Can sub assemblies be tested during a build?

Bob Simpson · Post by **Bob Simpson** » Mon Jun 29, 2009 4:32 pm

I'm thinking about checking the OT/PT/filter cap board, bias supply, relay power and relays...

Just to make sure they're working before putting the whole thing together.

Is this a bad idea, or would harm come to parts like that?

Bob

Structo · Post by **Structo** » Mon Jun 29, 2009 5:12 pm

It may be just me but I just verify that they are wired right about three or four times then put them in the amp.

I like to use a light bulb limiter when first firing up an amp just to be on the safe side.

If the bulb stays brightly lit, you have a short in the power supply or some other heavy current draw.

Baxtercat · Post by **Baxtercat** » Mon Jun 29, 2009 5:45 pm

Structo, that about describes exactly what I've done on the 4 or 5 scratch-builts I've made [mostly from yard sale and Goodwill salvage].

Look over the connections like a proofreader, plug it into the lite bulb limiter, say hail Mary, and flip the switch. For some reason every one has worked! [I probably shouldn't have said that. Now the next one will fizzle.]

Structo · Post by **Structo** » Mon Jun 29, 2009 6:31 pm

Heheheheh, yeah that is the moment of truth for sure.

It's like you are flipping the switch to a potential bomb!

For sure an anxious few seconds on the first power up.

M Fowler · Post by **M Fowler** » Mon Jun 29, 2009 8:08 pm

I also look mine over very carefully.

You can build the amp in stages starting with the power supply then test that, then test the rectifier stage, and so forth. I think most of us just build the whole thing at once because we are so sure of our selves, right!

Mark

Andy Le Blanc · Post by **Andy Le Blanc** » Mon Jun 29, 2009 8:31 pm

Test as you build, heaters, supply, powerside , inverter, etc....
I haven't had the experience of needing a bulb limiter this way.

Cygnus X1 · Post by **Cygnus X1** » Mon Jun 29, 2009 10:33 pm

I too...also...as well.
Double, triple check, and then I sleep on it.

So usually what happens is this-I wake up very early on Saturday morning (try 3-4 AM). This is MY time, when no one messes with me.
By the time I have half a pot 'o Joe it's 7:00 and I have examined everything for the powerup.

I'll make things as quiet as I can, start to fire it up, then right as I'm about to throw the switch I hear...

KEVIN!
THE COFFEE IS COLD!!!!

ZAP-the wife is up and the noise routine starts "I had a dream"....blah blah...
Love the gal, but she wakes up talking, and talking, and talking.
And I feel an urge to just walk away from the amp!

Now you know why I wake up so early to squeeze in my quiet time.

Uh, no-I don't test subassemblies and almost never had a bad startup.
Except one big one 15 years ago.
That's a whole other story.

Structo · Post by **Structo** » Tue Jun 30, 2009 12:25 am

Cygnus X1 wrote:
ZAP-the wife is up and the noise routine starts "I had a dream"....blah blah...
Love the gal, but she wakes up talking, and talking, and talking.

BAWAHAWAHAWAHAWA!!

OMG!!!

That is exactly how my wife is.
I never remember my dreams but she always does and feels compelled to tell me all about it.
Then asks, I wonder what it means.......?

Dunno, as I shuffle off to my "man cave".

As a side note, I guess I do allow some testing as far as continuity on under the board jumpers and such because they are such a bear to fix once the board is in.

Cygnus X1 · Post by **Cygnus X1** » Tue Jun 30, 2009 7:30 pm

Well I should clarify.
I do use the ohm/multimeter and poke around to see what the grounds are doing.
But testing sub assemblies, not really.

I do give it a very close eyeball inspection before power up.

tubeswell · Post by **tubeswell** » Wed Jul 08, 2009 7:07 pm

Man this thread pushes buttons for me. I love my wife and my kids, and I love building tube amps. How difficult can it be? right? All I wanna do right now is finish the amp I'm currently brewing, but I worked on it all day yesterday and half the day before and I know if I start on it again today (Its just gone 6:45am here - well it was 5:45 when I started this morning), and I know that if I keep going on it I won't be able to stop until way past dinner time, (and house keeping time, and family time). But the thing is that the more complete it gets, the more I wanna complete it. I get figitty when the amp gets to 90% complete, so how much longer will it take, another day? two? and then there's the troubleshooting - what's that; a week? (or two?) of completely absorbing weekends.

Baxtercat · Post by **Baxtercat** » Wed Jul 08, 2009 9:59 pm

brutha, that looks good. Stainless chassis, I suppose? Can't wait to see the front w/ that covering.

Yeah, it takes forever......and then someone inevitably says if I like it so much, why I don't quit my job and just make amps. I tell them 'Yes, if you'd like to work for 50 cents an hour!'

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Can sub assemblies be tested during a build?

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