Ampeg B200R Blowing fuses

[Enzo]

I don't know why you wouldn;t use a desoldering station on these or any other parts. A desoldering station is just a soldering iron with a hole in the end that sucks solder. The circuit board doesn;t know whether your iron has a suck hole or if you have a suck tool next to your iron.

[g1]

Maybe the caution was to do with static and mosfet's? But the same would apply to a regular solder iron. They are static sensitive devices and should be handled with caution.

[J M Fahey]

FWIW I never ever blew a Mosfet with static, only by *grossly* overheating them and a couple by untamed fierce oscillation, probably in the UHF range.
Rough beasts

[jpfx88]

So I got my new mosfets in and I am going to do the ole light bulb trick to check for more shorts. My question is, is it ok to test amp without a load (not hooking speaker to it)?

[Enzo]

Not only is it OK to run the amp without a load, it is important that you do it that way until we know the amp is stable and not making DC.

[jpfx88]

Thanks,
That's what I thought but just wanted some reassurance.

[jpfx88]

So I realized the only 100w bulb I had at home is blown, I went to go get another but can't seem to find anything thats truly 100w. They are all 100w "equivalent", which means they provide the same light but only use 72w. Is it cool to use that or do I need to keep hunting for some other suitable replacement for test?

[Jazz P Bass]

You do not require a 100 watt bulb for static voltage checks.
(if the amp draws 100 watts at idle, something is seriously amiss)
I use a 60 watter.

It must be an incandecent bulb (a filament).
CFC lamps won't cut it.

[J M Fahey]

If the "100W equivalent" 72W lamp is the kind which has a small filament inside a small transparent glass bulb enclosed in a larger, "standard 100W lamp" glass envelope it´s fine, only actual rating is 72W but no problem with that.
A compact fluorescent lamp (CFL) made out of pencil thin white glass tubes is NOT what you need.

FWIW I haven´t actually needed it yet (still have a small stash of 100W filament lamps) but for the near future I´m considering a lamp liliter based on "pencil" quartz lamps.

[jpfx88]

Yea, I knew it needed to be an incandescent bulb but wasn't sure how much you could vary on the wattage. I am going to try the 60w bulb because that's what I have at home, everyone agree that this 200w amp should do fine at idle with that?

[bsco]

If it is just sitting there with no signal going through it that should be fine.....if everything in your amp is ok the blub will probably light bright when you first turn it on and as the capacitors charge, the blub will go dim and may even go out....if you turn up the volumes a bit and try to pump a signal through you will find that the lamp will glow...if the blub lights bright and stays bright you have a major short somewhere...

[jpfx88]

so ive still got a short somewhere apparently, the bulb glows then just kind of idles at the same brightness and occasionally pulsates a bit. I've checked around trying to find other shorts with no luck, any ideas as to where i might go from here?

[bsco]

what is the wattage of the blub you are using?? I pull the fuse and connect the lamp in it's place...I'll see if I have the schematic......

[jpfx88]

I was able to come across a 100w bulb, at least thats what it says anyway and I already have the bulb in place of the fuse.
Here is the schem if you want to look it over and see what you think.

[bsco]

Thanks for the schematic.....I didn't have it......you replaced the output transistors right??? where the originals, shorted???.....are there mica insulators between the output transistors and the heat sink??....... if so, are they good????......when you turn the amp on, it should light briefly, then go out...do not connect a speaker to the output.....I am no expert but I would start at the beginning........I would remove the four mosfet transistors completely from the circuit and then turn on the power.....now....does the blub stay lit this time??

P.S. It is after midnight here now and I have been on the go since 6 AM....I'll check in with you tomorrow.....I have got to crash out....