Rotel RB-1010 power amp varistor! - Page 2 - diyAudio
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Old 13th August 2011, 12:16 PM   #11
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Default Fuses blowing!!!!

Hi all!

Tested the varistors and perfect with the suggested message from bob!

Now I have a very different problem! Decided to put the amp back togeather and test it!

So made all the neccessary connections speakers etc and powered it up! The lights came on but there was no click from the two protection relays and no sound!

I switched it off and on furhter inspection found two fuses to be blown inside the amp which were mounted on a board with 4 other fuses! these are directly connected to a rectifier and six big capacitors! changed the two fuses and selected all the correct ratings for the others as they were all wrong and then switched on again! This time one of the other fuses blew ( connected to the mains transformer, power switch, and mains lead supply) and no power at all dead!

I then changed top fuse and left the other two fuses out and the lights came on again!

Does anyone have any idea what the problem could be? I have read that blown rectifiers or shorted caps can cause this to happen but I guess the relevant question is why did it go in the first place!

Any help would be greatly appreciated!

Cheers! Ross!
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Old 13th August 2011, 07:53 PM   #12
burbeck is offline burbeck  United Kingdom
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hi Ross
never apply power to a 'repaired' amp with speakers connected or straight to the mains. this is a definate recipe for disaster.

as stated earlier this is a sofisticated amp and is not the sort of thing to cut your teeth on. the fault cannot be guessed at or by pulling parts and testing them. the job needs to be worked through methodacally, requiring a good level of understanding, skill and competence.

this is not a slur but an observation, i am very worried about your safety. for example fuse F801 is the mains fuse and is live at all times

which fuses are blowing F801 to F806 ? the answer to this is will narrow the problem down a bit

still think it is time for a technician
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bob
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Old 18th August 2011, 03:00 PM   #13
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Default Amp blowing fuses!

Hi folks!

Have recently rebuilt the amplifier after testing the diodes strings which tested correctly!

I now have a different problem! The amp blows 2 fuses immediately when I press the power switch! I have replaced many components and if you look through this thread you should get some idea as to waht exactly has been replaced.

Recently I have tested a rectifier and the components linked to it and they were all fine! I also replaced the six smoothing capacitors with brand new ones and still the same problem!

Does anybody have any ideas as to what could be causing the problem?

Cheers! Ross
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Old 18th August 2011, 03:18 PM   #14
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Default reply to bobs post!

Sorry bob didnt spot your reply!

Blowing fuses are as follows:

F802, F803

I appreciate what your saying about my safety and the complexty of the problem! right now I am pretty much at a dead end anyway! I had thought that there might possibly be a simpler answer as to why it is not working but that is not proving to be the case!

Any glimmer of light on the issue would be aprecciated!

Cheers bob and thanks for your help on this problem!
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Old 18th August 2011, 04:44 PM   #15
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Hi,
I checked the spec for the SVD4S and it is a zener diode 2.4V 1 ma. You said that you can not buy it. I found one that it is possible that you can use it. The BZX552v4 and is available in Mouser. In the spec it is show that the package is a 84. It looks like the diode is in a terminal lug so you can mount it in a chassis with an screw. My suggestion is buy it and glue it using RTV through the lug you crimp the wire. They are using it to compensate accordingly to temperature changes.
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Old 18th August 2011, 06:59 PM   #16
burbeck is offline burbeck  United Kingdom
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hi Ross
the fuses f802 and f803 are the HT fuses for the power output stage, for both channels.

i think that they are rated at 6.3A, these blowing has almost certainly damaged more components, possibly the same ones you have replaced.

this highlights what i said about the test setup using a mains lamp, this would have saved the fuses and any other parts from blowing again.

as to a glimmer of light on the problem, here is the very basics.

are you sure that only one channel is faulty?

i would first of all be sure of this, split the problem in half, that way already we are narrowing it down.

when i was sure of the channel that was good the next step is to remove and test all the semiconductors diodes and transistors and check they are the correct types and test them, working your way through methodacally,

when satisfied test the amp with 1 Amp fuses on the HT and the light bulb.
if the protect relay does not engage (click) then fault find.

as stated before this is the very basics. i cannot emphasis enough that this is a complex amp and cannot be repaired by willy nilly guess work.
time for a technician, please be safe
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bob
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Old 19th August 2011, 04:19 AM   #17
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Have u replaced any power transistors... If so, have u checked that they/any of them is not shorting to the heatsink.

Gajanan Phadte
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Old 22nd August 2011, 07:45 PM   #18
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Hi!

Sorry for the late reply! replaced power transistors on one channel and made sure that none were shorting to the heatsinks!


Hi Bob!

I will try what you have suggested and see what I can find if anything! many thanks again for the help provided!


Cheers Ross!
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Old 20th October 2011, 08:57 PM   #19
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Default Excess circuit board heat etc!

Hi everbody!

I managed to get the rotel working back at the start of september and have used it a couple of times and seems to work fine but I have two things that are concerning me and these are as follows:-

1.)The unit has one main circuit board which contains most of the amps running gear and a small circuit board which is attached directly to the end of it. When the amp is switched on the small circuit board starts to produce what I would call an unusual amount of heat. There is a power supply for this board which also produces a lot of heat. It will start to do this within the first five minutes of use whether the amp is producing sound or not. The rest of the amplifier remains cool and even after use at moderate volume levels remains this way.
2.)I have used the amplifier with both 4 and 8 ohm speakers but when the volume is increased using the 4 ohm units it can only power them to a moderate volume before the protection circuit cuts in. My old amplifier is a less powerful unit but is considerably louder and seems more able to drive the 4 ohm units (why?). Both amps are rated to be able to drive 4 ohm speakers.

I have made all the relevant voltage tests with a multimeter as described on the schematic and they all test fine and seem to be within the given tolerance ratings! I just wondered if anybody might have experienced a similar sort of problem or even whether somebody had actually owned one of these themselves and new how it should operate when it is functioning properly.

Any help or suggestions greatly appreciated!

Many thanks!

Ross!
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Old 16th June 2012, 10:40 PM   #20
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Default SV 02,03,04,05,06 Diode failures

In many years of servicing units using these diodes for bias regulation in output stages from Akai to Yamaha, these diodes fail after time whereas the momentarily open leaving the output stage in full conduction and subsequently destroying much of the related power amp. Testing them is almost futile BUT, if you attach a diode checker and subject the diode to extreme temps, like freon or the tip of a soldering iron, your test WILL indicate an open condition. The only problem now is finding replacements. I can almost 100% guarantee you that replacement of these devices will be your resolution along with the extensive collateral damage caused by the defective diodes.

I too have several amplifiers waiting for these diodes of which I had acquired 10, but got misplaced when cleaning up after a devastating store fire (ugh).

PEACE (and cheers)
Brian
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