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
Hi All:
This is a question for the experts out there. I am going to restore a recently acquired Beomaster 4000 type 2408 and have already ordered the kit and other parts I need.
Looking at the exterior, it is cosmetically good but after opening the cover...well, a picture is worth a thousand words...
...I took out the base because I could not see the connections of the two caps pasted onto the heat sinks and then I got really worried. Again, a picture is worth a thousand words...
...more caps. I assumed that the two extra caps were used in series because they could not get 5000uF 80v and used 8200uF 80v on the output instead. But when I saw those on the flip side of the output board, I was totally lost. It must have been working this way for awhile since the orange caps are all bubbled-up.
So, can anyone enlighten me on why this was done? What was achieved with the design change?
If you need me to post more pictures, just let me know. It will be awhile before I get all the parts, so we have time before I begin removing all that extra stuff.
Thank you for teachings and looking forward to knowing what was done here.
Hi,
Some previous owner made some modifications didn't they.The original reservoir capacitors could have easily been replaced so that is puzzling.I would remove all of the modifications and disassemble most of the insides of the Beomaster to get everything cleaned up again.While the boards are apart you can do the capacitor replacement. I would change the trimmers as well.Because there are sure signs of tampering you will need to look for other modifications to the board(s).
The Beomaster 4000 is a nice receiver but the 4400 is a huge improvement in my opinion.
Be aware that the Beomaster 4000 units very often have transformers that hum and buzz. They are epoxied inside but that becomes brittle over time and the humming and buzzing starts. The only way to fix it is with a new transformer. As you can see that is a very low profile transformer so you won't find a replacement for it off the shelf. Getting one from another BM4000 only buys some time. The better solution is to get a new replacement that is a low profile toroid type transformer. There are a couple of Beoworld members that repaired their BM4000 units that way. It isn't cheap though.
I would recommend removing the transformer and having it tested first to make sure it is hum/buzz free.
-sonavor
Thank you for the transformer tip, I will get on it as soon as I can.
-djagan
Oh, it was really "got-at".
The orange capacitors at the back of the amplifier board are not bulged, I believe they looked like this from new.
Seems like someone tried to "improve" something without knowing what they were doing.If the output series capacitors are fitted several in series, any point in attempting to improve the damping factor by increasing the capacitance is out the window.And they left the most trouble-prone components in place.
Something to backtrack and clean up...
Martin
This one has the newer amplifierboards. Trimmers aren’t just simple to change without proper instructions, load and a scope.
Backtrack and clean up is my only way out; totally agree with you.
I’m looking forward to this challenge and if I get over my head, I’ll just reach out to the experts.
thank you all for your insights.
Hi all:
I have some updates to add to this modification done by the previous owner that could unravel the mysterious caps.
Those two large caps were placed between the output transistors and the speakers.
The other orange ones were in parallel with the existing ones on the output board.
I had a 901, 3000 and 3400 previously and they all would blow the output transistors for, what seems like no reason. I often wondered if there was a way to protect those transistors as they were not cheap at the time. Could this be a way to protect them or is this an attempt to boost the output?Maybe the experts can shed some light on this.
dj
I've never had an output transistor blow for no reason. If the transistors are blowing out then there is a cause. The strange modifications on your Beomaster 4000 look like some strange experiment somebody attempted. I have no idea what they were trying to do.
Trust the original B&O engineers that developed the Beomaster 4000. They never would have released a product if it was susceptible to transistors easily failing. You can bet they performed rigorous testing when the amplifier was new.
Decades later when we here on the Beoworld Workbench attempt to restore these components we have seen a lot of strange cases. Many times the problems are just aging of parts. Sometimes the aging is accelerated by a poor environment the audio component was stored in. Then there are cases where someone attempted to repair/restore a component without really knowing what they were doing. Sometimes without a service manual. Sometimes with hardly any electronics experience. Those are the Frankenstein cases where you have to try and back all of the bad stuff out and try to get back to what was original. Occasionally the original parts are too badly butchered to fix.
I agree with Sonavor.
Never in my 40+ years of repairing B&O did I see a semiconductor fail because of age alone.There was always another reason; Short circuit, overload, lightning strike, static discharge, moisture (bad storing) etc.
None of the added capacitors will protect anything from anything. Perhaps it was an attempt to compensate for aging capacitors, which is a real thing,- Not that the solution would work anyways.
Boosting? No.Improving? No.Messing up? Yes.
I think you’re taking me literally...off course there were legitimate reasons for the failures as Martin indicated. You start feeling sorry for yourself when it happens and wonder why there were no protections. During that period some amps like phase Lerner, had some protection.
Please don’t take that seriously.
I’m moving forward with a complete original restoration and getting all that crap out. I was just trying to understand what was accomplished with these modifications.
thanks for your comments.
