davstev
Well-Known Member
I am not the best at it. I will get lost knowing how to troubleshoot, specifically where to test for voltage to troubleshoot this particular problem. Any pointers, I'd be thrilled.
Harman/Kardon 930 : dial won't light, bulbs ok
- Thread starter davstev
- Start date
I am not the best at it. I will get lost knowing how to troubleshoot, specifically where to test for voltage to troubleshoot this particular problem. Any pointers, I'd be thrilled.
davstev
Well-Known Member
Yes, I spritzed everything thoroughly. All pots, switches, everything.
davstev
Well-Known Member
I did. I checked the bulbs individually and then, from the start of the circuit board to the end, with bulbs installed. Checks out fine.
Interestingly there are no amperage markings on any of the bulbs, but they're not blown, and not fuses, I can see the tungsten filament in each.
Are these fuse style lamps ? Are they replacements or the originals as far as you know ?
davstev
Well-Known Member
I tested them individually (removed), and then tested the whole circuit board with them installed. By this I mean, from the first clamp (holding the bulb end) to the last clamp of the series of bulbs. Everything is fine. I also tested the wire leading to the board from the function switch. It's fine too. I also pulled apart the dial pointer and looked at the bulb, and it appeared fine. I had to run off to work and I didn't have time to test it but that will be my next test. If it tests out fine, then what it would imply is a lack of power flowing to the board with the lights, as well as to the dial pointer bulb.
All the function indicator lights are working, btw, it is just the AM/FM panel lights and possibly the dial pointer that aren't receiving power.
davstev
Well-Known Member
I can't say if these are original or not. They appear generic and have no markings of volts or amperage. In that sense I am trusting that they are the correct amperage, etc. I did put a working 8v 250ma bulb that I had on hand in as a test and it didn't work either.
I will test for 6.3 vac at hot side of the lamps when I am back at home. Just to be clear, this is with unit powered up, and testing every bulb, installed, at the same side of each lamp?
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Goldie99
Super Member
According to the schematic, with the receiver powered on, and AM or FM selected as source, you should be finding ca. 6.3 Vac on the hot side of the 2 meter lamps, and the hot side of the dial pointer lamp.
If the other lamps (function indicator - AUX, FM, AM, etc.) are working normally, there's no need to test those.
davstev
Well-Known Member
I appreciate this. This evening I'll give it a shot and post the results.
davstev
Well-Known Member
I am happy and perplexed. I just powered up and I have lights. The only change that I made was to take the dial bulb out of the housing. I have no idea what difference that would make but I now have full lights including dial pointer. This is a mystery. It is possible that I have a bad connection somewhere and they'll kick out again, in which case I'll be back at it. This could be an intermittent problem but since the receiver is new to me....time will tell. Sincere thanks for your help on this, avionic. Very helpful. All the best, David.
davstev
Well-Known Member
Yep, it's intermittent. There's something up with my function switch- bad connection somewhere. It is really hard to get it to kick in and make the lights function, but sometimes it works. Spraying it with a bit more deoxit just to see if that might help, but my fear is that it's not connecting somewhere and should be replaced. Helluva soldering job that would be, not to mention finding a spare function switch of this kind. Hmmm....
davstev
Well-Known Member
Less happy now, the problem persists.
Here is a major clue- When I spritz the first wafer of the function switch and it's dripping with deoxit, I power the unit up and the lights work. The deoxit actually slowly burns off, with a tiny bit of smoke as it burns off. When the smoke from the deoxit stops, and all of the excess deoxit has apparently burned off, the light slowly fades, and won't come back. So, it's only working when the first wafer is lubed up. As soon as it burns off, I have no lights. Repeated tests of this prove it to be so. So I did this to further test: I spritzed the first wafer while powered up, as soon as I spritzed, I got lights. Didn't touch the switch at all, just sprayed the wafer. So I don't get it. Deoxit is non-conductive, right? Is it temporarily improving a bad connection? Apparently so, but I don't get it, and I don't understand how since it's non-conductive. Here's a video of what I'm describing:
Here is a major clue- When I spritz the first wafer of the function switch and it's dripping with deoxit, I power the unit up and the lights work. The deoxit actually slowly burns off, with a tiny bit of smoke as it burns off. When the smoke from the deoxit stops, and all of the excess deoxit has apparently burned off, the light slowly fades, and won't come back. So, it's only working when the first wafer is lubed up. As soon as it burns off, I have no lights. Repeated tests of this prove it to be so. So I did this to further test: I spritzed the first wafer while powered up, as soon as I spritzed, I got lights. Didn't touch the switch at all, just sprayed the wafer. So I don't get it. Deoxit is non-conductive, right? Is it temporarily improving a bad connection? Apparently so, but I don't get it, and I don't understand how since it's non-conductive. Here's a video of what I'm describing:
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The wafer is not making good contact when dry. So either replace the wafer switch with a serviceable switch. Or try and disassemble the one you have and carefully ever so slightly bend the offending contacts to make a good positive connection.
davstev
Well-Known Member
This sounds like the easier and better option to me. I like the look of the unit with the dial lights on anyway, even if it means going through bulbs more quickly. If you are anywhere near the schematic, could you advise where this wire would go to/from? I can look it over too, but I am much more skilled at soldering than in making these decisions about re-wiring
. It might be evident to me once I look......Thanks again.