Cornman Posted February 3, 2006 Share Posted February 3, 2006 The photo your looking at Is of one of the circuit boards of an HK-930 reciever. I just bought this off of ebay, seller said It worked, but Its DOA for me. The panel lights up, but the transformers are cold(do not warm up). There Is no sound, not even static, from any source. In the photo there are 6 slotted cubes, 2 on the outer ends are very clean, but the 4 In the middle have a crusty carbonized coating although they do not smell burned. Can anyone tell me the name of these cubes, and would they kill all output If bad? Thanks, Cornman Quote Link to comment Share on other sites More sharing options...
ajsons Posted February 3, 2006 Share Posted February 3, 2006 How many leads per cube? Quote Link to comment Share on other sites More sharing options...
Cornman Posted February 3, 2006 Author Share Posted February 3, 2006 Three leads per cube. Cornman Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted February 3, 2006 Share Posted February 3, 2006 they ain't jus' crusty ... thier Smmooooked .... you got had, son ..... Quote Link to comment Share on other sites More sharing options...
D-MAN Posted February 3, 2006 Share Posted February 3, 2006 Power supply. Power supply. (power supply). Smoking means smoking, and you ain't got no smoking, because you ain't got no power supply. Kidding aside, if you had power available to the output transistors (the 3-lead "boxes", you would have at least a rather bad smell, unless they were both open rather than shorted, which is somewhat unlikely (but possible I guess) for both channels. In that case, the seller knew beforehand, and you got taken. If my deduction is correct, then something failed in the power supply during shipping, and the seller had no control over that. However, you still got taken, but by inept and savage baggage handlers instead. It's happened to me. DM Quote Link to comment Share on other sites More sharing options...
3dzapper Posted February 4, 2006 Share Posted February 4, 2006 Is there a power relay that is not closing? Rick Quote Link to comment Share on other sites More sharing options...
ricktate Posted February 4, 2006 Share Posted February 4, 2006 There are fusses on the bottom and top on the inside make sure the fusses are good first, i got a 930 i will go check tommorrow for you to see where the fusses are exactly if you want.The HK430 has a alot of fusses to protect it i know it has 3 on outside 5 on inside i have not taken bottom panel off my 930 yet to look.Dont give up on it yet....it is a tough reciever.Rick Quote Link to comment Share on other sites More sharing options...
boom3 Posted February 4, 2006 Share Posted February 4, 2006 I am pretty sure these are voltage regulators with heat sinks. The three leads are the giveaway. Yep, I think they're fried. Quote Link to comment Share on other sites More sharing options...
djk Posted February 4, 2006 Share Posted February 4, 2006 A 930 has only three fuses, all on the back. If any are blown, wire a 75W lightbulb in series with one side of the line cord before replacing and firing it up. I always do the lightbulb thing with any piece of unknown equipment, saves heartache and sorrow. Did you bother to wire the pre-out to the main in (use a patch cord)? Here's the service manual (for technician use only). http://manuals.harman.com/HK/service%20Manual/HK930%20sm.pdf Quote Link to comment Share on other sites More sharing options...
ricktate Posted February 4, 2006 Share Posted February 4, 2006 djk is right 3 fuses but the gunk in your pic is on mine to looks like glue to hold heatsink on so maybe nothing wrong with those parts there.Did you check to see if it has the right fuses and the holder is clean?Rick Quote Link to comment Share on other sites More sharing options...
efzauner Posted February 4, 2006 Share Posted February 4, 2006 Those are the pre-driver transistors. The main outpu transistors are mounted on the main heatsink. With the manual provided by fellow member you should be able to identify what is what. The pre driver transistors are rarely the culprit. First try the fuses. There are Power supply fuses and speaker fuses. That should be enought to protect things. I do not think what you see is "carbon" from burning. The transistors are in metal cans and have relatively low currents flowing thru. They would burn up inside without showing signs of too much stress on the outside. This is an old unit. If it was used regularly, the low heat from the transistor over many decades would be enough to discolor many glues or other compounds holding the heatsinks to the transistors. Don't be too alarmed. you got a nice amp and even if it is output or other transistors, they are easy and cheap to replace. Trying to put a light bulb in series with power cord is an OK idea. I use a standard rotary light dimmer in series and slowly turn the knob while measuring power supply voltage. Quote Link to comment Share on other sites More sharing options...
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