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 was a offered a non-working Beogram 4000 for 50EUR, how could I resist? External appearance was very good but there was clearly something wrong as the arm carriage was loosely sliding on it's trail and powering on the deck only gave light on the detector arm and the faint glow on the speed indicator. Other than that there was no life, except a rumbling noise when the arm movement switches were operated.
When I got the deck home, I opened it up and soon made the following finds:
- main drive belt was loose inside
- the whole red plastic indicator arm for the percentage display was loose inside
- the arm carriage drive threaded screw was loose, it's drive belt and wheel loose inside
- the up-down-left-right -control was slightly tilted causing the up switch being operated all the time
- at least two big capacitors next to the power supply board were replaced; however they were very loosely placed and under them there was a lot of black goo, perhaps even from an exploded capacitor?!
I have some pics in here.
Also during disassembly, one of the AC input wires from the transformed broke off the PSU board.
After having a long look around, I was positively suprised that just about all loose parts were still inside the case and looked about Ok. Nothing seemed to be missing at least. After some figuring out I replaced the parts and was surprised to see that I get the deck to power up, move the carriage, lower and raise the arm... looking much better!
Tracking is still not working, but that was soon traced to a burnt bulb in the sensor mechanism. I put a light source over the exposed sensor and the tracking seemed to work to both directions.
There are also some signs of a previous repair on the PCB next to the stroboscope lamp; at least one trace is cut and one red wire soldered to the non-component side of the board (see pics). About on the reverse side, there are some marks of heat on the board, and R23 looks like it has been replaced. Wonder why?
Other than these; the PCB looks very nice, the pots look like new!
There is like a bit of rust on the top of the mains transformer; should I worry about that and how should it be cleaned?
One thing I am not too sure; when powering the deck (without a record) it moves in to a 30cm record start point and lowers the arm. I thought it should sense the edge of the record and in this case, move into the 17cm start point? I tried blocking the sense arm but it had no effect. I can't get to my records at the moment so couldn't test it in a real scenario.
As if the faults mentioned above get resolved, I'd like to for a total re-capping as well (have a kit for that, Martin?).
Anyway, this looks like it's getting slowly back into one piece. Great! Really a great piece of engineering, especially I like the way it opens as the wood slides out and releases the aluminum pieces etc. Just lovely.
Great buy, and good work so far I guess!
First, the red wire. It's present on other decks too. So no worries here, leave it like that.
Then, you ask whether the arm should move on when no LP is detected. The answer's yes. The speed will also turn to 45rpm, and should no EP be detected either, the arm will go to its end stop and travel back to its resting position.
The capacitors that were replaced are the motor amp output one and the motor run cap. They (?) seemed to have leaked, but why the mess was not cleaned beats me!
Ideally, all of them should be replaced. However on my deck, they were all good, within specs. Yes, even the ominous orange ones!
R23 had obviously burnt, perhaps accidentally.
The transformer's rust is not important. Use some white-spirit.
You really want to post pictures right here by the way...
Jacques
I was too lazy to post the pics here, but I'll edit them in later and add some more
I watched a couple of YouTube vids, and on those it looks that without record the arm should move across the platter, return and power off. So it seems that something is wrong in my deck about that. I can see light coming from under the sensor arm, but I'd better see some more photos of working decks to compare. And finish reading that service manual!
Oh yes!
The troubleshooting guide is an absolute must-read! And that B&O techs did it so thoroughly makes sense - it was the first of its kind after all, so repair workshops had to have it to get the logic right.
There's a possibility that the sensor light is not perfectly aligned, or that the main belt has become slippery, so that the startup speed is too slow to send the correct pulses to the detection circuit.