1980s Ibanez FL-9 flanger repair

[clarisso11]

Hi everyone,

I've been working on repairing an original Ibanez FL-9 Flanger, and I'm quite stuck, to say the least. Here are the symptoms:

• Only dry signal coming through, no effect at all
• LED not lighting up (Had some intermittent LED signal, but couldn’t reproduce by moving wires)
• No audible difference when clicking footswitch
• Circuit board darkened from overheating and original solder discoloured from electrolyte leakage around IC103, Q102, C130, C131
• CP8 and CP13 fail, no wave (I think, don't have a great oscilloscope)
• CP14 fail, 6.6V when effect engaged (0.8V when off)

I have done some fairly extensive testing, without any luck:

• Tested all ICs by placing them in a working circuit (IC101-106)
• Temporarily replaced IC103 with TL072CP, no change
• Checked 5.1V Zener by measuring voltage drop (D105)
• Checked all electrolytic capacitors with ESR meter
• Checked Q103, replaced briefly with 2SC1815, no change
• Checked Q104 and Q105 against NOS 2SC2458, replaced Q102
• Checked D103 forward voltage
• Tested continuity between all wires and circuit board
• Visually inspected circuit board for bad/cracked solder
• Traced audio path with audio probe, no effect at pcb output point (3)
• Removed and jumpered Q103 to temporarily remove JFET switching circuit, no change
• Replaced C130, C131, C132
• Tested circuit using 9V battery or adapter

I do think that the low voltage at CP14 is an issue, but checking the recommended parts didn't help. I have a feeling I'm missing something obvious, but just can't figure it out.

Any help will be appreciated!

Attached is the service manual with my notes.
Ibanez 9-Series Service Manuals.pdf

[g1]

Is it the stock momentary switch in there? What are Q104 and Q105 collector DC voltages? Do they change after pressing switch?

[clarisso11]

Is it the stock momentary switch in there? What are Q104 and Q105 collector DC voltages? Do they change after pressing switch?

Thanks for helping out!
The momentary switch is stock. Q104 changes between 8.17V and 0.76V when pressing the switch, and Q105 changes between 0.66V and 7.4V.

[clarisso11]

I have just found the problem!

I was still confused by the fact that the LED had been on intermittently at some point, but I couldn't reproduce this by moving the wires. I finally figured I should check the potentiometers for a loose connection, and knocking on the controls and moving them around restored the LED, plus the effect! Looks like there was some dirt between one of the wipers and the track, cutting the effects signal pathway.

Lesson learned, should have checked the potentiometer lugs with the audio probe before spending hours removing and testing parts!

[pdf64]

Haha, it’s the lessons hardest learnt that are best remembered
Thanks for follow up.

[clarisso11]

Haha, it’s the lessons hardest learnt that are best remembered

Well said!