Dillen
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No need to be like this please. i misread the SM as L1 does need 30Ma. I fitted 80mA lamps and there is no change. Instead of shouting at me EXPLAIN why the lamps are so important. Nobody will learn anything like this, ok? I checked all transistors again. I reflowed more joints and the voltages are steady now (more or less) instead of falling / rising. TR7 reads (FM input, stereo signal): B = 14,85 C = 8,30 E = 7,51 I can check IC1, no problem Bert
Shout?
Sorry. I better let somebody else take over.Martin
The discriminator lamps are integrated components in the tuning system.
Look at the schematics and you’ll see how it connects together.Why do you fit 30mA and even 12V lamps when the manual calls for 6V 80mA?
Correct lamps may not be available on every street corner but they are not THAT special, they just
have to stay within certain specs (which means no cheap chinese toy lamps with specs all over the place).And I will ask the two questions again:
Does the voltage on TR7 base also change?
Or is the change in voltage coming from IC1?Martin
Check those lamps.
Correct voltage lamps is not enough.
The important thing is the current draw and their “working pattern” with varying voltages.Does the voltage on TR7 base also change?
Or is it coming from IC1?Martin
Wrong belt path.
The belt should run like this:
Sorry for this fast freehand, but I think you get the idea.
Martin
Have you checked the motor suspension?
There is a good chance the motor pulley is rubbing on the metal bracket due to failing suspensions.
Read here:Motor suspension rubber bushing grommet set f. several Beogram Beocenter models
Martin
Are both your tuning lamps working fine?
And of correct types/wattage?
Note that on this Beomaster model, the AFC-button also activates ST (Silent Tuning = quiet between strong stations).
This could be the key here.
Do you have a good antenna?
Tuner aligned properly?
Will it play with the AFC/ST not activated?Martin
(Thermistor or current limiter…)
Modifying only to compensate afterwards would make little sense in my opinion.Sorry to say it, but I would suggest replacing that lot of capacitors with single cans of good general purpose types.
I would fit can-types rather than PCB-mounts, exactly as B&O chose to do it. They have
a much nicer “oompfh” for this combination of motors, relays, solenoid and (at times sensitive to clean voltage) electronics.
This goes for the DC-motor versions as well.And remember – no low-ESR capacitors in any power supply filtering positions in the classic B&Os.
Also make sure to find a bipolar cap with healthy ripple current specs.
Phasing a motor is hard work for a capacitor.Mains has no reference inside the Beogram.
Chassis ground has no connection to any mains (it would potentially be lethal).
Mains go through the voltage selector and the fuses to the transformer.
Chassis ground is capacitively coupled to signal/electronics ground. If your deck has a three-prong mains plug, the chassis will be connected to the earth pin of the plug.
This means, that you can’t use chassis ground as reference for anything, really – not
for measuring around in the electronics either. Here you must use signal ground for reference.
For convenience I like to clip the meters negative pin to the common negative point of the large cans in the regulator circuit (after your modification no longer accessible in your Beogram).Martin
One thing that kills transformers in these Beograms is rush-in current.
This is an issue particularly if the Beogram stood unused for a long time, and definitely if someone put in low-ESR filter capacitors.
The latter can be seen as an almost dead short right at the moment when voltage is applied, which puts a huge stress on the transfformer (and rectifier etc.).
Always bring a long stored Beogram up slowly on the variac for the first time to save the transformer.Replacing one filter capacitor with two or more paralleled capacitors will only add to the risk of damaging the transformer as the resulting ESR (impedance) would be very low indeed.
The regulator would also be at risk, because of the reservoir capacitor it replenishes.
I wouldn’t recommend it.Also, I am not sure what you measuring in the two photos with the multimeter.
Looks like the meter is in DC voltage mode while you measure on the fuses (?). And where is the reference (meter ground) connected?Martin
Don’t change the value of the resistor.
Besides, a 5W resistor will dissipate just as much energy as a 3W if they are of the same ohmic value.
And don’t think a resistor is bad just because it runs warm.
