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
I decided to make one more check. With P51 disconnected on the power supply board I can take the BM8000 out of standby. So with that scenario I am able to verify there is +-15V on those two regulators. Does that mean there is a short in the relays RL1 and RL2 ? Or can it still be some component on the power supply board?Here are the regulators.
I forgot to mention I found something odd on the power supply board. In this picture you can see that one of the new, recapped electrolytic capacitors (C40) is bulging at the top. Maybe this is a result of the short? C40 goes from the -15V regulator output to ground (in parallel with D9).
Dom
2x BeoSystem 3, BeoSystem 5000, BeoSystem 6500, 2x BeoMaster 7000, 2 pair of BeoLab Penta mk2, AV 7000, Beolab 4000, BeoSound 4000, Playmaker, BeoLab 2500, S-45, S-45.2, RL-140, CX-50, C-75, 3x CX-100, 3x MCL2 link rooms, 3x Beolab 2000, M3, P2, Earset, A8 earphones, A3, 2x 4001 relay, H3, H3 ANC, H6, 2014 Audi S5 with B&O sound, and ambio
I replaced C40 but in doing so and reviewing the before and after pictures of the power supply board I realize that C40 was in backwards. So the bulging was from being installed incorrectly rather than the shorting of the 5V regulator.
With a new C40 installed correctly, the problem has now changed. Attempting to take the Beomaster out of Standby (with everything connected) still illuminates the Dim Bulb Tester but dimly now. I can go to Phono mode. When I try an FM station though, the unit shuts off. I checked the outputs of the voltage regulators again. I have a good +5V and +15V but no -15V.
Check the rectifier.It saw an overload too when you shorted the cap.
Martin
I replaced the -15V regulator. That only temporarily worked. When I tested the power supply with the new -15V regulator, power came on, the Dim Bulb Tester stayed very dim (so that is good). Putting the Beomaster into Phono mode displayed correctly on the display and the -15V regulator measured okay. I selected an FM preselect and the channel displayed correctly. The Beomaster remained on. So all looked good. I removed power and my test leads. I turned on the speakers and powered back on. When I tried to come out of Standby the Dim Bulb Tester flashed brightly and put the Beomaster back to Standby. The -15V regulator is now shot again. So there is something in its path that is knocking it out.
I removed all connections from the board and re-measured the input voltage through the rectifiers. They appear good. The D5 output is +11.51V for the +5V regulator. The D1/D2 rectifiers are producing +26.05V. The D3/D4 rectifiers are producing -26.05V. I checked the D9 diode that is in parallel with C40 (the electrolytic that was backwards). D9 measures okay out of circuit.
The input to the -15V regulator comes from IC9. I haven't checked that yet. I only have one -15V regulator left so I won't put another one in until I find what is likely causing it to fail. It is strange that it worked right at first. I don't know if the regulator would have failed if I let power stay on without engaging the speaker but I'm not going to sacrifice another regulator to find out.
The picture here shows what I have measured. The red bar shows the original short that caused this whole problem.
Just a tought.., for i'm just an amateur in electronic... but it's strange: i've blew the exactly the same cap a few months ago by doing the exact same mistake... (Maybe because it's strange to see two same polarity face to face i dont know...) it just exploded! However I just changed it and everything was back to normal... So perhaps you should continue searching in the area of the regulator?
by the way, thanks for sharing all this, i'm learning a lot...!
Guillaume
... What about the two small 180 ohms resistors linking the power supply to the rectifier, just at the right of the startup board? Mine was burned.. (the one linking the red wire). Don't know if the cap caused this however...
Yes, I was fortunate the misplaced cap didn't explode but it isn't related to the problem that occurred from the short on the 5V regulator. The incorrect installation of C40 was back at the beginning and had been operating that way for over a week. So lucky that cap was built for punishment. The shorting of the 5V regulator and subsequent attempt to power the Beomaster on with a new fuse and no Dim Bulb Tester in the circuit must have allowed a power surge in the receiver I guess. That probably damaged some other parts (including the -15V regulator). Whatever the problem is now, it doesn't seem to affect the 5V and +15V regulators. I'll probably have to start taking out and testing the transistors and diodes associated with the -15V path.
hamacbleu: ... What about the two small 180 ohms resistors linking the power supply to the rectifier, just at the right of the startup board? Mine was burned.. (the one linking the red wire). Don't know if the cap caused this however...
