Fault with Iain’s Yamaha FGXS730SC electro-acoustic guitar

The FGX730SC is the acoustic-electric version of the FG730S. Features inherited from the L Series, such as non scalloped X bracing and a reverse L block neck attachment, make it an instrument of high quality. Equipped with an A.R.T. 1-way pickup system (System 56), it delivers a clear, bright tone, typical of FG guitars, and performs just as well whether playing accompaniment or lead. Onboard electronics that include a 3-band equalizer with an adjustable mid-range frequency and a tuner make it a perfect instrument for performing live.

https://uk.yamaha.com/files/download/other_assets/9/742589/Electric_SYSTEM64_Manual_EN.pdf

Got this to look at but had no idea what the fault was, or if there even was one.
Straight off, the thinnest string is missing and so was it’s Bridge-Pin. Also, more importantly was that the 9V battery box had a very acid corroded terminal, so bought a new box from Andertons.co.uk…
https://www.andertons.co.uk/guitar-dept/electric-guitar-accessories/electric-guitar-parts/yamaha-9v-battery-holder-for-apx-fgx-cpx-series-guitars

On swapping out the box, I was then able to test if the guitar O/P to the amplifier worked or not – it didn’t!!

Further investigation showed that the guitar has a preamp module and 2 under-side ‘contact’ pickups.

On hooking a scope up to the pickups I was able to get a rising signal from each string approaching 100mV, so my assumption is that the pick-ups are ok.

After connection the guitar amp’s 1/4″ jack (this when inserted turns on the amp) to the guitar O/P, the scope signal was quite flat with no change from any strings. This was tried with a brand new tested 9V battery, so my assumption ?? is that the pre-amp is faulty.
The pre-amp is labelled model: AB1CBL, but a google search shows it is as similar to a ‘Yamaha WG320100’.

A new one from Australia (all I could find) is approx. $170…
https://reverb.com/item/25777387-yamaha-wg320100-system-55t-preamp-assembly-for-fgx730sca-and-fgx720sca

Ebay though have very similar & cheap ones , although the physical size may be different, as is the I/P’s & O/P’s, but may be worth the risk…
search : ‘4-Bands Acoustic Folk Guitar Preamp EQ Equalizer Piezo Pickup with Tuner‘…
https://www.ebay.co.uk/itm/4-Bands-Acoustic-Folk-Guitar-Preamp-EQ-Equalizer-Piezo-Pickup-with-Tuner/274433275351?hash=item3fe57f75d7:g:8zYAAOSwISFfDuXI
These have a plug-in battery box and a saddle fitted piezo transducer with a smallish mono jack.

UPDATE – have ordered the preamp from Ebay @ £14.14.

AND, if the preamp repair does work, it will still need new strings, new Bridge pins and maybe a new ivory saddle to sit in the bridge as a bit had broken off – although a bit super glue may do. I will tape the broken bit to the guitar.

If I end up having to get it repaired professionally, try ‘Harris’ at DM Studios in Dundee (he is often in late 5-10pm).
https://www.facebook.com/DundeeMusicStudios/

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