Hi, little while ago i picked up a Rotel ra611 that had distortion one channel, recapped and sounds great but when I went to set the bias idling current i was getting no voltage at the test points? I replaced the 5k variable resistors but no change, checked all components and all ok except for the component listed in the parts list as a KB-365 varistor and shown on the schematic as 2 diodes in series with a ring round it. Removed and tested, one from the right channel acts like a diode measuring .6v in forward bias and ol in reverse bias, the other from the left channel( the previous distorted channel) acts like a shorted diode with .1v in both forward and reverse bias. Anyone have any clues on if these are varistors or diodes and what i can get for replacements? There is no markings on them , the only mark is a yellow stripe which i think denotes polarity, have attached a photo of the circuit with the component marked up. The b+ and b- are correct at 30.5v . Also a photo of the component.
Many thanks for any help
Cheers Phill
Many thanks for any help
Cheers Phill
Attachments
Two diodes 1N4148 in series will work as a replacement!
In your case, both parts are defective. The one with .6V forward bias has one shorted diode. The other one with .1V forward and reverse bias has two leaky diodes.
regards
Reinhard
In your case, both parts are defective. The one with .6V forward bias has one shorted diode. The other one with .1V forward and reverse bias has two leaky diodes.
regards
Reinhard
That was Fast! Many thanks Reinhard, so is it a varistor or a component made from 2 diodes in series?
Many thanks Phill
Many thanks Phill
Yes, they are made by two diodes in series (as the symbol shows). They must be both in the same direction, of course. And mounted in the same direction as shown in the schematic or as printed on the PWB.
Regards
Reinhard
Regards
Reinhard