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
Being very new to B&O products, I have been completely bitten by the sheer "magic" of the technical engineering of all the vintage products. I have aquired 4 turntables,5 amplifiers, 1 tape deck, Beocentre, of which some are in working and beautiful restored condition. Then I have multple Beomaster amplifiers, 1001,2400,3000, and 4000.
Coming from a electronics background I have repaired and restored only a few B&O amplifiers. I,m still getting aquainted with fault finding and repairs. I do have a scope that makes things much easier with signal gens etc. I own some of the above, that is 3000 and 4000 Beomaster as well as Beocentre my pride and joy, I also own a Beogram 4000, for me this is the ultimate, perfect working order, as well as 1202, 1203 beograms. Both amplifiers a 3000 and 4000,switch on but on the 3000 there is no stereo, and on the 4000 only one ch is working. I found the problem with the 4000, that was blowing the drivers on one ch, it was incorrectly wired. I'm still working on the 3000 that is not working on stereo. I have also started recapping the 2400 amps (2 of them). Both when switced on are either muting or fault switch is "operational" Starting from scratch how do you repair this fault. Surely if there is DC on the output it should first power up and then switch off? I have checked the drivers and they seem to be fine. If the output caps(3000 microF) are faulty and no speakers connected (using earphones) it should power up?. I havent checked the fault detector or muting circuit components, that is the next step. As you can see I have multiple projects at the moment and will be busy for quite a while with repairs and restorations. I'm totally bitten and am a B&O hoarder. Just love it and needless to say I'm having marriage problems tongue in the cheek! Needles to say I have found plenty of "tips" and advice on this forum.
Are there still spares available for Beogram 4000/6000 turntables. One of the faulty turntables I have, the microswitches are totally broken. I dont know how it happened but it has? Being in South Africa, certain spares are difficult obtainable. Fortunately I have contacts in Australia, but not in the UK or Finland for that matter.
Tackle one thing at the time I would say.
DC at the output is "normal" to a certain point but zero is always best. It also depend on how the amp was built. Some have coupling capacitors at the output in order to remove that DC while others don't.
There is also the deferential transistors to check, these are usually perfectly matched to remove DC from the output. Shorted or blow output transistors, capacitors, resistors are all in the mix.
When working on a vintage amp, first I always recap then I check every single component. It is time consuming but it works all the time.
Good luck!
I started with beogram 2400, recapped, Power on and all indications are working, but sound is muted. Is it possible to "bypass" the mute switch?
I am resorting to my signal gen and scope to check further . I've spent too much time trying to get this working?
Assuming you are talking about Beomaster 2400 rather than Beogram 2400, which is a record player;If you are absolutely sure, that all lamps are correct wattage (wrong wattage lamps can cause muting due to the way source switching is done),check the lamp in the volume controls LDR housing.A clever little circuit monitors this lamps current flow, and if the lamp burns the Beomaster is immediately muted (or it would have gone to constant max volume).Bypassing isn't repairing, and you wouldn't enjoy using the Beomaster with its muting circuit bypassed.
Martin
Hi Martin,
At this stage I've got both units powering up, with all indications etc. Thanks for "convincing" me not to bypass the mute cct. At this stage one channel is working, and the left ch totally distorted and overheats even after replacing the darlington's with TIP 142, and 147. Can't get originals here. Next step will be to check all the voltages and make sure all the replaced caps are correct, which I've done 10 times and still found incorrect values. Replaced 22 with 2,2 microfarad caps . I'm now working with glasses, lots of light and magnifying glass. I am retired and with LD I've got time. Never enough. I've still got 7 more amplifiers and 1 Beogram 2400 waiting. My problem is also getting microswithes for beogram 2400?
Love this forum I've got so much info and tips, and always the right stuff.
regards,
Francois.
Hi Martin ,
I'm looking for beogram 4002 spares, not the 2400 as stated previously. Spesifically the microswitches (Travel start and stop) Are they still available?
Can orders be posted to South Africa if small enough? Thanks again.
Did you replace the idle current trimmers and adjusted them?
The next step will be the trimmers and checking all the other components. Thanks for all the info.
The voltages are totally incorrect, and there is no adjustment. I'm checking all the components in the amplifier section for a start.
Thanks for all the info once again, I got one 2400 working perfectly after recapping, changing the darlington's output on the left channel, repaired the balance slider and what a beatiful sound. Sounds quick and easy, you'll know it isn't but still gives me great pleasure working on these vintage beasts.
Morning Martin,
I've got the 2nd 2400 up and running.
It seems that there is no right ch. The problem seems to be the balance or volume control, any ideas.
I've opened the balance and repaired one sliding contact but still no joy? The volume works but right ch no or very low input. This counts for phono inputs and FM. There is no balance control, I've checked both channels are OK.
How do I order balance and treble 20K sliding pots? I need 4. I used the treble pots for balancing but still need to replace all 4 on 2 x 2400's.
Kind regards,
JFV.
I could only find 12V 1.1W. This means current consumption of at least 100mA? Will these lamps influence the working of the volume control as the indication and volume increase seems to work. If this is the case I also need to order pot kits x 4 for balance and treble sliders as well as lamp kits?
The stereo indicator is also not working on the one lamp. These lamps were all replaced by 12V 1.1W lamps.
I do require or order at least 4 x 20K pots (sliding kits) and 30 lamps 12V at 80mA?
How do I go about this. Can you send me a Quote or proforma invoice, I'll do the payment and post/courrier fares.
I requested this in my previous post but forgot to mention the lamps. How critical are the lamps in the volume control touch pads?
The lamps are critical for many functions. They form part of many of the operating circuits, volume control, tuning descriminators, muting during channel switching, bleed down at standby...
100mA is far too much.The correct lamps are not 12V 80mA and not 12V 1W either.Both are stated in some servicemanuals and both are wrong.12V lamps would be overrun (and draw even more current at that).(From memory) the correct lamps are specified something like 14,8V 83mA. And they are not T5 socketed types as I have seen listed on Ebay - they should have leads for soldering.I have the correct lamps. PM or email me.
You cannot use a treble potentiometer instead of a balance. (That could explain the missing channel).The three potentiometers Treble, Bass and Balance are all different.Bass and Treble have different ohmic values, and the Balance potentiometer has zero ohms at the center and channels working in reverse towards the ends respectively.
Did you replace the plastic bridges that hold the small sliding bronze contacts? That's what usually breaks.Kit here: https://beoparts.com/2018/01/13/beomaster-1900-2400-potentiometer-repair-kit/
Martin,
Thanks again for all the info, Just checked the balance, and right I used the wrong sliders. I have "filed" the original sliders and now can't find them.
Just checked the lamps and they are 12V 1.2W That's minimum 100mA.
Can you still get micro switches for Beogram 4002? Need at least 2 to do a repair? Part no 7400115.
How do I go about ordering?
So much info, what a pleasure to ask Martin for anything!!