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PharmRock
PostPosted: Sat Oct 22, 2016 1:46 pm 
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I set up the Tramp to do some recording today, with the goal of using different tubes and speakers as I've been promising for what seems like several years now. Drop D. Humbuckers. 6L6 as the power tube. Everything dimed, "tude" and "fat" engaged. When I played some really low riffs (open D, etc), the sound started cutting in and out. I noticed the power tube light up a little differently...some blue "swirling" is the best I can describe it...which coincided when the lowest notes were played. Turned off the amp, cooled down, replaced the 6L6 with a 5881, fired her back up with the same settings...same exact symptoms. I removed the back panel to see what was going on. When I played really low notes, the OT 5K/2.5K switch seemed to be arcing across the terminals or possibly from the switch housing onto the chassis. If I dial back the VRM to around 7 or 8, no problems.

I can't remember the exact rating of the switch for the OT, but if I recall correctly it was 6A or 10A@125VAC, 3A or 5A@250VAC, or something like that.

Is this likely just a switch failure when then OT is drawing a lot of current? Recommendations for an appropriately spec'd switch and supplier would be greatly appreciated. Any additional trouble shooting I should be doing here?

Thanks!
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PharmRock
PostPosted: Mon Oct 24, 2016 11:40 pm 
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I see on the schematic that a 5A DPST switch is called for in this application. A few questions:
Shouldn't this be a double throw switch?
I currently have a SPDT rated at 5A at 250VAC. However we are switching 400VDC thru this switch. Will this be adequate?
I'm thinking I should wire up a DPDT with the leads running through both sides of the switch, i.e the wire from pin 3 runs to both of the center lugs.

So what I've come across looks like a Carling DPDT switch rated for 10A @250VAC...perhaps this is overkill?
http://www.mouser.com/Search/m_ProductD ... 5mpnEos%3d

Could a DPDT mini toggle similar to the bias resistor switch be used?

Help greatly appreciated!
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PharmRock
PostPosted: Sat Nov 12, 2016 2:23 pm 
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I replaced the OT primary impedance switch with a new SPDT 10A@125VAC/5A@250VAC switch. Turned up Vol, MV and Level to 100%. 'Tude engaged and using the 6L6. Significant arcing across the solder lugs when bass notes played...like a power E chord.

I'm about to remove the switch and just go with the 5K primary wired directly to the socket, which is unfortunate as I like the option of running an EL34. If anyone has some suggestion before I go this route, please let me know.

Thanks!
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mmarsh
PostPosted: Sun Nov 13, 2016 8:06 pm 
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Hmmm, I was thinking about doing this mod, but I guess I won't. I've found my tube anyway :)
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coco
PostPosted: Tue Nov 15, 2016 12:58 pm 
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Across the SOLDER LUGS? You could insulate them This is not something anyone else has ever noted, but it seems you have done your homework so we will do ours. We have one right now so I will get a player to test is asap.
We do tend to use all the solder lugs in a switch like that to increase the current rating but insulating them with some shrink tubing might be good.

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PharmRock
PostPosted: Tue Nov 15, 2016 5:50 pm 
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The best I could tell is the arcing was across the solder lugs, but at one point it seemed as though it was from the housing to the chassis. Once it occurred I immediately stopped to prevent any possible damage from occurring. In any case, definitely some sparking going on that resulted in some popping noise through the speaker and changes in power tube activity. I made sure there were no stray wires that could have been the culprit. This only occurs when Vol, MV, Level are all very near (95%) or at maximal range.

I did not heat shrink the connections, although in hindsight it would have been the next logical step before removing the switch completely. I'll try reinstalling it tonight or tomorrow and use the heatshrink and see what happens and report back.
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coco
PostPosted: Wed Nov 16, 2016 11:17 am 
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We'd like to hear about your results!

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PharmRock
PostPosted: Mon Nov 21, 2016 10:39 pm 
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I ended up ordering a Carling DPDT heavy duty toggle:
2GL50-73. This one has the solder lugs. Available through Mouser . 15A@125vac and 10A@250vac. 1/2" mounting hole. Dimensions are 0.75" x 1 3/8", approximately 1 1/8" high including solder lugs.

I could only get a little bit of heat shrink around the solder lugs, but so far the switch is holding up. I ran the OT leads through both sides of the switch. Turned everything up 100%, Tude and fat mode...no issues with 6L6, EL84, or 5881. Problem seems to be resolved.
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No457 Snowy
PostPosted: Wed Nov 23, 2016 10:10 pm 
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Interesting, I've run my Tramp pretty hard for the last 4.5 years, maybe harder than many users since I primarily use the amp at loud (band level) volume settings, at times even running it hard into a Badcat Unleash for even more volume, but never came across this issue.

