ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hey All,
I'm brand new to the forum and rather new to restoring turntables as well. I found a rather good condition Beogram 4004 with a MMC 20EN in the attic (I know, I know, what a lucky find right) and have been restoring it over the last month.
I opened it and replaced the belts, removed the old lubricant and added new, oiled up all mechanics including the tone arm lower mech. I also repaired a broken dust cover.
It was all coming along great until it came to the signal. here are the details of my problem.
1) The Din cable was severed prior to my finding the unit so I figured I would connect RCA plugs directly into the severed Din cable by ignoring the blue and yellow wires, and soldering the red and white wires each to their respective RCA plug and twisting the signal ground from each RCA plug into the braided shield wires of the DIN cable. So to be clear, unlike most efforts to install RCA plugs, I have not made the change at the 5 pin connector on the Beogram board. Rather, I just spliced into the DIN cable. I did this mostly out of convenience and because I don't want to go through the effort or expense of purchasing and installing a quality tonearm cable if there are any greater issues with the tables electronics (at which point I would make a decision to sell or invest in professional help)
2) I attached a spade to the ground wire of the DIN cable as well
3) I plugged it all into my ROLLS VP 29 preamp (which works great with my Beogram 2400 and standard sony receiver). And put on a stereo LP.
To my dismay, there was no audible signal in the left channel. Right channel was crisp, clear, and the appropriate volume.
My deductive efforts:
1) My preamp receiver set up works great with my Beogram 2400 so I know it's not an issues beyond the 4004’s signal.
2) I pulled out my MM to check wires for continuance. All wires in the DIN cable tested positive for continuance. Also, tested continuance of my RCA connections and all tested positive.
3) Tested continuance of ground (not sure how that would affect left channel anyways) and it tested positive from many test points on the chassis
4) Lastly, if I unplug the right channel, and turn my receiver volume to maximum, I can hear the record very faintly. This makes me think that the signal path is uninterrupted but perhaps impeded. Or that some of the right signals is ‘leaking’ somehow into the left signal or something.
This is where my ‘intelligent’ observations end.
Other observations
1) When playing a record, I have attempted to check the resistance and DC mA across the right and left signal and the signal ground to see if I can spot a difference. Although there is no readable difference on the MM, contact of the test lead of the MM with the left signal wire produces a loud hum through the speakers. (as I write I can't recall if the hum was produced through both speakers). This hum does not occur when testing the right channel in the exact same way. Makes me think the left signal could have an independent grounding issue.
After looking online, I thought that I either have a cartridge issue (damn..) or that perhaps the automatic mute switch was failing to unmute the left channel…
However, I could not find enough info online to feel comfortable taking either of there things apart just for a look-see.
Please help!! Has anyone ever had a similar issue?