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 Forum index » DIY Hardware and Software » The Repair Shop
problem with marion systems prosynth
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trans alp



Joined: Apr 19, 2012
Posts: 2
Location: dresden/ germany

PostPosted: Sun Jul 28, 2013 1:44 pm    Post subject: problem with marion systems prosynth Reply with quote  Mark this post and the followings unread

hi, this is my first post here ...

i was searching for a marion pro synth for a very long time and finally managed to buy one. the seller stated the synth as NOS and it looks so.

there is only one thing that is annoying ... there is a high frequency "hiss" on four of its eight voices. for example ... when i turn down the filter cutoff to a low value - so that only a sine-like waveform can be heard - there is that high hiss on voices 3/4 and 7/8. it sounds like the high freq portion of the base waveforms is leaking through. this happens on any preset ... so it seems to be an hanrdware issue.

i took a look inside and checked the ic sockets. the only thing that looks not normal is that some of those (many) yellow caps (they are "blob" shaped and i guess they are the ceramic type) in each voice seem to be a bit leaky ... but this also could be just some solder flux. unfortunately i have no camera to docuent this.

is there anyone around who is familar with the marion systems pro synth an experienced something similar or can help me track down the error otherwise?

thanks in advance,
sebastian.
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drapdap



Joined: Oct 11, 2004
Posts: 194
Location: bp
Audio files: 1

PostPosted: Tue Jul 30, 2013 5:40 am    Post subject: Re: problem with marion systems prosynth Reply with quote  Mark this post and the followings unread

hi sebastian!

just read your post. i have a marion msr-2. maybe i can help.
i'm not knowlegable at all when it comes to these beasts, but mine is working properly after changing the psu caps and a full reset. im such a happy chap...

could be you have an issue that unit has been switched off for too long, and the power supply is not up to driving the unit properly anymore?
but hard to tell.
the bleed thru are the high frequency drivers for the vco?

measure the psu. i'd start there, rather than messing with the voice board.

robert
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trans alp



Joined: Apr 19, 2012
Posts: 2
Location: dresden/ germany

PostPosted: Tue Jul 30, 2013 8:49 am    Post subject: Reply with quote  Mark this post and the followings unread

hi robert, thanks for the reply.

i just have some basic knowledge in electronics, so i checked the caps on the psu only optically and measured the output voltages - wich have the correct value (as printed on the pcb). only one thing was wrong there - there are two voltage regulators (i guess) and one of them had a loose cooling element. is there anything else to check on the psu?

it really could be, that it was switched off for too long. i guess it never ever has been used before.

well, about the bleed thru ... i'm not even shure if it is one Embarassed it also could be distortion. in fact, when i turn down the cutoff, there are some high overtones, that are not supposed to be there. i can make an recording if it halps ...

sebastian.
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drapdap



Joined: Oct 11, 2004
Posts: 194
Location: bp
Audio files: 1

PostPosted: Wed Jul 31, 2013 5:50 am    Post subject: Reply with quote  Mark this post and the followings unread

trans alp wrote:
i checked the caps on the psu only optically and measured the output voltages - wich have the correct value


fair enough, but then you don't know anything about their capacity.
i'd change them to lot better caps...
but when you're getting the right voltages it's probably ok for now...

also in the first post, are you talking about leaky tantalums around the voices? they could be a culprit, but they go bad for a reason,
they are sensitive to heat and overvoltage. which is pretty easy to do for a bad psu, just let a big spike thru, and there goes your tantalums...

another thing, if you remove the bottom covering of the synth, you'll notice a battery in a socket under the psu. it's a cr2032, change it,
and reset the machine to factory settings... actually do this first, you might get lucky if it turns out just a corrupted memory/os... mine had that too...

trans alp wrote:
well, about the bleed thru ... i'm not even shure if it is one Embarassed it also could be distortion. in fact, when i turn down the cutoff, there are some high overtones, that are not supposed to be there. i can make an recording if it halps ...

sebastian.


yeah, maybe it does... let's listen. Very Happy

r.
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