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
About a year ago, I gave up my original 4002 after having its main board rebuilt by Menachim Yagad. I immediately must write the issues I have with that 4002 has nothing at all to do with Menachim's superb work. The turntable worked faultlessly for three weeks after I installed the rebuilt board and with the covers temporarily fitted - the issues started after final assembly and I can't even remember what they were.
I recently bought a second 4002 series 5511 which was a bit rough-looking outside but inside, absolutely untouched and unmolested. So I thought I will transfer the best bits from my original 4002 to the 'new' item to build myself a pristine example.
I carefully dusted the new one's interior, free'ed the arm drop solenoid and the adjacent hydraulic cylinder, cleared-out hardened lubricant, relubricated where required according to the manual and finally - I changed the earthing scheme by fitting an earth tag at the rear, two new rca jacks and an IEC socket.
When all the aforementioned work was done, I fitted a cartridge and commenced listening. All functions worked correctly repeatedly with no problems whatsoever.
Then I made the fateful decision to see if I could make my original 4002 work since I now have two so I could compare them side by side to see if I could see anything wrong, which I couldn't.
I then did something which in retrospect I think, was incredibly stupid. I wanted to see if the original's keypad was still working correctly as about a year ago, I fitted 7 microswitches below the brushed stainless cover. It worked correctly at the time but I wanted to be sure.
My stupidity was to swop the two keypads - I plugged-in the original 4002's (modified) keypad into my new 4002. When I pressed "Start", the two motors started working, the platter turned but the arms only moved towards the platter by about 1cm.
Then I got 'cold feet' and decided I cannot risk damaging my new working 4002.
I then disconnected the mains, plugged-in the new 4002's keypad and turned the carriage motor's pulley by hand past the stoppage point (there was no resistance or obstruction) and reconnected the mains current. The platter started spinning and the arms then moved freely in the direction of the platter spindle while the platter turned, stopped and returning to rest. During the arms' traversing, the keypad retained its functions such as speed selection and arm up or down.
With the new 4002's correct keypad reinstalled,I tried the keypad's functions once more and now it malfunctioned the same way as with the 'wrong' keypad - pressing "Start", things started working but the arms stopped after moving only 1cm, even when depressing the start key.
Now things get worse. With the power disconnected I scrolled the carriage motor pulley past the mysterious 1cm stoppage point and the keypad's functions returned. The arms move towards the spindle while the platter spins, arm up or down works, and the arm then returns to rest and everything switches off.
In order to continue troubleshooting the malfunction of the 1cm stoppage point, I used my bench powersupply set at only 4Vdc and touched the two solder pads where the carriage motor's two wires go.
The motors start turning and again the carriage stops after moving only 1cm.
I did not move or touch the perspex ruler and the two tripswitches behind the ruler are clean and undamaged.
There was no smoke or anything else I can see. Did I afterall damage a part or blew something by applying 4Vdc directly to the carriage motor?
Any assistance you can give, please.
Regards to all
dauphine
If the rest of the Beogram was unpowered, introducing 4VDC on the servo motor leads won't damage anything.Swapping modules and parts from one Beogram to another, however, can occasionally cause headaches.There are countless different versions of Beogram 4002 and far from all parts and modules are interchangeable.
Servicing tangential Beograms is not always easy.
Martin
Hi Martin
Thanks for your kind reply. Yes, there was no mains connected. I have already discovered that there are indeed countless variations on the 4002's.
It was a really stupid action to swop keypads and I will have to live with this headache until I find out what happened.
Regards
dauphine/andre