manfy wrote:

Congrats! Good job!

AntonvZ wrote:

Pic of my camouflaged 87040 transistor below. Would love to know why they did this thing with the paint? Inferior part they were disguising, attempt at hiding proprietary information ...

If those 87040 substitutes were mounted originally, it proves that even B&O picks any sort of substitute whenever there's a shortage of correct components 🙁 But on the upside it means that you don't have to worry too much about using any cheap alternative transistors as a replacement. 😐

 

Not just any sort, really.
B&O used RCA transistors extensively at the time. They were very good quality (I see them often and I rarely replace them).
I'm sure they were offered at a good volume price, but I wouldn't call them "cheap", really.
F.e. 2N5034/2N3055 were often replaced by RCA 60465 in Beomaster 1001/1200/1600;

Dillen wrote:

They were very good quality (I see them often and I rarely replace them).

Like my original post said this set has been in my family since new so they are definitely originals and I am sure that the one that failed was more likely due to an early act of stupidity on my part like a a shorted cicuit due to dropped solder, bit of wire snipped of from capacitor leads, multimeter tip slipping when measuring etc etc than an inferior part. And the rest of them of them on the PCB are still working fine, including pre-amp stage but more about that in my answer to Manfy in the next post.

I have learnt in a short time to treat working on electronics like open heart surgery. If you drop something you don't go on and don't switch on until it has been found. Also got myself two 50x50mm pieces of wood to act like spacers so that the set/board cannot touch the work surface where any of the above might have fallen.

Dillen wrote:

An excellent component - but not one you will often see elsewhere.

Yup had to google a fair bit to even find the scraps of info I got.

Best regards

Anton

manfy wrote:

you just need to adjust the idle current for the amplifier

Solid at 24mV

manfy wrote:

unlikely that there is something wrong with the input wiring, particularly since the left channel is working.

Nothing is wrong with the input wiring providing you plug in a Beogram on its original cord kinda proving my theory right.

To recap a bit - I have a 5 pin din to 2 RCA adapter cable, it works fine on both channels on QI and Tape with the following audio sources Ipod, Pioneer CD player and my Pioneer TT (but of course very softly on the TT which has no preamp)

If I use the same cable with the Pioneer TT (MM cartridge BTW) on QII the right channel is dead. Not intermittent. Dead.

You may recall from an earlier post that I recently acquired some other B&O toys, one of which was a Beogram 1001 with a busted stylus. So in the process of reading up a bit on the Beogram and looking at the circuit diagram I realized that B&O bridged left and right channel negative with the earth wire in the cable. The socket on the Beogram supports this, all the pins are bridged except left and right positive.

After a fluke chat with my vinyl guy I got put onto another guy who knew a guy who had a Beogram he wanted to get rid of.  Turns out it was also a Beogram 1001 and I got it with a close to perfect SP14 stylus for +- 50 Euro. The rest of this TT looks like it got driven over by a truck, whole baseplate is shattered etc but now I have a parts machine.

So this afternoon I plugged my new SP14 into my nice Beogram 1001, plugged it into QII on the Beomaster 1000 and both channels worked perfectly. Listening to opera at 45rpm - not so nice - but very entertaining. 

Thank you however for the above advice because I think I will need it shortly for my Beomaster 1001. There the one phono channel is intermittent. Its either the phono hi/lo gain switch next to the input socket or the phono selector switch, fiddling with either will make it work for a while but then the one channel just cuts out. Early days yet, haven't even figured out how to open that one.

Now I need to really beef up on the Beogram, figure out how to get into it, free up the fine speed adjustment which is seized solid and probably replace the belt so that Pavarotti does not sound like a duck on acid in a helium tank.

Best regards

Anton

Dillen wrote:

Not just any sort, really.
B&O used RCA transistors extensively at the time. They were very good quality (I see them often and I rarely replace them).
I'm sure they were offered at a good volume price, but I wouldn't call them "cheap", really.

Oh, I'm sure you're right!
I just read up a bit on the history of the transistor and I'd say it's safe to assume that there was no such thing as a "cheap noname transistor" in the 1960's. Certainly not for silicon transistors because they only started to be commercialized in the mid sixties.
Ultra-high volume low-cost production probably started only decades later.

I just came across a transistor crossreference book from 1963 and it contains exclusively semicon makers from the US, Japan and various European countries.

rgds, manfy

Excellent! So you have a fully functional Beomaster 1000 now.

AntonvZ wrote:

If I use the same cable with the Pioneer TT (MM cartridge BTW) on QII the right channel is dead. Not intermittent. Dead.

[...]

The socket on the Beogram supports this, all the pins are bridged except left and right positive.

Unfortunately this does not explain why the Pioneer turntable doesn't work on Q2. If anything, it's strange that both channels work on Q1, because on Q1 pins 1 and 2 are not connected, which suggests that the GND signals of the pickup coils are connected to GND in the 5-pin DIN to RCA adapter. All 4 coil connections are passed through separately to the output. I checked several diagrams from consumer turntables to high-end products.

Anyway, that's nothing to worry about now. It's just food for thought in case you encounter the same issue on other equipment.

Enjoy your restored Beomaster!

manfy

Check the condition and tension of the contacts inside the Q2 DIN socket.

Martin

Dillen wrote:

Check the condition and tension of the contacts inside the Q2 DIN socket.

Big thumbsup! That I can believe without giving it a second thought. The 3-5mV you get from a MM pickup can quickly turn to nothing when encountering the slightest oxidation on a 50-year-old socket.
Luckily those panel-mount DIN sockets are still readily available in any electronics store for little money if the original socket is beyond repair.

Hi Grissa, unfortunately have no detailed images of that part of the Beomaster from when it was disassembled and before I started replacing caps.  Suggest you hunt around on the web and in this forum. 

If you go through my post thread, the user Dillen is very knowledgeable and helpful. Could never have repaired my unit without his help. And Manfy, he also  helped a lot.

Good luck with your project.

Regards

Anton

The wires at my beomaster are soldered to the + capacitor and I'm not sure it's right ... Brown, black gray and orange .... it's anything and only photos on the 50v capacitor and the transistor side who can help me follow the wiring. Thank you

How I can add some photos?