!@#$%^&*) + Advice for Firefly builders (PCB)

[phector2004]

GRRRRRR!!!!!!

Finally got all my firefly parts shipped from mouser after parts that were in got back-ordered once the stuff that was back-ordered came in...

Started off as the most relaxing build i've ever had, until I hit trouble and it all came crashing down!

1. The pots had considerably wider pins than would fit in the board (If anyone building a firefly has this issue, you can easily solder new leads in, but it tends to wobble... Just a heads-up)

PITA Level: 2/5

2. When working with tubes, BUY A HOLE SAW! Otherwise a huge pain to drill a million holes

PITA Level: 3/5

3. Hammond Box started acting psycho. Unless it was the intense heat and humidity of my basement driving me crazy. Drilled the whole chassis without problem, until I got to the back and decided to use previous "drill a million times to make hole" method for the power jack. Ended up breaking 4 bits and making tons of skid-marks when every other face of the box was cut through like butter   Had to use pliers to cut an ugly hole... then I felt guilty abusing my unibit to make the output jack.
Unsolved mystery? Or does anybody have any idea why the box turned into adamantium as my frustration grew?

PITA Level: 4/5

4. Hammond transformers didn't come with mounting screws/nuts... Gee, thanks... (Firefly builders: Get M3 nuts when you order, or similar. I got longer M4 nuts and bolts)

PITA Level: 2/5

5. Hammond 269EX transformer "revised"... turns out you shouldnt assume the grey wire is just the "other" black one... Fried Fuse 1.
Here's a link for the updated transformer: http://www.hammondmfg.com/263.htm#263newpri

115V input --> White + Grey
125V input --> White + Black

I'm assuming Canadian power is about 110V, but any way to make sure White + grey is the right combo?

PITA Level: 5/5

6. Sizzle sizzle
Short on those stupid screw-in terminals I was uneasy on using. Nothing beats a solid connection, after all...
Turns out a stray wire strand from one red power cable came out and shorted with the other red while I was desoldering-resoldering the power transformer. Light went off after 1 second and sizzling noise made me yank the power out. Fuse 2 Burnt out. Out of fuses for the moment...

PITA Level: 7/5

Well I've just about had it now... Not even gonna touch the thing for the next while. Procrastinated much to get it running and now it won't even power up. Lessons learnt: Stock up on fuses, Buy a hole saw, Figure out what the wires on your transformer do.

Good luck to anyone building it, hope to hear mine soon.

[DougH]

Did you use this? http://homepage.mac.com/calhoun/.Public/Firefly%20PCB%20Guide%208.pdf

[gtudoran]

I'm rilly sorry man... but that was the fking funnyest part i ever read regarding amp build i was ROTFL on the part with the 2nd fuse 

Good luck!

Gabriel Tudoran
Analog Sound

[phector2004]

Did you use this? http://homepage.mac.com/calhoun/.Public/Firefly%20PCB%20Guide%208.pdf

Yup

PCB was a breeze, aside from the pots. The power transformer part could be revised though, as Hammond changed the transformers in 2009... Then again, I could have been careful and looked at the diagram on the transformer box/the website...

Thanks for designing this, btw!

I'm rilly sorry man... but that was the fking funnyest part i ever read regarding amp build i was ROTFL on the part with the 2nd fuse 

Good luck!

Gabriel Tudoran
Analog Sound

thanks! I figure its always better to laugh then cry 

[defaced]

Step drill, homie.  http://www.tuffbob.com/photos/PP_Titanium_Coated_Step_Drill.jpg
Fifteen bucks at harbor freight.

4. Hammond transformers didn't come with mounting screws/nuts... Gee, thanks... (Firefly builders: Get M3 nuts when you order, or similar. I got longer M4 nuts and bolts)

Most trannies don't.  But neither do tube sockets or IEC connectors.

I'm assuming Canadian power is about 110V, but any way to make sure White + grey is the right combo?

Don't assume; measure.  Stick your AC volt meter in the wall and see.  Then use the data sheet to determine how to hook it up. 

Turns out a stray wire strand from one red power cable came out and shorted with the other red while I was desoldering-resoldering the power transformer. Light went off after 1 second and sizzling noise made me yank the power out. Fuse 2 Burnt out. Out of fuses for the moment...

Don't let the HT touch ground.  Bad things happen, but it's not quite as bad as what happens if you're in the circuit. 

[mydementia]

Great post!!  I think those of us who have built a few tube amps have experienced some or all of your frustrations...
Allow me to provide recommendations to the folks who might be afraid of the Firefly project by your 'hurdles'...

1) I bought the pots from Mouser on the rev8 BOM (313-1510F-1M and 313-1510F-250K) - these are standard PCB Mount 16mm pots... these are different, however, from the previous board versions which used 9mm pots (I built two rev4 PCB Fireflies).

2a) Buy a Uni-bit (http://www.harborfreight.com/1-4-quarter-inch-3-4-quarter-inch-high-speed-steel-step-drill-44460.html) and a punch set (http://www.harborfreight.com/knockout-punch-kit-91201.html)
2b) Drill the hole large enough to get the large punch tool in, and punch it out (if you buy the Harbor Freight punch set, throw away the small punch and bolt - it's trash!).

