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 Post subject:
PostPosted: Sat Sep 09, 2006 4:14 pm 
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Thanks. I'm away on business for the next few days, so hopefully when I return there will be a care package waiting for me.

The rock is sitting there, trapped inside. The output transformer is the key to letting the rock out. :)


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PostPosted: Sat Sep 09, 2006 11:51 pm 
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synthetic wrote:
Who brought the marmalaide? Because we got toast. 0 ohms between any of the secondaries. Kids, let this be a lesson to you.

I guess I'll be contacting you about another output transformer. At least it wasn't an expensive part that I smoked. :roll:


Thats bizarre...... Usually when they fry its open not shorted. Unless it all melted together. that would be one hot OT. 0 ohms? All of the secondaries? Sounds fishy to me. Is there any isolation between the different secondaries, or all the wires on the seconday are shorted no matter which ones you test?

Bob


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PostPosted: Mon Sep 11, 2006 10:44 am 
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My voltage testers are not very accurate at 1-50 ohms. However, my 8-ohm load measured at around 3-5 ohms, so it's reading something there. The secondaries measure 0-0.5 ohms, so I suspect they are crispy on the inside, juicy on the outside.


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PostPosted: Fri Sep 15, 2006 1:24 pm 
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Replacement finally arrived. So much for 3-day delivery. "Blame Canada...." :D

Can't wait to hook it up tonight. I was driving the mailroom guy crazy checking in several times a day.


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 Post subject:
PostPosted: Fri Sep 15, 2006 1:29 pm 
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Close, but no cigar considering it was sent last Thursday.

Good luck tonight! Keep us posted. I'll be you want to skip out and finish this off eh? :wink:

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 Post subject:
PostPosted: Sat Sep 16, 2006 12:44 am 
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So I hooked it all up, plugged it in and had audio for one minute. The TMB channel wasn't working, but the 18W channel was, so I figured I was getting close. Then the sound went away completely. I checked a few things, and I had hiss as I turn the volume up, but no more sound. Cut the secondaries, measured... yep, all 0 ohms. So for some reason I'm blowing through output transformers. It's going 8 ohms into my Blues Junior and should be working fine.

I don't know what to do now. Aside from walking away from it for a few days, I'm pretty seriously bummed. Not to mention afraid to hook up another transformer and waste another ~$80.


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PostPosted: Sat Sep 16, 2006 9:09 am 
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Ouch and Ouch again. Really? Very strange. Specially considering you had sound for a bit.

Is there any chance the output jack is defective, or the wires to it are not soldered properly? Check continuity.

There are several builders in CA, maybe you could get together with one of them if this persists.

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 Post subject:
PostPosted: Sat Sep 16, 2006 1:30 pm 
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I'm really sorry you're having the trouble, man. I've been having similar issues, but not with the transformer, thankfully. I get a click sound when I touch my voltage meter to the choke wires that connect to the power tubes of my Lightning, and that's helped me know whether or not the problem is with my output or with my board (since I wouldn't get sound through my speaker if it were output related).


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PostPosted: Sat Sep 16, 2006 3:18 pm 
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It doesn't appear to be the jacks. Is there a way to wire the cliff jacks so that there's a load if none is present, even if I have to sacrifice the second jack to do it?

I think the next step is to buy the cheapest output transformer that will get sound out of the amp. I don't want to keep throwing $100 bills at this problem. Once I have a stable amp, then I can upgrade to the correct transformer. Any suggestions?


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 Post subject:
PostPosted: Sat Sep 16, 2006 4:03 pm 
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How long would it take the transformer to melt with no load? 1 second? Is there a more robust one that I can use? Surely this isn't the case for all amps, since most guitar players have no brain.

What if I put my 8 ohm load in one jack, 8-ohm speaker in the other, and set the impedence to 16 ohms? That way if the speaker has a problem, the load will be wrong but at least there's something there to keep it from melting. Would this be good enough protection, even if it didn't sound as good?

This isn't my first project. I've built an API mic preamp, an SSL stereo compressor, an 1176 limiter and a MOTM modular synthesizer, and worked on many other units. I think my construction is solid, and my voltages all add up. But I don't know what to do. I'm close to selling it at a loss. Please help.