That is a different transformer than the one that supplies the 5V and +-15V power. That is up on the +55V and -55V rail supply. I haven't checked that but I will just to finish checking the power.
I have been checking components in the -15V path before the regulator and after. I had measured -26V at C34 (2200uF) so I was pretty sure D3 and D4 were fine but I measured them anyway. I also checked the IC9 Darlington at the input of the -15V regulator. It measures okay out of circuit. I went ahead and checked C38, C40, D9, D8, R39, D14 and TR18. I couldn't find any faults. I didn't go over to the modules that get -15V (from P46 and P53).
So I am considering putting the components back. Using my last -15V regulator and leaving P46 and P53 disconnected (as well as leaving the speaker switches off). That will verify the circuit before the regulator is good. I also checked the -15V regulator to make sure all three contacts were isolated from each other and the heatsink it mounts to. No problems detected there.
Here is a diagram that shows the -15V components I have checked so far.
I installed my second (and last) spare -15V regulator. I checked all of the power supply components the precede the -15V regulator and they all checked out good. So I put them all back along with the new regulator. After that I re-installed the power supply board and connected almost everything back up. What I did not connect were the three power supply connectors I suspect the fault to be from. Those are P51 (the connector to the +-55V rail relays), P46 (-15V power to the preamp board), P53 (-15V power to the filter and tone controls board). I kind of suspect P51 as the most likely. If something went bad in the relay that could affect the IC9 Darlington on the power supply board. That same node sends -24V to the -15V regulator input and to one of the relays for the +-55V. If that relay control took the regulator input to a voltage less than the output, would that take out the regulator? In any case, I think I can say the problem is in destination of one of those three connectors.
Here is a diagram of what I currently have disconnected.
The Beomaster power supply is doing fine with the three connectors I have left disconnected for now. The 5V, 15V and -15V regulators are working good. Today I decided to look at the start up module [7] that is the destination for the power supply connector P51 that I have removed. That connector controls the start up relays the allow AC voltage in to the large Beomaster transformer that supplies the +-55V. With that disabled and no -15V to the preamplifier board or the filter control board, my -15V regulator is still alive.
I checked the 5.6 ohm, large resistors on the start up module as well as diodes D1 and D2. Everything measured okay. I also went ahead and checked the two 180 ohm resistors (30R1 and 30R2) that the +-55V power goes through to get to the power supply board (connector P50). Those look okay. I haven't tested the 30D1 and 30D2 rectifiers yet.
Here is a picture of the start up module.
I put the BM8000 power startup and power supply back together again and verified I am still at the same place. The 5V, 15V and -15V regulators are all good with everything except P46, P53 and P51 connected. After verifying that the start up components look okay, I am having trouble figuring out how a failure in that path would take out the -15V regulator. I am not seeing the connection. So I left the 30D1 and 30D2 rectifiers alone (I didn't pull and test them).
The +-15V supplies power to a number of opamps on the preamplifier board and that power comes from the P46 connector on the power supply board. I decided to risk the -15V regulator and plug the P46 connector back in. So far that test is passing and the regulators are still good. Tomorrow I will reconnect the P53 connector on the power supply board. That goes the filter control board. I have a feeling it will test out fine too. If it passes, it will take me right back to the P51 connector and to the start up circuit. It seems like if there is a problem down that trail, it has to involve the +-55V rail voltages and the power amplifier boards. But I haven't found the relationship there to the -15V regulator.
...a lot of ifs so I will just have to try one connector at a time with the startup connector being last.
In my previous post I connected up the power supply board connector to the Beomaster preamplifier board. I accidently referred to the connector as P53. It was actually P46. I corrected the previous post so it does say P46 for the preamp connector.
Today I connected P53, the connector to the filter control board. Testing the BM8000 functions with that connected was successful. I still have 5V, 15V and -15V as I sequence through Phono, tape and FM.
