Nooo! Almost have this amp built!

[andry1]

So I ordered one of the STA-45 kits from Lighthouse Electric a little while ago. Ended up getting here on Thursday and I've been putting it together on and off during the weekend.

I'm pretty sure that the kit didn't include all the right parts... looked like I had a few too many of one type of resistor and not enough of another, and I had a missing stand-off screw, but that wasn't too big of a deal.

In any case, a couple trips to radio shack to refill my supply of spare resistors and misc. wiring/etc., many hours, and a lot of profanity later, I get to the point where I can try to start running some tests with the multimeter while it's plugged in and live.

Get through about halfway, and much to my surprise, everything is checking out. "Sweet! It's all down hill from here, I'll be listening to some sweet, sweet, tube goodness in no time flat!" I say to myself.

Next test, put the probes in the right place, flip the power switch, flip the standby... *pop* down one fuse.

Checked a few other things, re-did a few connections just to be sure, wash, rinse, repeat... and I kiss the four extra fuses I picked up earlier goodbye.

Of course, about two seconds after I toss the last fuse out, I notice that I had a wire very obviously soldered into the wrong place that I had missed before somehow.

I'm pretty sure that woulda fixed it, but radio shack is closed and I'm out of fuses

*sigh* There's always tomorrow...

[nigelwright7557]

Originally posted by andry1
So I ordered one of the STA-45 kits from Lighthouse Electric a little while ago. Ended up getting here on Thursday and I've been putting it together on and off during the weekend.

I'm pretty sure that the kit didn't include all the right parts... looked like I had a few too many of one type of resistor and not enough of another, and I had a missing stand-off screw, but that wasn't too big of a deal.

In any case, a couple trips to radio shack to refill my supply of spare resistors and misc. wiring/etc., many hours, and a lot of profanity later, I get to the point where I can try to start running some tests with the multimeter while it's plugged in and live.

Get through about halfway, and much to my surprise, everything is checking out. "Sweet! It's all down hill from here, I'll be listening to some sweet, sweet, tube goodness in no time flat!" I say to myself.

Next test, put the probes in the right place, flip the power switch, flip the standby... *pop* down one fuse.

Checked a few other things, re-did a few connections just to be sure, wash, rinse, repeat... and I kiss the four extra fuses I picked up earlier goodbye.

Of course, about two seconds after I toss the last fuse out, I notice that I had a wire very obviously soldered into the wrong place that I had missed before somehow.

I'm pretty sure that woulda fixed it, but radio shack is closed and I'm out of fuses

*sigh* There's always tomorrow...

With new builds you have to check and check again all components and connections. Its tedious but saves on blown up components and fuses.

[astouffer]

radio shack is closed and I'm out of fuses

What do you think aluminum foil is for

[DigitalJunkie]

Just don't use a bolt like my friend did on a PC PSU..A small fire ensued!

I've managed to take a single strand from a piece of stranded wire,and solder it back into the fuse body..usually good enough for lower current applications.

[andry1]

Lol... I have to admit, in the true spirit of diy I considered "just making it work," so to speak, but as it was getting late and I had been staring at (by my estimation) 1.8 quadrillion tiny little wires soldered to an equal number of tiny little terminals and had managed to miss a fairly obvious mis-wiring problem... Well, I decided discretion was the better part of valor, and decided to just hit radio shack on the way home from work today

[tubelab.com]

What do you think aluminum foil is for.... Just don't use a bolt like my friend did on a PC PSU..

In my days as a repair tech at a stereo store I made the discovery that a volume control shaft fits perfectly. Clarostat made replacement controls with scored shafts that could be snapped off at most of the common lengths. The leftover portion was exactly the same length and diameter as a fuse. I used one to find the intermittent short in my old Pontiac. After the fire gods danced around on the AC fan speed switch it was obvious where the short used to be.

Note: I was young and stupid when I did this. I am not young anymore!

[Pyre]

Originally posted by astouffer


What do you think aluminum foil is for

And for the real adventurous a .22 long cartridge. Had an old second hand dodge truck that employed three of them in the fuse box until I saw them and had a minor stroke.

[gingertube]

Pyre,

.22 cartridge as a fuse !!!!

The previous owner of your truck obviously missed the "Myth Busters" episode where they showed that a .22 cartridge used as a fuse DOES fire in a fault current situation. A "Self Annunciating" fuse.

As my reactionary old coot of a grandpa used to say, someone should have put a "Warning Shot" through his ears.

As they say on all those shows:
"Kiddies - DO NOT TRY THIS AT HOME".

Jokes aside - this is incredibly dangerous. Given a short circuit in that line the bullet WILL explode.

Cheers,
Ian

[Wavebourn]

Originally posted by gingertube

Jokes aside - this is incredibly dangerous. Given a short circuit in that line the bullet WILL explode.

Probably that's why modern fuses for cars have so different shape.


When I was a kid there were books for DYIers with tables of correspondence of wire diameters to currents, so it was easy to make a fuse from scratch... I remembered lot of useful numbers... However, when I got my MS EE diploma I forgot all that simple tables...

[andry1]

Well I sure am glad I didn't have any .22 cartridges lying around

On the upside, I hit Radio Shack on the way home last night and I think bought every 0.5 amp fuse they had "just in case" (knowing full well that by doing so I'd only need the one).

And, of course, I only needed the one .

So now I have a working STA-45 amp! Well... one channel's worth, anyway. I've got a short in one of the RCA jacks (I'm about 99% sure that's what it is, anyway). Not surprising given that in order to connect it to the pots and pre-amp board it involves soldering this impossibly thin, stranded speaker wire and it's even more impossibly thin, stranded shielding to two bits of the back of the jack that are about half a nanometer apart. That shielding tends to get unruly and go everywhere.

I was thinking of just redoing all the runs that involved the shielded speaker cable that came with the kit with CAT5, which I have tons of lying around the house and is serving as pretty decent speaker cable elsewhere in my system right now.

Anyone ever tried that? If I'm going to be building more of these sorts of things in the future, I'd definitely like to find an alternative to the audio signal wire that came with this kit that would prove to be a little easier to work with.