HK AVR335 problem (no sound)

mattau2000 · 12th January 2009, 02:11 PM

hey guys.
i've just got a harman kardon avr335 recently for free,
free because the two PCB's on the side of the transformer were snapped however i've repaired these and the unit now turns on (with proper voltages on both boards).

problem is there is no sound, nor can i get any signal out of the RCA pre-outs on the back.

i've tried coax and rca inputs on all of the ports to get no signal.
i've also taken the whole unit apart and put it back together finding no visible faults. i dont think theres any use in measuring the bias' yet?

i _think_ its a problem between the "input" and the "output \ transistor stage" boards, in which the input board is directly above the other. has anyone ever had any experiance in repairing these sorts of problems?

fairly sure that theres no "mute" on. can hear a slight crackle if you disconnect or connect speakers while the unit is turned on.

sorry if i've posted in the wrong forum and\or wasted your time

thanks!

PM650 · 12th January 2009, 03:59 PM

Download the AVR diagnosis doc:
http://www.eserviceinfo.com/download.../Kardon_AVR%20(all).html

It includes the AVR330, the model previous to the 335, it should be similar enough.

AVR135 Service Manual:
http://www.eserviceinfo.com/download...AVR%20135.html

The 235 and 335 are similar as well, however I only have a service manual for the 340. I can email this to you if you want, it is quite large (13mb).

You may want to check fusible resistors supplying the lower voltage rails, they'll be attached to the main transformer, before any bridges. I recently repaired a similar age AVR(135?) receiver and two fusible resistors went out due to a ceramic capacitor that shorted mysteriously. However the resistors are designed such that they do not burn externally and were only found after testing with a dmm.

mattau2000 · 13th January 2009, 01:21 PM

ahhh.
Thanks for your help!
I've found two (out of 4) dead fusible resistors, all of which are 0.47 ohms and 1 watt. I've now rung around and I can't find anywhere local that sells any sort of fusible resistors, nor a 0.47ohm resistor.

I'm assuming that when they blow they are designed to do this without exploding\catching fire etc, but for testing purposes my choices are:

option 1:
using 2, 1ohm resistors (1 watt) in parallel , to bring them down to ~0.5ohms, however I think that this will let too much current through before blowing and I could end up with more expensive components damaged,

option 2:
use 4 1.8ohm, 1/4watt resistors in parallel which is approx 0.45ohms, and I think this may add up to 1 full watt like the original specifications.

I think option two would be the way to go?
If it catches fire, it catches fire

PM650 · 13th January 2009, 06:26 PM

Wattage/exact resistance doesn't really matter, I replaced mine with 1.5R/2W flameproof. If the old ones blew, then something is very likely shorted. Testing will only consist of connecting resistors temporarily and using a dmm to determine the current through them while the receiver is powered on very briefly, maybe a second (not enough time for your resistors to overheat and blow). After you've measured the current, you can determine if something is shorted and begin searching for what has gone bad. Once you find out what's shorted, then worry about sourcing resistors; can't say I know of any suppliers over there, you may have to do some searching.

Also, you can just replace the fusible with flameproof. Different name, same function. Flameproofs are quite often used in TVs, especially in projector TV convergence circuits. May want to try some friendly TV shops or something.

12th January 2009, 02:11 PM	#1
mattau2000 diyAudio Member Join Date: Apr 2006 Location: Gippsland, Victoria	HK AVR335 problem (no sound) hey guys. i've just got a harman kardon avr335 recently for free, free because the two PCB's on the side of the transformer were snapped however i've repaired these and the unit now turns on (with proper voltages on both boards). problem is there is no sound, nor can i get any signal out of the RCA pre-outs on the back. i've tried coax and rca inputs on all of the ports to get no signal. i've also taken the whole unit apart and put it back together finding no visible faults. i dont think theres any use in measuring the bias' yet? i _think_ its a problem between the "input" and the "output \ transistor stage" boards, in which the input board is directly above the other. has anyone ever had any experiance in repairing these sorts of problems? fairly sure that theres no "mute" on. can hear a slight crackle if you disconnect or connect speakers while the unit is turned on. sorry if i've posted in the wrong forum and\or wasted your time thanks!

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12th January 2009, 03:59 PM	#2
PM650 diyAudio Member Join Date: Jul 2005 Location: Tennessee	Download the AVR diagnosis doc: http://www.eserviceinfo.com/download.../Kardon_AVR%20(all).html It includes the AVR330, the model previous to the 335, it should be similar enough. AVR135 Service Manual: http://www.eserviceinfo.com/download...AVR%20135.html The 235 and 335 are similar as well, however I only have a service manual for the 340. I can email this to you if you want, it is quite large (13mb). You may want to check fusible resistors supplying the lower voltage rails, they'll be attached to the main transformer, before any bridges. I recently repaired a similar age AVR(135?) receiver and two fusible resistors went out due to a ceramic capacitor that shorted mysteriously. However the resistors are designed such that they do not burn externally and were only found after testing with a dmm.

13th January 2009, 01:21 PM	#3
mattau2000 diyAudio Member Join Date: Apr 2006 Location: Gippsland, Victoria	ahhh. Thanks for your help! I've found two (out of 4) dead fusible resistors, all of which are 0.47 ohms and 1 watt. I've now rung around and I can't find anywhere local that sells any sort of fusible resistors, nor a 0.47ohm resistor. I'm assuming that when they blow they are designed to do this without exploding\catching fire etc, but for testing purposes my choices are: option 1: using 2, 1ohm resistors (1 watt) in parallel , to bring them down to ~0.5ohms, however I think that this will let too much current through before blowing and I could end up with more expensive components damaged, option 2: use 4 1.8ohm, 1/4watt resistors in parallel which is approx 0.45ohms, and I think this may add up to 1 full watt like the original specifications. I think option two would be the way to go? If it catches fire, it catches fire

13th January 2009, 06:26 PM	#4
PM650 diyAudio Member Join Date: Jul 2005 Location: Tennessee	Wattage/exact resistance doesn't really matter, I replaced mine with 1.5R/2W flameproof. If the old ones blew, then something is very likely shorted. Testing will only consist of connecting resistors temporarily and using a dmm to determine the current through them while the receiver is powered on very briefly, maybe a second (not enough time for your resistors to overheat and blow). After you've measured the current, you can determine if something is shorted and begin searching for what has gone bad. Once you find out what's shorted, then worry about sourcing resistors; can't say I know of any suppliers over there, you may have to do some searching. Also, you can just replace the fusible with flameproof. Different name, same function. Flameproofs are quite often used in TVs, especially in projector TV convergence circuits. May want to try some friendly TV shops or something.