So that leaves the last connector, P51. It will probably be tomorrow before I can get back to my bench. Once I connect that connector, the Beomaster will be able to get +-55V on the output amplifier boards. I have been here before. I do have a few more -15V regulators now (they are less that $1). I also plan to connect my scope to the input and output of the -15V regulator and see if I can catch any failure event. For the first step, I will leave the speakers disconnected and just test the voltages with all of the connectors (P53 included) connected. If that goes well I will check the amplifier section with headphones. If that test passes I will try a speaker load. Note that I haven't replaced any components in this path (P53). I removed, measure and re-installed some components on the start up circuit but that is all. So I am expecting something to take out the -15V supply again. I just hope I can catch and figure out the source of the problem.
I went ahead and tried the start up circuit connector (P51). There is still something wrong in that path. Fortunately my -15V regulator survived the single test I ran. Prior to the test I checked the -15V regulator input and outputs with my scope just to make sure I had everything setup to catch the problem. I tried a single trigger for the power on and then again for the power off (opposite edge of course). I was hoping then to re-connect P51, turn on power, go into Phono mode measure -15V, then catch it going off. However, when I pressed the Phono mode everything goes to fast. The start up relays for +-55V click on and off as the Dim Bulb Tester goes bright (then off). I still had my scope in auto trigger so I didn't catch the event. I disconnected P51 and went back into Phono mode. The -15V was still there.
It appears that when the Beomaster tries to get the +-55V rail voltages going, it is forced to immediately shut the startup relays back off. Since the Dim Bulb Tester goes on bright during the event I think that is telling me something is shorting out. I need to find a way to remove the +-55V path to the destinations (output amplifier and power supply +-30V). That would help isolate the problem to either before or after the +-55V is created.
I removed the +-55V connections from the two output amplifier boards and from the power supply board (P50). I am thinking that will eliminate those parts of the circuit from being suspect in the power problem. With those connections removed, when I try to turn on the Beomaster, I still get a flash on the Dim Bulb Tester and kicked back to standby. So the startup circuit relays try to engage but immediately click off. Does that mean I have a bad relay? Can it mean the IC9 Darlington that provides -24V to the -15V regulator and the RL2 startup relay has a problem driving both?
Here is a diagram that shows where I have the power disconnected on this latest test.
I went through the task of disconnecting the AC wires from the 30D1 and 30D2 rectifiers. Then I was able to check the diodes. Both sets were 0.44 across PN and open the other direction.
I am thinking though that I should have left the AC wires off the rectifiers for a while so I could see if I can engage RL1 and RL2.
Hi,
do you have the Beomaster 8000 Technical Product Information here from this side downloaded? There are very interesting details about the function of several parts of the different circuits in the Beomaster.
Try starting the beomaster without your dimbulb tester, maybe this helps to get the BeoMaster running. The switching on of the big transformer is done by the microprocessor and the two relays to reduce the input rush current when the trafo gets powered. This might interfer with your dim bulb tester.
Ralph-Marcus
Well, this is interesting. Maybe my measurement of 30D1 and 30D2 isn't correct. I decided I did want to see if the start up circuit relays RL1 and RL2 were involved in the problem. I felt that RL2 might be because it gets power from the same source as the -15V regulator...and that regulator has failed twice now. So I went back and disconnected AC from the 30D1 and 30D2 rectifiers so no power is coming in through that 30T2 transformer. That means relays RL2 and RL1 can engage without really connecting anything.
With that test set up I still left the P50 disconnected but and I connected P51 (the connector I found was related to the problem). I was able to turn on the Beomaster and the Dim Bulb Tester remained dim. The start up circuit relays clicked. That points back to 30D1 and 30D2 rectifiers. I will measure them again but they appeared to measure the same. Should I suspect one of the big 10,000uF capacitors?
RaMaBo: Hi, do you have the Beomaster 8000 Technical Product Information here from this side downloaded? There are very interesting details about the function of several parts of the different circuits in the Beomaster. Try starting the beomaster without your dimbulb tester, maybe this helps to get the BeoMaster running. The switching on of the big transformer is done by the microprocessor and the two relays to reduce the input rush current when the trafo gets powered. This might interfer with your dim bulb tester.
