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Old 6th November 2007, 02:51 PM   #1
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Default HK330A Stereo Beacon Issues

After finally getting this unit powering up and working fine, the stereo light glows very bright and burns out. I put a meter on the leads and find 39V steady, even if I move the dial off a station, so there is definitely something going on here, it should vary and turn off when no longer tuned to stereo. Any ideas? Schematic is attached, it is on page 9. The stereo indicator is in the upper left hand corner of that page, the other side of the circuit (B5) continues on the lower right.

http://manuals.harman.com/hk/Service.../hk330a sm.pdf
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Old 6th November 2007, 07:27 PM   #2
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Default Re: HK330A Stereo Beacon Issues

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Originally posted by DreadPirate
After finally getting this unit powering up and working fine, the stereo light glows very bright and burns out. I put a meter on the leads and find 39V steady, even if I move the dial off a station, so there is definitely something going on here, it should vary and turn off when no longer tuned to stereo. Any ideas? Schematic is attached, it is on page 9. The stereo indicator is in the upper left hand corner of that page, the other side of the circuit (B5) continues on the lower right.

http://manuals.harman.com/hk/Service.../hk330a sm.pdf
Hi

Transistor TR 304 must be shorted, inspect...

Greetings
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Old 7th November 2007, 12:20 PM   #3
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Thanks Jorge, I have a replacement on order, it seemed like the most likely culprit, but why would that result in a 39V reading? B5 is showing 30V is what should be read.
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Old 7th November 2007, 04:21 PM   #4
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Quote:
Originally posted by DreadPirate
Thanks Jorge, I have a replacement on order, it seemed like the most likely culprit, but why would that result in a 39V reading? B5 is showing 30V is what should be read.
Hi

See if you have 30 Volts , between B5 and ground.

If not, inspect R 931/932/933...
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Old 27th November 2007, 03:21 PM   #5
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I've taken some additional measurements and posted the result on the attached schematic. Several voltage appear to be about 10V high. Is it possible that the transformer output voltage has risen by 10V? Can diode failure of some kind result in a 10V boost in output voltage after rectification?

I was able to confirm 931, 932, and 933 are on spec while hot, the others are tightly wrapped and I'd rather not tamper with until other faults are ruled out.

http://img124.imageshack.us/my.php?i...330a240dh4.jpg
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Old 9th December 2007, 03:28 AM   #6
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Default Hk 330a

Quote:
Originally posted by DreadPirate
I've taken some additional measurements and posted the result on the attached schematic. Several voltage appear to be about 10V high. Is it possible that the transformer output voltage has risen by 10V? Can diode failure of some kind result in a 10V boost in output voltage after rectification?

I was able to confirm 931, 932, and 933 are on spec while hot, the others are tightly wrapped and I'd rather not tamper with until other faults are ruled out.

http://img124.imageshack.us/my.php?i...330a240dh4.jpg
On page 9 it shown supply B5, but B5 is 17 volts not 31. Look at Page 17. It marked that supply is from B4 which is suppose to be 31V. May be you can tell better when physically check on the set.

Check on R916 / 750 ohm 2W on power supply to see if the value increase? If the FM stereo Ind is conected to B4, that is the only reason i can imagine of that cause 31 Volt to rise up to 39 volts. That rise of voltage also kill the TR 304 (C,E short circuit).
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Old 9th December 2007, 05:32 PM   #7
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Thanks for your help. I did solve this problem with comments from someone on AK. I was taking the readings with the lamp out of circuit, apparently, the lamp needs to be in circuit for it to work properly. I went ahead and placed a proper bulb in and it has now worked fine for a couple of weeks.
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