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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022

 

missing BG4000

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Craig
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moving on....the replacement transistor soldered in 

Craig
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Bolted down and following a quick check around for any loose or accidently disconnected wires i powered up.....and was rewarded with a fully functioning solenoid assembly.....drops nice and smooth.

sonavor
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sonavor replied on Fri, Oct 29 2021 3:50 PM

Craig:

John

Thats really interesting....do you know if Rudi has a kit for this mod? unlikely I know, could you let me have a bit more detail around the manufacturer and model of the LED's you used.....i take it the full wave rectifier is a standard component along with the trimmers....this may turn out to be my only recourse ;¬)

Craig

Since this was just a one-off we didn't make it into a kit.  However, I can put together the parts list I used and send it to you. It would be easy for you to make.

John

Craig
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Craig replied on Sat, Oct 30 2021 7:58 AM

Yes please John 👍

sonavor
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sonavor replied on Sat, Oct 30 2021 4:47 PM

Here is the modification I made for adding the strobe functionality to a Beogram 4000 that did not have the 220 VAC secondary available on the transformer.  The circuit again is found towards the bottom of this Beoworld Forum post.

I used a 7.62mm x 7.62mm Red/Green LED.  The ones I used are not longer made I think (Bivar R50RG2-F-0160).  I also tried the Bivar R50RG2-5-0080 which just has a different viewing angle.  

I cut a small piece of prototype board to fit in the strobe lamp housing.  The wire colors match the LED color they go to for mixing the red and green color.


This photo shows the circuit powered up.

I installed it that way so I can always tweak the color if I want.


The LEDs will strobe at the frequency of the AC applied just like the original neon strobe does.

John

 

 


sonavor
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sonavor replied on Sat, Oct 30 2021 4:59 PM

Here is the installation.

Note that the yellow wire from the power supply board was spliced and became a blue wire in the twisted blue pair of wires from the power supply board over to the strobe circuit.


-John

 

 

 

Craig
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John

Thanks for that....I've ordered the components and will have a go, I have had to order the Bivar R50RG2-5-0080 LED's as like you said the other is no longer available. Moving on...I have given the slider switches some attention, they don't look in bad shape but these switches can cause a lot of grief if they don't operate  cleanly. All the switch contact surfaces can be cleaned by removing the saddles...except the 25/30 switch that has to have the leaf spring removed.

Craig
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Saddles cleaned up....I used a glass fibre pen for this exercise.....  

Craig
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All cleaned up

Craig
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Saddles back in place

Craig
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Craig replied on Sun, Oct 31 2021 4:33 PM

I've just had an epiphany, or as some may say "a lightbulb moment" regarding the strobe lamp.....can anyone come up with a reason why I cannot connect across the 240vac incoming supply fuses through the reed relay and then into the strobe lamp? I seem to recall something about back EMF generated when disconnecting a coil i.e. an ignition coil on a car engine....could this be an issue bearing in mind the reed relay would open when the set is switched off?.........any thoughts would be welcome Wink 

Craig
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With the neon lamp moved to the back burner for now I've looked inside the control panel....the lamps are working but are a little dim, and grimy.

Craig
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As Justin sent me two sets of LED's when I worked on his other 4000 I decided to replace the incandescent lamps with the new LED's...

Craig
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However I'm not too sure about the colours.......Justin, It's your call. I can leave the scale as is...or revert to the incandescent lamps?

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chartz replied on Thu, Nov 4 2021 12:34 PM

Aren’t the LED’s too bright?

Jacques

chartz
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chartz replied on Thu, Nov 4 2021 12:34 PM

Aren’t the LED’s too bright?

Jacques

Craig
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Yes they do look a little sudden I agree, Justin has sent me these replacement LED's.......much better result ;¬)

Craig
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As Justin is pursuing a replacement transformer I decided I would have a pop at a neon lamp replacement, just for my own amusement as I'm intrigued by the concept Wink 

Craig
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And the other components underway....I will test this out with my variac 

Craig
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spent a bit more time on this little project today....

Craig
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component side....

Craig
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set my variac to 10vac..............

Craig
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looks good to me, I'll keep this in the box of miscellaneous spare parts Smile 

Craig
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Control panel switch contacts look quite tarnished.........need to remove them and clean them up

Craig
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Of course the F and FF switch contact needs both the saddle and the leaf spring removing to get at the stud underneath....

Craig
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Craig replied on Sun, Nov 14 2021 10:02 AM

Just as an aside......Justin is still pursuing a transformer for this unit, I believe he's received one quote and is waiting for a second, I know this is a long shot but does anyone out there have a 240vac transformer going begging Whistle

Craig
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Craig replied on Wed, Nov 17 2021 8:38 AM

Craig:

I've just had an epiphany, or as some may say "a lightbulb moment" regarding the strobe lamp.....can anyone come up with a reason why I cannot connect across the 240vac incoming supply fuses through the reed relay and then into the strobe lamp? I seem to recall something about back EMF generated when disconnecting a coil i.e. an ignition coil on a car engine....could this be an issue bearing in mind the reed relay would open when the set is switched off?.........any thoughts would be welcome Wink 

well....so much for that bright idea, tried it out and it didn't work......when I connected the neon lamp to the incoming fuses I found that the voltage dropped to around 106vac when the transformer was powered up, well below what's required for the neon lamp. I tried measuring the voltage at the fuses on a working unit and found the same reading........could a faulty bridge rectifier be responsible for this loss of 240vac on the secondary side (Martin.....I'm looking at you) Wink

Craig
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Ok.....took some resistance measurements of the 240v secondary windings of a working machine....1.3kohm

Craig
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Now the problematic transformer readings..........0.9 kohm, quite a difference in winding resistance

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Craig replied on Fri, Nov 19 2021 8:24 AM

So....I'm not sure how transformer calcs go, however...the voltage out of my working machine measured at the neon lamp terminals = 230vac, the voltage coming out of the suspect transformer = 165vac (approx 28% difference)

The secondary 240vac windings resistance of the working machine = 1.3k, the winding resistance of the suspect transformer = .9k (approx 30% difference)

looks like the figures tie up......

