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
John, the first part of your repair and the short was interesting, but now I think you are into writing a classic how to guide. Your determination and descriptions are perfect, I will return to to this thread when I have improved my knowledge and my toll stock.
Collecting Vintage B&O is not a hobby, its a lifestyle.
I have been wanting to go through the tuner section tests of a service manual for a while now. It took me some time to locate and get the proper equipment but I have slowly been acquiring them (for over a year now)...although it appears I am still missing some items. I am also trying to build another test interface to compliment Frede's Classic Audio tester to enable me to run the PC audio test software on power amplifier sections. Hopefully that will all work.
In the meantime, regarding this venture into the tuner section, I just feel that if my goal is to restore the Beomaster 8000, then I need to also make sure the FM section is performing like it should. It would be a shame to have the 8000 system sitting in my living room and have to tell people it works...except for the tuner. However, I am not declaring this tuner section bad yet. Something just doesn't seem right so I first want to be able to measure it to make sure, then see where I have to go from there.
For this restoration project I think I have three more things to test -1. The tuner section2. The phono section (I still haven't connected a Beogram to try it)3. Measure the frequency and distortion of the power amplilfier section (I am missing the PC interface for that but have the parts to build it).
John,
A great job.
3 points here -
Regarding the Dim Bulb tester - I'm not sure what size wattage lamp you're using, but I keep a bunch on hand, from 60W to 500W.. In this case, I would have used a 500W lamp - still gives protection, but it has to be a REAL short to make it illuminate, not just an inrush peak which it appears is what you had.
Regarding the short - I have made plenty of those mistakes, but only once, each type. There is always a new type which will jump up and bite you. Bottom line - you cannot be too careful, but accept that it does happen from time to time. My stupidity bit me most recently, about a month ago, while repairing a DVD. Be careful if you get into the new SMPS circuits - you'll need a differential scope-probe to stay safe.
Regarding the 10,000uF capacitors - in today's world, any capacitor over 3000uF can be expected to be below the rated capacitance - that's why the manufacturers cover themselves by stating +/-20%. So, my rule of thumb is always to buy the next higher rated cap, to be CERTAIN that I'll get what I really want. In this case, I'd buy 12,000uF caps, provided you can find one that physically fits. And you'll see that a 12,000uF cap will measure at about 10,400uF, which is just fine for this case.
Menahem
Thanks Menahem. Yes, I checked and the bulb I was using is a 100W bulb. On the big 10,000uF capacitors, I am still trying to decide about whether (or when) to replace them. Three measure close to the 10,000uF and the fourth is at 8,600uF. So I am thinking do I change just one or should I go ahead and change all four...especially if I don't really need to. I wonder if the 8,600uF cap has always measured that capacitance. that is in the 20% tolerance so it might be okay.
If I replace it I am looking at a Vishay MAL210118103E3 10,000uF replacement. It has a load life rating of 10,000 hours, is the correct size and not terribly expensive (around $24). There is also a Panasonic T-UP series (ECE-T2AP103EA) is only about $11. It is also the correct size but has a load life rating of 3000 hours. The Panasonic capacitor is rated at a 100V though while the Vishay is a 63v rated cap. The original 10,000uF caps are also 63V. I found an article at EDN.com where the author reports that for each degree the capacitor operating temperature drops, the life is doubled. The ratings on the two capacitors I listed above are at 85 degrees Celsius (185 degrees Fahrenheit). Looking at where those Beomaster 8000 capacitors are located, I don't think they ever get close to that temperature which means their expected life should be much, much longer. If that is true, then the Panasonic T-UP series should work fine.
While waiting on my test equipment pieces, I was inspecting the Beomaster 8000 FM and FM Interface boards again. In the photo here, I have marked the trim pots that look aged and discolored compared to other trim pots in the Beomaster. Is the discoloration just cosmetic or is it an indication that there has been heat and the trim pots might need replacing? Also, I just noticed that R21 (47 ohms) on the FM board is badly discolored. It looks like I should probably pull it out and check it. The R21 resistor has a triangle symbol by it in the schematic to flag that the same type, wattage and value must be used when replacing it. The parts section lists it as 47 ohms, 1/4 Watt. Is it a carbon film resistor? Another group of components on these two boards are the tantalum capacitors (the little green components). There are ten total. It looks like four of those are in the signal path. I know there is sometimes an argument regarding whether those tantalums should be left alone or if they should be replaced with electrolytic caps. So now I am trying to decide on whether to replace the four big 10,000 power supply caps, the FM and FM Interface board tantalums and the five trim pots that look discolored. I think R21 needs replacing.
