MCL2 AV no 5,5V

[Madskp]

I have aquired a MCL2 AV for some testing purposes.

first test of it with 15V power, tranciver, speakers in powerlink socket, and beocord 3500 in tape socket. No reaction to remote. No led light in the tranciver.

tried to do some measurements, and there is no 5,5V after IC20

I got 11.6V before IC20 where the servicemanual says 10.6V

i got 12V after IC21 and 6V after IC12 asit should be

any clues what to look for?

[Madskp]

Am I right in assuming that the MCL2 AV will start up and work stand alone without connection to a MCL master?

[Guy]

Madskp wrote:

Am I right in assuming that the MCL2 AV will start up and work stand alone without connection to a MCL master?

Yes – I used to use one like that as a stand alone amp for my PC. It even gave two-way IR in stand-alone mode!

Are you using the offical Power Supply, or the supply feed from an MCL2P? Mine worked with both.

EDIT: I know you’d like to see my neat cabling …. ?

[Madskp]

Yes thats the way cabling should look like in a man cave ?

I dont have the original PSU so I am using a bench power supply with wires soldered to the PCB. It should be ok as I am getting the right voltage levels other places on the board except that 5.5V that is not showing up.

[Guy]

Have you checked the connection/wiring of the IR eye?  I think that is one of the ‘users’ of the 5.5V supply, hence could be shorting it out if wired incorrectly?

[Madskp]

Hi again and thanks for the hint.
the problem persists without the IR eye connected, so may not be that. Right now im suspecting an SMD transistor

[Madskp]

Guy, is there a pin connection drawing on the PSU for your MCL2-AV if you have it handy?

thsnks in advance

[Guy]

Here you go:  (I am getting better at finding things!)

[Madskp]

Thank you very much. Then I can rule out errors regarding these specifications

[Guy]

Not sure if this helps – I think this is quite a late model without the passive speaker or RF connections.  The label says Type 2032.

[Madskp]

Thanks again. Mine is type 2020 and has a lot more going on

guess the same applies to the bottom og the PCB.

but great to have some sort of reference.

I had some corrospondance with the seller and he tells me it didnt work with a power supply for him, but it did connected tol the MCL2P.

cant really see what difference that should make?

[Guy]

The one that I used as a stand-alone was also Type 2020 – you can see the TV co-ax socket in my first photo.

I suppose that the 2020 is older therefore has more chance of a fault.  Perhaps someone has connected an incorrect PSU in the past, or reversed the polarity and damaged IC20 (or one of the many extra components in the earlier model).

I just checked my PSU with no load and it measured 23V.

 

[Guy]

With the PSU connected to my Type 2032:

Input leg of IC21 is reading 20.4V

I get the correct 12V and 5V readings at IC21 and IC20 outputs respectively.

Maybe carefully increase your supply voltage?

[Madskp]

Ok thats interesting. I will try that when I have the time to sit with it again

[Madskp]

Ok, tried a little back and forth with the MCL2AV, but have only got small timeslots to work with it.

Carefully applying higher voltage did not change anything. Guess under normal circumstances it will work within a certain voltage range as all input voltage either goes through the voltage regulator IC21 or to activating a relay switch.

I then have controlled most of the Caps in the power circuit, soldered the out and tested the with a component tester and all seems to be within range still after all these years.

As mentioned earlier I suspected a transistor, and ended up testing TR10, TR11, TR12, TR13. TR13 is the only one of the who fails the test. It only shows up as a diode on the tester.

To further test the unit I tried to apply 10.6V after this transistor before IC20 as shown on the diagram in the servicemanual, and the the unit was alive. Could control a Beocord 3500 with remote and get sound out on powerlink.

So hopefully replacing TR13 will make it work fully again. Ordered a bunch of the on Ebay, and gotta get practicing on my SMD soldering skills with hot air.

Will update when I have the new part.

 

[Madskp]

So got the transistor. I ended up buying BC807-25 instead of BC808-25 (they have alomost identical data) as it was easier to come by.

desoldered the old TR13 with hot air, and soldered in the new one.

Testing and red light turns on in the IR eye. Meassuring with multimeter shows 5.46V so very close to the specified 5.5V.

So now I just need one Bench supply for it until I find a 15V power brick.

unfortnuatly the ribbon cable to the PL connectors broke of in the proces so need some extra repair work before its ready for further testing

 

 

 

 

 

[Guy]

Madskp wrote:

until I find a 15V power brick

Great work fixing the fault!

If you intend to use it with passive speakers you could perhaps look for an MCL2P with its built in 15v power supply?

[Madskp]

Guy wrote:

Madskp wrote:

until I find a 15V power brick

Great work fixing the fault! If you intend to use it with passive speakers you could perhaps look for an MCL2P with its built in 15v power supply?

Thats right. Don’t know what the final use will be for it for now, but it sure has some possibilites

[Author]

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