Beocenter 7007 Tonearm Resets

[Nebojsa Jankovic]

Hello, after a month ot two in standby, I just wanted to play a record on my BC7007. Started it, tonearm lifted, went to the beginning of the record, landed, played for 2 sec, then liftrd and went back to the park position. Tried several times, powered the system down, with no change! Now the arm resets within a second of landing down on the record, every time. Please advise if this is a known failure mode and how to remedy it! Thanks in advance for any HELP!

Location: Eindhoven, NL
Favourite Product: Beogram 4002/04

[Nebojsa Jankovic]

An update from myself. As I wanted to test another set of speakers on my Beocenter 7007, I used the radio as a sound signal and found out that the system shuts itself down after about 20-25 seconds. Turned back to the turntable and it played the LP (Steely Dan Live) properly for about 25 secs and again system shut itself down! So, this leads me to believe that this symptom has to do with the power supply and/or supply circuit itself. Any ideas, please?

Location: Eindhoven, NL
Favourite Product: Beogram 4002/04

[Dillen]

Check the idle current settings.
Check for DC on speaker outputs.

Martin

[Nebojsa Jankovic]

Thanks Martin! Will get on with it, as I also accidentally noticed that one of the “Speaker 1” outputs does not work, as I have always used “Speaker 2” channels…

Nebojsa

Location: Eindhoven, NL
Favourite Product: Beogram 4002/04

[Nebojsa Jankovic]

Hello Martin, if I may ask, in order to reach the solder side on the main board of the BC7007, do all of the components, that are now on top of it, need to come out before the board itself would be removed or is there a way to get to its solder side by removing the bottom pannel of the beocenter?

Thanks in advance for any help!

Kind regards, Nebojsa

Location: Eindhoven, NL
Favourite Product: Beogram 4002/04

[Nebojsa Jankovic]

Hello again, as I feel it is essential for the success and value of our forum, to provide an update on the successfull resolution of my problem on the BC7007! I had reported two issues, primary of the system power-down after 10-30sec and secondary of the issue on the left channel on the Speakers1 output. Both causes had to do with failure mechanism of component wear, logical and expected on a 50-year old system!

Power-down was diagnosed to go back to the surface corrosion on the two potentiometres (adjustable resistors in either left and right amplifier circuit), that provide bias required to be precisely at 1.1V on the emitter of transistor Tr210, see attached photo of this part of the circuit for the left amp (R224 and TR210, circled red and green respectively). After cleaning of corrosion with contact spray onboth potentiometres and fine adjustment back to 1.1V, power-down issue went away permanently!

Speaker output issue was traced miracleously to a short inside the Line-in plug on the rear connections terminal (white/light grey cap), so this was permanently fixed by going a step inward, bypassing the plug jumpers by creating permanent connection on the back board of this circuit located in the back of the in-out terminal. Additionaly, as during this exercise, issue of channel output began moving back-forth between Speakers 1 and 2, this was traced to intermittent function of the speaker 1/2 buttons on the main system control panel, so their respective back contacts had to be also cleaned by contact spray!

I hope this may help our team members, as they experience similar symptoms!

Kind regards!

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Location: Eindhoven, NL
Favourite Product: Beogram 4002/04

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