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Alright, so I got the Triwatt fully assembled. Double checked my work, tested the PT, all checks out.

Flip the switch to standby, and poof - fuse pops.

Unsoldered the PT secondaries and did another PT check - all tests out. PT secondaries show 350v on the nuts, so my best guess is that I miswired the zener diode setup. Now the key is to figure out if it can be fixed (which I don't think is possible) or ordering a new zener diode setup (diode and DPDT switch).

For troubleshooting purposes, I can yank the tap from the rectifier and measure my B+ from the recto without hurting anything, correct? Would that be the best place to start troubleshooting? I should see somewhere around 500vdc off of the rectifier, correct (70% of 700v)?

Fuse popping is usually a sign of a short in the amp, or sometimes the fuse itself was weak. I don't see how that zener would be the cause. Even if it blew you would just get around 15V higher B+, like you would when the amp's set for KT66s.
On the nuts??? I hope you meant turrets...

So you want to disconnect the CT to ground connection? I don't see much point in doing that if you've still got the secondaries connected to the rectifiers. If you want to disconnect the CT, then also disconnect the PT connection to the rectifiers. Check the OT primary connections and power tube connections very carefully for shorts. That's where most of the current goes when you take the amp out of standby, and anything wrong around there could blow a fuse.

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Great tones come in small glass jars!

Weathered... I'm in Mpls and, though I'm no expert.. My amp's up and running... let me know if you want to do some sort of side by side comparison... or have another set of eyes look at your amp?

zack@metroprovider.com

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dig it

To troubleshoot, is there a means to bypass the switch completely to verify if the short is past that? That's the only area of the amp that I'm not confident in my wiring of.



Actually, this was with the secondaries disconnected from the turret board - I just meant that they were measuring right at 350v. "On the nuts" meaning right on.



It's blowing before I take it out of standby - the pilot light comes on for 1-2 seconds, then the fuse pops.

The spot that I wanted to pull was the B+ line past the rectifier diodes that runs to the power tube switch - that would show me if the short is in the rectifier or past that. Is that a safe spot to pull to measure the initial B+ and test for shorts, or would that cause trouble?

OK I suggest you completely disconnect the high voltage secondaries (including thee CT), and tape the ends up for safety. Next, with the amp not connected to AC power, check the heater wiring for shorts between the two sides, as well as to chassis. Also check how you've wired the 120V AC side of your amp against the wiring pictures of Malcolm's amp. Be aware that the two sets of contacts on the power/standby switch or respectively on the left and right hand sides and not above and below each other, like you might expect. If you put an ohmmeter or cintunuity tester across the contacts you can see how they work. HTH

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Great tones come in small glass jars!

I already did check the heater wiring - the amp is stable when the PT secondaries are disconnected from the board. Heater wiring meters at 3.16v per side.

Since it's stable with the secondaries disconnected, it seems to me that the issue would be in the power tube switch or the can cap wiring - I'll double check that tonight.

In thinking about it, I seem to remember wiring the rectifier diodes all in the same direction (meaning that two of them are reversed) - any chance that might cause it to act like a short at all?

I think you will get a short across the OT secondary on alternate half cycles of the AC waveform. Then no conduction at all during the other half of the waveform. Probably no permanent damage done.

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Great tones come in small glass jars!

Well, that'll be the first thing I check when I get home tonight. I honestly seem to remember all of the diodes facing the same way.

In case you can't tell, this is my first amp with a SS rectifier.

Welcome to the big league! Just check the SS rectifiers in both directions with a continuity checker, that they're not shorted.

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Great tones come in small glass jars!

Beautiful - swapped the diodes, B+ voltage is now perfectly on spec.

Powered on with no tubes - measured voltages on the power tubes:

V5 -

Pin 3 - 450v
Pin 4 - 420v
Pins 5&6 - 0v (cold solder joint is my guess - no time to diagnose right now as I have band practice)

V6 -

Pins 3 and 4 identical to V5
Pins 5&6 - 42v

Looks like I have a cold solder joint, but that should be quick to reflow.

I may have a working amp sooner rather than later....hopefully nothing else is an issue.

It's ALIVE!!!!!

Apart from some very minor squealing when the OD is opened up all the way, it's REALLY quiet noise-wise, too. Even with my Tele plugged in.

Through a 1x12 loaded with a Celestion H30, it's got a nice plump bottom and very present midrange.

Now to go get some chopsticks.

Good news. emohawk had a small problem with lead dress and therefore squeal. Check out his posting for some tips.

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

Stephen - I just want to tell you that you have a true winner on your hands with this design. Spent about a half hour with it today at practice/gig volume and it's precisely what it's billed as - a Hiwatt without having to destroy all hearing. I'm simply blown away by it.

Edit: Just tried a TS 12AX7 in the PI. Wowza. This is the tone I've been wanting to have for a long, long time.

Now to work out that pesky OD squeal. In all fairness, it only happens when the OD knob is turned past 3 o'clock, and it doesn't seem to matter what the channel volumes are set at, so I think I've got that narrowed down a bit.

Awesome. Very pleased with that.
Now, a nice review on Harmony Central wont hurt!

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