What is the correct fuse value for the power supply on a Beogram 4000? If I am reading the manual correctly it is part 6600000.

I am using two 250ma 250 volt buss fuses and have been told that the correct fuse is a 300ma 250 volt. Which is correct for a Beogram 4000?

Jeff

250mA or 300mA doesn't really matter much. Put 300mA in, it will blow if anything goes wrong.

Martin

Thanks Martin,

I am looking for a bit of direction. This Beogram 4000 has performed very well for 10 months until it blew a fuse mid way through playing a record.

With the fuse replaced, the 4000 platter turns, the arms go to the correct play position and begin to drop.

But then something very odd happens, instead of dropping completely to the record, the tonearm begins to move to the right (the wrong direction) and then the flues blows.

This whole process takes about 5 seconds. Does this tell you anything?

Jeff

I would take a look at the transistors in the H-bridge driving the arm motor.

Martin

Thank you Martin for your valued and learned advice.

On the home page of the forum section it states that “there are no stupid questions,” with that thought in mind I hope you will allow me to ask what well may BE a stupid question.

The first time the fuse blew was with the tonearm midway through playing a record, so I assume you are thinking the problem is with the horizontal tonearm motion and the motor that drives it? Is that correct?

Also I am a bit concerned that the sound quality was a bit off just before the fuse blew. Sound quality, I wouldn’t think would have anything to do with the H-bridge transistors. If this is another stupid question, I apologize, but I am no expert, which is why I am asking YOU.

Another thing that disturbs me is that I was under the impression that all the capacitors had been replaced, but in looking over the repair bill provided by the previous owner, I find that they were all re-soldered, not replaced, so they are original.

There are no qualified B&O technicians anywhere here on Vancouver Island, so if this Beogram 4000 is going to be repaired, I am going to have to do it myself.

The best thing to do would be for me to send it to you or Frede, but after what happened to this 4000 is transit from New Jersey, the thought of another international shipment sends shivers up and down my spine. (Shipping is tough but customs are worse!)

The real tragedy here is this Beogram sits side by side with my trouble-free Beogram 4004 with its NOS MMC 20CL cartridge and the 4000 consistently out-performed the 4004 sound quality-wise even with its used MMC 20 CL cartridge (one of my discarded cartridges from years ago).

One way or the other I am determined to get this 4000 up and running.

Thank you for all your assistance!

Jeff

Jeff,

These are not at all stupid questions.

Yes, I was thinking that about the blown fuse.
It also fits perfectly with the symptoms you describe, trying to play a record.
There's a H-bridge consisting of, I think, 8 transistors. One shorts and starts the landslide and some others will have suffered an overload because of that. They are fairly cheap components so I recommend you replace the lot.
Of course, it would be nice to have the Beogram here for repair but shipping costs and risk of transport damage makes it an unattractive solution.
Having said that, I have repaired a couple of circuit boards sent to me from overseas but give it a try yourself.

There are no electronics in the signal way apart from the muting relay so any faults in the sound reproduction will have to be found in the relay, cartridge, plugs or cables.

Martin

Martin,

Thank you for the excellent direction.

I will see what I can do with these transistors.

I would have no concerns about shipping the board, however if I find this project exceeds my ability, perhaps I could purchase a good H-bridge from you and then send my defective one back as an exchange… if that is how this sort of thing works.

Jeff

The H-bridge is a circuit on the main board so I would need the whole board but take a look at it yourself first, it may not be as hard as it sounds. Find the motor in the schematics and you'll see which transistors to focus on.

Martin

Sure thing.

Everything about the Beogram 4000 is intimidating in the beginning, but once you get started, it really is not all that difficult.

I will take a good look and let you know what I find. I am tied up with a major family gathering this weekend, but after that, I will give this matter the attention it deserves.

Thank you again for ALL your help.

Jeff

Martin,

My current game plan it to tackle these transistors after I am finished with the big family birthday party coming up this weekend.

However, it occurs to me that while I may well be able to replace these 8 transistors, there are numerous other components of questionable value, as I have no real knowledge of the motherboard’s history.

Do you sell refurbished motherboards for the BG 4000 and if so could I purchase one from you? That way I would KNOW that all the components are in good shape with the workmanship beyond question.

