ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I have 2 of these tunerboards that cannot tune stations by themselves, but if you enter the frequency manually, if will tune, but not in stereo..
In the service manuals it says that they recommend exchanging the boards, but I would guess that since it "works" it might be something simple as a dead cap causing noise on the tunerboard ?
Unfortunatelly I don't have an oscilloscope (or the knowledge since my education as engeneer did not go well ;) )
But maybe the first step could be just changing ALL caps on the board and see what happens :)
/Weebyx
They can be fixed in most cases.They do suffer with leaking/exhausted caps,particularly the small low profile 47uf.
I've also come across problems with the upc interface ic(ic3).If there is staining to the pcb,which looks like water marks,suspect the ic.It's a smt device,but it is possible to replace with time and patience,and of course well worth the effort.
Regards,
Nick
Thanx, I will try to change some caps at first, and see what happens ;)
IC3 I have changed some years ago, but that was because the tuner did not work at all, it thought it was a japanese version, but that fixed the problem, I think this might be caps only problem..
Already fixed?
If not: i found on several tuner boards (and the tuner box itself...) missing solder joints. Surprisingly these boards worked for quite a while...
I will change all caps this weekend, and see what happens, but will look for missing/bad solders also.
will keep you posted :)
/weebyx
Ok, So I have now changed ALL caps, but no difference at all..
The tuner can play radio if you enter the freq manually, but only in mono, it cannot find ANY stations by itself...
I guess B&O really was serious when they wrote "The unit is a single unit, in case of failure replace the unit. However the list of components are specified under the parts list", in the service manual :)
Hi,
if tuned manually to a strong station in FM do you get the station name via RDS? If so the HF and IF part of the tuner module should be ok.
Can you manually switch to stereo if you connect the point between R102 (39K) and R56 (1K) to ground?
Does PIN 14 of IC3 (LC7218) toggle from high to low and vice versa if you switch mono to stereo?
I hope this helps a bit
Ralph-Marcus
RaMaBo: Hi, if tuned manually to a strong station in FM do you get the station name via RDS? If so the HF and IF part of the tuner module should be ok. Can you manually switch to stereo if you connect the point between R102 (39K) and R56 (1K) to ground? Does PIN 14 of IC3 (LC7218) toggle from high to low and vice versa if you switch mono to stereo? I hope this helps a bit
My unit does not have RDS, so this I cannot test. I will test the other tonight, but I might just order a new LC7218.. apparantly these IC's have issues, had to change one some years ago, where the tuner thought it was japanese. That was fixed by the new LC7218..
So maybe some part of the IC is dead or very weak ?
Pin 14 is always high (6,2v and measured between pin 6 as ground) no matter what the display says when tuning and manually changing from Mono to Stereo.
So maybe this IC is done for ?
If pin 14 is always high the stereo decoder is forced to mono.
Do you get a stereo signal to hear at the headphones / speakers if you pull the connection of R104 (39k) and R65 (1k) to ground?
RaMaBo: If pin 14 is always high the stereo decoder is forced to mono. Do you get a stereo signal to hear at the headphones / speakers if you pull the connection of R104 (39k) and R65 (1k) to ground?
Pulled the R104(6.4v side) to ground, and nothing happens, the stereo signal is not doing anything. Measured 0v when pulling low on the pin 14 of IC4, so its pulled down fine..
I almost certainly have a spare tuner PCB but it will be next week before I can look it out
Stuart
Well, the news is that I ordered a new LC7218 IC as I have seen problems with this before.
No change in behaviour what so ever !! So All caps and LC7218 changed..
Any bright ideas ?
Did you get any further sorting out this problem?
/Dennis
Dennis: Did you get any further sorting out this problem? /Denis
/Denis
Yes, I came to the conclusion that it sucks and I don't wan't to spend more time on it :)