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Solnia Capacitor Blowup

A client of mine phoned me in a panic one evening. Something blew up in his Solina String Ensemble, and there was smoke coming out of it. He also said that the stink was unbearable.

After calming him down, I told him to unplug it, and bring it over. I already knew what had happened. A capacitor exploded.

Not Exactly What I Was Expecting

Usually when a capacitor explodes, it's in the power supply. This also causes tiny bits of paper, foil, and electrolyte (goo) to splatter on the inside of the case. However, when I opened up the Solina, everything looked normal (other than the stench).

Unfortunately there are no exciting photos.

Bad Oscillator Caps

Bad Oscillator Caps

Bad Oscillator Caps

Bad Oscillator Caps

After a very close inspection, I noticed that both capacitors on the master oscillator board were bulging a bit, and one of them had ruptured. I actually had to use my nose to sniff around the circuit boards to find the trouble! You can barely tell from the photo, but the larger capacitor has failed. There is enough of a leak to let out lots of bad smelling smoke, but the foil and goo stayed inside.

If you look at the lower-left, you can see that Ali inspected this board. I'm assuming there were no problems with it in 1979.

New Oscillator Caps

New Oscillator Caps

New Oscillator Caps

New Oscillator Caps

Here is what it looks like with new capacitors.

Power Supply Re-cap

Power Supply Re-cap

Power Supply Re-cap

Power Supply Re-cap

Power Supply Re-cap

Since this keyboard is at least 35 years old, the capacitors in the power supply were also over-due for replacement. Here is a before and after photo.

Service Manual Surprise

Service Manual Surprise

Service Manual Surprise

Service Manual Surprise

Surprise!

A nice surprise was the original service manual, tucked away behind the circuit boards. After I dutifully scanned the pages, I replaced them for the next repair technician to find.

34 comments on Solnia Capacitor Blowup

1 2 3 > [last]
Pascal LIEGEOIS
When I play more than a note(mark) on the left part of the keyboard, that lowers gradually the volume of the machine, excepted(except) the sounds of monophonic basses which stay there.... I am an electronics engineer and I try to repair Solina of a friend... You Have an idea where from to look, I ... Read More
October 5th 2014 09:50 EDT
Keith
Hi Pascal, I don't have a Solina in my studio any more, but here are some insights from my notes that might help you... Both the bass and the string sounds go through the same final VCA. So, if the bass sound sustains when you leave the keys down, then it isn't the final VCA. The VCA is on ... Read More
October 5th 2014 21:18 EDT
Keith
Pascal, Another thing to look at would be the crescendo ciruit. There is a crescendo trigger generator on the 'gate' PCB (TR1 and TR2), which turns on a transistor on the 'register' PCB (TR9), which charges a 22 uF capacitor (C168). The voltage across this capacitor is fed into the ... Read More
October 5th 2014 21:19 EDT
Vincent
Hi, i confirm for tr1. Test the twodiodes behind.
if you don't find a transistor for change tr1 bc107b, 2n3904 is good (npn )but be carefull isn't the same pin configuration..
June 29th 2017 19:21 EDT
Pascal LIEGEOIS
Hello
Thank you very much,Heith. I am going to explore this way and I inform you....
Cordialy

Pascal
October 6th 2014 05:58 EDT
Pascal LIEGEOIS
oups, not Heith, but Keith, sorry
October 6th 2014 05:58 EDT
Pascal LIEGEOIS
changed the following components:
Gates circuit board: Tr 1 and Tr2, IC427 ( 709 ), C420
Registrer circuit board: D173 (one Tr10 bases), Tr9, Tr10, TR3 (control VCA), IC60 (VCA, 709)
Bass circuit board: IC4 and 43 (of 709)

No change, I'm desesperate.....
October 6th 2014 10:04 EDT
Marin
Hey, nice to see someone else playing with this also! Ok, i have same on my desk now, there are two problems.....first that there is no E and F key not working on whole keybord, so when either E or F are pressed no sound in either mode.....and second problem is bass section don't works, either ... Read More
January 17th 2015 15:05 EST
Marin
Case closed (almost)......the reason bass wasn't working was some bad electroliyc caps in bass board, and bad SAJ410 (110) od divider board.....now, to find parts :D
January 17th 2015 17:16 EST
Keith
Hi Marin,

Thanks for posting this information. It's sometimes difficult for me to troubleshoot issues for people if I don't have their malfunctioning synth in my studio.

-Keith
January 17th 2015 19:12 EST
Marin
Hi Keith! That is so true, most of the time people called me and try to explain problem before they gave me equipment to service...... Anyway, do you know any source for SAJ410 divider? I know some SAJ210 but they run up to 11V, and this is older solina with 12V supply on this ic's....also i ... Read More
January 18th 2015 05:25 EST
Keith
The SAJ410 dividers are hard to find. You may see them on eBay from time to time, usually parted out from an old synth or organ. Have you tried contacting Vintage Chip? They specialize in old divider and TOG chips for organs and string synthesizers. I don't have the URL handy, but if you search ... Read More
January 18th 2015 11:18 EST
Shawn
hi guys!

any chance one of you would know which specific Mullard Capacitors I would need to replace these 7 damaged ones?

see pic here

http://tinyurl.com/kp8faea
January 19th 2015 22:54 EST
Marin
It's not a problem to find them, the values i mean. You have written in service manual which you have for download.....if you can't handle to find them let me know, i can check on this unit i have on service now, currently is moved away in storage room while waiting for SAJ dividers, untill ... Read More
January 20th 2015 07:38 EST
Shawn
hi Marin

would like to ask you about a few parts for the solina

I'm having troubles finding a few
March 16th 2015 03:35 EDT
1 2 3 > [last]
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