A quick update.I pulled the R21 resistor and checked it. While it looks awful, the markings are completely gone...it actually measures 46.9 ohms. I have a replacement in my stock though so I replaced it. I also started replacing the trim pots on the FM boards. I also pulled the two FM boards from another Beomaster 8000 (a supposedly dead unit that won't power up). With those two boards, the Beomaster project unit FM reception is good. I still can't execute the service manual measurements for the tuner for some reason but that is a different story.
An interesting thing about the second Beomaster is that the FM boards have electrolytic caps instead of the tantalums. It could be that the previous owner had the unit updated but it is odd that someone would recap the tantalum caps and not the electrolytic caps. Unless this recap was done back when this receiver was still relatively new. If that is the case, when I get around to working on this second Beomaster, I will probably do all of the caps again. I will post a picture of the new set of boards later. There were a couple of other odd differences I want to post pictures of as well to see if anyone out there has seen them on a BM8000 before.
Here are the two FM boards from the other Beomaster 8000. The capacitors that were tantalums on my project Beomaster are marked by bright green marks. Are they replacement caps or did they come from the factory like that?
The display board of the second Beomaster is interesting. It has the blue covering over the Clipping lamp. Maybe the Clipping lamp wouldn't go out like my receiver so the solution was to hide it?
The microcomputer board is also different. The connectors to the front panel are mounted differently and the shield box for the computer is different. On my project Beomaster, the top and bottom shield box pieces were soldered together by metal tabs that go through the board. This Beomaster has a box frame that is soldered to the board but the box has a removable lid that pressure fits in place (like the one on my Beomaster 6000). I am thinking this Beomaster is a newer unit that the project unit.
To compare...here is the microcomputer board of the project Beomaster 8000.
The second Beomaster 8000 also has something extra on the preamplifier board. I can't tell if it is an after-market add on or something stock. It is circled yellow in the picture. There are actually two of those plastic round discs, one for each channel?
Large Caps - Panasonic are fine.
Trimpots - replace every single last one - don't even think about it. Piher PTC-10LV - in stock at Mouser
Those blue caps look like Chinese replacements - can you read the manufacturer label?
R21 - In those days, AFAIK, the resistors which B&O used, were all carbon composition (CC), not Carbon Film (CF). If original CC resistors have failed in the POWER SUPPLY circuit, replace with CERAMIC resistors. The price of CC resistors today has shot through the roof, because of virtually no more demand, and are not worth paying the outrageous prices demanded. Ceramic resistors do everything that CC resistors did, and do it better. Never use Carbon Film in Power supplies.
I am using the FM boards from the spare BM8000 unit for now. Meanwhile, I have the original FM boards on my bench to replace the trim pots and check the other components. I have Piher PTC-20LV trim pots for all the values except 25K ohms. For that I bought a Bourns as Mouser doesn't carry that value by Piher.
That R21 is on the FM board, not the power supply. I replaced it with a carbon film resistor. It is only a 1/4W resistor.
Those blue replacement caps are made by Marcon. The orange replacement is a Rubycon.
Once I get the original boards updated with the new parts I will try them out again. If they don't perform as well as the two replacements I will switch the replacements back in and move on. I will revisit learning how to perform the Beomaster 8000 tuner tests later. Before that I plan on learning on some other tuners. The BM8000 service manual instructions for the tuner adjustments is just not translating well for me. I think I have the tests set up correctly but I am not seeing the expected signals (even with the replacement boards). Using the same test signals on another tuner, like a Yamaha TX-900U, I can see the tuner respond to the test signal down at a low input amplitude of 20dBuV EMF. The BM8000 isn't responding until the signal amplitude is up over 60dBuV EMF. Yet the Beomaster is receiving FM stations so I must be missing something in the instructions. I will go off and do some homework on tuners and testing them so I will be better equipped (mentally) to try this in the future.
