Question about the fuse value for the Kaiju

[ebag4]

It appears that we now have 3 confirmed builds blowing fuses at the recommended value starting with the HV test.  From the builds reported I believe that is 100%.  What value fuse did the builds for Doc's amps end up with and if still 1.5 what is the difference between those and our amps?

Thanks,
Ed

[fullheadofnothing]

1.5A being used at BHHQ.

My best guess is that since the most convenient power input on the bench is the variac, first power-ups have been gradual rather than being slammed with the sudden inrush that they are at homes. Furthermore, the variac isn't going to overvoltage like what might be coming out of your wall. I still think this problem is limited to when the caps are still being formed, so when plugged in other locations (such as in the house system rather than the lab), the 1.5A holds.

[Doc B.]

I am at home, and thus away from the amps. As far as I know the amps at BHQ have stock 1.5A fuses in them. I have previously suggested trying 1.5A or 2A slo blo if the stock fuse is not working for you. I have seen this phenomenon of fuses blowing on delivered kits when the specified fuse holds just fine on our prototype with other kits over the years. I have no theory as to why this happens, and Josh's idea that the first start on the Kaiju prototypes was made gentle by the Variac is probably the most solid theory. My original production prototype 1994 version S.E.X. amps still work too and yet all the others seem to have blown their power transformers. Perhaps I naturally emanate a current inrush surge suppression field.

Anyway, try the slo-blo. Once you get past that first power-on the current inrush seems to abate a bit as the caps form.

[ebag4]

Thanks guys.  I have to use 2 amp slo blo in mine, standard 1.6 and 2 amp blow immediately.  My amp has been running for a week, about 60 hrs. so far, so no issue from caps charging now.  I also noticed that a standard 2 amp would hold through the HV test, but once I put the 300bs in, I had to go with a slo blo.  As an FYI my household voltage runs about 121v, since we were talking about bringing up the voltage gradually via a variac.

No issue, just curious as to where the difference might be.

Best,
Ed

[drewh1]

Thanks for getting a clarification on this Ed. I need to order some 2a slo blo fuses I guess

[mpdd]

I finished my Kaiju tonight, the 1.5A fuse survived all the voltage tests but when I plugged it in it blew a fuse. I replaced the 1.5 with the second 1.5 and got about 30 seconds into "The Well" before the second fuse blew. I'll pick up some 2.0 Slo Blo tomorrow.
A great kit. Thanks Bottlehead.

[mpdd]

The Kaiju blew two 2.0 Slo Blo tonight and a 3.0. I don't want to put in another higher value fuse. Where should I start looking?
There were no problems at the glow test, I did have some trouble at the driver test, I'd left a piece off one of the circuit boards. After that it tested fine.
It ran for about 2-3 minutes tonight before blowing the 3.0 Slo Blo.

[Doc B.]

A slo-blo failing after 2 minutes is odd behavior. It could be a connection that is shorting or opening as the amp warms up. I suspect you will have to measure voltages again to know what is going on. It might also be worth reflowing any suspicious looking joints.