Fuse blowing on start up

[STURMJ]

What are the values of the resistors in the R1 position on the large board?  I cant tell by the pict. but on mine the R1 positions on the large board has a smaller resistor  (1/8? watt 31.6 x2). Parts may have changed, but that's what stood out for me.

 

[crappyjones123]

the resistors are 33ohms. the kit does come with 31.6ohm but long story short, i screwed something up and had to use the 33ohms. the 31.6 ohm resistors are otw. the only other thing i can think of i might have done incorrectly are the MJE350s on the smaller boards. i didnt get either with the metal backs (mine have all plastic enclosure) so i checked online to find out which the "back" side was. the way they are soldered in right now - the face that reads mje350 (and has 3 circles) faces away from the leds on both boards. did i get that backwards?

 

[InfernoSTi]

Here is the proper orientation for the MJE 350's without a metal plate.

The great parts famine of 2010 has forced us to look for substitute parts for many of the kits we manufacture. These substitute parts are of equal or better quality, but some look rather different than the original parts we used in producing the assembly manual. The latest case is one that will cause some confusion -

For the past 14 or 15 years we have used MJE 350 transistors that have a "front" black plastic side with the MJE 350 designation printed on it. The other, "back" side of the transistor is metal.
The current batch of Fairchild transistors we purchased do not have a metal side. One side is printed with the MJE 350 designation, and this corresponds to the "front" side of older transistors. It can also be identified by the three small dots imprinted in the plastic around the center hole. The "back" side, that corresponds to the metal side on the old transistors, has a more matte finish with no printing except for one small dot impression.

 

[STURMJ]

33 ohm should be close enough (4%) Everything looks good from the top side. I guess the best thing is to be sure that the wiring is correct.  Are you using .5A fuses or 1A fuses? I had this problem with a early edition of the crack (see my previous thread http://www.bottlehead.com/smf/index.php/topic,677.0.html ) maybe that's it?

 

[crappyjones123]

hmm, i grabbed a handful of 1/2A fast blowing fuses from radio shack. should i get 1/2A slow blow or 1A slow blow now? wonder if that is all that is the issue...

also, the orientation of mje350s is correct in my build in accordance with the post. rechecked all the wires and solder joints again. everything is going where it is supposed to go.

thanks again for all the help guys.

 

[STURMJ]

I would go 1A fast since .5 seems to be the intended fuse,  and it dose not seem to be quite enough (forgive me if I'm wrong). The 1A gives more room, but the fast blow will die faster than slow, if something is REALLY wrong, which has to be a good thing.

 

[Doc B]

should be 1A slo blo

 

[crappyjones123]

running the amp with .5A slow blow. everything works and sounds great. dismantled and reassembled the whole thing 4 times for nothing >< hehe. the speedball kit really does help. moar impressions later need to spend the rest of the day listening to some toones. man this amp sounds great.