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Hi all, this is my first post on the forum. I was really inspired by the prototype Lightning build since I love building things (although I am a total newbie at tube amp stuff). Besides that my Epiphone Valve Special was beginning to sound really dull and lifeless.

So I set about grabbing a decent quality Hammond AO-43 off of Ebay. I think this unit turned out to be in very good condition, with very little use (according to the owner) and all the original tubes.

I decided to play it safe and replaced all of the can caps with F&T 22mFs and Xicons for the two 33mFs. The build took quite a while. At every stage I would check and double check the layouts and schematic on the Lightning page.

At this point it is nearly finished - the amp works great and sounds awesome, even with the cheap old Epiphone speaker. I was getting 325, 0, 325 for my secondaries as I recall - I hope that is not too high for this particular circuit. I remember reading in another post that this PT may be too much for the EL84s. I hope everything is in order - the amp is extremely loud and full-sounding - I hope it lasts.

I'd love to post images - but I get an "attachement quota"?

Quota lifted. Please post away. Did you make a lightning or what design was used?

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

Thank you. Here are a few snapshots.



It's a Lightning - I followed Trinity's layout almost exactly except for a few differences. I was worried about the quality of the original can caps, even though the amp itself looks like it's in excellent condition (supposedly played only a few times). I used 4 22mF and 2 33mF filter caps instead of only 5 total in the Ceri@tone circuit (any tonal differences?). I did, however, add a bleeder resistor (same as in the Ceri@tone layout).



For the the rectifier, I added the two diodes also seen in the Ceri@tone layout - but I hope the original rectifier is still in good shape and will last for a while.



The amp has two star grounding points, just like the Trinity Lightning, one right next to the rear of the PT (with an extremely short path from the filter cap ground), and the other beside the two input jacks.



For the EL84 cathode resistor I ordered a 10W 120 wirewound, but when the order arrived it was only 5W. To be safe, I went to my local electronics store and bought the closest value I could get (100 ohm) at 10W. I also bought one 150 ohm version. Possible tonal differences?



I used metal oxide resistors in quite a few places, just to be safe (following the Trinity schematic notes). I wonder how much tonal difference there would have been if I had placed a few carbon comps in there somewhere.
As you can see from the pictures, it is really cramped in there. This was also my first amp build, so keeping everything neat and pretty looking didn't turn out as well as I had hoped. But everything sounds great. The amp is very quiet, which I was extremely relieved to hear.

Any and all comments/suggestions would be much appreciated. I am especially concerned about this particular PT working well with the Lightning circuit. Everything seems to sound great, the PT and OT don't get too warm to the touch after quite a bit of playing. The EL84s do look quite bright (I don't think the plates are glowing red, if I'm not mistaken)...this being my first amp build, I don't know whether that is just fine or perhaps a sign of something to come.

This looks very familiar!! Yes, it is tight.

Can you measure the voltages, especially the B+ i.e. at the first filter cap. In the original, it worked fine, but the voltage was high. We dropped a lot with some resistors, but there is a better way. B+ should be 350 -360.

I assume you used the power supply choke as well?

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

Thank you for the tip. I got 376V at the first cap, and then, in order, 218, 328, 366, 274, 337. Do you feel like they are within a safe range or should I put some limiting resistor? If so, what value, and where?

Yes, I moved the choke like you did and placed it opposite the filter caps (with the chassis between).

Yes, I would get a 18-20 V, 5 Watt Zener diode and put it in the ground connection from the Power centre tap.

Like as on this post: viewtopic.php?f=12&t=3218

Omit the switch.

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

Unfortunately, connecting zeners into the PT centre-tap to ground connection isn't actually very good practice. This is because the zener ends up carrying raw chopped AC. As a result it reduces the voltage by an amount which is somewhat less than the spec zener voltage, and also the device suffers more stress than if it is being fed DC. The centre-tap method is also not normally usable with fixed-biased amp, which fortunately isn't the case with this amp.

The recommended way is to put the zener(s) in the B+ line, somewhere after the first filter cap. Then it will behave more as expected, and have less risk of getting damaged.

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Great tones come in small glass jars!

Hmm...so would you recommend placing it after the first filter cap but before the choke? Stephen, what kind of results/performance did you get out of your arrangement (Zener on center tap)? I have ordered and received the Zener diode from Mouser.

Yes, exactly. The strip end of the zener faces back towards the power rectifier.

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Great tones come in small glass jars!

Forgive my limited electronics background, but shouldn't the Zener diode cathode end be facing the choke which leads to the next filter caps and from there goes to the ground connection?

Never mind that previous post. It's now my understanding that a Zener diode limits the current running though it when it is reversed? A friend of mine advised against Zener diodes in an amp, claiming they would mess with the tone and add noise. Any truth to this?

No, not at all in the power supply circuit. I am an EE by profession, and I've designed and built many amps with zeners in the B+ rail, with no problems of that kind at all. BTW I'm *real* fussy about noise levels and tone - just ask Stephen. Plus hundreds of people round the world have built amps with zeners installed this way, and not reported any such problems. Even Trinity's Triwatt has a zener in the B+ line, and that's a very quiet amp. Also having the rail voltage too high will alter the tone too.

_________________
Great tones come in small glass jars!

Well, it's finally finished folks. My very first amp. And what a journey! Thank you all on the forum for your invaluable advice. I put a Warehouse Guitar Speaker in it, build the head and speaker cabs from scratch. It's not the neatest tolex work, but then again this was my first time tolexing! Sounds so huge and lovely. I can't believe the thing started out as an electric organ amp. Believe it or not, the faceplate is simply illustration board painstakingly cut to size. I tried to use as inexpensive materials as possible, since I am a starving student. The grill cloth was acquired from Jo-Ann's fabric for about 2 dollars.

Hi all, Nice builds!
Total Newb but ,I am going to give it a shot.
Wondering how to re-wire the exsisting 50uf caps?
What additional caps are needed?
thanks, jeff

Well some home work paid off.
Here is a link for any other noobs.
http://antiqueradio.org/recap.htm

cheers