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
Hello Everyone.
As it's my second post (the first was to reply about tape belt replacement on the french forum), I would say a little word about me:
I'm French, new to the B&O world and stepped in with a BS2500 fully working, followed by an Ouverture I bought to train myself on small repairs and which is now fully working too and a BS3000 sadly with faulty eprom.
Next gift will be a pair of nice Beolab, 6000 or 8000 if i can afford them.
In the meantime i've got two sets of Beolabs 2500 with are the reason why I'm here.
One of the Beolabs was silent with the red light on. I take it to a friend of mine, pretty comfortable with electronics. Long story short, the NTC (Thermal protection, PCB N°25) prevent the speaker to turn on.
I just disconnected It and now it's all running fine. I'm currently listening music from it, monitoring the heat at the backside of the enclosure.
But i also noticed something weird: the desing of the main board (PCB 22) don't match the diagrams in the service manual. Some capacitors or resistors don't have the expected value but even more, the R19 and R20 fuse resistors are replaced by a strap and the two vertical circuitry for adjusting bass and treble are not their either. Also, the NTC plug is horizontal where i believe it is usually vertical. I've add a picture of the main board.
Despite this, the beolab sound well and the sound match the other pair to my ears.
So here are my two questions:
- How "really" dangerous is to run the speaker with the NTC off. Never listening music at moud level but usually for several hours long.
- Is somebody aware of changes in the design of the Beolab 2500. As far as i know, R19 And R20 are protection, and first thing to look at when the speaker is silent: how can fuses be replaced by straps?
Thank you for your answers.
Hi,
the NTC has a resitance of 330K Ohm, which is quite uncommon, but sometimes available. I would recommend to replace it so that the BeoLab is well protected.
Concerning the two resistors / jumper wires you should read this .
As you can see they changed some things during the production cycle which might also be the reason for the orientation of the pin header for the NTC connection
Ralph-Marcus
Thank you RaMaBo,
I did find that post some days ago and it gave me peace to find that I was not stocked with any experimental prototype or something. But still no clear answer about this: why replace fuse which belong to the basic servicing program bu jumpers. Anyway…
Finding for some answers on the web, I also advise that the power Amp was not the same either. I've got a STK4172II when it's usually a STK4191. I did some search and if I read correctly the charts, the 4172 as less power output and more harmonic distortion (THD). Not a big deal for me since i don't listen music loud and don't be even close to notice any harmonique distortion at all. In one word, I'm fine with these 2500's!
For the follow up, i'm still using it with the NTC disconnected and so far no problems. But i'll carefully follow your advice to replace the resistor in the next weeks.
By the way serial is 14652xxx, but i dont know ho to read it (in the other post, higher number seems to indicate earlier production).
Cheers.