Fuse blowing on start up

[timbro52]

This is my 3rd Bottlehead kit and i've made my share of goofy mistakes. But for the life of me I can't figure out what I have or haven't done this time (and no I'm not on crack, yet). Checked all my solder joints, resistance test is fine, but when I flip the switch I blow the fuse. Anyone out there with suggestions would be greatly appreciated.

Thanks,

Tim

[Doc B.]

If it's one of the first run of the kit there may be errors in the manual:

http://www.bottlehead.com/smf/index.php/topic,657.0.html

[Grainger49]

If the above is not the problem recheck the direction of the diodes.  Then check the power supply capacitors and be certain the stripe is on the side indicated in the pictures.  Doc puts excellent pictures in his manuals. 

[timbro52]

Thanks Doc and Grainger, 

I have the newer manual and the diodes are correct and the caps as well.
I guess I'll check all my solder joint again.
Thanks,

Tim

[Grainger49]

The fuse blowing indicates high current.  That could also be a short in the power supply.  Possibly a piece of wire that was cut landed in the wrong place. 

If you find nothing try pulling the tubes and then turning it on.  You can leave it on for a few seconds and then check the fuse. 

[timbro52]

Thanks Grainger,

I'll give it a try. By power supply do you mean the transformer? If that's the case I don't see any lose, stray, or miss placed wires.
If the fuse doesn't blow with the tubes out where does that leave me? I realize this is a process of elimination but I'm a newbie to this stuff.
I'm out of fuses, so it's off to the hardware store.

Thanks again,

Tim

[Grainger49]

By power supply I mean the transformer (not likely), the diodes, the capacitors or the heater circuit.

If the fuse doesn't blow with the tubes out it indicates a problem around or in the tube.  It could be a shorted tube or a problem with the plate or cathode circuit.

[Paul Birkeland]

Hello Tim, did you double check the orientation of the power supply capacitors?  How are the resistance checks?

[levlhed]

I am wondering where can I get these fuses?
I had the first one ever blow (and it really really freaked me out for a bit....I couldn't figure out what happened!)  Still not sure really, other than I was plugging/unplugging/rearranging things and it must have been a result of that somehow.
I was able to rob a fuse from one of my DJ lights (250v, slightly lower rating though) and I went and bought what I thought were the right ones @ Radio Shack, only to find they are too big!  I guess they are 1.5" and I need 1"? 

Where is a common place to find the right ones?

I need to use my DJ lights this weekend...

[ironbut]

Hi Dan,

My local Radio Shack has the right fuses on and off. I usually have to dig through the fuse drawer to find what I need.
Now days I stock up and buy them from Amazon (what don't they sell!). If you just search for slow blow fuses it brings up about 4 pages.
I have Amazon Prime so I can get stuff shipped "2 day" to me for almost nothing.
Sign up for the free trial for Prime and you'll get like me. I buy my socks, underwear, tennis shoes, computer stuff ,.. well, you get the idea.
Now, all I need to do is figure out where I put things like fuses.

[levlhed]

what are the full specs I should be looking for?

It occurred to me that the fuse that came with mine may not be "stock".

[ironbut]

Here's the ones from Amazon (I don't know what's up with the price since they were under $2 for a pack of 5 when I bought some a while back).
They actually come from Parts Express where they're still $1.29 a pack but you'd have to pay extra for fast shipping.

http://www.amazon.com/Littelfuse-500mA-Type-20mm-Slo-Blo/dp/B000XPT21A/ref=sr_1_38?ie=UTF8&s=electronics&qid=1283379471&sr=8-38

[levlhed]

local Radio Shack had what I needed, I just didn't look hard enough.
thank you!

[Grainger49]

I bet that the parts list has a good description of the ratings and type fuse that is included.

[levlhed]

Probably, but I didn't get a parts list with mine.  I bought the already-built Speedball prototype that was @ CanJam.