sonavor:

I came to the conclusion that while B&O equipment is often difficult to work on, that challenge is part of the attraction.  That and the satisfaction at the end that you have a beautiful piece of equipment working again.

I too had some problems with the switch assambly, but the BM 6500, BM 901 and BM 2400 are a lot easier to work on.

No hurry with the dim bulb tester, will take time before I get a variac.

A Happy New Tear to you too

Soren

Soren just wire a bulb in series mate. Variacs are of course very usefull for slow start and controlling the voltage in but a series lamp or resistance is useful without variac in many ways especially if you can't diagnose without blowing a fuse!

Søren Mexico:

Back again from my vacation, very good job indeed, and love your explanations, thanks a lot for a good thread, you are way ahead of me, not only in the work, but also in knowledge. I hope to get back to my 4000 in the weekend, did some thinking and drawing reading during the vacation. When I get hold of a used variac I will come back to you for the drawing of your dim bulb tester, saw a simpler version somewhere, but yours is a lot better.

I saw a few used variacs at my Friendly Local Electrical Surplus Store yesterday in the $80 to $120 range.  Is that Good, Bad or Ugly?  Sorry for no pictures - only had my (Android) phone with me.

I paid around $70 (including shipping) for mine.  That was a used one.  It is single-phase, 120 VAC, 60 cycles, handles up to 12 amps of current, 1.4kVA.  So it is for the US.  It also has a fuse to protect it...which I have blown a couple of times.  I checked the prices of currently advertised variacs on ebay and prices of ones that have sold on ebay as a comparison to the one at your local store. It looks like $80 to $120 is probably in line.  How many amps can the $80 one handle?  I would want a minimum of 5 to 7 amps.  For my project I was looking for 10 amps when I found the deal on the 12 amp variac.

I'll go back to the FLESS next week some time and take some notes and pictures of what's available.  If memory serves, the "best looking" one was 10 amp and was an even $100.  A much larger, much older appearing unit was 15 amp and was $120.

As the amateur I am, I am trying to learn, where I am totally without knowledge, is in the use of tone generators and oscilloscopes, all manuals shows that most ajustment are made with the help of these, could some of you experts recommend some literature for a novice like me, how to use and where, and which types are good for our kind of use (Beo vintage).

When I get into troubles during failure finding on mecanicals I go back to my base knowledge, which is what I learned as a pupil industrial mecanic, I don't have that base in electronics so when failures occur I have to search the forum, get help from the forum or go by trial and error.

By the way I think I found the failure in my BM 4000, if I'm right it is so stupid that you will laugh from here until next Xmas, will be back with more on the thread tommorrow

I doubt it could be more stupid than miss-wiring a +15 VDC rail wire to a ground plane.  One of the most important rules to follow in working with electric circuits is to triple-check everything before turning power on!  If you get in a hurry it is easy to make a mistake.  It is also easy to mess up when you haven't had enough sleep.

One good basic book that goes over all basic audio electrical stuff is "Making Sense of Sound": The Basics of Audio Theory and Technology by Alvis J. Evans (Prompt Publications).  It is a small paperback book that gives a nice overview of everything.  I was glad I bought it. 

Another book I bought is called "Troubleshooting Analog Circuits" by Robert A. Pease.  While it is not a book specifically about audio equipment, it does cover components in analog circuits.  It goes into some high level stuff that is beyond what I needed but it also has a bunch of good basic information about testing. 

For learning about using equipment like signal generators and oscilliscopes you can usually Google search and find PDF files from university labs used to instruct their students.  Sometimes they even have posted some tutorials.

Here is the wiring diagram for my dim bulb tester that incorporates a variac, a VAC volt meter and an AC ammeter.  The socket is where the unit being tested plugs into.

NOTE: See the later post with the updated diagram

Worth noting the fuse is in the wrong place on that diagram, or at least the wire feeding the socket is, should be placed the other side of the fuse!

sonavor:

Here is the wiring diagram for my dim bulb tester that incorporates a variac, a VAC volt meter and an AC ammeter.  The socket is where the unit being tested plugs into.

Thank you John, archived for future use, and thanks for the book titles

I should have explained that fuse better.  The fuse in the diagram is one that came with the voltmeter to protect it.  There is a second fuse I don't show that is built into the variac.  Sorry about the confusion.

Here is an updated wiring diagram that shows the fuses better.  The 1 amp voltmeter protection fuse is there per recommendation by the voltmeter manufacturer (Blue Sea Systems - 9353 AC Analog Voltmeter 0-150 Volts AC).  The ammeter is an NU 0-10A AC Analog Current panel meter that I bought used off ebay.

Søren Mexico:

sonavor:

Here is the wiring diagram for my dim bulb tester that incorporates a variac, a VAC volt meter and an AC ammeter.  The socket is where the unit being tested plugs into.

Thank you John, archived for future use, and thanks for the book titles

 

Make sure you replace the diagram with the one below Soren.

@ Sonavor might be an idea to delete or ask a mod to delete your first diagram, just to be on the safe side!

Done...I was able to removed the original image and placed a note to explain.