankly, because they're shielded. All my shielded leads from the 4 inputs and the volume pot are tucked under the board...and the amp is quiet.

Granted, you've mention that moving the leads above the board has improved things...so who am I to argue....anyway, a few suggestions to try:

*) Get some chopsticks (or other similar non-conductive sticks) and start playing around with lead dress. You might hit upon a wire lead that is the culprit. When you find it, either reroute, shorten or in a worst-case scenario...shield it. s2 has a downright ingenious method of shielding leads. He's been using stewmac copper tape. He runs the leads along the chassis and then tapes the leads to the chassis. Since the stewmac copper tape is conductive through the adhesive, it connects to the chassis and creates a ground that effectively 'shields' any leads that happen to be under the tape. I've been using monster brand guitar cable, which is thinner than regular guitar cords, but still quite thick...so the idea of my input leads taking up less room is really attractive. Using this copper tape method, you could literally shield everything in the amp....and it wouldn't really be too difficult to do so...

*) Tap components on your board with the chopsticks and see if you get any squealing or noise...you might have a bad solder joint or bad component.

*) On the idea of grounding, I see you're using a copper bus for the ground. Are all of your grounds solid and soldered well? With the amp off, tap each joint on the bus hard with something like a screwdriver or again, a chopstick....if the solder joint is suspect it might break lose on some minor abuse. I had this problem with one of my solder joints and I had to rectify the problem with a stronger soldering iron...

*) Twist the OT leads....it can't hurt. You can also twist the plate leads from the PI and the grid leads to the el84s...as those are out of phase with eachother. Dr. Z does this with his amps....I had a lightning build that gave me some trouble and I twisted anything I could that was out of phase and it certainly helped!

Most of all, be dilligent....we'll lick this!

-F

I agree with you on the shielded wire. I may have moved something around in the process because it was better for a while then it has gotten worse. I mave have unkownly disturbed the culprit in the process. I have taken a soldering gun to the buss and grounds instead of my iron to make sure I got the buss hot enough. All of those connections look good. I will put it on the bench again here in a little while and try some of your other suggestions. Would it be worth while to ground the speaker output jack to the chassis?

I always tend to run my shielded cables around the chassis rather than over the board, if your squeal is only happening on the TMB it may make sense to redo those connections. The shielded run that goes from the TMB volume to V2 I have put under the board but stuck to the chassis with either gaffer tape (quick solution) or a couple of spots of silicon glue.

http://kirkby.com.au/g2/main.php?g2_vie ... itemId=487

Good luck
Nigel

I definately had to do this to mine to stop a squeal.
Nigel

Ok, here's what I got. I may have made some incorrect observations. I have two humbucker guitars. One with Duncan customs and nickel covers and one with a Duncan 59 and a JB / no covers. After probing with the chopstick and moving the shielded leads around I could not get the squeal to change. I checked all the grounds and connections. What I finally realized was that the guitar with nickel covers would squeal sooner than the one without covers. I think this is why when I moved the shielded wire in the first place I thought it had gotten better because I probably grabbed the guitar with no covers and it seemed better. This would also explain why sometimes it would start to squeal with the master around 7-8 or so and other times I could get it to 9 without trouble. So after Nigel seemed to agree with grounding the speaker jack I decided to give it a try. I used a rat shack jumper with clips temporarily. This made it a little better. Well I was really thinking it was a lot of pickup feedback at this point. So I went to my son's room and grabbed his Ovation electric with cheap humbuckers. Now here is the cool part. I left the jumper on the speaker ground and dimed the amp and guitar and there was zero squeal. I could lift the jumper and it would start to squeal again. What I am wondering is why it still squealed some with my guitar (I was using the one with nickel covers which if I remeber correctly are more prone to feedback anyway). The jumper lead is really small wire and is just clipped on so I am going to take it to the garage here in a bit and install a permanent ground. I hoping the better ground will cure it. To be continued. Also could you guy's take a look at these voltages and see if they look ok. Thanks!

V1
1 151
3 .96
6 151
8 .9

V2
1 177
3 1.6
6 263
8 177

V3 (PI)
1 210
2 50
3 73
6 210
7 49
8 73

V4
3 11.4
7 343
9 332

V5
3 11.4
7 346
9 332

V6
1 300 AC
2 357
3 300

I ended up using all metal switchcraft style for the speaker jacks that ground themselves. BTW my squeal only made it's appearance when I started messing around using different primaries of the OT and it was there nearly all the time however it sounds like you might be onto something.
Nigel

It looks grounding the speaker jack got rid of most of it. I only get feedback now in the neck position when the guitar volume is on 10. If I roll it back to 8 or 9 it stops. I can dime the amp and guitar in the bridge position with no problem. It may be a good idea to put the metal switchcraft jacks in. I have some laying around here. I still might try twisting the OT leads.