Back in the days, when i was a trainee, at a small electronics plant making inverters (way before the solar boom), we also wound - or coiled - our own transformers (don't know the correct term).
When done, we would put them in an old aluminium milk-jug, maybe a quarter full of lacquer, pull vacuum with an old pump from a fridge, wait an hour, let drip and bake for a few hours till the lacquer had dried up.
You could easily DIY the same with an old humming trafo.
Just my €5.
UPDATE : I see there's a spray called 'Synthite AC-43' especially made for this type of application.
Jesper
Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400, Beomaster 5000, Beogram 5005
That would be an interesting treatment to try out. Are you offering to do that for humming transformer owners :-) ?
Sorry but no I don't. But since it's an easy DIY project, anybody can do it at home. Just forgotten all about it until i read your post. Only thing that triggered my memory was that it's an old trafo, difficult to find and expensive to replace. Sad to see it go in the bin.
Use a glass jar and any vacuum pump. Have a quick search on Youtube on how to do your own vacuum chamber ? Or maybe go to your nearest electro shop, who will do the exact same procedure in a little more pro manner
Thanks for the information. If this works as you say it could resurrect a number of Beomaster 4000 transformers.
It has been about eight years since I have looked inside a Beomaster 4000 unit.However, I did find these photos in my archive when I was working on mine. I probably have this BM4000 unit somewhere in storage.I remember now noticing the additional board on this Beomaster and took these photos.
Perhaps Martin can shed some light on this board.
I found a couple of photos in my archive of a Beomaster 4000 without that xxxx2135 board. The components are mounted differently but that circuit is still there. I will look on the schematics to point them out.
I found this diagram of the 8002135 circuit in my archives.
Yes, you can do that.Actually, there is only one reservoir/filter cap (the center one). The other two are output series caps, but you can put 5600uF 80V in here as well.
Can someone verify this issue with the output PCB?
As a reminder; this BM4000 type 2408 was modified by the previous owner and I am trying to get it back.
I've had to go through everything since things were added and now I think, moved around.
I need help to verify if these CAPS and resistors were swapped or is this the way they should be on the circuit? They do not match the semantics that came with the unit.
Thank you for your expertise.
There are several different versions of Beomaster 4000.You cannot always be 100% sure, that the included schematic is the correct one for your specific version.
I suggest you check the solder side and compare to the schematic.
I have found this a couple of times where two components are changed around, in my cases its made no difference to the circuit operation....its just a little bewildering when first discovered.
Craig
This is the solder side. It looks like they are in series so I guess it won't make a difference.
I agree.
I just ran into two more items that are not on my schematics for the BM4000 and would like to know if they should be removed or left alone.
These are two CAPS (1uF 35v) that are on the solder side of the FM PCB. They look original so I just need guidance from those more knowledgeable than I am. Martin, these were not identified on your kit nor did you provide a replacement for them.
Thanks for your responses.
So now we have proof of an extra-tantalistrial situation!
Far from all production changes, sub-revisions, aftermarket modifications and territory specific versions are equally well documented.Some aren't at all, which makes putting together the kits quite a task and feedback and information from owners valueable.
I agree they look original, but I cannot tell you exactly why one tantal was added across TR18 C-E and another to decouple the supply to part of the IF.The latter could be to counter for a particularly troublesome batch of IF Amp ICs (OpAmp CA3012). I can't say.Perhaps that could explain both of the tantals, really.
Of course I will look into this and see, if the kit should be updated with this info, as I always do when new information turns up.Can you tell me the serial number of this Beomaster 4000?
I will happily send two new tantals to you, just say the word, but if on the bench here I really wouldn't worry about leaving both of them in place.
Thanks.This makes it a very late production individual.No voltage setting switch, so an export (US) version as well.
No.Unless they cut and rearranged the connections at the solder side.
The original rectifier has both AC pins at the same end (upwards in the photo). The new one has them diagonally across.B40C1500 is much better than the original.
Can you give me a little more insight on why this does not affect the operations of this part of the circuit when one of the ACs is switched with the negative pin? (Please forgive me for the inverted text on the schematics).
Unless the wiring at the solder side of the board was changed to suit (it doesn't look that way in your photo on the previous page), it willmost likely have killed one or two diodes in the rectifier, leaving it running only on the remaining.I suggest you replace it. Check the connections at the backside and make sure to fit it right.
What Martin is telling you is that the new rectifier pin layout is different so you have to make sure you connect the pins to the right spot.I think your original question may have been whether the new device is plug-n-play compatible with the old one? The answer to that is that it is not.Perhaps there was some confusion there.
Hello Djagan
I do not have an answer to your question - yet - sorry.
But I also just bought an old 4000 and want to upgrade it.
I just cannot find any supplier of the so called "Service Kit Beomaster 4000"
Where did you get yours? Or what does the parts list contain?
Thanks in advance
Best regards
Michael