 

 

 

Craig
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Moving on with the control panel switch clean up.....almost there.

Craig
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Well......in anticipation of sending the transformer off for a rewind I removed the item, however.....and there is always an "however" the company who originally quoted the job decided against it when they where pressed for a delivery address, Justin is distraught......

Craig
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This is the offending item..........as it is now out in the open I decided to do some more measurements to see how it shapes up, I made the assumption that the primary winding Green/Black/yellow wires, that are all bundled together in the same yellow sleeve where connected to terminals 8 3 and 1 of the voltage selector switch respectively, while the remaining primary white/red wires, also bundled together in a yellow sleeve, where connected to terminals 2 and 4. 

Craig
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Based on that assumption I roughly sketched this out........but when I started to measure up the resistances it didn't pan out. The green wire, connected to terminal 8 of the selector switch, was open circuit with both the black and yellow wires with which it shares a yellow sheath? The yellow and black wires measured 44.5 ohms.....the red and white wires connected to selector switch terminals 2 and 4 respectively measured 44.4 ohms.

This made no sense to me as the transformer would never power up.....as can be seen if the green wire is open circuit to both black and yellow we are going nowhere......and I know this isnt the case. (click on image below.....poor drawing I know) Surprise

sonavor
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sonavor replied on Mon, Nov 22 2021 9:04 PM

When I started out on my BG4000 (with the bad transformer) I was excited at first because I found a transformer repair shop that said they could fix the windings.
Once they received the BG4000 transformer they sent it right back and said they couldn't repair it because the windings are epoxied together.

That's when I went the route of having the Toroid company design me one.  That worked out okay in the end but I didn't realize at the time that I would need the 220V for the neon strobe.  If I were to do it over I would have had them include a secondary for that 220V.  However, I am also happy with my 10V powered LED strobe substitute.

John

Craig
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John

The toroid transformer looks very nice too.......however i recall you saying it was an expensive option? I have cleaned up the drawing I made last night to reflect the actual wiring....it now looks far more plausible and all the measurements tie in, doesn't help Justin of course but I'm happy to have got to the bottom of it, it more or less resembles the schematic shown in the service manual for a 240vac supply machine 

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manfy replied on Tue, Nov 23 2021 12:21 PM

What makes you think that the transformer is spoiled?
The trafo in your picture looks good and so do your resistance measurements. You have two 0.25A fuses in the primary and if they don't blow, an overload is rather unlikely.

Now that you have it removed you can make some simple measurements in idle condition. You'd have to wire up the primary so that you can connect it to 240VAC and then you can measure the idle voltages at the output windings.
The 220V secondary winding should show some 220V +/-10%. Then connect your neon lamp to this output and see what happens to the voltage. If it drops to 160V without the lamp lighting up, the neonlamp is spoilt - replace it. Don't worry about back EMF in that circuit because there's no voltage-sensitive component in it. Besides, the series resitsor of 27k limits the max. current to some 8 milliamps, thus also the back EMF will be negligible.

Craig
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Craig replied on Tue, Nov 23 2021 1:01 PM

Manfy

Thanks for your input.....as I said  earlier in the post when I installed a working neon lamp from one of my working decks the neon lamp wouldn't energise, however it works fine in the working deck. When I measured the voltage at the neon lamp terminals of the suspect transformer I was only getting 165vac whereas I get 230vac at the same points on my working machine.....also when I measure the resistance of the secondary windings of the suspect transformer I get 0.9k ohms....working transformer gives 1.3k ohms. 

Those are the only differences I can find.....I will however do as you say and power up the transformer and measure the idle voltages just to be sure, I'm not up on transformer winding calcs or loadings and I did ask the question earlier if anyone thought a fault in one of the bridge rectifiers could pull down the secondary voltages across the transformer......but nobody seems to know (do you?) Wink

Regards Craig

manfy
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manfy replied on Tue, Nov 23 2021 1:50 PM

Ah, ok! I skimmed your posts but didn't quite get all of it.

If you used a confirmed working neon lamp on this transformer but got the same symptom, it points in a different direction. My first guess in this case is a corroded contact in the voltage selector switch. Corrosion causes increased contact resistance and can cause a significant voltage drop as soon as current flows.
But since you removed the transformer, you can now exclude this switch as the source of the issue when you carry out the idle voltage tests.

Generally speaking, a faulty rectifier could theoretically cause a voltage drop on the transformer if it overloads the trafo just a bit above its working point. But it is unlikely because the fuses would probably blow before you see a significant voltage drop.

There exist only 2 primary failure modes in such low-volt transformers: an open, ie. a broken or burnt wire in a winding, or overload, which practically always leaves some visual marks on the unit. Another effect of overload could be degraded wire insulation, which would cause a short circuit between multiple windings and thus a reduced voltage, but you would recognize this by measuring distinctly different or odd resistance values.
(Of course, additional fault scenarios do exist, but they only happen in high-power grid transformers and for all practical purposes, this can be excluded in our case.)

Craig
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Craig replied on Tue, Nov 23 2021 2:06 PM

Great stuff.......I will tie the primary windings together this evening and do the voltage checks with the selector switch out of the equation, It would be nice to find that this was indeed responsible.

Craig 

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