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Harman Kardon 330b Receiver - blowing main fuse Help!

redpackman

redpackman

Active Member
OK, I just picked up a very nice looking HK 330b receiver. Nice looking cosmetically, so there's some good hope here. BUT as soon as I turn it on the main fuse instantly blows (not the speaker fuses, but the main single 2.5A power fuse.

I'm a shade-tree. For those of you who know this receiver and electronics, where are the first three or four places you'd look? Thanks for the suggestions.
 
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I would start with the output transistors, check for collector to emitter shorts or any two legs that have zero resistance, can be done in circuit, may get low reading like a 100 ohm or so but if you get a dead short, that is a problem. If transistors seem ok, check resistance across main filter caps and the diodes feeding them. IF there is a short there, try unhooking things until you find what is shorting.
 
OK, an update. Thank you for the good advice. I went inside the unit and here's what I found: the power supply was shot. I took it out and took it apart and it appears that it got quite hot at one time. Smells a little burned, but all old electrical stuff has "that" smell, so I'm not 100% sure. Also two of the four rectifier diodes (both of them polarized in the same direction) were shot and open. The remaining two seem to be operating well according to my diode checker with readings of 500+ in one direction and OL in the other direction. I've ordered a replacement transformer from eBay and some diodes are on the way.

So my question for you gurus is: with both the burned out (non functioning at least) power transformer AND the two rectifier diodes being shot, does that tell you anything? In particular can I reasonably hope that those two (or three) components failed and didn't take anything else with them or should I expect a daisy chain of destroyed components? Remember the fuse blows IMMEDIATELY when power is applied to the machine (until I took the power transformer out). I did check the power output transistors - no dead shorts between C and E legs etc. Checked the filter caps and they seem to read as OK and do not seem to be dead shorted to the chassis. Thanks for the counsel! Keep it coming.
 
Next step is to replace the parts you found to be bad, then start it up with a dim bulb tester, lot of info on that on this site, and test voltages. The main voltages to test would be across the main filter caps, will be less than schematic values while using DBT, but still be about half or better if there are no shorts.
 
at least good news is the outputs tested good. Follow above lead. Might install a lower amp main fuse for safety sake for testing.
 
OK, another update. I put in the new transformer and rectifier diodes. I paid attention to the polarity of the diodes. The transformer works and didn't immediately blow the main power fuse! I am using a dim bulb tester with a 40w bulb in it. OK, here's where it gets interesting: the bulb barely glows (which is what it should do, right?) if I do not have the speaker fuses in. However, if I put the speaker fuses in the bulb glows BRIGHTLY, and I shut the thing down immediately.

So, what would you check next? I thought I checked the output transistors (no zero readings between the transistor legs) but I checked them IN circuit, so I'm not 100% sure even there. There's one large capacitor and a number of varying ones in smaller sizes. I disconnected the largest one and it tested within range with a cap tester I have. It does not seem to have a dead short in it.

I am assuming now that the main failure wasn't that the transformer and diodes croaked first but that something else did and took THEM out. But that's just an ignorant guess.

Ideas? What's next?
 
that's a mighty odd fault you have there .. first thoughts are shorted speaker outs but would /should blow speaker fuses not the transformer ..
 
Hey, we all go through this.. try 8 weeks on a cracked (finally diagnosed cracked main board... there is a limit to my $ ,too. )

have some other stuff will see the recycle even so pretty? can't get the damned stk's.

life is good.
 
Hi Redpackman, I too have a problem with my HK 330B. RH Speaker Fuse blown as soon as I power the thing. No other connection is made. I think thinking of replacing the Output Transistors (2SC1107) but I can't source them. What happened to your HK330B? Can you send me the mainboards? if you don't have any plan to do with it ... Thanks,
 
there arent any speaker fuses ..but there are rail fuses for each channel .. must be that fuse that blew .. will be output transistors and or drivers plus more possible damage .
 
Hi PeteHall347, Thanks for your response. There are 2 fuses in the back, shown as FU2 and FU3 in the attached diagram. FU3 keeps blown up. On the second diagrams, there are 4 transistors (2SC1107), I am not sure if I should replace these transistors? should I concern about others? which one in this diagram would be the output or the drivers ? what other possible damage that I should look for. Thank you so much for your help. I am new here and inexperienced.
 

Attachments

they are not speaker fuses although it does say that on the diagram ,,they got it wrong .
hold on a minute the manual i have here must be for a different revision ..
outputs are on the large heatsink ..4 of them ..what numbers are written on yours ?
where did you find your manual ?
 
petehall347 said:
hold on a minute the manual i have here must be for a different revision ..
Click to expand...

There are at least two different versions of the HK 330B and, maybe, three.

The story goes that the demand for the new HK 330B exceeded manufacturing capacity, so they took a bunch of HK 330A boards and "built" new HK 330B units from them. In a different factory. In a different country.

So, there are two technical or service manuals. One says "HK 330B" and, inside, it shows two different schematics and calls the second set of them "for models with serial numbers ending in the letter 'A' ". The second manual is very short and is titled "Technical Manual Addendum Serial Number 7322984 to 7327986".

I have not compared the diagrams carefully. I just found the one that 99% matched my actual two units and used that.
 
Quang Nguyen said:
Hi PeteHall347, Thanks for your response. There are 2 fuses in the back, shown as FU2 and FU3 in the attached diagram. FU3 keeps blown up. On the second diagrams, there are 4 transistors (2SC1107), I am not sure if I should replace these transistors? should I concern about others? which one in this diagram would be the output or the drivers ? what other possible damage that I should look for. Thank you so much for your help. I am new here and inexperienced.
Click to expand...

There are several different transistors that could be used in the manufacturing of your 330B. There are four output transistors. You should remove them from the main amp board and test each one to see if any are still working. If you have even one that is not working, you should replace all four with MJE15030G transistors from ON Semi.

Before you do that, you'll want to test the otehr transistors on the main amp board and the control amp board to see if any of them are blown. You should, at a minimum, test the four trimpots on the main amp board as even a temporary failure or short of one of them could damage the transistors. You should seriously consider replacing all the electrolytic caps.

I hate saying "you should do this or do that", but I'm no expert and I can only share advice from my own limited experience. I had one blown channel in my first HK330B, I replaced all the electrolytic caps, all the transistors, all the trimpots, and all the components of the two power supply / rectifier boards. That's the "shotgun" approach and it is all I can suggest since I don't know enough to advise otherwise. Perhaps more people here will chime in with advice. However, I heartily recommend you start a brand new thread, one just for your repair, so you get 100% of the attention and so you don't get confused between replies about this thread (developing a BOM) and your thread (repairing a blown channel). I bet all the people here will join in to help you in your new thread.
 
The 4 transistors on the Heatsink is 2SC1107. The diagram I cut from the Service Addendum and my machine looks just like the diagram ... I found this in VynilEngine website. Think that is the one for SN ended with letter "A"
 
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