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
Nigel....a member of the site returned a BM4400 to my "workshop" for some attention, I sold this to him some years back and it had stopped receiving FM transmissions......the front end and IF section where fine and I just needed a slight adjustment to the stereo decoder fortunately.....there remains a slight issue with the headphones jack as Nigel reported it didn't work, I haven't got any headphones to check it but the output at the connections to the socket show good on my scope.......however I digress....Nigel also dropped off a BG4004.
The hood could do with a polish though on initial inspection there are no deep scratches, the hood is loose and i discovered that one of the securing bolts to the rear is missing the male part of the assembly....I suspect its only a machine screw but will investigate further in due course.
The internal alluminium trims are in very good condition too and the cartridge has a stylus still connected...all good signs
Unfortunately someone has tried to polish out a mark of some description from the platter resulting in a horrible mess....I thought I didnt have one of these platters laying around, however I do so thats another piece of good luck.
Keypads are also in very good shape......
Opened her up and had a look inside......the belt was off as you would expect and there where bits of suspension damper all over the bottom of the set.
Otherwise the insides look remarkably intact and clean, The tone arm was found to be seized and wouldn't respond when the solenoid arm was pulled in, will require removal and freeing up.
There was also a cute little brush lying on the bottom with the B&O logo.......for the stylus i expect, I will power her up once i free off the solenoid and damper mechanism with my variac, providing the current doesn't go through the roof, and see what functionality we have. There will remain the usual capacitor change out and replacement lamps I expect, new belts and anything else that's past its best. Overall this looks like a very nice find .......
Hi Craig
Thank you for starting a thread on it!
You have a platter??? I'm going to have to rent a van to get all the wine I'm going to owe you! That's fantastic!
It's amazing how many of those stylus brushes find their way into the innards of Beograms...
The person I bought it from said her father hadn't opened the lid on it for the last 30 years or so which explains how clean the innards are.
Cheers
Nigel
Ok removed the pickup arm lowering lever and spring assembly to lubricate and ease it back to life......
cleaned up and ready to be reassembled........
The arm replaced i have taken a look inside the internal fusebox and discovered one of the 125mA fuses has been destroyed.......so replacing the blown fuse with my multimeter i connected up my variac and slowly powered up whilst watching the current flow....at 150mA I stopped as there is clearly something amis.......I will start with the transformer and move on to the power supply side of things.....
Removed all the connectors from the main PCB and powered back up slowly and measured 24vac delivered by the transformer with around 10mA load....so reconnected the power supply to the PCB and read around 20mA
Popped a fuse in and connected the supply to the main PCB and was able to measure a healthy 30vdc at the reservoir capacitor......fair enough.
Reconnected P7 to the main PCB and measured no increase in current pulled.....
Reconnected P6 and two things happened when I powered up again.....the drive motor kicked into life and the 33rpm display came to life.....I wasn't expecting that to happen and operation of the keypad switches failed to stop the motor spinning.....there was however no significant increase in load measured at the fuse box...so I powered down and, as ever in times like this, opened a bottle of sauvignon blanc.............
One down...
I've just noticed that the cartridge is a SP15 which I don't think would have been originally supplied with the turntable.
If I've researched it properly these were only ever supplied with the Beogram 4000... could be nearly 50 year old...
Nigelthe SP15 belongs to me, your original is on test in a working deck and sounds great 😉
It just keeps on getting better!
Thanks Craig
I could do with a service manual for the 4004 actually......looking in the products library throws up a 4002 with some references to the 4004......its a little confusing trying to follow, anyone got anything better than this? or am I missing a trick here?
Craig
However.....this small detail aside i have now replaced all the connectors into the main PCB and the current pulled stays reasonable until I replace the connector P8 on PCB8......the current goes high very quickly. Closer inspection of PCB8 reveals a scorched 8D11 diode....
Testing reveals a dead short across the diode, however I cant find any reference to this diode in the circuits i am looking at........
Ohh....and its a type 5527
Shorted 8C14?
Martin
I emailed you the Beogram 4004 schematic for that board 8 output board. It shows that remote control circuit you are referencing with the burned out 8D11 diode.
John
Great stuff John!
I can now see I need a IN4148 and our man from Denmark is bang on the money once again.........shorted 8C14 2.2uf tantal, looks like this circuit is only required for remote control of the BG4004 via a hardwired link on the PHONO DIN connector....I believe I have both components to hand so will push on, thanks guys......as always I appreciate your help ;¬)
Replaced the two offending components and re-installed the PCB8 complete with all connectors...powered up and was pleased to see the unit pulled no more than 10mA at the fuse point.
I imagine the 10mA was the power ON diode at the front of the cabinet glowing......put the platter and belt back in place and run a disc and was rewarded with what I think is a flawless operation..........
Hooked up to a BM4000 and the sound is excellent too......went after a 45rpm test and this was equally flawless, I think.....the pickup dropped nicely onto the 45 disc and played...however it didn't change speed automatically like the BG4000 would and I had to change speed manually...still worked fine but as I have no user manual I dont know if this is normal operation or not?
It’s not. The speed should change to 45 automatically.
More failing tantals, would be my guess.It's quite typical to see, that if one tantal is found bad they will all be more or less the same.
Could perhaps also be the carriage position switches being oxidised?
I had never heard of the term tantal before this thread!
Somewhere along this thread tantal capacitors were discussed at greater length.
https://archivedforum2.beoworld.org/forums/t/25190.aspx
More good news..........had a look at the automatic speed change switch circuit and as I have a couple of 4.7uf tantals to hand replaced 1C21, which appears to be fundamental to the switchover, and to my dismay the old one measured up only slightly out of spec.....non the less I reassembled everything and gave it a go......all is now well! speed changes over to 45rpm just before the pickup reaches the 45 disc and then drops nicely onto it....not sure if the tantal was totally responsible but never the less everything seems to be working as it should....that said I am happy to move on with the restoration now we have a fully functional unit.....
Ok....with a "beta" version of a BG4004 restoration kit on its way from Martin (what a grand chap) I decided to entertain myself with the replacement of the transport lock bushes....I had these made sometime ago with a little help from a member of the site, by a laser printing outfit who for the life of me I cant remember....it wasnt Rudy but someone in the UK.....and when I came to fit them found the originals where still in perfectly good condition....so kept them.
I know everyone has seen these replaced a hundred times......however this was the first time I have seen this particular arrangement so thought it worthy of recording......whoever within B&O decided to replace the brass leaf spring with Bellville washers ought to be garrotted! particularly for arranging thre of the little devils on the underside......
After multiple attempts to keep them the correct way up, 2 facing each other and one facing away, and in place while assembled I reverted to a spot of superglue to hold them together and managed that way
With the bottom assembly complete the top one went very easily.....im sure there must have been a good reason for this small design change.....
Hi Craig,
Yes, I have seen a few different configurations of those chassis locks. All of the Beogram 4004 units I have come across have the separate little washers though. The BG4004 were the last of the Beogram 400x series so I guess B&O felt that was some sort of improvement. At least B&O switched to the metal eccentric trim washers by this series. The earlier 4002 models were usually plastic and typically broken by now. So in improving those cabinet washers I think that they probably made the chassis lock change as an improvement. Like you I don't really see what that improvement is. The individual washers are a little more difficult to manage.
john