3)  For IEC jacks, use a nibbler (http://www.harborfreight.com/nibbling-cutter-97636.html) - you drill a hole large enough to get the nibbler in, and chomp away - makes nice square holes...

4) True - need to provide nuts - I recommend M3 lock nuts if you bought the bag-o-100 M3 screws in the Firefly BOM.

5) Always confirm the schematic on the box of your power transformer matches your build documentation...

6) Always tin your wires before screwing them into terminals... especially when it's AC wiring!  After tinning - make sure there are no strays sticking out... then install into the terminals.  You'll find the terminals allow MUCH more flexibility when you want to mod this circuit later...

Good luck getting your build working... sounds like you're close!!
Mike

[MikeH]

Rather than try and drill the chassis so the holes for the tubes on top, and the holes on the face plate match up perfectly (and they have to), I just used panel mount pots, jacks and switches with solder lugs and soldered leads to the pcb to give plenty of room for error.  Also allowed more options in terms of where the tubes sat in relation to the trannys.  And I also used a unibit to drill the large holes; they're so damn expensive, but once I finally bit the bullet and got one, I use it ALL the time.

[phector2004]

Unibits are godly. Unfortunately, the home depot near my house only has it up to 1/2". Got one for 20$ and I use it a ton, but I'd need a hole saw kit for anything bigger, and those cost a good 50$. Nibbler is on my to-buy list, but I got impatient this time and started without one. Now I have a bruised palm from tearing the aluminum with pliers.

Good to know the new boards are designed for 16mm pots. A complete newbie would sit there scratching his head for hours trying to get it to fit!

Definitely gonna tin the leads, just to make sure. The power tranny shouldn't have been damaged in the few seconds the amp was shorting, would it? I've seen microwave transformers being driven red hot on youtube and still running after!

[defaced]

Try these on for size, max hole of 1-3/8, http://www.harborfreight.com/2-piece-titanium-nitride-coated-high-speed-steel-step-drills-96275.html.
You'll want some solid restraint with the larger holes.  They can move a chassis and drill with ease. Not fun.   

The PT will likely be fine. 

[phector2004]

Thanks! Those could help with some other projects I have too!

How's Harbor Freight's quality? Never really heard of them before

[defaced]

For 15 bucks you get two bits, who cares? 

It's imported Chinese stuff.  Some of it is good, some of it is junk.  For the hobby builder, these are plenty good, especially if you're drilling aluminum.  I have mainly used mine on 16g cold rolled steel and haven't had an issue. 

[mydementia]

How's Harbor Freight's quality? Never really heard of them before

Agree with defaced about Harbor Freight stuff - some is good... some is crap...
I bought the large HF step-bit set and they suck.  Last year Costco had a two-pack of the 'good' uni-bits for $30... wish I'd bought a pair as my Sears uni-bit has about 7 years of holes on it...

[petemoore]

1. Yup, the right pots or otherwise
PITA Level: 2/5 On this type of build-method.

2. Hole Saw, the right bits go a long way.
PITA Level: 3/5

3. Hard square starts at low RPM, then light pressure and a bit speedier as the bit exits, otherwise the spiral/edge can try to grab more metal than it can chew.
PITA Level: 4/5
4. Mounting tranny is a whole project in and of itself, careful consideration of the safety issues involved may take time to contemplate.
PITA Level: 2/5
5. http://www.hammondmfg.com/263.htm#263newpri
I'm assuming Canadian power is about 110V, but any way to make sure White + grey is the right combo?
PITA Level: 5/5
  Using a wimpy AC output [such as a small 2vAC wall wart], to get the numbers to do the math to find the voltage ratio in order verify whatever the best plan of winding connection actually measures some AC voltage on the secondary that looks like it's in the ballpark enough to be worked with. The math goes...2v...if 2v was [what is the voltage you measure that you'd connect the primary to?]...if this 2v was a different voltage.
  Say 2vac on the primary puts 10vac on the secondary. 2:10 ratio.
  Say 110vac on same primary...that'd be what...550v ! DON't connect the primary to the operating supply, stick with the testing supply from the wimpy transformer wall wart 2vac until the next best plan gets a ballpark voltage.
6. Sizzle sizzle
Short on those stupid screw-in terminals I was uneasy on using. Nothing beats a solid connection, after all...
Turns out a stray wire strand from one red power cable came out and shorted with the other red while I was desoldering-resoldering the power transformer. Light went off after 1 second and sizzling noise made me yank the power out.
  It is wise to test for stray and exact connectivity according to the plan before applying the 'big strong power'. Checking for correctness and non-shorts each time a connection is made...by eye or DMM, never hurts.
  Fuse 2 Burnt out. Out of fuses for the moment...
  Take a break, for a time or two. these things don't go by and schedule per-se', especially 1offs, prototypes etc.
  Any alternative to working amplifier is generally a good choice if time is pressing electronics learning and production simultaneously...she has proven to be most unforgiving when these conditions exist. 

