Vintage synth drifts out of tune

DBeck · Post by **DBeck** » Thu Aug 02, 2007 5:04 am

Hi!

I recently acquired a Farfisa VIP-400. However, it seems to no longer be able to process C (the note) for very long. After some time of being on, C will gradually shift up to Eb about. Before I go scouring the internet I figured I'd ask here if you guys had any information about how to fix this. I understand the oscillators can be tuned but wasn't sure if this is easy. And how much does a repair like that cost?

I understand analogs will drift but wasn't sure if they tend to do that with only one note. (Also F is affected a little too since they are harmonically related)

It sounds awesome and I'd love to be able to play in more keys

Thanks and I'm glad I discovered this site!

Post by **wiss** » Thu Aug 02, 2007 5:20 am

go to Farfisa.org it should have the tunning chart....most fairifas already have it marked once you open it up

1. this could be a sign that your oscillator is going bad

2. I had an oscillator rebuilt and I need to tune it about every two weeks while the others are fine,

Automatic Gainsay · Post by **Automatic Gainsay** » Thu Aug 02, 2007 6:35 am

Analog oscillators do drift, but usually in voltage controlled synths more than divide down synths or transistor organs. If you have an oscillator (as it seems you're saying) that noticeably drifts... or audibly drifts in realtime... in a transistor organ, then it is indicative of a failing oscillator, I would think. The oscillators used in divide-down arrangements are actually very stable and do not drift like voltage controlled oscillators do in analog synths. They may drift, but it is over time, and it is really only likely to go out of tune, not to change to an entirely different note.

Post by **Maschinengeist** » Thu Aug 02, 2007 2:21 pm

The ideas presented above are likely. So it bad trimmers.

I don't personally have the VIP-400 service manual but I can get it. I'm not very often requested to work on Farfisa instruments.

For a tuning chart: http://karensavoca.com/gifs/freqchart.gif

DBeck · Post by **DBeck** » Thu Aug 02, 2007 2:27 pm

Wow thanks for all the quick replies! I'll crack it open today and see what's inside. What's weird is that it affects all C notes across all octaves. Maybe that is an indication of what type of organ it is. Thanks again

Post by **Maschinengeist** » Thu Aug 02, 2007 2:38 pm

DBeck wrote:Wow thanks for all the quick replies! I'll crack it open today and see what's inside. What's weird is that it affects all C notes across all octaves. Maybe that is an indication of what type of organ it is. Thanks again

Only Cs? Could be the trimmers... but it could be something else. I can theorize but I'd like to see the service manual first.

Let us know how it turns out.

DBeck · Post by **DBeck** » Mon Aug 06, 2007 5:56 pm

Well I got the service manual for it. But before I get into can anyone give me some pointers. The service manual is just a bunch of schematics and I'm new to all this so I don't really know what I'm doing. I was hoping the manual would say "how to correct drifting"

but nothing's ever that easy.

Automatic Gainsay · Post by **Automatic Gainsay** » Mon Aug 06, 2007 7:16 pm

DBeck wrote:Wow thanks for all the quick replies! I'll crack it open today and see what's inside. What's weird is that it affects all C notes across all octaves. Maybe that is an indication of what type of organ it is. Thanks again

Combo organs use a divide-down scheme. That means you have 12 oscillators (usually the top octave of the organ, but may be even higher in frequency), which are the 12 notes of the scale. Each subsequent lower octave is achieved by taking the frequencies of the 12 oscillators and dividing them in half to achieve a lower octave. Basically, you have 12 oscillators, and a set of 12 dividers for every subsequent lower octave. In essence, all of the C pitches are obtained from a single oscillator... so when one oscillator goes bad, each note of that note name will cease to function.

DBeck · Post by **DBeck** » Tue Aug 14, 2007 4:03 am

Well . . .

I opened her up and was able to tweak the trimmers (I guess that's what they are) and manually adjust the pitch for each note. All 12 of them were pretty in-tune. But like usual C will gradually go sharp the longer the organ is left on. I was hoping I could keep adjusting the trimmer to adjust for this but it seems that it will keep going sharp indefinitely. Any suggestions?

Post by **Maschinengeist** » Tue Aug 14, 2007 4:09 am

There is the original service manual on eBay. I'm willing to split the bill with you for a readable copy.

http://cgi.ebay.com/FARFISA-VIP400-Orga ... dZViewItem

DBeck · Post by **DBeck** » Tue Aug 14, 2007 4:22 am

Well I already got the service manual in pdf from this guy
http://www.markglinsky.com/ManualManor.html.

I guess I can just email you a copy. He did charge me for it but I'm not trying to proliferate it across the internet or anything.

your response time is uncanny.

Post by **Maschinengeist** » Tue Aug 14, 2007 4:28 am

Thank you: I try to be everywhere at one. I'm still at the shop repairing synths for customers.

I know Mr. Glinsky: a really helpful guy. His Manual Manor is godsent.

I gladely accept your offer. The email is tech[NoSpam]@muzikelektronix.com.

In return, I'll help you track down the problem and fix it gratos. Is that cool?

DBeck · Post by **DBeck** » Tue Aug 14, 2007 4:56 am

Awesome!

Post by **Maschinengeist** » Tue Aug 14, 2007 5:34 pm

I've sent you emails about the tuning problem. I noticed you use Yahoo: sometimes they consider us as spam. Just to let you know.

DBeck · Post by **DBeck** » Fri Sep 14, 2007 5:23 pm

Well the strangest thing . . .

I haven't had any time to address the problem so it's been sitting in the corner for a month. I hooked it back up and now it doesn't seem to be drifting anymore. I feel like there's a knob that I turned down that solved the problem. I just have no idea what. When I get off work tonight I'll give it a longer play session and see if it drifts.