Jeff

I don't sell refurbished boards but I have repaired quite a few that were sent to me.
I recommend to keep your own board, you see the board has some adjustments that will need to be set to match the given turntable chassis so transplanting a board from one machine into another may not work without re-adjusting.

Replacing of the transistors alone will not require any readjustments but give the 8 transistors a check with the ohm-meter to confirm my diagnose first, there could be other reasons for the fault in your Beogram but to me it sounds likely that one or more of the 8 transistors have a short.

Martin

Martin,

Then I will plan to replace these 8 transistors and see what happens.

If memory serves, during my protracted purchase negotiations for this Beogram 4000, the NYC shop replaced the mother board.

The fact that it worked well for nearly a year says the job was done correctly, but doesn’t give me the sense of security that I would like with a turntable that I regard as a treasure.

Jeff

Martin,

I know that you sell a capacitor kit with instructions and diagram, would you consider doing a transistor kit for these 8 transistors with instructions as to which transistors goes where? (If they are all the same value, kindly forgive the idiotic request.)

I have the BG 4000 manual, but I have a certain degree of insecurity about getting things right.

Soldering the transistors I believe I can handle, however obtaining the correct ones and installing them in the right spot is intimidating me.

This badly tattered Beogram 4000 means a lot to me and I want to repair it correctly.

Thank you for considering this.

Jeff

Jeff,

There's not a kit ready for this but I will be happy to help you to the correct components etc. but please put an ohmmeter across the transistors first so we get the diagnose confirmed.

Of interest is TR26-33 (incl.), let us know if one or more of them has very low resistance.

Martin

Martin,

This is new territory for me, however since I do have an ohmmeter; I will make every effort to test these transistors this Sunday, when I can give the project the attention it deserves.

As soon as I have the results I will report back to you my findings.

Thank you for your valued assistance.

Jeff

Martin,

I found the time this morning and here are the results with the multi-meter set on X1k ohm:

1^st row:

2.75

1K

2.5

2.5

2^nd row:

1k

2.5

200

Infinity (no movement)

I don’t know which readings are good and which are not, but there is a variation, so I would think there some are not good.

Jeff

Hi Jeff,

Good job so far.
The 200 ohms reading is a bit strange.

Does your multimeter have a range for testing diodes/semiconductors ?
Usually marked with the schematic symbol for a diode (arrowhead with a line in front of it).

If it does, the readings would be clearer and we will need readings of both ways (pos/neg and vice versa).

Alternatively, a continuity checker (beep'er) ? 

Martin

Hi Martin,

I will need to purchase a multimeter with a wider range of tests and plan to pick one up tomorrow.

I had thought of borrowing a friend's excellent tester, but decided that this is likely going to be an on-going situation, so I might as well get a proper multimeter.

Will advise as soon as I have the new tests done.

Jeff

Hi Martin,

I attempted to purchase a good multimeter at Home Depot last night with no luck, so today I am going to a specialty store to purchase a Fluke multimeter.

Are there any other tests that you think you may need performed other than testing for diodes and continuity? I ask so that I can purchase a multimeter that will accommodate all your requirements.

Jeff

Normally, every car parts store will have a small and fairly cheap multimeter with the basic functions that will be fine for your needs.

Martin

Martin,

You would be astonished at the poor selection of multimeters at Home Depot. I didn’t give a thought to an auto parts store.

As such I went to a speciality store and purchased a very nice Fluke 115 which will provide exceptionally accurate readings.

I plan to test the Beogram 4000 tomorrow and will report back with my findings.

Thank you once again for ALL your help…. Which is most appreciated!

Martin,

Here are the test results you wanted:

So what do you think?

Jeff

A Fluke is a fine instrument, I have one myself.

Not much hint in the readings though. What happened to the 200 ohm from previous ?

Martin

Martin,

Don't know exactly what to say about the previous 200 ohm reading other than I was using a primitive auto tester that I happend to have.

So if I understand you correctly, these readings are satisfactory. If so, where do we go from here?

Just as a reminder, when the 4000 failed the first time it was mid-play, about half way through the record AND I noticed that the sound was just a bit off.

Now it failes BEFORE the arm can fully drop.

Jeff

Hmmm... I must dig out my thinking hat.

Martin