Today I went on to rebuild the power supply board (#6) of the current Beomaster 8000.
Here is a picture before replacing the electrolytic caps:
The big yellow cans often are out of spec at this age. In this Beomaster, however, they showed reasonable ESR and capacitance values....nonetheless out they went with all the other electrolytics. Here is a pic after putting in quality 105C caps:
I cleaned all the headers on the board and coated them with DeoxIT D100. Then I plugged everything back together, and the Beomaster came on without fuss. I hope the Mundorfs will soon arrive that I can replace the main reservoir caps to put this Beomaster fully on a solid footing.
My 8000 died. I get no standby power. I'm getting ready to do some power supply testing and replace the caps as you have. Do you replace the ceramics too, or only the electrolytics?
ReplyDeleteUsually only the electrolytic ones need replacement. Did you measure the voltage on the 5V rail? If it is low, I would think it is the 10uF cap that is soldered directly to the 5V voltage regulator on the heatsink to the right of the power supply board. Good luck!
ReplyDeleteThanks for your quick reply. I will test for 5v when I get home tonight. I saw that 10uF and did a double-take.
ReplyDeleteFor the 5v rail test I'm assuming you mean pins 3 and 4 of 06P48?
ReplyDeleteI would start at the source. Simply measure across the 10uF capacitor at the regulator. If you get 5V there, check pins 8/9 at P76 on the u-processor board (on its right side) and see if they read 5V.
ReplyDeleteI checked the 10uf (supposedly that's C35) and I get 3.6vdc there. I did replace it with a 50v 10uF because the original cap read 16uF. I removed and checked C31 and get .3uF. I don't have a spare 4700uF, so I'll have to order one. Looks like it's time for the full cap replacement on the power supply. Do you replace the film caps (C32, C37, C38 etc.), or just the electrolytics?
ReplyDeleteExcellent! Did that restore the 5V and the standby function? It does not matter much if you have 10 or 16uF there...larger is actually better.
ReplyDeleteNo luck on the 5v. I'm getting 3.6v. And C31 only reads .3uF instead of 4700uF
ReplyDeleteIf C31 is dead(OC), I would expect the 5V being affected due to the huge ripple coming out of the bridge rectifier....do you have an oscilloscope? If yes, measure the signal at C31. It should be constant (about 9V). If you see a sine wave of significant amplitude this capacitor needs to be replaced.
ReplyDeleteI'll give the scope a try.
ReplyDeleteI am pretty confident that the cap needs replacement. I think if you use a multimeter in DC setting 3.6 volts is about what you'd expect at the regulator output if the bridge rectifier lost its capacitor and has a large ripple. Good luck!
ReplyDeleteI haven't used my scope too much and apparently I don't know what settings to use to get a reading. I connected across C31 and hit Auto to let it decide the default settings. If that is correct, I get a ripple (high wave, medium wave, and low wave). It's not a sine wave. But, I cannot tell from the wave form what the voltage is. I looks like I'm getting 500mV peak to peak. I did remove the cap as I mentioned earlier and got .3uF instead of 4700uF. I ordered a replacement set of electrolytics. They should be here in the next few days. I did not remove the IR receiver cover, so I won't replace any caps under it.
ReplyDeleteReplaced all electrolytics. I powers up and plays! Tested the ones I removed with capanalyzer. Most were nearly gone. Some were dead completely. Time to replace the caps on remaining boards? This 8000 was a real prize and I want it to last a long time. Cosmetically, it's fantastic. It's worth saving.
ReplyDeleteAwesome! Congrats! I would urgently recommend to rebuild/recap the output amplifiers while you are in there. The most important part there is to replace the quiet current trimmer with a modern multiple turn precision trimmer. Rotten caps on the power supply board clearly indicate that this beomaster was not stored very well etc...i.e. there is a real danger that the trimmers go open circuit, which would burn out the output transistors. Does the heatsink get hot on either side while you run it at low/no volume? If they get hotter than ~30C at low volume the trimmers are about to go. How do the big caps in the back look like? Any signs of leakage at the top? They should probably also be replaced if the caps on the board were gone...
ReplyDeleteI replaced the trimmers several years ago. I got this BeoMaster from a colleague who didn't know what to do with it. He said it got hot and didn't want to use it. When I got it home I did some testing and as you said, the trimmers were bad. I replaced them got the voltage where it was supposed to be, and all is good now. Temp is nice and cool.
ReplyDeleteI've been replacing the LEDs with SML-LX0603IW-TR. They are a perfect replacement and have the same MCL output as the originals. I'm also making the LED boards removable with rows of pins and headers. DigiKey BBL-106-T-E. The big caps look ok. But I will test them when I get to that part of the system.
Looks like you are on the way to have a fully rebuilt Beomaster 8000! Nice work!
ReplyDeleteI really appreciate your help. I wasn't really sure where to start looking.
ReplyDeleteLast weekend I fixed my X-2000R. Kept blowing a fuse. After 30 hours of hunting and pecking I found a shorted tantalum cap. Replaced it, and voila, it works again. The trick is knowing where to start.
I've tested as much as I can. I do not have a signal generator so my testing was limited to the Amplifier no load current, offset output, and tuning voltage. Everything checks out. I did notice the Auto/Manual and Stereo/Mono bulbs are burned out. What replacement do you recommend? I found Mouser 560-1730 which is a 6v bulb with .04A and .03MSCP. It is a T1 3/4 which is a pretty close size to the originals.
ReplyDeleteI recommend using red LEDs. You need to put in two to get even illumination of the compartments. Search my blog. I recently wrote about this in detail with some nice pics.
ReplyDeleteBeomaster przepala główny bezpiecznik 4A ,jednak dzieje się to tylko czasami,kondensatory 4x 10000 uf wymieniłem na nowe .Co może być powodem ?
ReplyDelete