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
Beomaster 8000, one channel distortion at low volume.Fault located to the power stage (PCB no. 5). Idle current & DC offset adjusted according to service manual.
Distorted sound all low volume, mostly in the low frequencies. At higher volume (over 3.8) there no audible distortion.
Where to start look? I'm thinking input cap C200 or TR201/202.
Ideas?
//Bo.A long list...
Capacitors ?
Martin
OK, I now recapped the board, found some bad caps. Readjusted Offset and Idle current.
Still same problem with distorted low volume.
Is the distortion there coming out of the preamp board?
-sonavor
No, signal from PCB3 and PCB4 is undistorted.
Speaker switches... Is the distortion on both speaker sockets ?Is the distortion also in headphones ?
On both speaker sockets but not in the headphones!
Sometimes you look in the wrong places
It turned out that this little thing was the culprit!
Found out when connecting the speaker directly to the pcb. Since the sound was good in the headphones i suspected the speaker switches, but when the distortion still was present i started to suspect the speaker! Thanks to Martin who put me on the right track!
Still have to solve the input-card problem. The TP1 switch is malfunctioning.
The switch keeps the TP1 active on one channel even when not activated, thus stopping the signal from FM/PH/TP2.
Temporary solved by bridging, but then I have no TP1 input.
You haven't found a modern replacement IC switch device? The control for the switch has to come from the switch panel. Have you checked that the connection from there is working? I have had some outages with my volume control and FM station dial - those were the result of connections (wire connections) starting to break where the ribbon cable connects to the button panel board. In fact, many of my Beomaster 8000 issues have just been connections.
sonavor:Have you checked that the connection from there is working?
The same control signal and IC is used for both channels and only one channel have the problem.
There is a possible replacement: AD7512
http://docs-europe.electrocomponents.com/webdocs/077f/0900766b8077fdee.pdf
Alternatively a mechanical relay will do the job.
Mouser carries the AD7511It is an expensive little device.
I ordered some AD7512DIKN from China. Lets see how it works out, when and if they arrive!
They will be fakes, make no mistake. Oops, too late!
Jacques
Maybe or maybe not. I've ordered components from China several times and has not been disappointed so far!
Of course I know there's a risk, but its always a risk buying something on the Internet.
http://www.ebay.com/itm/1X-AD7512DIKN-Protected-Analog-Switches-AD7512-/121017773933?pt=LH_DefaultDomain_0&hash=item1c2d38af6d
BO:Maybe or maybe not. I've ordered components from China several times and has not been disappointed so far!
For my solar water heating system I ordered pump and controller from China, 1/10 of the price in the US, And same quality, as most of these items are China made and only has a different brand name attached.
Collecting Vintage B&O is not a hobby, its a lifestyle.
I meant this particular, unavailable component. I steer clear of miraculous finds like this. But you might be lucky indeed.
I wish myself luck, but it's not that difficult to find.
Analog Devices AD7512DIKQ
I tried replacing the switching IC's with relays and it really made a difference, much more detailed/clear sound on my BM8000 +M100 speakers. I am terribly allergic to audiophile upgrade nonsense but I really like the result on this one.
Could be the combination of BM8000+M100 though, I have yet to test how it sounds with the MS150 I just bought but they need recap first.
Maybe the new AD7512 will also have clearer sound than the old IC.
Do you hear a difference in sound with the wire bridge in place?
Premiumverum:Do you hear a difference in sound with the wire bridge in place?
Arrived today. Let's see how it works out.
They look genuine.
Keep one for me!
chartz: They look genuine.
I don't know.I never saw the triangular Analogue Devices logo that big and in front of the rest of the lettering before.They were always like this http://image.usatradekey.com/usa-on-sale-1029580-AD7512DIKQ.jpgor had no logo at all.- But they could be genuine.
Success. Its working!
Nice!
Excellent! Does it sound good then?
chartz: Excellent! Does it sound good then?
Great news. If the new components pass your burn-in tests the supplier could be a good source to go back to.
Now the board fully recapped with some upgrades (film caps & "better" OP-amps)
Which op-amps did you replace and what did you replace them with?
Hi,
the old standard chips IC1,3, 5,6,7 and 101 / 201 (LF 353N or TL072CP) were replaced with new, better OPA2132PA (could be seen on the picture).
At least IC 3,5 and 7 but i guess he did all in the signal path.
You can search the forum for OPA 2132 and will find quiet a few threads about changing the original OpAmps against better rated, new ones.
Those OPA 213x are very low noise, high slewrate (good for high freuencies) and direct replacement because of the pinout.
Ralph-Marcus
RaMaBo: Hi, the old standard chips IC1,3, 5,6,7 and 101 / 201 (LF 353N or TL072CP) were replaced with new, better OPA2132PA (could be seen on the picture). At least IC 3,5 and 7 but i guess he did all in the signal path. You can search the forum for OPA 2132 and will find quiet a few threads about changing the original OpAmps against better rated, new ones. Those OPA 213x are very low noise, high slewrate (good for high freuencies) and direct replacement because of the pinout.
Correction. Its the OPA2134PA.