Harman Kardon 490i Receiver works 1/2 way?

[jleon92f]

Hi, Me again.. Boy I have my work cut out for me this week. This receiver was in with a Cassette deck and a turntable that pmsummer was nice enough to pick up and repack for me and ship in two boxes. I bought it not working but, it works, it produces sounds out of both channels using the AUX so far.

I can see that the lamps do not light up indicating what input I am using,Etc.
The receiver section is dead also? No FM/AM? I have a Dipole antenna hooked up. Any ideas on this one? Looks very good inside, see pictures. Nothing burnt up.

Thanks as always,
John.

 

[jleon92f]

Amp Section works...

The amp section works so far, I am playing a CD, sounds really good.
I am going to play a tape and TT ,LP..
I am thinking the FM IC's are blown out for the display?

Thanks,
John.

 

[jleon92f]

I am playing a tape now, No problem here. It is just the FM/AM section.

Anyone know where these IC's are avaiable?

Thanks,
John.

 

[Hokieman]

When I got my 680i with a non-functioning digital tuner section, turns out it was because of a bad cap and three burnt resistors on the power supply board in the circuit powering the tuner. Might want to do a quick pass through there (the power board) with your multi-meter to see if any resistors show up with really high off-spec values.

Here's the link to the service manual
http://manuals.harman.com/hk/Service Manual/hk490i sm.pdf

On p. 17, power board, circuit tab "B1", the fusible resistor R61 (220 ohm) looks like a good first place to check. The voltage at the positive side of cap C12 just behind it should be 27.5 V - if it's 0.0 V then the fusible resistor is probably fried.

 

[Jon_Logan]

See if you can download the manual (Service manual). It may be as simple as switch cleaning. Sounding like a supply problem, though.

 

[jleon92f]

When I got my 680i with a non-functioning digital tuner section, turns out it was because of a bad cap and three burnt resistors on the power supply board in the circuit powering the tuner. Might want to do a quick pass through there (the power board) with your multi-meter to see if any resistors show up with really high off-spec values.

Here's the link to the service manual
http://manuals.harman.com/hk/Service Manual/hk490i sm.pdf

On p. 17, power board, circuit tab "B1", the fusible resistor R61 (220 ohm) looks like a good first place to check. The voltage at the positive side of cap C12 just behind it should be 27.5 V - if it's 0.0 V then the fusible resistor is probably fried.

Thank you very much, Nice sounding receiver.

Thanks,
John.

 

[vintage-man]

Yeah, it's probably supply problem. First check fuses with an ohm-meter, if it isn't blown - then measure all supply voltages for tuner and compare to voltages values wrotten in service manual. You should begin behind wires of transformer.
In my hk570i tuner was interrupting signal and displaying together when I hit harder. Reason? One of wires for tuner supply sometimes shorting to chassis. One day I hit again - burnt 39 ohm, 1 watt resistor in voltage stabilizing circuit for tuner.

 

[shimniok]

ah right, looks like my 680i has a separate power supply for the tuner... best of luck in the fix...

 

[jleon92f]

Thanks for all the help. Should be an easy fix then. I will post the repair when I get it apart.

Thanks,
John.

 

[rogerbent]

HK490i Fix

I got a HK 490i at Goodwill for $7.50, believe it or not, but it definitely had "issues!" When I plugged it up and tried the AM or FM section, I got roars, hisses, and crackles. I pulled the botom cover and saw the problem right away. To make a long story short, several of the lavender colored capacitors on the tuner board had leaked and corroded not only their leads, but the circuit traces underneath. I ended up replacing all the lavender caps (several different sizes) and cleaning off the corrosion with a brass-bristle brush, parts cleaner (VERY carefully applied to the trace side only!!! And with NO CHANCE of getting to the styrene capacitors on the component side, lest they melt!) then used a tooth brush and compressed air to clean as much as possible. I used the leads of the caps to restore the etched away circuit traces and now I have a very functional HK! I also noticed corrosion on other boards (preamp board, tone control board) - either from the bright blue caps or the lavender ones! If you want pix, email off line at rogerben@bellsouth.net. May the Lord guide you in all you do!