Harman Kardon FL 8450 (serv.man10) Service Manual / Technical Bulletin ▷ View online
harman consumer group
80 Crossways Park West, Woodbury, New York 11797 Phone: +1 (516) 496 3400 Fax +1 (516) 496 0812
Warranty labor rate: MINOR repair
Date:
16-May-1995
Our reference: 950516-1
To:
Geoff Matthews, Convoy
cc: Steen Michaelsen
From:
Peter Philips
Subject :
AVR-25 noise rear ch, AVR-20 tuner, AVR20/25 cracked PCB, FL8450
Dear Geoff,
Indicated below are the answers to your questions:
Indicated below are the answers to your questions:
1) AVR-25 noise rear channels, see attached diagram and Schematic:
I have good news for you. Our distributor in Holland found an easy fix on the DOLBY board last week.
A)Locate Jumper J583. J583 supplies 5 volts to R576 and R577. Cut J583.
The improvement in noise is dramatic. The lower frequency buzz is gone.
The purpose of J583 was to provide a small DC offset to Pins 8 and 10 of the LV1000, thereby
reducing the Dynamic DC offset inside the LV1000. However, the bad side effect is a large amount of
audible noise.
After J583 is removed the Signal to noise ratio between 40Hz and 800 Hz. is improved with 10 dB!
I have good news for you. Our distributor in Holland found an easy fix on the DOLBY board last week.
A)Locate Jumper J583. J583 supplies 5 volts to R576 and R577. Cut J583.
The improvement in noise is dramatic. The lower frequency buzz is gone.
The purpose of J583 was to provide a small DC offset to Pins 8 and 10 of the LV1000, thereby
reducing the Dynamic DC offset inside the LV1000. However, the bad side effect is a large amount of
audible noise.
After J583 is removed the Signal to noise ratio between 40Hz and 800 Hz. is improved with 10 dB!
B)Locate pin 10 of the LV1000. Solder 10 nF Ceramic cap between Pin 19 and the ground foil under the
LV1000. This modification reduces a whistle sound. Audible improvement is good.
When measured the change is only 1.5 dB
LV1000. This modification reduces a whistle sound. Audible improvement is good.
When measured the change is only 1.5 dB
C) Remove C543 and replace with a jumper.
Remove J561 and replace with C543. Watch polarity! Hiss noise is reduced. This change
is not measurable.
Remove J561 and replace with C543. Watch polarity! Hiss noise is reduced. This change
is not measurable.
2)AVR20 Temperature sensitive problem with LM7001:
I have not heard of any complaints so far. Please describe the symptom from a user point if view.
I have not heard of any complaints so far. Please describe the symptom from a user point if view.
3)AVR20/25 solder joints and cracked PCB, loose plugs, sockets, ribbon cables:
We noticed the same, the vendor has been advised.
We noticed the same, the vendor has been advised.
4)FL8450 “grinding” sound when operating the tray:
We noticed the same. Add some glue to E-clip W-6 and Bracket 50. This glue will prevent shaft 52 from
rotating. The vendor has been advised.
We noticed the same. Add some glue to E-clip W-6 and Bracket 50. This glue will prevent shaft 52 from
rotating. The vendor has been advised.
Best regards,
Peter
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