grebe: CR9

I am restoring a Grebe CR-9. Does the unit require an external detector and amp to operate? I tried to connect the filament voltage and detecter / amp voltages to the terminals but i am not getting anything from the speaker. In fact the tubes are not even powered.

Have anyone successful fired up a Grebe CR-9?

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Dear Dino,

could you please specify which type of speaker you used? Preferably, this should be a high impedance type, say 2000 Ohms or even more.

If a low impedance speaker (e.g. 4 Ω)  is used, virtually nothing will be heared.

Did you check the tubes already? Even if the output tube drains a few mA only, this will be sufficient for a high impedance speaker. The anode current of the output tube can be measured directly if a meter is connected to the loud speaker posts.

If you can't measure an anode current, try the switch contacts of the 2nd stage. Are they clean?

You also can check the 2nd tube in the same way if it is plugged into the output stage.

If you can measure anode currents, you may touch the grid pin. Then a sratch and/or a hum will be heared with an appropriate speaker (or in a high impedance headphone).

Also the AF transformers should be checked with an Ohmmeter. Sometimes, old transformers suffer from interruptions of their coils (mostly near to their posts).

Regards,

Dietmar

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I managed to get the unit to work. I always use a high impedance speaker. the output transformer was bad but i had already replaced that. The issue was the CR-9 unit needs you to plug into the 2nd stage headphone jacks with a special plug. i used a stereo headphone plug and got the unit to work!

Thanks for your help though!

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Any ¼" standard phone plug will do the job, regardless if mono or stereo type, to connect the speaker terminals to the output stage.

There is no output transformer, so one of the two interstage transformers must have been defect. Open secondary, I guess?

Regards,
KoBi

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Thanks for the reply, yes the second interstage transformer had a open primary.  all is good. Thanks again.

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