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 Post subject: Brandbridge scart switch issue
PostPosted: Wed Mar 26, 2014 3:17 am 



Joined: 01 Feb 2013
Posts: 34
Location: Champaign, IL
I have had one of these scart switches in the image below for awhile hooked up to my PVM 2950Q.
My turbo grafx, genesis, snes, all hooked up via composite video to an lm1881 sync stripper. Works fine.
I recently hooked up a 32x via composite sync as a new input to the switch. However, it keeps losing sync randomly.
If I hook it up to input 5 it is fine, but all other inputs and it loses sync.
Anyone else ever had any problems like this with scart switches?

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 Post subject: Re: Brandbridge scart switch issue
PostPosted: Wed Mar 26, 2014 7:38 am 



Joined: 17 Sep 2012
Posts: 386
Not sure if it's the same issue as I encountered, but I had to cut a trace on the 5th input for all the inputs to work properly for me.

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 Post subject: Re: Brandbridge scart switch issue
PostPosted: Thu Mar 27, 2014 2:40 am 



Joined: 01 Feb 2013
Posts: 34
Location: Champaign, IL
eightbitminiboss wrote:
Not sure if it's the same issue as I encountered, but I had to cut a trace on the 5th input for all the inputs to work properly for me.

Image



Yeah cutting that line didn't seem to do anything. And I verified there is no continuity there anymore. It seems to be connected to a diode and +5V. No idea why. Possibly to isolate other lines somehow from taking the +5V.
I did notice there was yet another diode below the cut trace diode, and when I jumped the diode the sync starts working. When I remove the jumper wire, it stops working again. I checked the voltage and the diode appears to be dropping the voltage from 5V to 4.7V. Which I guess is enough to make the sync stripper stop working. I wonder if they are expecting voltage there higher than 5V.


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 Post subject: Re: Brandbridge scart switch issue
PostPosted: Thu Mar 27, 2014 5:02 am 



Joined: 01 Feb 2013
Posts: 34
Location: Champaign, IL
LaC wrote:
eightbitminiboss wrote:
Not sure if it's the same issue as I encountered, but I had to cut a trace on the 5th input for all the inputs to work properly for me.

Image



Yeah cutting that line didn't seem to do anything. And I verified there is no continuity there anymore. It seems to be connected to a diode and +5V. No idea why. Possibly to isolate other lines somehow from taking the +5V.
I did notice there was yet another diode below the cut trace diode, and when I jumped the diode the sync starts working. When I remove the jumper wire, it stops working again. I checked the voltage and the diode appears to be dropping the voltage from 5V to 4.7V. Which I guess is enough to make the sync stripper stop working. I wonder if they are expecting voltage there higher than 5V.


For any future people who might have been brought here by a search for "Brandbridge" and "Scart Switch" and "composite sync" and "not working". Well just remove the two diodes from the PCB and replace them with jumper wires. They were stealing voltage needed for the lm1881 sync separator Everything seems to work now.


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 Post subject: Re: Brandbridge scart switch issue
PostPosted: Thu Mar 27, 2014 4:27 pm 



Joined: 17 Sep 2012
Posts: 386
LaC wrote:
LaC wrote:
eightbitminiboss wrote:
Not sure if it's the same issue as I encountered, but I had to cut a trace on the 5th input for all the inputs to work properly for me.

Image



Yeah cutting that line didn't seem to do anything. And I verified there is no continuity there anymore. It seems to be connected to a diode and +5V. No idea why. Possibly to isolate other lines somehow from taking the +5V.
I did notice there was yet another diode below the cut trace diode, and when I jumped the diode the sync starts working. When I remove the jumper wire, it stops working again. I checked the voltage and the diode appears to be dropping the voltage from 5V to 4.7V. Which I guess is enough to make the sync stripper stop working. I wonder if they are expecting voltage there higher than 5V.


For any future people who might have been brought here by a search for "Brandbridge" and "Scart Switch" and "composite sync" and "not working". Well just remove the two diodes from the PCB and replace them with jumper wires. They were stealing voltage needed for the lm1881 sync separator Everything seems to work now.


Interesting, glad you got it to work after some further cutting. Weird though that you had to cut in 2 places though when I only needed the one.


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 Post subject: Re: Brandbridge scart switch issue
PostPosted: Sat Apr 05, 2014 5:37 am 



Joined: 19 Jul 2013
Posts: 265
As I recall I had similar problem with a syncstripper, the issue was that it lost the neccisery voltage on the pin that supplies the power to the stripper so I got an external powered syncstripper and it works flawlessly even with 2 of those scart switches daisychained.


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 Post subject: Re: Brandbridge scart switch issue
PostPosted: Tue Jul 15, 2014 7:12 pm 



Joined: 19 Apr 2012
Posts: 16
The diodes are 1N4004(for surge protection or something). D1 links selected input pin 8 with OUT pin 8, so the LM1881 didn't get enough volts. D2 links selected input pin 8 with AV5/VCR pin 8 and causes some consoles to power on, most likely intended for some SCART VCR mumbo jumbo.

Maybe a better solution is to replace D1 with a jumper wire(= no voltage drop on output) and remove D2 (= no more power to AVR5/VCR when not selected & no trace cut necessary).

BTW the screw covers goes of easy when pulling with Blu-Tack.

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