Eugene, this weather is ridiculous!

Btw, just walked out of a soldering lab, we made 9v buzzers with some blinking LEDs from a kit.

Apparently my instructor has set aside nearly 6 hours of class time for this. We will continue next class on monday but my instructor is advancing me inti the next class so I won't get bored!

I just received a Beomaster 3000-2.

The positives first:
It actually works, at least on the radio (haven't tested the rest)
No significant damages on the front panel
It seems to be untouched by amateur repair. The schematics were still in the envelope and looked like new.

The negatives:
It stinks! It has clearly belonged to acigarrette smoker.
It is dirty, both on the outside and inside.
One of the rear corners seems to have been slightly damaged in shipping. Should be repairable.
A small aluminum part at the end of the front panel is missing. This is hardly noticeable though.
Two light bulbs need replacing.

The main problem with this unit seems to be the dirt, probably the cigarrette smoke. The volume slider has contact problems. There are dead spots in certain positions. Maybe this will go away with some exercising, maybe not.

Currently I'm cleaning the front panel and everything that can be cleaned with a micro fibre cloth.

A question: Is it advisable to take the "slide rules" apart to clean the clear plastic on the back side? 

Most likely, you won't be able to remove the yellow color from the nicotine.
It settles within the material.
I have heard of solutions involving soaking in bleach or chlorine but I haven't
tried that myself so I cannot advice.

The sliders will need proper cleaning. Take them apart and clean the slider track,
that's the one next to the resistive track. It's almost always this track that develops
dead spots. A glass-hair brush is the best tool for this.
Give the sliders contacts a fresh amount of tension while in there.

I may be able to find a part to replace the missing aluminum end cover, let me know.

Martin

I was pretty lucky with my 3000-2. It looks perfect, but the seller used incense quite a lot but it went away after a while.

Somehow the little windows on the sliders have water spots behind them... How, I cannot figure out.

This is a project I really need to get cracking on. I've been putting this off - I am a bit scared honestly!

I have to figure out where all the sound went then do some cleaning and replace the a few bulbs.

This is one of the sliders in my BM3000 when I took it apart just a few days ago. I had "cleaned" it once before by spraying contact cleaner into the slider but here you can see clearly that the slider should be opened and cleaned properly!

This is the same slider after some cleaning:

And yes, it does sound much better now...

That's exactly the thing to do !
There's nothing like a clean potentiometer.
Contact cleaner losens oxidation but it doesn't remove anything, it just allows the dirt
to be shifted around until the cleaning agent eventually evaporates (typically overnight
and you have the fault back).
In the best of cases the cleaning agent doesn't add to the mess.

Menahem, you have a reply to your BM1600 thread.

Martin

OK, so you can take them apart without unsoldering them. That's good because then you don't risk resoldering them the wrong way. I'll take them apart for sure. But what's the best way to open up the slider shells?

Eugene:

my front yard is a mess

You got off easy! Trade?

Update on the BM1600:

Rewired according to Martin's picture - works fine.

Now I did some improving - 3 AA119 germanium detector diodes in the IF section had more leakage than I like, so I replaced them with new AA119's, selected for very-low leakage (they all have leakage to some extent).

And an OA90 (very-high leakage) replaced with a very-low leakage AA143 (Martin - thanks for that tip!).

The signal voltages are back on the SM's spec now, and the radio signals are crystal clear - I had no idea that this vintage unit was capable of such spectacularly clear FM reception.

I'll run through the RF alignment process, but listening to this now, I'll be very surprised if it needs any adjusting at all.

Menahem

lausvi:

This is one of the sliders in my BM3000 when I took it apart just a few days ago. I had "cleaned" it once before by spraying contact cleaner into the slider but here you can see clearly that the slider should be opened and cleaned properly!

This is the same slider after some cleaning:

And yes, it does sound much better now...

 

OK, so I milled off the "heads" from the studs that holds the shell together. Then I could separate the shell without forcing anything.
It turned out mine were not terribly dirty inside, but of course I cleaned them anyway.

Now the question is if I should add some kind of special grease before I put them together. In that case I need to purchase it, because I don't have anything suitable.

You can add a little silicone grease to the slider
grooves in the plastic casing and also to the center
metal plate if your sliders have it.

Martin

I've had a really interesting time with this CD4 demodulator - not finished yet, but it has been a real learning experience for me. This is the first time I've ever had one with such levels of defects.

So, In the BeoGram section, I've put up a Workshop on this - I'm not finished yet, more to come!

Menahem

Dillen:

You can add a little silicone grease to the slider
grooves in the plastic casing and also to the center
metal plate if your sliders have it.

Martin

 

I just realized what caused the dead spots on the volume control.