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 Post subject:
PostPosted: Sat Sep 16, 2006 5:42 pm 
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I've decided to take it to a qualified tech. Some of the best in the world are right here in LA. No use continuing the slaughter of output transformers. So I'll just buy one more transformer, bring the mess to someone who knows what they're doing, and be done with it. Perhaps I'll buy a new speaker cable while I'm at it.


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 Post subject:
PostPosted: Sat Sep 16, 2006 10:52 pm 
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You could add an 8 ohm load to one switch jack so it's in play when there is no plug in it. But you'd have to remember to use that jack.


If you put 2-8 ohm speakers on it, set the impedance to 4 ohms.

The OT should be able to handle a no load situation for much longer than 1 second. Not sure how long exactly as I've never had this happen.

Can you also send or post a pictures of the build.

Possible causes:

No speaker attached;

Failing/shorted output tube - this can overheat the output transformer and/or power tranformer;

Bad speaker cable /plug = No load - check.

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 Post subject:
PostPosted: Mon Sep 18, 2006 12:13 am 
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The only voltage I should measure on any of the transformer leads is the B+, right? That's something I can test tomorrow.

You show a diagram of the four "channels" of the impedence switch linked together. I read this to be optional. And none of the pins are shorted together, so that's probably not it.

I managed to flex my speaker cable in a way to make it short, so into the bin it goes. Maybe that was the problem. Ugggh.

This thing sounds really good, right? Eyes on the prize. :)


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 Post subject:
PostPosted: Mon Sep 18, 2006 8:06 am 
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Don't take my word for it, check out
http://reviews.harmony-central.com/reviews/Guitar%20Amp/brand/Trinity%20Amps

It might be a good idea to 'hard wire' your speaker to the OT leads. Bypass the jack, use a new cable etc.

If you could short it ( i.e. 0 ohms ACROSS the two wires, then it's possible that one could have been open as well. Get a new one or fix it.

Those "channels" are not linked together. There is a line out option on the 8 ohm only position.

Voltage at CT of OT is full B+, correct.

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 Post subject: backwards cap?
PostPosted: Mon Sep 18, 2006 4:05 pm 
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It was hard to tell but from that wide shot, it looked like the cathode cap from your power tubes is backwards... Is it? My old eyes might be failing me.


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 Post subject: Re: backwards cap?
PostPosted: Mon Sep 18, 2006 4:34 pm 
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teletroy wrote:
It was hard to tell but from that wide shot, it looked like the cathode cap from your power tubes is backwards... Is it? My old eyes might be failing me.


Yes I agree good catch. I think that both of the blue electrolytics are backwards. I cant make out any of the other ones On those ones the arrow points to the negative (ground).

Paul


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 Post subject:
PostPosted: Mon Sep 18, 2006 5:49 pm 
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You mean the 47uF cap on the left? Yeah, that's backwards, huh? Thank you.

http://www.jefflaity.com/misc_pix/amp2.jpg

What about the 16uF caps? I assumed that the crease on one end of the can was the positive side, like a diode. There was no + marking on the part. The photo of the sIII board showed the crease facing down, even though he has big orange caps and I have smaller blue ones.

I can post a much larger resolution photo if that would help.


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 Post subject:
PostPosted: Mon Sep 18, 2006 6:06 pm 
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that looks like you have a 470uf cap in there instead of a 47uf.. The 16s look ok- but it's hard to see the in the pic


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 Post subject:
PostPosted: Mon Sep 18, 2006 6:57 pm 
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That's what came with my kit. The schematic says 470uF/63V for C10 and the layout says 47uF/50V. I probably should order a replacement anyway, so which should it be? Or doesn't it matter if it's polarized the right direction? :oops:


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 Post subject:
PostPosted: Mon Sep 18, 2006 7:24 pm 
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either should be ok as long as it's orientated correctly- it will probalby just alter the sound.


If you look at this page- one layout shows it as a 47 the other one shows it as a 470, and the schematic shows it at a 470.
viewtopic.php?t=689

I've never actually built one, so I don't know. you might ask Coco.


Good luck! You're one step closer.


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