gk800rb

oo3 · 11-11-2009, 08:18 PM

so a shorted speaker cable crawled into my cable case - i then used it with the gk 800rb and of course blew the fuse - so far i have only found 1 shorted output - Q20 - plan on replacing it and Q24 - what else would you check? - hmmm i see they use the same outputs in the 100wt section for biamp i dont use --no no,i wont do that - on side note - about 1/3 of amp set on end in katrina water for about 1 day - cleaned it up and working fine until now - oo3

Enzo · 11-12-2009, 12:32 AM

If an output transistor blows, then always check the resistors associated with it. No schematic handy, but I assume there are some ballast resistors - the 0.22 ohm or whatever types. And then we always want to check the driver transistors.

Work with NO speaker load until you know the amp is not blowing fuses and not putting DC on the output.

This is exactly the case where you want to bring the amp up on a variac while watching the mains current.

oo3 · 11-13-2009, 06:31 PM

thank you for input - i am out of practice in this area - checking some more still only finding the one transistor shorted - will have to order some parts - oo3

grooveman1961 · 11-23-2009, 05:15 PM

I work on these alot...

I would recomend r48, 49, 50, they make test ok, but you may want to look on the potted side for cracks or discoloration,maybe consider just replacing them since you have to unsolder one side anyway.... also D10, R47,51

Also, a 60 watt light bulb in series with the transformer primary will keep you from reinjuring your newly installed components if you've missed something. ( unless you have the aforementioned variac and amp meter)

Phostenix · 11-23-2009, 08:20 PM

Quote:

Originally Posted by grooveman1961

Also, a 60 watt light bulb in series with the transformer primary will keep you from reinjuring your newly installed components if you've missed something.

Hmm. Seems like I've heard about that somewhere....

grooveman1961 · 11-23-2009, 08:33 PM

Quote:

Originally Posted by Phostenix

Hmm. Seems like I've heard about that somewhere....

Yeah, back in the day when i was so broke I couldn't pay attention, I started working on a blown rb800 that I bought as a box of parts. I can't remember where I saw it either, but I made a rig with a ceramic bulb base. It saved me alot of parts.

It may seem hokie, but it works.

Enzo · 11-23-2009, 08:46 PM

Hi groove, welcome to the forum. I think Phos is funning with you a little. "Light Bulb Limiter" is a favorite around here.

grooveman1961 · 11-23-2009, 08:52 PM

Quote:

Originally Posted by Enzo

Hi groove, welcome to the forum. I think Phos is funning with you a little. "Light Bulb Limiter" is a favorite around here.

I'll take your word for it.

Phostenix · 11-23-2009, 11:12 PM

Quote:

Originally Posted by grooveman1961

Yeah, back in the day when i was so broke I couldn't pay attention, I started working on a blown rb800 that I bought as a box of parts. I can't remember where I saw it either, but I made a rig with a ceramic bulb base. It saved me alot of parts.

It may seem hokie, but it works.

I was thinking more of this:
Acoustic 370 blows internal fuse when turned on

As always, Enzo is right.

11-11-2009, 08:18 PM	#1
oo3 Junior Member Join Date: Aug 2008 Location: nola Posts: 6	gk800rb so a shorted speaker cable crawled into my cable case - i then used it with the gk 800rb and of course blew the fuse - so far i have only found 1 shorted output - Q20 - plan on replacing it and Q24 - what else would you check? - hmmm i see they use the same outputs in the 100wt section for biamp i dont use --no no,i wont do that - on side note - about 1/3 of amp set on end in katrina water for about 1 day - cleaned it up and working fine until now - oo3

11-12-2009, 12:32 AM	#2
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,332	If an output transistor blows, then always check the resistors associated with it. No schematic handy, but I assume there are some ballast resistors - the 0.22 ohm or whatever types. And then we always want to check the driver transistors. Work with NO speaker load until you know the amp is not blowing fuses and not putting DC on the output. This is exactly the case where you want to bring the amp up on a variac while watching the mains current. __________________ Education is what you're left with after you have forgotten what you have learned.

11-23-2009, 05:15 PM	#4
grooveman1961 Junior Member Join Date: May 2009 Location: Minnesota Posts: 7	I work on these alot... I would recomend r48, 49, 50, they make test ok, but you may want to look on the potted side for cracks or discoloration,maybe consider just replacing them since you have to unsolder one side anyway.... also D10, R47,51 Also, a 60 watt light bulb in series with the transformer primary will keep you from reinjuring your newly installed components if you've missed something. ( unless you have the aforementioned variac and amp meter) Last edited by grooveman1961; 11-23-2009 at 05:26 PM.

11-23-2009, 08:46 PM	#7
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,332	Hi groove, welcome to the forum. I think Phos is funning with you a little. "Light Bulb Limiter" is a favorite around here. __________________ Education is what you're left with after you have forgotten what you have learned.

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11-13-2009, 06:31 PM	#3
oo3 Junior Member Join Date: Aug 2008 Location: nola Posts: 6	thank you for input - i am out of practice in this area - checking some more still only finding the one transistor shorted - will have to order some parts - oo3

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