Yes, I was wondering about interference by the Dim Bulb Tester. I know on the Beomaster 6000 (the newer one), that the Dim Bulb Tester prevents it from working. However, I was wanting to make sure I don't really have a short before I take it out here. Also, so far, most of the circuitry appears to function okay with the Dim Bulb Tester in the last few days. As I said, I just wanted to make sure there isn't a short somewhere that might damage some other components.
I do have the service manual and technical manual. I will go through it again.
I checked the rectifiers again and I think they are good. The four 10KuF power capacitors measure okay although three are between 10K and 11K with the fourth one measuring 8600uF.
I guess the next step is to connect everything back up and try power without the Dim Bulb Tester in the path (I can hear voices in my head about another Dim Bulb if this turns out to be my issue).
I have a working Beomaster 8000 again. I would declare success but it is more of a recovery from a blunder so not much glory there.However, I would like to give a big thanks to Ralph-Marcus for bailing me out of my lapse in knowledge. The Dim Bulb Tester is highly useful but it has limitations and can't be used everywhere. So far it has bit me on the Beogram 8002 and now the Beomaster 8000. On the Beomaster 6000 (types 225x), the receiver wouldn't power on with the Dim Bulb Tester in circuit so I discovered early that it couldn't be used there. Today I reinstalled the 30D1 and 30D2 rectifiers and reconnected all of the places I had disconnected (P50, P51, power amplifier +-55V). I checked that the Dim Bulb Tester had the bulb out of the circuit and I powered the Beomaster up. The first test was to just see that I could turn the receiver on. The speaker loads were off. That worked so I tested the receiver with headphones. That worked and I continued to the speaker test. The sound is back and it still sounds good.
So now to regroup where I am at. This Beomaster had a problem where the Clipping Lamp would always illuminate even though there was not a clipping condition present. That turned out to be a couple of bad transistors. During the recap process I found a few out of tolerance electrolytic capacitors. So far I have recapped the two power amplifier boards, the power supply board, the display board, microcomputer board and the preamplifier board. I replaced the 10uF capacitor on the 5V regulator which was, of course, the place I made the horrible mistake of not noticing the Beomaster was only in Standby and not completely off. That led down the whole messy power diagnostic exercise after my -15V regulator failed for some reason. I am the type that always looks for a bright side. Two things came out of the mistake - I learned a lot about the Beomaster power sections. I also learned to not get complacent and always triple check my recaps. That is because I did have a second blunder and that was the electrolytic capacitor on the power supply board that I had installed with reverse polarity. Amazingly it did fail hard over. It puffed up a bit but my short-circuit blunder allowed me to find and fix the incorrectly installed cap.
What is left now is the recap of the FM, FM Interface and Filter/Tone Controls boards. I don't know if I will have to change out any trim pots on those boards. Visually, a few look like they might need replacing but I am not sure they need to.
Learning by doing can be very effective
So finally the beast is working again
the one elco in the 55V power supply section reading about 8000µF could be replaced too to get the job very well done, It's nearly out of tolerance this could be due to high temperature and age. If you find a elco with about 10000µF and the correct voltage (or a bit higher) and with the same size (maybe a bit smaller) you could change this one too. Saves you same trouble in a few years maybe.
RaMaBo: the one elco in the 55V power supply section reading about 8000µF could be replaced too to get the job very well done, It's nearly out of tolerance this could be due to high temperature and age. If you find a elco with about 10000µF and the correct voltage (or a bit higher) and with the same size (maybe a bit smaller) you could change this one too. Saves you same trouble in a few years maybe.
I was thinking that too. That one is close to the limit of the 20% tolerance....but it is in tolerance. I did look for suitable replacements. I found several brands that make 10000uF at 63V, 80V and 100V in the 40mm (D) and 80mm (L) size. They vary in price from around $10 (Panasonic T-UP series) to $70 (Cornell Dubilier). Vishay, Nichicon, Epcos and Kemet have them in between those prices. Some of the components are 35mm diameter instead of 40mm but those should be fine.
