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Diagrama del circuito Gallien-Krueger 800RB - GallienKrueger Gallien Krueger 800rb

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Repeatedly blows fuses

It's probably not your outlet, but try to get it into another one so you are sure.
It could probably be that something is wired short, so the amp draws extra amperes, therefore blows fuses.

Feb 27, 2014 | GallienKrueger Gallien Krueger 800rb

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I just bought an 800RB (been WANTING one for DECADES, finally put "cash-on-hand" together with "the SWEET one came along"). I want to know if the speaker jacks for the 300-watt amp are...

Here is the schematic AND everything you need to know about the speakers:

Scroll down to "Get Manual" on the site and click on it to download. It appears that the MINIMUM impedance on the trebel upper set is 8 ohms and MINIMU on the woofer is 4 ohms at the jack in each case.

Apr 26, 2011 | GallienKrueger Gallien Krueger 800rb

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Hello I have GK 1001 bass amp that stoped workirepng. I removed it from the case to get at the circuit board. Once I got down to the component level I descovered that several of the power transisors...

Yep... happens all the time. That is why I cold start an amp like this with an incandescent lamp in series to act as a current limiter. I will tell you what is wrong. You did NOT go back far enough in finding the bad parts. Also some that were not shorted MAY have been degraded. The real problem lies in the driver transistors and the bias regulating circuit and the transistors in that area. This amp has a mass number of components and there are many that if they fail they wipe out a bunch. When you think you have it repaired run it a while with a 150 Watt light bulb in series with the power input cord. Here is your schematic:

Scroll down to the link "Get Manual" and click to download. In the schematic there are over twenty transistors involved with power output and bias stability. This is one of the most complex amps I have seen. They get voltage capability by having two series banks of transistors to each voltage rail. The biasing network is a nightmare!!! Pot R28 sets the rest bias which you measure between J5-1 and J5-2 which is 1/3 of the rest current across a total of .4 ohms... whatever it is supposed to be. Q3, Q7, Q16 and Q17 are ALL real critical to the biasing as well as the smaller Q12 and Q13 and all the others. The problem when you have a feedback amplifier is if any of these components are sick, the feedback will still attempt to balance the amp even though it sloowly fries other parts. Frankly, this is going to be a miserable one to fix. Use the light bulb trick and a Variac. There are a few voltages marked n the schematic USE THEM TO CHECK the operation. When certain transistors go, they will take a bunch with them... NOTICE the FUSIBLE resistors up near the rails a couple stages back... need to check all of those and replace with IDENTICAL ones if they are blown or way off value. There are a lot of Zener diodes that ALL need to be checked as they afect the bias levels. You will need nearly full voltage during checking which really makes it tough. With the light bulb if too much current is drawn from the line the light will light absorbing the power line voltage. The light should remain off when repaired AND voltages should be near what is shown on the schematic. I would expect to see half the rail voltage across each of the sets within the banks when at idle. Good luck... from an electrical engineer with 50 years exp.

Apr 17, 2011 | GallienKrueger Gallien Krueger 800rb

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I have a Gallien Krueger Backline 600 head rigged to a GK Blackloine 410 BLX-II cab. There is a crackle sound emitting from all the speakers, so I'm guessing there is something wrong with the head. Have...

i) If the crackle is there with all input signal cables removed, then likely to be the head.

ii) Does the crackle vary noisily with control settings? If so, move noisy control to & fro about 10 times to wipe any dirt from internals (temporary solution).

iii) If ii) is not a problem, then tap head casing to check whether a dry solder joint or poor internal connection is the cause. Was unit dropped?

iv) If none of the above, then suspect possible component breakdown.

Jan 24, 2011 | GallienKrueger Gallien Krueger Backline...

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I would like to buy and convert a Gallien Krueger 800RB bass head from 110Vac to 240Vac operation. Do the new ones have multi tap primary windings at the transformers that can be converted to accept...

GK does have a version that runs under 240Vac, but it may not be available in the US. I would check with GK directly. Also, an option would be to use a tramsformer for this unit. These are available for around $50 or so for the power requirements of the GK unit. This would allow you to use the amp at either 240 or 110 without the need to change anything inside which would void any warranty.


Nov 02, 2010 | GallienKrueger Gallien Krueger 800rb

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If you drive it too hard or block airflow, it may be protecting itself against overheating by turning off.

Sep 16, 2010 | GallienKrueger Gallien Krueger 800rb

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Last weekend while I was playing, I smelled that smell. After I turned my 800RB bass amp off I saw smoke coming out of the foot switch input so I hooked up my spare amp. When I took the amp apart I found...

They are NOT called motherboards, just circuit boards.

Sometimes the board can be restored by carving out the black and re-insulating it and repairing the cause and bad components.

Likely the power transistors have shorted that are associated with that side and burned compnents.

Many shops will only replace the whole board rather than do the labor to restore the board... Yes, either way it will be expensive to repair.

Causes of these failures can be overdriving the amp. bad speakers and or cables. Loose speaker connectors that vibrate can lead to this.

Another problem can be if SUPERSONIC (can't hear it) feedback is occuring at high frequencies that overloads the amp.

Aug 08, 2010 | GallienKrueger Gallien Krueger 800rb

1 Answer

My 800-rb won't power up.Nothing lights up...checked fuse and its ok.

Starting point is to open the unit and verify first that the +/- 60 volt power supplies and the +/- 85 volt supplies are producing.

Next check the +/- 15 volt regulators.

You will likely find one or more of these supplies are defective.

Cause could be blown parts or cracks in circuitboard or bad wiring.

Jul 12, 2010 | GallienKrueger Gallien Krueger 800rb

1 Answer

Hola,tengo un yamaha portasound PSS-290 que no funciona, necesitaría el diagrama del circuito para repararlo.Gracias

Just to help I can translate this: Hello, I have a Yamaha Portasound PSS 290 which does not work. I need a circuit diagram to repair it, thank you.

Apr 16, 2010 | Music

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