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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
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?
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.
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.....
Yup, tried that switch too - no difference. Is there a way to test the display if it works at all?
Problem solved:
Display data input ground wire was missing. Now all is working fine :-)
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 ?
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.