The resistor in question will run warm. If the lamp has been out – or the
Beomaster hasn’t seen use for a long time, dust on the resistor may emit a warm smell
and even a little smoke for a minute or two as it warms up for the first time.
Not unlike many valve-based items.
That’s all normal.If the resistor has indeed gone bad or measures very wrong, I suggest you ask at Beoparts-shop for a possible replacement.
Beoparts-shop is a webshop, it requires no membership or login.
http://www.beoparts-shop.comMartin
“A lamp 12v/80mA has the same characteristics even bought from beoparts or elsewhere.”
True.
But quality could be the difference.
From Asia you can often buy very cheap lamps meant for use in plastic toys.
They typically have a rated lifespan of, perhaps, 200 hours (and tolerances not worth mentioning).
You will often find these listed on Ebay and similar places for next to nothing.
If you go for this quality it would be a good idea, as suggested in the linked thread, to buy
lots of ten or more and, if you use your Beomaster on a regular basis, you will also
develop good lamp replacement skills.Lamps from Beoparts-shop often have an expected lifespan of 2000 hours, some even 5-8000 hours.
Some lamps sold there are actually custom produced.And the resistor will run warm.
That’s Ohms law.Martin
Check for cracked solder joints, particularly where connectors and the piggy-back boards are soldered in.
Does it run warm on the cooling fins? If so check the idle current settings.Martin
That’s a homemade solution.
The spring plate is not supposed to sit under the keyboard like that.Martin
The recitifier board pulls right up when you pry away the small black claw that holds it.
The regulator itself has three pins that goes into a connector. The regulator stays with the chassis.The filter capacitor is a “soldering star” type – not a snap-in. They are known to go bad.
Also check the rectifier diodes. I’ve seen cases where owners fitted schottky types, – not sure why, presumably in a misunderstood attempt at improving something,
– and they are no good in this position. They typically go with a bang.Martin
You can find test/calibration/alignment records in good shops, on Ebay or f.e. here:
https://www.discogs.com/search?q=stereo+test%20record&type=allNote, that test records should not be bought “used” unless you trust the seller.
If a test record was played using a bad needle, it could be damaged and absolutely worthless.Martin
Our beograms do not have (unless I’m mistaken) a lot of (if any) adjustments beside tracking force. No azimuth, no anti skating, no “whatever it is named I don’t even know what it is”…
Eh, what?
Which model Beogram are you talking about?
The term azimuth is mainly used with tapedecks, but the angle of the cartridge (rotation and/or parallelism) can be adjusted in many Beogram models.
So can anti-skating, even if a knob or dial for this is not in direct view.Test records are good for countless things.
Many of the following parameters and properties can be checked using
one or more test records, – and most can be adjusted or manipulated in some way;
Tonearm height, tonearm parallelism, tonearm rotation, (& tonearm length for tangential models), tracking angle, tracking force, anti-skating, platter speed, wow, flutter, rumble.
Also general stylus condition, channel separation, distortion, frequency response (stylus and RIAA) etc. can be checked using test records.Martin
Originally, a special tool was available in order to align the spindles position.
This tool is nowhere to be found, so in most cases a careful check for free spinning of the spindle is all we can do to get it right.
The coil block and the two plates holding the bearings can be moved in relation to each other.
It’s not a lot, actually very little, but even an ever so tiny move could result in a much more free rotating spindle. As can a little wiggling of the spindle to make bearings run “clean” on their inside races axially rather than rub on edges.
Rotate the spindle by hand, and watch the run down time. The spindle should run for as many seconds as possible.The motor will normally run a little warm after some minutes, but not hot.
If it runs hot there is something run. Has its coils been correctly electrically connected (in series and not parallel etc.)?Martin
Sure you have the spindle aligned correctly axially with the bearings?
Does the speed adjustment move the small magnets all the way out and away from the brake disc?I take it this is not a 60Hz (US) deck running on 50Hz (europe etc.)?
Martin
Does it lift slow?
If so – dry or wrong lubricants?Has it worked while in your possesion?
If not – wrong cam wheel for this model, perhaps?Martin