I don't know where you find the perseverance, John. Good work.
Rich: I don't know where you find the perseverance, John. Good work.
Well, its just the "we never give up" drive, and John has it. And John keep them coming we really enjoy it.
RaMaBo: We need your valuable inputs more often.
Collecting Vintage B&O is not a hobby, its a lifestyle.
Thanks for the nice comments. This is a very enjoyable hobby and I really appreciate the support you guys provide on this forum. I wouldn't be able to get through these projects without it.
-sonavor
Nothing too exciting today. I recapped the three last boards (FM, FM Interface, Filter & Tone Controls). There were a couple of uh-oh moments but I was kind of expecting them. To recap the boards I disconnect the wires and pull the boards out of the Beomaster. After putting the boards back, I had some problems receiving the FM signal and I lost the left channel. The connections are very touchy. I went over all of the connectors again, still no left channel. But the FM tuner started working again. The left channel was out in both the headphone jack and the speaker outputs. I ended up pulling the connector on the left output amplifier board that gets the preamp output and connected my scope to see if a signal was getting that far. Sure enough it was. So I plugged the connector back in to the output amplifier and checked my headphones. Sound was in both channels. Next, the speakers. Sound in both channels there. One or more of the connectors I touched must not have been making good contact.
Here is the recap on the FM board (just three electrolytic caps on this one). C44 is the only replacement cap on the signal path.
Here is the FM Interface board (just two caps replaced on this one).
Last, here is the Filter & Tone Control board (seven caps replaced here).
I think the FM tuner on this Beomaster 8000 is not up to the level it needs to be. One check I always try in my workshop is to take my coax antenna connection off my Beomaster 4400 and try it on whatever tuner I am testing out. When connected to the BM4400, I get almost full scale on the strength meter and the sound is really, really good. So using that connection on the BM8000, I get just an okay reception and the signal strength is around 3 or 4 on the scale. Before the FM section recap, I was getting about the same signal level. Maybe a little less.
The signal meters can't be compared directly because there are used completely different chips for FM demodulator. As far as i remember the CA3189 (used in the BM8000) has an logarithmic scaled output for the signal strength whereas the TCA chip in the BM4400 has a somewhat different scale. So don't give to much on the reading of the signal meter.
What's an ok reception on the bm8000? is there a bit hissing in the background? If so try mono reception is it better then?
i never heard both but i once had a self made receiver with the CA3189 and TCA4500 and it gave me a fine reception with an external antenna about 30 km away from munich. it gave me a really nice sound from FM, even Austrian radiosation from Salzburg (about 100km) was receivable in stereo nearly hiss free. But it depends also on the tuner frontend.
How far away is the station you are listening to, local or distant radio station?
The stations are within 40 miles and I have a large FM antenna in my attic. I see what you are saying about the meter scales so that wouldn't be a valid comparison. My comparison right now is just by ear. But I own several tuners and with the same antenna source, it appears the BM8000 is not receiving quite as well.I would like to go through the FM adjustment procedure without adjusting anything at first...just look at the measurement results. FM testing is something I want to learn but I am not familiar with yet. I have a Panasonic VP8193A AM/FM Signal Generator available to me as well as a 200MHz oscilloscope. The procedure as outlined in the BM8000 service manual is not very clear to me. The service manual says: Connect a sweep generator to the aerial input and set the receiver to 87.5MHz. Connect an oscilloscope to 1TP22 via an RC-probe. Then look for a symmetrical IF curve. It doesn't say what to set the generator to so is that measurement with nothing applied? I am guessing the manual is implying that the generator is set to 87.5MHz. But is that just a sine wave and what should that be a 1mV signal?The only thing I checked so far is the first step which is to verify 3.0V is at 2TP21. I measured 3.06V so it appears okay.
I started looking at what I can do regarding measurements on the Beomaster 8000 FM section. The FM testing is going to be new to me so I wanted to see a known FM frequency come in on the antenna and see the expected modulation frequency coming out of the tuner section. Looking at the BM8000 service manual I decided to set up the signal strength meter test. The service manual says to connect a signal generator to the aerial input, set it to 94MHz and to yield 1mV EMF (allowing +-75kHz tolerance).Tune the BM8000 receiver to that frequency (94MHz) and measure 2.0VDC at 1TP30.
