Ibanez SST acoustic gutar preamp

[petr_ruca]

Ok problem fixed. I'd like to share in case someone can find it useful.

I troubleshooted it 'looking for' the signal with a jack cable. One side connected to my soundcard for monitoring and the other side: ground to ground and hot to a probe (like a multimeter probe), to be able to move it around and listen if there's sound or not.

I changed the IC (TLC2264) first and still had no sound. The tuner was functioning well, so this means it's getting the signal from the guitar and the problem should be later in the circuit (after U1 pin8).
Thanks to dmeek for posting the schematic, it was really helpful and definitely saved a lot of time of reverse engineering. I thought that the transistor was not working properly. This is used as switch muting or letting the sound pass based on if the tuner is on or off, so I probed both sides of Q1 and I could hear the signal. After Q1 the signal goes through a capacitor, probably to isolate the AC signal from the guitar and the DC that Q1 needs to function. I probed C7 and I couldn't find the signal after it goes through it. Then I changed C7 and found the signal. Still no sound from the Jack. I follow the same steps until I found that C21 was faulty too, changed it and now the guitar works as a charm.

So in my case U1, C7 and C21 were faulty.

[dmeek]

I haven't run into bad electrolytics on these preamps before. That's good to know.
Maybe not long before the others go bad?

[wbfnz]

Hi. Not sure if this thread is being monitored or not, but I need to locate the tuner switch. Dose anyone know where to get a replacement? everything else is working fine but the tuner will cut in / out while playing, and it seems that the switch is faulty, but no indication as to what it is. Any help greatly appreciated.

[Stratocort]

Hi

I changed the old pré-amp (5AEQ43F) by a bring new one on my guitare (AEG10EVS1202).
All is ok but it still a little ground noise.
This hum be quiet when I touch at the same time preamp and strings.
Is there a ground link between preamp and strings ?
Something is not logical. I don't understand.

Can you help me please?

Vince.

[redstrat984]

Hi
i'm new user from rome....
i've problem with sst preamp..... my preamp make a very very low volume sound.... i can hear somethings only if i use my amplificator with maximum volume or a distortion to increase gain.....
the tuner is ok, the bypass is ok, i've a correct voltage 6v3v and -3v.....
where can i investigate to found problem ? i think next step is try to change c2 C21 c22 c7 c102
any suggestion....?
thanks to all

[eidling]

Searching for a solution, I found this thread. I have recently acquired an Ibanez PF5 ECE-NT-14-01 with the Ibanez AEQ-SST Shape Shifter Preamp. After reading this thread, I guess I am fortunate, because everything is working except the tuner. It isn't dead - it lights up, cuts out the sound and the note letters light up, but they do not correspond to the notes being played. Any ideas?? Thanks.

[DLT]

Ok, so here's my experience with the AE10E bass with Fishman SST pre-amp: Changed R64 to 4K7 with little improvement. Low gain was improved by:

1) adding 470R resistors in parallel with R26 and R31 resulting in about 330R+330R (this immediately gives 2x gain (+6dB) on the balanced output and brings the output impedance to about 330 + 330R which is a better match for a standard 600R mic-type XLR input)
<Dont >try to remove \ short out these resistors as they also help with the stability of the quad op-amp chip when connected to the outside world on long cables...

2) adding a 680R resistor in parallel with R5, which provides about 4x gain (+12dB) on both balanced XLR and unbalanced jack. You can play with this further if you want you want a little more output...

Will be using the bass at a gig soon so will report on how it performs after the above mods

Thanks to all who have contributed notes and circuits, it certainly made my life easier!...

[DLT]

Oh, and on the circuit diagram kindly provided - the output goes "phase switch - resistors to ground - series resistors to XLR", not "phase switch \ series resistors \ resistors to ground", as the latter would create a pad \ attenuator and lose even more signal...!
(Those resistors to ground are 10K by the way... next to R26 and R31))
(Also, TLC2264 op-amp (pins 1,2,3) is wired as an inverting stage with 22K input and feedback resistors, resulting in a gain of -1 for the "B" leg of the balanced output...)

[dennis66]

I just repaired a SST that did have sound out, i.e. the FET switched, but the volume was not as loud as it should.

I started to add a 5K2 resistor parallel with the 47K, to ensure switching correctly. No improvement.
Then I added 470R resistors as in post #52 to increase gain, No audible improvement.
After that I shorted the FET. No change at all, which means the switching works as it should.

Next thing was to replace the C7, which are in the signal path directly after the FET.
That did the thing! Now the sound volume was a lot louder, and as it should.
I didn't replace the capacitor before the FET (C102), but maybe it could be a good idea for the future, if age degrades the capacitors.