tune issue with farfisa compact

[interference]

Hello guys,

New member of the forum. I recently picked up a farfisa compact, sound is OK but I noticed after a couple of minutes (something like 20 - 30) some notes are not tuned anymore.
The E becomes a F# as well as the B. Do you think I should wait before rtying to tune it? Do you think this is something related to the capacitors? Do you think the tone generators are impacted or do I need to check the capacitors in the alim block? other ideas?

Thanks all!

[Drawbar Dave]

Based on personal experience restoring two Compact Duos, I believe the tuning drift relates to some transistors on the oscillator boards. I located my bad ones with freeze spray. Ultimately I replaced every electrolytic cap on the oscillator boards and all the other boards too. This gave stable tuning, full tone and volume. Best of luck with your project!

[interference]

Thanks for your reply Dave, any suggestion on the capacitors and transistors to use If I decide to replace the old ones? You recommend to find them on ebay?

[Drawbar Dave]

I usually use CPC Farnell as a supplier of components or there is Digikey, RS etc. I go for a decent brand of capacitors such as Panasonic. Many of the capacitors in the Compact will be the same value such a 1uf or 10uf especially on the tone cards. Some cap values are rare now but you can use a slightly higher value. Make sure the voltage rating of the new cap is the same or higher. Those are the only two things to consider apart from whether the capacitor needs to be radial or axial. And of course these electrolytic caps are polarity sensitive. This is repetitive work but not difficult so please don’t be put off. It will be worth the effort. My Duo is still perfectly in tune five years later.

For transistors I have a trustworthy source in the UK. If you are buying transistors on ejBay, check the reputation of the seller and make sure they are a proper supplier.

I would replace all the electrolytic capacitors first before worrying about transistors. Those old Falcon caps were apparently never reliable.

Best of luck!

[interference]

Ok great thanks!

[eric appla]

Drawbar Dave, so what type of transistor you used to replace the old germanium parts? Just a common general use transistor such as BC546/556 or you went for NOS germanium? If you went for germanium did you had to hand select them for beta or have you just used them as they were?

[Drawbar Dave]

Yes they were hand selected.
One on my MK1 on a generator board that went off tune after a couple of minutes and the MK2 which I kept had one rogue on the tremolo circuit and one in the mixer board.