My most successful posting to date (measured by the amount of comments) is my tutorial for fixing the Harman/Kardon AVR 35RDS receiver. In the comments section I thought about an English version of the tutorial, as surely the receiver was sold internationally as well. Below is the translation of my original post. Please notify me (or simply write a comment), if my explanations are not coherent.
Lately our receiver lost its adjustment for volume, radio stations, and digital input, after switching it off. Unfortunately the default volume is „20“ on a scale of „0“ (very loud) to „64“ (nearly silent). Thus „20“ does not blow our speakers, but is much louder than our average volume of around „45“ („30“ is very, very loud).
suspected the storage battery that is used for saving adjustments was faulty. Yesterday (07-07-07) I searched the net and found a thread in the HiFi-Forum (German language) about the receiver forgetting its adjustments (Vergessen der Einstellungen). In this thread several courageous men described their attempt to fix the storage capacitor.
Yes, a capacitor. H/K did not use a battery but a supercapacitor, a high energy density capacitor. This capacitor seemed to have conked out. Unfortunately this capacitor is located behind the display which is located on the board behind the cover.
Tools resp. material required:
- a middle sized crosstip screwdriver
- a small side cutter or pincer
- a small needle-nose plier
- a soldering iron (and solder)
- a replacement capacitor (supercapacitor, 5,5 V, 0.1 F)
- cable ties
Steps to be taken:
- Pull the plug. Don’t forget! Don’t skip!
- Unscrew the receiver. I recommend separating the different screws from each other in order not to mix different sizes.
- Detach the cover so you are able to unscrew the board from the cover. In order to do so, you have to cut several cable ties and possibly disconnect some plug-and-socket connections.
- Detach the board from the cover, remove the bass knobs, and the volume knob as well, unscrew the nut of the volume potentiometer.
- Bend the display until you can see the malfunctioning capacitor.
- Pinch off the faulty capacitor, solder the new capacitor (pay attention to polarity, and constructional depth, the display has to fit in afterwards; see remark at the end of posting)
- screw the board down and connect all(!) disconnected cables
- screw the cover down, screw the receiver down, finished
It is good to have somebody around to help and reassure you who also looks out for loose cables. Below there are several pictures to illustrate the aforementioned steps.
Some advice from Maschbauer in the comments of the original posting: I found a clever tip in another blog: instead of soldering the capacitor directly, just solder two cables in order to place the capacitor at another, better accessible place. Now you only have to unscrew the receiver in order to replace the capacitor.
Thank you very much for your helpful description on replacing the supercondensator. Normally I would not dare to try and replace something like that myself, but in this case I tried, and I partly succeeded…..
I replaced the condensator with a new one, with exactly the same specs (supercapacitor, 5,5 V, 0.1 F), and also paid good attention to polarity. But as I now start up, it still does not remember programmed radiostations when turned off. Only if I keep the receiver in standby modus it does remember programmed settings.
Any idea what could be wrong / what I can have done wrong?
Thanks for your reply.
it’s a pity the solution did not work for you, unfortunately I cannot help you with your problem except for overall suggestions such as: are alle your cables connected?
Sorry, greetings, Ekkart.
I double- and tripplechecked that all cables are properly connected, so I will propably just sell it with the error.
A shame as it is a very good device! 🙁
Thank you for your reply anyway!
Just a quick update; I could not resist opening the receiver once more to check again what I had done wrong. Seems that one of the connections of the condensator was not fully connected.
Fixed it and it is up and running…..without loss of memory 😀
So I will keep it after all!
Greetings from one happy Dutch guy!
He, great news. I’m glad you found the bug.
Thanks for all the information. I have the same problem with my avr 35rds so i think I will try to replace the capacitor. I have another problem also; because of the loss of radiostations I dont turn off the receiver completely but turning it on completely again and trying to connect to a radio station takes a lot of time and cracking noises. Does this also have to do with the capacitator, or is this caused by something else?
I honestly don’t know, I’m afraid you just have to try if replacing the capacitor fixes all problems 🙂
Thank you my dear frien very much!!!!
One of my friend asked me to help repairing his HK arv 45. I tear it apart. I knew (tip) that there must be a supercapacitator somewhere, but I couldn’t locate it.
You article was a HUGE help, 35/45 seems to be 99% identical.
Thank you again!!!
I’m glad this article was helpful. I think HK does not change the layout very much, therefore this could be a help for an long time…
Thank you, Ekkart. You are good future teller, because now we have 2018 A.D. and your tips are still helpful. I got HK AVR-200 and went your way successfully. Different models, but the same capacitor (0.1F 5.5V PANASONIC) located on the left side from display. and yes, polarity is important- arrows on capacitor are pointing to negative contact. negative contact is shorter. I soldered capacitor to another side of PCB- for the future… So thanks and good luck.
Thanks for the kind words and good luck with your renewed HK 🙂