With a 10,7Mhz IF the AF126 should be OK.

Guess what's waiting for repair in my pile of 'when I get the time...'.a 900 with a bad IF transistor!

OK, I am not totally familiar with FM detector circuits but it looks very much like this uses a ratio detector, and the sudden loss of sensitivity would point at an issue with either the diodes or capacitor(s) in the ratio circuitry, which would be d8/d9 and the associated local capacitors. I will test these this week and see if I can find an issue. Any pointers in the meantime would be gratefully accepted!

Hi Dillen (and everyone else)!

I'm new on the forum and found this discussion about B&O 900K problems. I have the same issues as explained here, but I don't know what to replace with the AF126 or AF109r.

Is it all four caps saying "AD139 / 332" on the backside?

Is there any particular components on the circuit diagram that explains what to solder, and how pins are connected?

I have the manual, found a circuit diagram and know some basics in electronics.

Check this image:

Calle,

Welcome to Beoworld!

Don't get me wrong but from the wording of your post, I can tell that the job of repairing the IF circuits is not for you.
The "caps" at the backside are not caps, they are transistors and they are part of the stereo amplifier output stages.
The IF transistors are AF116 or AF117 and are found on the main circuitboard - not particularly easy to access.
I admire people with an urge to Do It Yourself, but I have an even greater respect for people who stop when they get into too deep waters.
I think you (and the Beomaster) will be best off leaving the job to someone with the skills, experience, tools and instruments needed.

Depending what transistors you fit, their bias may have to be corrected, typically done by changing resistors to suit.

Martin

Tanks for your reply Martin!
Yes, you are certainly right about letting someone else do the magic. I just find it very exciting to have a look into the world of electronics!

For what I understand when I look at the circuitboard, printed on board AF126/1 and AF126/2 are the IF transistors TR3, TR4, (both with printed AF116 on them), on my 900K due to the servicechart 1725 (Beomaster 900K, 900M, 900RG), located almost straight in from the extra speaker outlets, close to the edge of the circuitboard and one other in between of the metal boxes.

What would be the easiest/best transistors to replace them with?
My idea is to get the spare parts since I found this forum, and let someone who works with electronics to repair this for me.

/Calle