So I set up my FM generator to 94MHz. The generator has selectable 1kHz and 400Hz internal modulation frequencies (as well as allowing you to use other ones from an external source). I just used the 1kHz. I wasn't sure of the amplitude and modulation settings on the generator so I set the modulation at 100 percent and looked at the generator output on my 200MHz scope. I didn't get a signal until I increased the amplitude of the output to around 60dBuV EMF (the output units on the generator). Now that I could see the FM signal, I connected it to the BM8000 aerial input. I hooked up a DMM to the TP30 of the FM PCB because the manual says I should measure 2VDC there when the test is all set up correctly. I also pulled the connector from the preamp to the power amp on the left channel so I could measure that preamp output with my digital scope.
In order to get a signal on the BM8000 preamp output, I had to set the BM8000 tuner to 94MHz and increase the volume so I had an output. I didn't have a good signal at first until I increased the FM generator amplitude to above 60dB. Then I get the expected 1kHz sine wave out of the preamp section.
As for the signal strength, in order to get 2VDC at the 1TP30 test point, I had to increase the FM generator amplitude to 102.5dBuV EMF. The service manual says the input signal should be 1mV EMF. In looking at converting units to see where my test setup is in relation to the service manual configuration, it looks like 60dBuV EMF should match up with 1000uV EMF which is the desired 1mV EMF. This is for a 75 ohm load. This is from EEWeb but I must not be translating the units correctly since I am having to set the generator output to 102.5dBuV EMF.
So I still have to figure out what I am looking at (and doing) before I even think about adjusting something.
With the FM generator input set to get the 2V on the signal strength meter test, the meter reads about 8 on its scale. I don't find anything in the manual that says what the meter should be showing when the signal strength meter test point is at 2V.
I found this formula -dBuV = 20log(uV)
So if the output of the FM generator is shown in dBuV as 60, that would mean a uV value of 1000uV. That would be 1mV EMF that the service manual calls out. As a check, I connected the FM generator output to the 200MHz scope again to measure the signal out with a 60dBuV amplitude. The scope had to go to its minimum voltage scale (2mV/division) and the peak-to-peak was right about 1 division. That should be 1mV RMS so I think the Beomaster FM tuner should be handling the input at 60dBuV out of the generator. Right now it doesn't look like I get an output from the tuner for a 60dBuV EMF level signal. If I am right, I need to determine what FM tuner adjustments to make first. I think I want to just look at adjustments that involve measuring a voltage level and adjusting a trim pot. I don't want to mess with adjustments where the inductors are tuned.
I am still researching this. Being new to these measurements, it is taking me a bit to filter through all of the information. I did review the FM generator calibration test results when I sent it off for checking last year. The VP-8193A was pretty much right on the money for frequency and output (measured as dBuV EMF). So I am pretty confident that what I set on the FM generator is what I get out. What I am not sure of is my connection from the FM generator 50 ohms output to the Beomaster 75 ohms antenna input. Can I just run the coax cable to it or do I need a 50 ohms to 75 ohms conversion pad? With my present, direct connection I can see that the signal will get there but I am unsure if the amplitude is correct for making any measurements/adjustments per the BM8000 service manual. The same is true for my FM generator signal check on my oscilloscope. I am not sure of the voltage I am getting there when just connecting the generator cable directly to it. According to the RF Unit Conversion tool at the EEWeb web site, I should see a peak-to-peak voltage of 1.4mV for an FM generator output of 60dBuV EMF. I was seeing about 1.4 to 1.6 divisions on the scope at 2mV/division. So about double what I am expecting (but is my expected value correct?).
It looks like I need a 50 ohm termination on the FM generator cable connection at my oscilloscope. From what I have read, not having the termination will result in reflection and doubling my measurement...which is what I am seeing.
On the Beomaster antenna input though, I believe I do need a 50 ohm to 75 ohm matching pad in line with the generator signal. So I will get those pieces for my test setup before I continue.