What about the picture I posted of the preamplifier from the second Beomaster 8000....regarding those round, inline devices on the white and blue wires. Any idea what those are?
They look like telecom easy grip connectors don't they? Scotchlok?
Jacques
chartz:They look like telecom easy grip connectors don't they?
They do indeed. The telecom connecters are "insulation displacement" and are available dry or vaseline filled. Never seen a green one.
Here is a closer picture. They are some sort of splicing connector and Jacques is right, they are Scotchlok. I can see the name embossed on the plastic case. The white and blue wires were tapped and taken somewhere. I haven't opened up that Beomaster completely yet to see where those wires go. My project Beomaster doesn't have that. I am wondering if that is some modification someone made after they bought it.
I don't want to disassemble the other Beomaster 8000 completely yet but I opened it a bit and it looks like the splice wires route from the preamp (blue and white wire) to the left side, rear of the receiver. The project Beomaster has that same opening in the chassis but there isn't anything there. The second Beomaster has a connector there. Here is the best picture I can provide right now.
http://tinyurl.com/qj9cjsf
I will identify what preamp connector wires were spliced and so I can tell what is being routed to the unidentified connector.
That side connector is -15V/Gnd. I still need to verify that is the destination of the two wires but I am pretty certain it is. The blue wire is the -15VDC from the Power Supply board and the white wire is ground. The connector on the preamp is P17 and the power supply connector is P46. I guess the previous owner needed to provide -15V to some external device?
sonavor:I guess the previous owner needed to provide -15V to some external device?
Your Beomaster has obviously been owned by a telecom installer who can't solder
--mika
Yeah, it has to be some modification for some purpose. When I get around to work on this unit (probably next year), I will try to put it back to original. Even after that, I may have to use this second Beomaster as a test device or parts for another Beomaster 8000. Cosmetically, the rear, right channel heat sink is dented and the front corners of the front trim got dinged. So even with that Beomaster functioning 100% electrically, it probably won't look new without getting some replacement pieces for the trim and heat sink.
Finally, some good progress on the project Beomaster 8000. It started off not so good as I tried the original FM boards with new trimmer resistors. Then I found a major issue - the connector to the FM board from the aerial had a loose signal wire. It was touching the shield. Of course that really improved things but the original FM boards still are not producing great results. While the original boards were in the Beomaster, I recapped the original electrolytic caps on the second set of FM boards. I decided not to do anything else to that board as I don't want to risk more tuner problems. I now have the second set of FM boards in the Beomaster and the FM tuner is working great. The signal strength on the strong stations is up to 8 (out of 10). That is what I was expecting from that antenna as my other tuners that connect to it all have good reception.
I think I am ready to wrap up this Beomaster project for a while. I am torn on the power caps but they are all in spec so I think I will leave them alone and enjoy this new receiver for a while. I will test out the turntable input on the BM8000 tomorrow.
As for the original FM boards, they will be part of my continuing education on learning how to work on tuner sections. I have a lot of work to do in that area and I won't make that part of this thread. I hope the next pictures I post can be a fully re-assembled Beomaster 8000 driving a pair of MS-150 speakers.
I am happy to report the Beomaster phono section works as it should. The test wasn't without a little drama though. When I set up to test and started to connect the Beogram 8002 phono cable, I discovered the DIN socket in the Beomaster was loose (actually, the plastic mount is broken and missing the outer, plastic frame). I was able to carefully work the plug in place but when I played a record I got no sound. So there is something wrong with that socket. To fix this latest problem I decided to swap out the music source input assembly from the other Beomaster 8000. All of its sockets were good.
My back is now sore from all the lifting and moving around of this receiver again but I got the new input module in place and had a listen to the Beogram 8002 playing the Doors first album. I will post pictures of the finished Beomaster later today.
