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I built my last year and actually completed it in August 2011, almost exactly a year ago. This thread some of the build questions as well as a bunch of post build stuff:
viewtopic.php?f=7&t=3010&start=0

The amp has worked absolutely perfectly since last August. Then something happened...

Out of the blue, about a week or two ago, I turned it on and got no sound.
1. Flipped the power switch on and got the usual indicator light turn on
2. Waited a few minutes like usual
3. Flipped the standby switch and got nothing. Zero. Not even a slight noise.
4. No smoke, no flash, no smell, no nothing. Just absolutely zero sound.

At the time, I was in the midst of testing some pedals I'd built, so I just used another amp and postponed the inevitable stress of troubleshooting. But yesterday, I checked some things. Additional facts:
1. I was concerned that maybe one of the kids had done something and the amp wasn't connected to its cab. But no, not possible. The amp is on a wire rack and the kids aren't big enough to move it. I checked and everything was plugged in properly and the impedance switch was set correctly.
2. I was concerned that maybe the cab had a loose wire or my speaker cable was no good. Nope. Hooked it up to another cab with a cable that I know works and it still didn't work. I'm convinced that no cardinal sin of playing without a load was committed!
3. Pulled out the fuse to see if it was blown. Looked fine to me, but then again, I haven't changed an amp fuse in about two decades!
4. With the chassis still in its head cab, I turned off the lights and turned on the power. From the little I can see through the vent screen, it looks like the heaters were glowing. Weird.
5. Tried EL84 mode and 6V6 mode. No difference. No sound in either mode.

I know I'm going to have to open it up and start doing stuff, but before doing so, I thought I'd make this post and explain the exact current condition before asking for advice. Again, the amp worked perfectly for the better part of a year. I'm hoping it's something really, really minor.

Any ideas or advice on what to do/check first?



Kind of ironic in that I was planning on installing a VRM after I finished the pedals I was doing ... and I finished them this past week! I was looking forward to opening it up to "improve" it. Now I have to open it up to make it functional again.

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Go Buckeyes!

Well, you got to open it up. When you do, check cathode voltages on power tubes and see if they are good. If not, possibly the switch went defective??

Assume you tried all inputs & channels & nada?

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

Could also try swapping tubes, might have had a dead one.

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http://pdfelectronics.com

Thanks for the two replies.

Coco,
Yes, I tried all 4 inputs with the same results. Also had the same results in both output tube settings.
Will check those voltages when I open her up.

Kurtlives,
I assume you mean the preamplifier tubes. I'll try swapping when I open her up.


At least now I have a starting point.

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Go Buckeyes!

Just to clarify, are you suggesting I measure the B+ voltage coming off the standby switch? That's the switch you mean, right? Not the power tube select switch.

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Go Buckeyes!

Hope this isn't inappropriate.

This amp now for sale. See my divorce papers sale on th sale forum.

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Go Buckeyes!

wow man...thats too bad...i've started my build and have been following your posts...
good luck with the future!

Reviving this thread!

Life is settling down, so I think it's finally time to get off my backside and figure out how to make this amp work again! Haven'ttouched a soldering iron, amp or pedal in months. Only played one guitar (my acoustic) one time since the middle of August. Time to get on the ball...

Any more suggestions on what I should likely focus on before cracking her open (probably this weekend if at all possible)?

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Go Buckeyes!

If you have tubes, sub one at a time. If not, sounds like you got to open it up and start checking voltages.

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

I finally got to this amp. Here's what I see so far.

1. To recap, with power on, I get the pilot lit and tubes glowing. Flip the standby and zero sound.
2. Opened up the back and rechecked it with the lights dimmed/out. Looked like all tubes EXCEPT v1 were glowing. Hmmm...
3. Replaced that v1 12AX7 (which was only a year or so old) with another. It also shows no heater glow.
4. Took out the chassis all the way for further tests.
5. For all three 12AX7 tube sockets, got roughly 3.1 or 3.2 VAC at the pin 4&5 unions and at pin 9.
6. Got roughly 3.2 VAC at pins 4 and 5 for both EL84 tubes. Didn't bother with the 6V6 tubes since the silent issue is apparent in all modes.v
7. Got 292 VDC at pin 3 of the rectifier tube. This voltage is also read at the first side of the standby switch...and both sides when the switch is engaged.
8. Turned off the lights and looked closely at the tubes. Weird, but v3 really glows well, in line with all the successive tubes. But v2 glows very weakly and v1 doesn't glow at all (at least to the naked eye). All four power tubes and the rectifier tube all glow obviously along with v3, but v2 is much dimmer. I'm at a loss because all of the preamp and power tubes show the 3.2ish volts.

Please help!

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Go Buckeyes!

For the heck of it, I plugged the amp into a different cab. Now I'm worried.

With the volume and gain knobs cranked, I can here a definite hum coming out of the cab with standby flicked on. With standby off, it goes away. That seems about right. I can increase the level of the hum by turning those knobs all the way up.

Problem is, I get absolutely nothing out of a guitar cord plugged into the front. The hum is completely independent of any signal. What does this mean?

Is it possible that the original problem wasn't amp related, but due to a speaker wire coming lose in the cab? Could that damage the amp so that it displays its current behavior? Would that indicate some sort of transformer issue?

