• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

harman kardon 630 FM faint sound

Using an electrolytic cap (10 uF would be best, but anything 1 uF or greater is OK for this test) Jumper across C303 and see if you get any audio through. If not, IC301 becomes our major suspect.

No voltages shown on the schematic (that I have), but an old data sheet does indicate some nominal voltages. (section attached) The listed voltages are for a supply of 12 volts, but the schematic indicates that this unit is using +14, so expect a bit higher than the datasheet numbers. Check and post the voltages on pins:
1 - (expect about +14 volts), actual =?
2 - (expect about +3), actual =?
3 - (expect about +4), actual =?
9 - (expect about +14), actual =?
10 - (expect about +5), actual =?
11 - (expect about +10), actual =?
12 - (expect about +10), actual =?
13 - (expect about +5, actual =?
14 - (expect about +2). actual =?

Screenshot 2021-01-07 225219.jpg

If you have an oscilloscope, you can clip on TP5 and you should see a 38KHz sine wave.
 
The 1uf capacitor jumping C303 had no effect.
IC 301 pin voltages
1 - (expect about +14 volts), actual = 12.81
2 - (expect about +3), actual = 2.95
3 - (expect about +4), actual = 3.94
9 - (expect about +14), actual = 13.21
10 - (expect about +5), actual = 4.81
11 - (expect about +10), actual = 11.54
12 - (expect about +10), actual = 11.46
13 - (expect about +5, actual = 4.89
14 - (expect about +2). actual = 0
I don’t have a scope
Thanks for your help with this
 
None of those voltages looks far enough off to be suspicious.

Let's try this... Grab that 1uF cap and connect the - side to the board pin 1. Connect the + side to IC301 pin 11. Do you get any audio through to the left channel? Now move the + side of the 1uF to IC301 pin 12. Any audio from the right?
 
I have a Velleman HPS 10, I wasn't sure it worked or how to use it but figured it out and I have about 38.4 khz
 
OK, if the IC was bad, the last should have given you at least some audio. Measure and post the voltages on the emitter, base, and collector of TR304 and TR305.
 
Tr303 E-C .685mV
e to base 4.4
base to c 5.2 v
Tr304 E -C .673 mV
base to emitter 4.4 v
Base to collector 3.7v
 
Let me ask that in a different way...
TR303 voltages
Emitter to ground:
Base to ground:
Collector to ground:

T304 voltages
Emitter to ground:
Base to ground:
Collector to ground:
 
T304
Emitter to ground 1.7
Base to ground 1.786
Collector to ground 5.575 center
T303
Emitter to ground 1.03
Base to ground 1.712
Collector to ground 6.28
 
Looks like T304 is bad. Emitter is at 1.7 and base is at 1.786, giving a Vbe of 0.086 volts. That should be fully off, but the collector voltage indicates it is drawing current. T303 looks better, but since they are coupled at the emitters, I would suggest pulling both of these and testing each with a transistor tester or the diode range of your DMM.
 
  • Like
Reactions: 002
Thank you I will do that in the morning.
Thank you again for all your patience and help.
Looking at the diagram thread # 25 it has D301 a diode? Mine just has solid jumper and it looks factory.
 
I found the base and they tested good out of the circuit.
Base to Emitter 7 v Base to Collect 7
Emitter to base 0 Collector to base 0
Emitter to collector open
 
jimcheri said:
I found the base and they tested good out of the circuit.
Base to Emitter 7 v Base to Collect 7
Emitter to base 0 Collector to base 0
Emitter to collector open
Click to expand...
Sounds promising! What transistor is that?
Oh geez, I read that wrong.. the transistor is good.....
 
jimcheri said:
I found the base and they tested good out of the circuit.
Base to Emitter 7 v Base to Collect 7
Emitter to base 0 Collector to base 0
Emitter to collector open
Click to expand...

I'm going to rephrase, and you tell me if it is correct...

Base to Emitter: 0.70 volts
Base to Collector: 0.70 volts
Emitter to Base: Open
Collector to Base: Open
Emitter to Collector: Open
Collector to Emitter: Open

The above measured with a DMM on the diode range.
 
Well, the in-circuit voltages were all wrong, so something in that area is not right. I believe you said you replaced some of the electrolytic caps. Double check to make sure they are installed with the correct polarity. Check the board in that area looking for any bad solder joints or cracks in the board. Reinstall the transistors and repeat the measurements at post #48, being sure you know which lead is the base, emitter, and collector.

Reviewing... You had said the stereo light does not come on. That is consistent with the voltage reading you posted for IC301 pin 14. You may want to bite the bullet and order a replacement for IC301. Finding an actual MC1307P is likely to be problematic, so you may have to settle for a generic replacement, the NTE722.

But do also recheck in the area of TR304 and TR305.
 
I found the whole board and bought it. After removing and testing the transistors I installed it this morning and it works as it should.
I am new to this trouble shooting and apologize for not understanding how to test and take readings properly. I appreciate your patience. I have learned a lot. I bought a Velleman pcsgu250 usb o scope this morning on eBay.
I have an jvc 5030u with the same FM problem and an HK 430 that needs it and other help
I am hoping to keep learning and be able to fix them.
Thanks to everyone at AK
 
You must log in or register to reply here.
Back
Top Bottom