[ddr]

Try these on for size, max hole of 1-3/8, http://www.harborfreight.com/2-piece-titanium-nitride-coated-high-speed-steel-step-drills-96275.html.
You'll want some solid restraint with the larger holes.  They can move a chassis and drill with ease. Not fun.   

Use cutting fluid also:

http://www.grainger.com/Grainger/items/4F963?Pid=search

[PRR]

General-purpose transformers never come with screws. Army wants green chromate, Navy wants stainless, Mercury uses washers, I like old-SAE sizes while much of the world rushes to Metric.

The guy who puts the whole box together will do a lot of screwing and "presumably" has stock of the screws the final customer expects to see.

> I'm assuming Canadian power is about 110V

I would ass-ume it tends near US practice, which is currently a lot closer to 120V than 110V.

You should use the "125V" connection. This will tend to give low final voltage. This is not a "power" amp. If 120V into a 125V tap makes 6.1V come out of the "6.3V" winding, the tube will run just fine. When you come to my house, when the pump is not starting, you will be just-right.

Hammond had to change the tapping because while they have not changed in 50+ years (we been saying "117" since the 1960s), the utility companies started at 100V in 1890, rose to 110V in the 1930s, and nearer 120V in recent decades. Many-many houses are wired at 125V. In the year 2020 most of our walls will be tending toward 125V if not 130V, and the "125V" tap will be the best setting.

Harbor Freight is a junk-shop. You get cheaply-made tools for 1/2 to 1/10th the price of a Good tool. I've been quite happy with their stuff for lightweight work. Most electronics is lightweight by the standards of "real" mechanics and metal-mongers.

[phector2004]

thanks for the heads-up. Pretty interesting too. Any reasons why the increase in voltage? Better transmission nowadays?

would my cheap R**** Sh*** DMM give me a good reading if I set it to AC and plugged it into the power outlet? Or would it fry the fuse? I've been good at doing that since high school, guess soon I'll be an expert 

[defaced]

Should be plenty good.  Input resistance on the voltage setting of a DMM should be in the 1 to 10M range, so run ohms law and see how much current that is at 120vAC.  I'd recommend going to harbor freight and buy 3-5 of their 2-3 dollar DMMs for trashing.  I've actually found them to be pretty ok, and have intentionally trashed them to keep my real meters out of dangerous situations. 

And before someone pipes up about "real meters" and how you should have one, let me get on my soapbox.  I've roasted my works Fluke 87 by doing stupid crap like trying to measure the B+ of the amp while the meter was set to measure resistance.  Bad, bad, bad.  300 dollar paper weight bad.  Good meters can't account for user errors, and tube amps aren't precision devices in the slightest.  +/- 10 percent is plenty accurate to produce a working amp. 

The only thing that really makes tube amps "harder" than pedals is when you screw up, it usually counts and it usually costs lots of money to fix.  Usually. 

[Brymus]

This would have been a good build to power up with the light bulb safety tester,
Sorry I dont have a link but if you try google you should find one on every DIY audio forum.
GEO I think has a diagram how to build one,Duncan Amps,The Amp Garage,ect
Probably one buried in this board too.
You basically use a small wattage bulb to limit the current to your build until it powers up then you give it full power when it doesnt ,sizzle ,sizzle.
Sorry about your troubles.
FWIW the step bit I bought at Lowes or Home Depot IDK which,starts out really small and goes up plenty big for octal sockets too,
I use it for pots,1/4 inch,DC powerjacks as well.
I also got a small needle file set at Ace for 6$ that works amazing for the price,I use it for slide switches and IEC jacks.
Anyplace I need square holes.

[phector2004]

This would have been a good build to power up with the light bulb safety tester,
Sorry I dont have a link but if you try google you should find one on every DIY audio forum.
GEO I think has a diagram how to build one,Duncan Amps,The Amp Garage,ect
Probably one buried in this board too.
You basically use a small wattage bulb to limit the current to your build until it powers up then you give it full power when it doesnt ,sizzle ,sizzle.
Sorry about your troubles.
FWIW the step bit I bought at Lowes or Home Depot IDK which,starts out really small and goes up plenty big for octal sockets too,
I use it for pots,1/4 inch,DC powerjacks as well.
I also got a small needle file set at Ace for 6$ that works amazing for the price,I use it for slide switches and IEC jacks.
Anyplace I need square holes.

http://www.geofex.com/tubeampfaq/tubeampfaq.html
Section 8 if anyone's interested.

Might try it when I get new fuses... IF I'm patient enough 

[davent]

Hello,

Does Harbor Freight exist outside of the US? In Canada (except in PQ last i checked) you can get equally cheap S. Asia junk (and some good stuff) at Princess Auto.  If you want a really good step bit or hand tools in general, a city the size of Montreal must have several dedicated woodworking/machine shop stores where you could pick up a great quality, but not cheap, Irwin bit, in various sizes, that should easily last a lifetime of light aluminum use.

This past Monday at 5pm (peak time of use) with the temp. over 36ºc plus high humidity the voltage out of the wall was still reading just over 120v, i usually measure a bit higher but we're still well up there even with the grid under heavy stress.

dave