Lost and concerned...

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Go Buckeyes!

" I was concerned that maybe the cab had a loose wire or my speaker cable was no good. Nope. Hooked it up to another cab with a cable that I know works and it still didn't work. I'm convinced that no cardinal sin of playing without a load was committed!"

So thought this was not a problem. Well, it's back to basics. And all the voltage measurements you would do at start-up, including AC voltages.

That 3.2 you mentioned should be the AC volts from heater pin to ground or 6.3 VAC across the heater wires for all tubes. Rectifier too.

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

Thanks for the reminder and sanity check Coco.

Yes, I get 3.1 or 3.2 VAC between all the heater pins and ground (chassis) for all three 12AX7 sockets.

I get 6.3 VAC across the heater pins on only v2 and v3.
Across the v1 pins I get ZERO VAC. I still get the 3.1 or 3.2 VAC between those pins and ground, but zero across that socket. That can't be good! Measured 5 or 6 times to be sure.

What could this mean? This amp worked fine for months. Couldn't have been zero then, right?

Measurements seemed crazy, so I double, triple...quintuple checked. I thought maybe I was misssing the pin with my meter probes. After all, there's a lot of stuff in and around the v1 socket. I even went so far as to confirm each side to ground (showing that 3.1 VAC) and then make sure I held one probe in place and moved the ground probe to the other heater side to be sure. I did this for each sides. Even held the probes for half a minute to be sure. Still just zero VAC between the pins.

Can't wait to hear some ideas!

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Go Buckeyes!

It's been a while since I built this kit. Are those voltages still (were they ever?) available somewhere on this site?

I poked around the resource section and saw some sIII voltages without tubes installed, but I haven't seen a complete listing for the sIII v6 with and without. I could have sworn there was some sort of big table of voltages somewhere (AC and DC) for the whole amp. Just can't find it.

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Go Buckeyes!

Take v1 out and measure from the pin side of 4/5 and 9

OK. I'll do that tonight. Still at work here on the West Coast.

Of course, there's that matter of the Buckeye Sweet 16 game first...

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Go Buckeyes!

OK. I'll do that tonight. Still at work here on the West Coast.

Of course, there's that matter of the Buckeye Sweet 16 game first...

_________________
Go Buckeyes!

The manual had a voltage table.

Good suggestion from sassafraz

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

Thanks Coco and sassafraz.

Fixed it! Amp is working fine again.

Forgetting to take the tubes out when measuring those voltages was a big brain freeze.

Went at it again last night. Before doing any more measuring (per Coco and sassafraz's directions), I went ahead and swapped a few more tubes just to be sure - including a brand new rectifier tube. Nothing changed. That meant more measuring, and this time the right way!

This time, I began by taking out v1 and v2 (for a start) and measuring voltages and continuity with my meter. Immediately, things looked different. (The light bulb above my head began coming on!) As expected, I got the 3.15 or so volts from pin 9 to ground and from pins 4/5 to ground on v2. I also got the 6.3 volts between pins4/5 and pin 9 on v2. Nice, everything looked good there. A nice baseliine, if you will

But once I moved over on v1, I only got that voltage on pin 9, not on pin 5/6. Ruh-roh! Of course, I also didn't get the 6.3 volts across the heater wire pins (as I did on v2). Something was clearly up!

I flipped the chassis over and measured all the voltages again, but this time from the tube side (all others were from inside the chassis). I poked my gage probes right into the little holes. Sure enough, I got 3.15 volts on pin 9 of v1, but nothing on pins 4 and 5. As I checked v2 again, things got more interesting. I got the 3.15 volts on pin 9 and pin 4, but not on pin 5. What? That was weird. Double and triple checked it. I did not get the proper heater voltage on pin 5. And obviously, I wasn't getting it on pins 4 or 5 on v1 (which is fed by the wire from v2).

Upon further inspection, it looks like my solder joint that connected the following items wasn't very good:
1) connection of pins 4 and 5 of v2 to...
2) heater wire coming from pins 4/5 of v3 and ...
3) heater wire going to pins 4 1nd 5 of v1
The voltage was arriving at v2 from v3, but wasn't getting sent to v1. It was only showing itself on one of the two joined (I push them together) pins 4 and 5 at that tube socket. And given the orientation of the jumble of wires at those two pins, it wasn't getting to the one wire that left to supply v1.

This is crazy since the amp actually worked perfectly for months. I either had a cold solder joint, a really weak solder joint, or (I embarassed to say) a joint that I totally forgot to solder. Yikes! Must've simply shook free. Looking at it as best I can (given my 44 year old eyes that aren't what they used to be), I can't rightly say that I soldered that joint. Amazing, since when I look at the entire chassis, everything else looks fine.

I simply heated up the gun and re-flowed (or just flowed) that one connection. Bingo! All voltage readings now look fine and the amp plays like a dream once again.

You couldn't have wiped the (albeit sheepish) grin off my face if you tried.

Thanks to everyone that provided me with some direction, especially sassafraz for the reminder to take the darn tubes out before measuring those voltages. D'oh!


Now that it works again, I may need to start looking into VRM...

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Go Buckeyes!

Excellent!,perseverance pays off!

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