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Beolab Penta Mk I with Mk II display

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thch
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thch posted on Thu, Feb 14 2019 12:07 PM

Hello y'all.

 

I have a set old refurbished Penta's Mk I, bought several years ago. No display units in them.

Recently I found a set of Mk II displays, and am trying to make them work on the Mk I Penta.

First off all, both displays needed a full recap, which I have done. But i can't get anything out of them....

10V AC (to pin 2 and 3 on the connector) from the AMP is good. I have a signal on the DATA line (pin 4).

System is connected to a BM6500 (tried Beosound Ouverture too without any luck).

The TP1 on the diagram shows 1V DC.

Bonus info: I had a small success at one point where the disply lit up for a short time - it froze on a certain setting and would not turn off when the speaker amp shut down. After this I have had no response from the displays.

How do I test these circuits?

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thch
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Answered (Verified) thch replied on Thu, Feb 21 2019 6:55 AM
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Finally problem solved:

Pin6 on the display (audio/video signal) - When audio signal is fed via the RCA plug, this pin is grounded - must be high to turn on display.

Removed pin6 on the plug resolved my problems :-)

 

Has anyone modified the resistors/LDR resistor on the Mk II display - output is pretty low and hard to see when the acrylic covers are fitted. 

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Beobuddy
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The mk2 and mk3 display has to be told to which data they have to listen. Audio or Videomaster. You're missing a switch at the bottom which switches a mode line to ground, or not. 

Just compare the diagrams and look for differences.

thch
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thch replied on Thu, Feb 14 2019 1:33 PM

That switch is included on the pcb (goes to the audio/video input on IC2). I believe I have tried to switch that one too.....

thch
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thch replied on Thu, Feb 14 2019 4:37 PM

Yup, tried that switch too - no difference. Is there a way to test the display if it works at all?

thch
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thch replied on Sat, Feb 16 2019 3:08 PM

Problem solved:

Display data input ground wire was missing. Now all is working fine :-)

thch
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thch replied on Wed, Feb 20 2019 8:57 AM

Well... not quite true!

This one is really bugging me.....

Scenario:

Beolab Penta Mk I with refurbished Penta Mk II displays. Display is connected via the 2 pins on the DIN plug. Audio is connected via the RCA plug. Source is BeoMaster 7000 using the Powerlink output. (Please recall the the Penta Mk I does not have the Powerlink plug - only DIN, RCA and speaker terminals)

No display when the 2 parts are connected. When audio RCA is pulled out, the display works as it should!

I am beginning to suspect the AMP in the Penta's - could it be that the digital ground is shorted to the audio ground and that is why display is off when audio RCA is connected?

Anyone here who has a picture of the correct wiring from the plugs (DIN & RCA) to the AMP circuit ?

thch
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Answered (Verified) thch replied on Thu, Feb 21 2019 6:55 AM
Verified by thch

Finally problem solved:

Pin6 on the display (audio/video signal) - When audio signal is fed via the RCA plug, this pin is grounded - must be high to turn on display.

Removed pin6 on the plug resolved my problems :-)

 

Has anyone modified the resistors/LDR resistor on the Mk II display - output is pretty low and hard to see when the acrylic covers are fitted. 

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