Beogram 4002 - 5513 - I can almost feel this thing working... but it isn't.

9 replies
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gammatest (archived2)
Bronze
Posted December 17, 2018 at 19:29 GMT
#2225402

Alright, 

Thanks so much for all your help thus far. I am making progress since I last reported... I started adding a fresh set of RCAs to this 4002. The cartridge that is on it has a broken cantilever; however, I just wanted to test the new RCA cable from the output board by connecting it to a DJ Mixer w/ Headphones (that is fully working for other tables (Technics SL-1200).

I am using this diagram from beolover to assist my testing.


Here are the test results:

1. With no cartridge installed - both R and L channels BUZZ (not hum) super loud. I'm not sure if this is normal behaviour or not. Once the output relay switches on -- buzzzzzzzzz.

2. With the cartridge installed - only the L channel buzzes - the R channel does have a bit of hum (that stops if I touch any piece of metal in the ground path), but would still be listenable (though not enjoyable).

3. If I bridge System Ground (shield) and the Signal Return Ground - no effect in hum.


What are your thoughts... what do you hear on your BeoGram 4002 with no cartridge installed? Is there a crazy ass buzz? Is it silent?

I feel so close (yet so far)...

Thanks for all your help so far!

DI
Offline
Dillen
BronzeModeratorFounder
Posted December 17, 2018 at 20:31 GMT
#2225403

A buzz is to be expected with no ground control of the signal.
In theory, without the coils in the cartridge, what you have is an open and very high impedance arial connected
to an amplifier with a thousand times amplification, connected to speakers.

You may even be able to hear if you just near a finger to the cartridge socket.

Martin

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gammatest (archived2)
Bronze
Posted December 17, 2018 at 21:36 GMT
#2225404

So, if one of the coils / channels was damaged - it is possible to cause that buzz in just one channel with the cartridge attached?

Do you think it is possible to use a jumper wire from the "good" lead on the cartridge while not plugged into the tone arm - with the jumper wire connected to the correct lead L/R in the cartridge socket in the tone arm to test this theory?

I just want to make sure my signal path hasn't been compromised before I drop a lot of money on a cartridge. The tonearm looks very difficult to rebuild if something is wrong with the wiring.

DI
Offline
Dillen
BronzeModeratorFounder
Posted December 17, 2018 at 22:52 GMT
#2225405

You can test the cartridge with an ohmmeter across the signal leads.
If you do it from the outside - that is back into the signal cable to the amplifier - you will also be able to confirm your
work with the cabling - just make sure the Beogram is in play mode (muting relay drawn) or they will all be grounded.

Martin

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gammatest (archived2)
Bronze
Posted December 17, 2018 at 23:17 GMT
#2225406

Thank you for your prompt reply!! It is much appreciated.

 

Could you please explain this procedure:

1. What do I set my ohmmeter to? 

2. The negative lead of the multimeter goes on which pad from the graphic below?

3. The red lead of the multimeter goes on which pad from the graphic below ?

 

The graphic below is of the tonearm, but I will use the corresponding pins on the cartridge.


 

DI
Offline
Dillen
BronzeModeratorFounder
Posted December 18, 2018 at 13:13 GMT
#2225407

gammatest wrote:

Could you please explain this procedure:

1. What do I set my ohmmeter to? 

2. The negative lead of the multimeter goes on which pad from the graphic below?

3. The red lead of the multimeter goes on which pad from the graphic below ?

 

The graphic below is of the tonearm, but I will use the corresponding pins on the cartridge.


 

1. Ohms...

2 & 3 The polarity is not important (the coils are not polarized) . Just measure across the coils, one at a time.

But you cannot measure the cartridge and wiring from the cartridge socket. Then the cartridge (and its coils) wouldn't be connected.....
Fit the cartridge on the arm.
Play the deck.
Measure from the signal cable amplifier end (not connected to the amplifier), from ground to signal L/R respectively.
Expect 300-800 Ohms or so for both readings.

Martin

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gammatest (archived2)
Bronze
Posted December 31, 2018 at 16:23 GMT
#2225408

I bought a brand new in box MMC20 S-R cartridge to see if I got the same buzz.

I do. This is not a good sign. 

 

There must be something happening in the signal path between tone-arm and where it connects to the board with the 8 on it. Any troubleshooting tips on tracing the path between tonearm and the output board? Or what else may be causing the crazy buzz in the one channel?

 

 

G(
Offline
gammatest (archived2)
Bronze
Posted December 31, 2018 at 16:23 GMT
#2225409

I bought a brand new in box MMC20 S-R cartridge to see if I got the same buzz.

OK.

 

If I press on the cartridge a bit - the buzz goes away... leading me to believe the connection from tonearm to cartridge is compromised somehow.

Anyway... there is still a little hum (no buzz) - I'm going to put this together (FINALLY) and see if I can play some nice jazz records.

 

 

 

G(
Offline
gammatest (archived2)
Bronze
Posted January 1, 2019 at 02:30 GMT
#2225410

CLOSE THE THREAD... turntable works... no hum... there is a loose connection between the cartridge and the tonearm, but with a little pressure is now operational.

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