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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi everyone,Just a quick one, hopefully someone can help me out.
I recently acquired a Beogram 4002. Aside from a blown 33rpm lamp, its also got a bit of a hum.
I opened up the DIN socket and inspected all connections and they appear fine. I gave it a good clean with alcohol and some swaps to get all the junk off the external connections.
The hum is heard through my Beomaster 1900 when the volume is above half on the Beomaster which is required as I run 8ohm S55's. The hum is not very loud but annoying nonetheless, it cant be heard once music starts playing however it is audible when there is no music.
The hum is not present if the TT is not plugged into power. Once the TT is plugged into power the hum comes through the speaker straight away. I tried removing the cartridge whilst the power was turned on and the hum persisted. The hum does not change from standby to when the Beogram is playing the record.
I tried to run an additional earth lead from the Beogram's rear panel to the Beomaster and this did not remove the hum. I also tried to touch the earth lead from the BM to the body of the cart as has previously been advised in other threads and this did not remove the hum.
So it appears the hum is not on the cartidge side of the mute relay but somewhere between the muting relay and the Beomaster and is only present once the unit is receiving power. My unit does not have the CD4 decoder.
My service tech friend is having a look at the unit in a few days, are there any suggestions for where to look?
You help much appreciated.
Andrew
When you opened the DIN plug was there a wire (black I think) connected to the tin can?
It's a long time since I had a 4002 but I think this wire is connected to the chassis of the deck via a small capacitor.
Regards Graham
The Din plug had both the signal negative and the ground leads connected.
Inside the unit I did not see a capacitor for ground? Is it in line with the ground wire to the chassis? If so where is it located in the unit and what size cap should it be?
Any other possibilities? I thought being a non CD4 unit that the electronics for the signal would be relatively simple...
Thanks
I have several BG6000's but no longer have a 4000 or 4002 so my comments were from memory.
If I'm not imagining it, thhe connection to the chassis is somewhere near the termination of the output cable and there is a small green capacitor.
I could be talking crap here so will someone with a 4002 please remove the r/h rear panel and have a look!
Graham, you're absolutely correct.
IIRC, it's a 470nF or 47nF 400V ceramic cap.
I don't have any here to photograph it, but if that is broken, the hum will appear.
Menahem
So there should be a ceramic cap between the earth wire and the tag to which it is soldered?
Probably not, from the look of that very original wiring in your photograph!
Thanks for your help everyone.
The hum ended up being a number of things, we replaced the red capacitor on board 8 shown in the picture above, we also cleaned the mute relay contacts with Deoxit and installing a new DIN plug.
We ended up doing a complete overhaul of the Beogram including new filtering cap 50v 4700uf, repairing numerous dry joints on the main PCB, new 5k pots for the 33 and 45 circuits, a few new caps on the PCB, Deoxit D5L on all existing pots and on both the speed and mute relay circuits as well as all keys on the keyboard, and new 22v globes for the speed dials and a bit of machine oil in the motor.
I cant stress how good the Deoxit D5L was for the keyboard contacts, I had previously cleaned them with contact cleaner and it was requiring a decent push to activate them (although all contacts and sprung pieces looked fine), the D5L has decreased the amount of push required dramatically.
Speed is stable, and it really looks the part, enjoy!
Drew
Don't they just look the business, superb!
Glad it's working now.
Welcome to the "Couldn't Be Happier We Own BG4002s Club."
Don't recognize the record in your photographs - what is it?
Thats a 180g pressing of Coexist by the XX, a UK group, very ambient and relaxing, well worth a listen.