To be sure I will find the failures and get this BL working properly I had to get a new tool, my Xmas gift to myself, I will get it down here around December 5th, I will then have to learn how to use it, but with all the experts on this forum that should not be a problem, I am already surfing the web "Oscilloscope for dummies" 🙂 For the interested link

Got my Oscilloscope on Sunday, used Monday and a little on Tuesday to get used to the basics, and today could start using it.

With a square wave signal I checked (signal from computer) at the aux input, OK not clean as the signal when adjusting the probes, but the same in both channels. From there it goes to D on amp II, still OK both Channels, then to base on BC 109, still good both channels, But at F and G the left channel signal goes way down. Checked all components left and right from BC 109 to F and G, no differences L to R, desoldered BC 109 tested with diode tester, shows good.

I must say this is an amazing instrument, wonder why I didnt buy one before.

Any ideas or good advises ?

fr

I haven't had the pleasure to work on a Beolab yet but from what you are showing of the problem I think I would try swapping the two transistors (one at a time) with the right channel and see if the problem follows or remains. You have checked the continuity between the switches involved (and made sure there isn't a path shorted to ground)?

John

Hi Søren,

1. I would check the DC voltages.

2. re-check the cap's (correct polarity)

3. check for short circuits

4. re-place the transistors (both)

Did you receive my mail ( sent a week ago or so) ?

/Frede

Didnt have much time to concentrate on this, and will have to go working until the weekend,

I have checked the DC voltages and idle current various times, they are all spot on, but as the signal disappears after BC 109 there could be a short in the switches coming after amp. II the F and G connections goes there, after work today I will check further.

Frede I didnt recieve your mail, please resend to nielsen@nigraph.com

I dont have BC 109 in stock what else can I use there (it will take at least 2 weeks before I can get them)

Hi Soren,

you can use a BC239 or BC549 to rule ou a defective BC109and replace it later with an 'original' BC109.

Thanks Ralf, I have the BC549 in stock and will replace later if needed, I will go after and change all small TRs that I didnt change yet, keeping the originals is not a priority anymore. but finding the failure before that is.

A day off, and time to get at it again, Ralfs remarks about the transistors got me thinking again, the only thing I didnt check 4-5 times since changing all the black drop TRs was the polarity of the same, so I took a good look at the BC 154 (now BC 560) and yes it was inversed, desoldered checked it and soldered it back in, also the BC 109 came back in, and there it was, I could now follow the signal to the out put amp at the volume out, shifted the square wave signal on the computer to some music from Amazon, perfect very good sound in both channels, connected the BM to tuner, found a good station and success, good sound in both channels, I must say the stereo channel separation is something I never heard before in any of my receivers, even better than the BM 4400, and testing with CX 50 speakers, so now I have Tape, Aux and tuner working, missing the phono, but at the input jack I get a very funny signal using the signal generator from the computer, will have to check jack and plugs again tomorrow, but I am getting very near to have a working BL 5000 system

Here the Oscilloscope pics from the signal at the Aux in jack

And here at volume out to the end amp (different scale)

I am waiting for a DIY signal generator kit I hope this will give me a cleaner signal

Hi Søren,

It sounds like you are really getting close. Congratulations! 😁

You really WORKED for this one! 🤒

Jeff

Hey Søren...where's the nice action shot(s) of the test connectors hooked up to the Beolab?  🙂 We have to have some more pics.

John