Beolab Penta Mk I with Mk II display

6 replies
TH
Offline
thch
Silver
Posted February 14, 2019 at 12:07 GMT
#2209661

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?

Beobuddy
Offline
Beobuddy
BronzeFounder
Posted February 14, 2019 at 13:10 GMT
#2209662

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.

Location: Utrecht

Quite a challenge to achieve "Less is More" while having the Beovirus.
TH
Offline
thch
Silver
Posted February 14, 2019 at 13:33 GMT
#2209663

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.....

TH
Offline
thch
Silver
Posted February 14, 2019 at 16:37 GMT
#2209664

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

TH
Offline
thch
Silver
Posted February 16, 2019 at 15:08 GMT
#2209665

Problem solved:

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

TH
Offline
thch
Silver
Posted February 20, 2019 at 08:57 GMT
#2209666

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 ?

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