The contact points on the wiper were completely worn down! This Beomaster must have been used a lot!

I replaced the contact points with silver points and moved the wiper to the bass control, which isn't used as often. We'll see how that works.

ordering components parts caps, transistors, diodes etc. I have run out.

Now I have installed the belts Martin sent me in the Beocord 5000. I'm happy to report that this sems to have cured all faults with this deck. As far as I can tell, it now functions exactly as it should. Some trimming might improve it even further but as it is, it sounds good recording new tapes and playing back old ones, made on other machines.

There is just one niggle and I suspect this isn't even a fault: The recording level is too low when connected to my Beomaster 901. Did I read somewhere that B&O changed the standard for this? If not, the fault could just as well be in the BM901.  

BeoGram 6000 CD4 repair complete - see the details with pics in the BeoGram section.

Menahem

Agent00soul:

Now I have installed the belts Martin sent me in the Beocord 5000. I'm happy to report that this sems to have cured all faults with this deck. As far as I can tell, it now functions exactly as it should. Some trimming might improve it even further but as it is, it sounds good recording new tapes and playing back old ones, made on other machines.

There is just one niggle and I suspect this isn't even a fault: The recording level is too low when connected to my Beomaster 901. Did I read somewhere that B&O changed the standard for this? If not, the fault could just as well be in the BM901.  

I need to order belts for mine at some point. Mine will only open and close with assistance seems to want to play OK but it will only engage the tape mech for a second or two then it goes back into standy. Havent really spent much time with it. I have another beocord 5000 as well but have never even plugged it in to test it.

Eugene

Even after replacing the belts, you may still have that problem. The cause is that the rubber roller wheels have hardened, and aren't gripping the downwind axles. 

Solution - DeOxit Rubber Restorer.

Menahem

Agent00soul:

Now I have installed the belts Martin sent me in the Beocord 5000. I'm happy to report that this sems to have cured all faults with this deck. As far as I can tell, it now functions exactly as it should. Some trimming might improve it even further but as it is, it sounds good recording new tapes and playing back old ones, made on other machines.

There is just one niggle and I suspect this isn't even a fault: The recording level is too low when connected to my Beomaster 901. Did I read somewhere that B&O changed the standard for this? If not, the fault could just as well be in the BM901.  

 

After doing some more testing, I have identified ine problem:

There is no monitoring during recording. So if you record from the aux input jack, you can't hear what you're recording.

I have followed the signal on the schematics and it looks like the input signal should be routed to the output during recording inside the Dolby chip. Any ideas? Is this normal?

Agent00soul:

After doing some more testing, I have identified ine problem:

There is no monitoring during recording. So if you record from the aux input jack, you can't hear what you're recording.

I have followed the signal on the schematics and it looks like the input signal should be routed to the output during recording inside the Dolby chip. Any ideas? Is this normal?

I looked and measured some more:

There is a 4066 (IC 107) that mutes the output signal and this is controlled via two diodes: D107 mutes it during stop only and D106 mutes it during recording and record-ready (signal labeled "record silence").

Why should the output be muted during recording? It seems that unsoldering D106 would solve my problem.

Agent00soul:

I looked and measured some more:

There is a 4066 (IC 107) that mutes the output signal and this is controlled via two diodes: D107 mutes it during stop only and D106 mutes it during recording and record-ready (signal labeled "record silence").

Why should the output be muted during recording? It seems that unsoldering D106 would solve my problem.

I removed D106 and now the Beocord works exactly the way I want. I can now monitor the signal that comes in on the AUX input, both during record-ready and recording.

Now the only remaining problem is that the recording output signal is too weak from the Beomaster 901. There are two ways to fix this:

1. Add an opamp inside the BC5000 that amplifies the signal.

2. Remove/short the 33k resistor that the BM901 has in series with the recording output.

The BC5000 has a 22 kohm imput impedance (the recording level pots) so removing the 33k resistor should more than double the signal level. I'm not sure this is enough, but it could be.
Modifying the Beomaster of course makes it non-compatible with old tape recorders but it's a simple task to add a 33k resistor inside those recorders. From a sound quality standpoint this ought to be better than to add an extra amplifier stage inside the BC5000, or what do you think?

Not B&O, but will be very usefull diagnosing faults in B&O equipment!

Not one, but two ESR meters, the circuits of which freely available on the net...

 

 

The top one seems to be working well, I am having teething problems with the bottom one at the moment. Hopefully the top one might look somrthing like this if I can master my plasticard skills...

 

 

I am still going to complete my digital ESR meter, but I have given up on printing the rather complex double sided board for now, so that can wait!

 

Didn't know Plasticard was still available! I remember doing some stuff with it as a kid