Beogram 2400 (5716): Reset automatic system

[Mark Eversoll]

I am resurrecting a long unused US model 2400 type 5716.

The automatic system is out-of-time. Once the tonearm is settled in place, the mechanism turns off the power.

Can someone explain how to reset this part of the system? The service manual explains the theory of operation but I’m not sure I grasp how to do this.

Thank you in advance.

[Mark Eversoll]

Update: resolved. Now to eliminate the hum. Surely these old filter capacitors are to blame.

[Mark-sf]

Your hum issue is likely an improper ground between your turntable and amp. Does your 2400 have a DIN cable or RCA Phone cable. If the former are you using a proper Phono DIN to RCA adapter with a ground wire or are you connecting to a phono DIN input?

[Dillen]

There are no electronics in the signal path in this Beogram.
I agree, that the hum must come from improper grounding.

Martin

[Mark Eversoll]

I would tend to agree with both of the above replies. However, the turntable is grounded to the receiver. Continuity of that ground between their respective chassis is confirmed. And true, there aren’t any electronics between the cartridge and the patch cord. This is an American market unit and not equipped with the typical DIN plug; it is equipped with RCA cables which have been replaced.

At idle, there is no hum. However once the motor is running, the hum is present . Low level, but present and it shouldn’t be.

The service manual found on the internet does not address the 2400 (5716) model in particular. The parts lists and even component locations on the PC board don’t match.

I suspect I have a ground loop within the turntable or an issue in the power supply. It’s been in my hands since new and has never been in a shop. I’ll report what I find as it may be useful to others with this model in general.

[Mark-sf]

The fact that it is silent when the mute switch is engaged is indicative of an improper ground configuration. This can happen when cables are replaced. With the table unmuted and the RCA cables disconnected, take the following measurements with an ohm meter:

1. Measure between the ground wire and shield of each RCA and you should see an open connection >1Mohm.
2. Measure between the ground wire and the ground of the circuit board and should read 0 ohms.
3. Remove the cartridge and measure between the ground wire and the copper tang at the end of the tonearm – should read 0 ohms.

If any of the above are not correct, you can get a hum.

[Mark Eversoll]

Thank you for your suggestions. I find no connection between the board ground and the chassis ground when unmuted (or muted for that matter). I have checked each of the hot/cold left/right channel connections between the tonearm and the RCA’s. The search continues as time permits.

• This reply was modified 2 days, 22 hours ago by Mark Eversoll.

[Mark-sf]

If you do not have continuity between the cartridge body clip, board ground, chassis ground and external ground wire you will get hum.

• This reply was modified 2 days, 12 hours ago by Mark-sf.

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