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missing BG4000

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Craig
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Craig posted on Tue, Oct 19 2021 11:56 AM

Following a protracted delivery process Justin was finally able to get this to me, seems it had fallen off DHL's radar a week or so ago and we feared the worst........


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Craig
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Took it out and after a bit of a clean put it back properly....


Craig
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Re assembly started I thought this was a good time to straighten the audio muting switch that I suspect wasn't opening when the solenoid pulled in....this would result in the absence of one of the channels if it was to remain closed.... 


Craig
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Finished up mechanically......the whole assembly is now free moving and smooth.


Craig
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Turned to the neon lamp next and decided to just replace the existing lamp with a new one supplied by Justin, thought I may get lucky!


Craig
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Craig replied on Sat, Oct 23 2021 11:09 AM

And as those two items comprised the total of the ifentified issues I gingerly powered her up via the variac...no sudden bangs of flashes, smokey smells or anything else untoward.

With the platter in place i hit ON, platter spun, carriage moved inwards past the drop points and back again juas as it should, popped a disc on the platter and hit ON again, carriage moved to the 33 RPM drop point and stopped as it should......however the solenoid remained at rest, and I could dee no light from the neon lamp!....so on to the circuit diagram for some inspiration ;¬)

Craig
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Craig replied on Sat, Oct 23 2021 4:39 PM

Just as a test I have installed a neon lamp from one of my working beograms......now when I press ON the neon lamp flashes briefly and goes out, it displays this behaviour when I press the 33RPM switch also.....brief on and off. I will try the spare neon lamp provided on my working unit and see what happens. However this still doesnt help with the solenoid issue....I'm suspecting reed relay contacts.

chartz
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chartz replied on Sat, Oct 23 2021 7:33 PM

Hi Craig,

Yes, I had to replace them too. An easy task!

 

Jacques

sonavor
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Hi Craig,

Verify the AC voltage from the transformer secondary that powers that neon strobe lamp.  I believe those neon lamps have to have around 220 VAC in order to work.  I don't know what their operating voltage range is but I learned that they won't come on at 125 VAC :-)....which is what I was trying to use at the time. 


John

Craig
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Craig replied on Sat, Oct 23 2021 8:07 PM

Thanks for that John.....I was measuring 160vac at the terminals when the lamp was removed, there is a 27k resistor in series that will need to be removed and measured, god forbid its a transformer issue Erm..

Craig
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Well.....following on I have measured the voltage at the terminals of the neon lamp in a working beogram and get a steady 230vac....as expected. Back at the workbench I've disconnected the secondary windings which provide the power to the neon lamp, effectively bypassing both the series resistor and the reed relay switch.....and only measure 165vac...bit of a worry....


Craig
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While I was on  a roll I installed the spare neon lamp Justin sent into my working beogram only to confirm that its kaput!....I did notice this marked on the rear of the plastic bag which contained said lamp "used".....perhaps it should have said "goosed" (sorry Justin) Surprise


Craig
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While this sinks in I have continued to follow up on the failing solenoid action.....the switch from Hi to Lo at the base of TR10 is present and correct when the carriage reaches the drop point for the tone arm which is encouraging, the solenoid resistance is floating around 7.5 ohms which is also good.....ID3,TR10 and TR11 all measure up good....however OTR4 has failed. 


Craig
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So....I'm looking for a TIP41A to replace this little fellow......


Craig
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TIP41A on order....will await delivery, meanwhile I decided to take a look at 6D1 and 7R1 (connected to the emitter and collector of rogue TIP41A just to ensure any failures in those components contributed to the demise of of said transistor.....the Diode checked out fine, when I came to the resistor I had to remove the carriage slider switch activator and travel indicator....this is what I found, a deep scar melted into the transparent plastic arm......


Craig
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I have seen this before I'm thinking to myself.....and indeed I have, on the arm of one of my own beograms, in almost exactly the same place.


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