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 wise wizards of Beoworld!
Last week I returned home to find my beloved Beomaster 8000 putting on its own christmas light show!
The unit is always plugged in and on standby. Luckily I have developed the habit of turning off both Speaker 1 & 2 switches when not in use. When I walked in after work the entire display panel was flickering wildly and all controls were unresponsive. The mono switch still illuminates its little indicator but no other controls work. After power cycling the mains multiple times I have diagnosed 4 potential states that it ends up in.
1. Straight back into crazy flickering, unresponsive controls
2. Straight into standby (just the small standby segment glows) again, unresponsive controls.
3 Random static characters/numbers displayed, unresponsive controls
4. Completely normal operation!
The crazy thing is that one in 20 or so attempts results in perfectly normal function. I have left the unit operating for an hour (playing an ipod through T1) and the unit exhibits no strange behaviour at all!!!
Then I will power it down and I'm back to square 1 with one of the 4 options above.
Evey time I disconnect the mains I hear an identical double relay type click. As per normal.
Initially I did try turning on the speakers during one of the non functioning states but the amplifier was generating a low level earth type hum so Ive been reluctant to try again in case my S120s or S45-2's end up barbecued!
Now I'm confident soldering on small and tricky boards but my diagnostic electronic skills are not amazing. I do however know my way around a multimeter.
My question to you all is where to start and what to look for. I'm currently recapping a Beogram 8000 but the Beomaster is a whole new level of complexity and I'm just not entirely sure where to begin!
Thank you all again in advance! - Yuri.
Beomaster: 8000
Beogram: 8000
Beovox: MS-150, S120, S45-2
The hum in the speakers indicates that you should start looking in the power supply section. Bad capacitors, bad solder joints, or even defect rectifiers.
Well at least I would start there.
//Bo.A long list...
The flickering indicates to me that the CPU/logcic controller board has a fault.
My re-capped M75 are my precious diamonds.
Ripple on the DC current may cause the CPU to act strangely.
Have a break in my work, so I am haveing a quick look at the Service manual.The flickering could be a digital problem,The board has two main controller ICs, IC3 and IC4.I could find in the list that IC3 is a TCA 4500, but couldnt find the name of the IC4.These circuits could be failing.Another issue is that these two ICs seem to be fed by clock generator solution..Blurry on the diagram there seem to be a CMOS 4013 flipflop IC that is in conection with IC5I asume that these to feeds IC3 and IC4 with a clock pulse.If this clockpulse is not stabile the result could be that the controller ICs 3 and 4 would have a completly irrational function.The more experienced workbenchers then I on this forum, what do you think ?Christian
Good thinking Bo., I agree, to first check the quality of the the power supply.
C
Bad connectors at the processor board and/or processor/display boards interconnects.
Martin
Thank you all again folks. Now I have somewhere to begin. After the Christmas madness has subsided I shall open the beast and begin the diagnosis! My other option, of course, is to just never switch it off but I think my electricity costs may end up astronomical and the neighbors won't be too impressed! But for now:
Yuri....Christmas madness......I certainly agree, all my cozy calm long B&O workbench sessions are completly pushed to 2014....feels like ages until I can sesrious get started again.
Just an update folks, the patient has now lost all life signs so it looks like I will be starting at the Power supply end and working my way from there
Yes go from the power supply, Martins shared experience of bad internal connectors is a very highly valuable knowledge.I would dive very focused into Martins tips, if I were youBad internal connectors could make any machine die