Solving the remaining problems

As said before I had to clean the lower keyboard again because I was not thorough enough the first time. I used the same method as for the upper keyboard http://eminentunique310restauration.blogspot.com/2008/10/cleaning-upper-manual-key-contacts.html.
This time the result was perfect.



Also in the upper keyboard print there where two defect germanium diodes. I replaced them the same way as for the lower keyboard. http://eminentunique310restauration.blogspot.com/2008/09/repairing-non-sounding-note.html

Troubleshooting string ensemble - part II

Problems to be solved on the string ensemble :

• Sustain of the lower manual does not function together with the 4' or 8' lower manual string ensemble
• Sustain of the lower manual does not function when 'Lower Manual Sustain' is switched off
• When the sustain on the upper manual is switched 'on', the sustain of the lower manual does not function any more.

On the string ensemble print I found a faulty germanium diode. Lucky I still had some spares from the last repair. When I placed a bridge over the diode the sustain functioned normal again. The diode refused to let the current pass.

I desoldered the diode and replaced it by an OA90 germanium diode that I had lying around. Problem is fixed.

Troubleshooting string ensemble

The problem to be solved :

• The 8' button of the upper manual string ensemble is supposed to switch on the 8' strings. The strings however are only heard in the background, and do not sound loud enough
• With the 4' button of the upper manual string ensemble the same problem occured

Again searching the problem I found a non functioning capacitor.

The capacitor of 2,2 µF shorted the sound of the upper string ensemble to the ground. Replacing the capacitor solved the problem.

Troubleshooting

I noticed the following problems :

- The solo and principal group sound less loud then the tibia's
- Percussion switch and slider do not seem to have any effect
- The vibrato slider does not seem to have any effect
- The light of the on/off switch does not work
- The light in the volume pedal does not work

At first I suspected all these problems had a different cause. But studying the schematics learned me all these problems had something in common.

They are fed by the -20V supply off the power supply. Doing some measurements on the power supply I found out the -20V supply was completely dead.



Then I found a fried resistor (picture red arrow). Seems I have shorted the -20V circuit while working on the organ. I remembered the first day I was working on the organ the power light was still working, at some point it stopped working. I thought it was just the bulb that had gone dead.
Exchanging the resistor with a new one fixed the problem.

Cleaning upper manual key contacts

During my experience cleaning the contacts of the lower manual, I learned cleaning the contacts has to be done very thorough, to have a good result.

Therefore I decided to remove all of the plastic spring guides, so I could reach the bus bars and the springs very well for cleaning. In the first picture you can see the key contact print with the plastic spring guides removed.

For cleaning I scratched the bus bars and the springs with a small flat screw driver. It takes a lot of hours scratching every spring a few times and the bus bars on every spot where the springs are supposed to make contact.

Now the hardest part; getting the plastic spring guides back in. It is very time consuming to say the least if you have to do it without an aid. I gave it some thought and put threads in the springs to make them longer. Then it is easier to guide the springs into the holes. After you have put the plastic spring guides in, you take the threads back out.

Here you can see how is necessary to make the springs longer, to guide them in the holes.

Repairing the balance slider

The malfunctioning pot, is the second one from the left on the picture.
Looking trough the openings of the pot I already could see there was something wrong. Only one half of the slider had a moving copper contact. At the other side the copper contact had come loose, and was forced and deformed, pushed to the end of the space in the slider.

The pots are mounted with melted plastic to the board.

With a screwdriver I broke the plastic away so I could take out the pot, and I unsoldered the connections.

The pot is closed with small copper rivets. I decided to drill out these rivets in order to open up the pot.

Opening the pot showed me that the pins on the white plastic slider had broke off. These pins should hold the copper contacts. One of the copper moving contacts was deformed but this could be repaired by use of pliers.

No, this blog is not sponsored by Pattex. This is the glue I used to glue pins into the white plastic slider.

I drilled holes on the spot where the pins used to be. In the holes I could stick new pins and glue them in. For the pins I used two stiff wires. Ordinary wire you use in electronic projects.

The new pins now can hold the copper contacts again.

A view of the opened slider. The inside was sticky, so I cleaned the internals with isopropylalcohol. I only cleaned the upper resistance counterfoil, not the graphite counterfoil below. I did not want to take the risk the graphite would solve into the isopropylalcolhol.

Remounting the slider was not easy, and had to be done very carefull. I closed it up with thin copper wire, just in case I ever have to open it up again.

Then I glued the slider back in with Tec 7.

Now the balance slider is working again perfectly without any crackling.

Defect Balance Slider

The next problem I encountered was a defect balance slider.
The symptoms :

• A lot of crackling while moving the slider
• The lower voicing is not working at all, or working intermittent

The slider is a pot 2x50k of the make 'Preh'.

On the website http://www.eminent310.nl/ I found out this is a common problem. Again I contacted Huib De Bruijn of http://www.esbdebruijn.nl/ to ask if he had this type of pot in stock. No luck there.

So there is only one solution, try and repair the pot.