Faultfinding vintage fl9

[Nortube]

Hi. Great forum.
My first post. Sorry if this is the wrong category.

I recently aquired an old ibanez fl-9 flanger. But it's a bit dodgy. It only seems to work at high speed level settings. I've narrowed the fault down to the LFO.
http://www.mojotronics.com/images/FL9.pdf

I can see the oscillating sawtooth signal on cp8 only when The speed pot is put on full speed (the width pot also needs to be set a bit high)
I've desoldered the orange 47uF capasitors and measured them to about 50ish uF.
All DC voltage looks good.
Cp 1-7 looks good on the scope. I use a signal generator with a 5kHz sine wave to the input.
There is some discolouring on the solders under the caps.

Could the caps be bad even if the reading is good?
Could anyone give me some good advice?

Cheers Roger

[GibsonGM]

Hi Roger, welcome!   The 'debugging' thread is here, the info you'd provide by answering it in your post here would help us help you.  http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

At any rate, sounds like you do understand how these things work?  Have you checked the pot, have you cleaned it with contact cleaner??

Yes, the caps could be leaky, esp. the electrolytics.    Why it only works at high speed, I can only guess, other than a mechanical fault with the pot, bad solder joints, or those electro's...

[PRR]

> measured them to about 50ish uF.

Just replace them.

OK fast stall slow suggests leakage. 1970s e-caps were not as good as today's, and they don't improve with age. Also these sit with no constant forming-voltage. And the LFO current is small at low rate.

[Nortube]

Thank you.

I've checked all the pots. They're fine. I've also cleaned and freshend up the solder joints.
I'll just change all electrolytic for new ones and see how it turn out.

I'll let u know how it turns out.

[Nortube]

Sucsess!
Swapped all electrolytic caps for new ones. It's working perfectly now and sounds awesome.
Thank you

[bloxstompboxes]

Had a similar issue with an FX60 I bought on fleabay. Seller said it worked but that the rate pot didn't. Well, not only did the rate pot not work, but the signal was so low I could barely hear anything with volume on 3 on a 65watt amp... much less any effect. Replaced all the electros and she fired up beautifully and sounds great. Now I am waiting on a new switch since it doesn't turn off well either.