There is a new glitch in my 8000 system though. It isn't serious ... but a nuisance. The display on my restored Beogram 8002 has started acting up. It displays odd characters but seems to display 45.00 okay. Everything else on it is functioning fine so I will have to go back into that unit in the future and fix the display. I do have spare BG8002 control and display boards now. I think I will rework those at some point, then swap them in the Beogram and see if that corrects the problem.
sonavor:The test wasn't without a little drama though
That was a lot of hard work to get to this point so just enjoy it.
Save the niggles for a wet winters day.
I definitely am enjoying it. Although I won't try and choose a favorite between the Beomaster 4400 and this 8000, I have grown to really like this latest receiver. Maybe it is just human nature after putting a lot of work in. But if you read up on it, the Beomaster 8000 is quite a piece of engineering work. I definitely will want to refurbish another one. For my next step I have pretty much decided to start on the Beocord 9000 so I will have a great tape deck in the system.
Next week I should receive my first cartridge repair from Axel Schürholz. I had an MMC 2 that the right channel went out on a few years ago. It has been sitting around while I decided what to do with it. A few weeks ago I decided to contact Axel and arrange for a repair. He finished last week so I expect it sometime this week. I am anxious to see how it sounds in this 8000 system.
Here is the finished Beomaster 8000 along with other components in the system. The cassette deck is missing from the cabinet as it is out on my work bench. Last night was the first time I connected a pair of MS-150 speakers to the BM8000. They sound fantastic.
One last picture of the 8000 system with the cassette deck (Beocord 9000) in place.
One word John, SUPERB!
Brengen & Ophalen
Great Job!
Sometimes one has a project which is the biggest learning experience of all. I think this was yours.
Impressive! Congrats!
//Bo.A long list...
Love it!
/***
What a fantastic job you did! I just bought one myself and can't wait to work on it. Maybe I will look into replacing some of the wiring system reading how delicate it is?
- Dennis
Dennis: What a fantastic job you did! I just bought one myself and can't wait to work on it. Maybe I will look into replacing some of the wiring system reading how delicate it is? - Dennis
Congratulations. I also picked up another one to refurbish in the future. I want to go back and work on the FM boards I swapped out of my completed unit so this latest one will provide a test bed for that. Looking back at this completed receiver, I'm not sure I would re-do the wiring. The connections are touchy but I got to where mine always work. Changing the wiring would mean changing connectors. It could be done but I think it would be a painstaking job. I think it is easier to just be aware and be careful with the existing wiring. I also put a little contact cleaner on all the connections when I went through mine. The end result is very rewarding. I really like this receiver now.
-sonavor
This weekend my Beomaster 8000 started losing sound from the Left Channel. I was worried there was an output amplifier problem but troubleshooting has shown that the signal is being lost coming out of the preamp board (03) going to the tone control board (04).
With the Beomaster opened back up, I am able to play music through it for a couple hours straight and not encounter any problem. Close it back up, the problem returns. Figuring it could be a solder joint on the preamp board, I pulled the board and reflowed the solder joints of the connectors. That didn't fix the problem. I also reflowed the P27 connector on the tone control board as that is the destination of the stereo output from the preamp board. Same result.
When the problem shows up, I have not been able to get it to go away by moving any of the cables. I am able to get the problem to clear by connecting my scope probe to the Left Channel output of the preamp (at P16-1). So I could have a cold solder joint around that node. I will resolder R158, TR103, TR104 and C136.
Here is the schematic of the area involved . Only the right channel details are shown on the schematic but the Left Channel components are the same as the right except the designators are in the 100 range instead of 200.
Here is a picture of preamp board with my scope probe on the R158 node that goes to P16-1 (Left Channel output to Tone Control board).
In cases like this with channel dropouts I like to play around a bit with the volume setting trimmers at the left sideof the Beomaster.They are rarely used so will often oxidize and cause intermittent problems.
Martin
I pulled the 03 module (preamp board) and reflowed the solder joints on the left channel output circuit components. I couldn't remember if I cleaned the input level trimmers for the inputs when I originally restored this receiver so I cleaned them as well while I had the board out.
It looks like the Beomaster is back to 100% again. I have played it for a couple of hours tonight and the left channel hasn't dropped out once.