Did you manage to reproduce this Stephen?
Jumping the gap across solder lugs or from a lug to the chassis would take some serious juice. I wouldn't like to be touching the chassis.
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PharmRock
PostPosted: Thu Nov 24, 2016 9:58 am 
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Hey Snowy,
Yeah it seems weird that's for sure but I had it happen with two different switches. Not sure if I would've even known it was going on but I happened to have the back panel off while recording and that's when I noticed it.
While doing some research, I came across this thread on ax84 about switching primaries on the OT.
http://ax84.com/bbs/dm.php?thread=456665

There seemed to be some concern about switch ratings for DC current especially during surges.

Anyways, all seems to be fine with the new switch. It could've just been a faulty couple of switches I had. The arcing was either across the solder lugs or from the housing to the chassis...hard to tell
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No457 Snowy
PostPosted: Thu Nov 24, 2016 11:23 pm 
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Ah, I see now, I think I have my amp set up differently, I didn't install the optional switch for EL34 and KT88 (2.5K) so my Brown/Yellow wire (5K) from the OT is hard-wired straight to pin 3 on the power tube socket and doesn't pass through the optional switch. My Brown/White wire from the OT (2.5K) for EL34 etc is unused and tied off. I only wanted to use 6V6 or 6L6GC tubes so I don't need that switch, no wonder I've not seen the problem you've described. :? One day I will learn to read people's posts properly. :oops:
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coco
PostPosted: Fri Jul 05, 2019 8:27 pm 
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We were testing a head today and were pushing it hard - and we got arcing! The switch internal contacts seem fine but the issue seems to be between the lugs and the switch body.
So I put in a new switch and wired it very carefully to maximize the seperation. Then I painted the lugs and switch metal body parts with liquid electrical insulating tape!
I will see how this performs and get back on it.

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Hankules
PostPosted: Sat Jul 06, 2019 1:11 pm 
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Thanks, Stephen! Now I'll know what to do when I build a second Tramp w/ the smaller switch.

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Hankules
PostPosted: Wed Jul 24, 2019 1:35 pm 
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coco wrote:
We were testing a head today and were pushing it hard - and we got arcing! The switch internal contacts seem fine but the issue seems to be between the lugs and the switch body.
So I put in a new switch and wired it very carefully to maximize the separation. Then I painted the contacts and switch metal body parts with liquid electrical insulating tape!
I will see how this performs and get back on it.


Coco, have you finished checking your solution and is this fix working? Also, do you recommend any particular brand of liquid electrical tape? (Edit:) Lowes has Gardner Bender Liquid Electrical Tape 4 oz. bottle or a spray version for $8. 3M brna for about $31 to $35 a can w/ brush applicator. PS Did you mean ".. contacts and body" or "..lugs and body"?

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coco
PostPosted: Wed Jul 24, 2019 6:41 pm 
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I used Permatex brand. About $10 with brush applicator. We didnt have any issues after we did this. It seems to be a reasonable solution to using the carlin switches. I think the lugs are just close to the metal body and they can arc under duress. I also think if you soldered the wires on parallel with the switch lugs, and then shrink tubed them right to the bottom of the lug, that would work too.That is how I am going to recommend this switch installation going forward.

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Hankules
PostPosted: Wed Jul 24, 2019 6:45 pm 
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Thanks, Coco :thumbsup:

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coco
PostPosted: Wed Jul 24, 2019 6:49 pm 
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Your second Tramp kit is coming. Waiting for new panels to arrive.

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marcF027
PostPosted: Sun Sep 15, 2019 6:19 am 
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PharmRock wrote:
I set up the Tramp to do some recording today, with the goal of using different tubes and speakers as I've been promising for what seems like several years now. Drop D. Humbuckers. 6L6 as the power tube. Everything dimed, "tude" and "fat" engaged. When I played some really low riffs (open D, etc), the sound started cutting in and out. I noticed the power tube light up a little differently...some blue "swirling" is the best I can describe it...which coincided when the lowest notes were played. Turned off the amp, cooled down, replaced the 6L6 with a 5881, fired her back up with the same settings...same exact symptoms. I removed the back panel to see what was going on. When I played really low notes, the OT 5K/2.5K switch seemed to be arcing across the terminals or possibly from the switch housing onto the chassis. If I dial back the VRM to around 7 or 8, no problems.

I can't remember the exact rating of the switch Demenagement entreprise for the OT, but if I recall correctly it was 6A or 10A@125VAC, 3A or 5A@250VAC, or something like that.

Is this likely just a switch failure when then OT is drawing a lot of current? Recommendations for an appropriately spec'd switch and supplier would be greatly appreciated. Any additional trouble shooting I should be doing here?

Thanks!

Hello!
This is a good article because there are many tips and also many advices that will be very useful to me.
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