[sdiy] Bizzare Solina Problem

[Michael Ruberto]

Correction. I had my resistors mixed up. The one I circled and labeled hot 
is not the resistor that is getting hot. The circled resistor is actually a 
47 Ohm so there is a discrepency with the schematic.

Now the resistor that IS the hot one is part# 39 470 ohm in the .pdf schemo. 
The value of this resistor should be 448.9 taking into account the 10K in 
parallel with it. It measures at around 180 ohms. big difference.

Still not groking the solder bridge deal but I'm a step closer.

M. A. Ruberto

>From: "Michael Ruberto" <frankentron at hotmail.com>
>To: synth-diy at dropmix.xs4all.nl
>Subject: [sdiy] Bizzare Solina Problem
>Date: Sat, 21 Jul 2007 10:28:58 -0400
>
>I am repairing a friends Arp Solina with many issues. So far I managed to 
>fix everything but the bass section which generates the cello and 
>contrabass presets. These don't sound at all. While going over the circuit 
>I find a blob of solder connecting pins 5 and 6 on the top 709 (refer to 
>.jpg schemo below). Naturally this becomes my first suspect and I remove it 
>with my solder sucker. Problem is I get no sound at all now, even from the 
>other voices which are generated on a different PCB. Even weirder, is that 
>the bass PCB does not connect to the other voice PCBs and has it's own key 
>bus...
>
>After a thorough signal tracing I find that all note tones are working and 
>the combined audio from them  can be found on pin 5 of the bottom 709 when 
>keys are pressed. However, that's where the signal ends. There is no output 
>from the bottom 709.
>
>Looking back at the top 709 I find that the 470 ohm 1 watt resistor at it's 
>output is too hot to touch. The output also remains constant at ground 
>level when keys are pressed. Since it isn't producing a trigger the audio 
>is not passing through the crude VCA-like circuit of the bottom 709.
>
>So my next step is to try replacing the top 709 and I have the part on 
>order. What's still bugging me though is the solder bridge. When I short 
>pins 5 & 6 on the top 709 all the other voices come back and this is very 
>bizzare and puzzling to me. Anybody have ideas on this?
>
>
>http://www.somnium7.com/samples/solina-bass_02.jpg
>http://www.somnium7.com/samples/07.pdf
>
>M. A. Ruberto
>
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