Semi-acoustic guitar pick-up

[Skywave]

First, I appreciate that this thread may be in the wrong place at this forum. If so, moderators please re-locate it. Thank you.

Secondly, what I have here is a pick-up processing* pair of PCBs from a Gibson semi-acoustic guitar. It was passed to me by a friend of a friend; apparently, it doesn't work. I was asked "Can you mend it, please?"
[ * This is probably an inappropriate name, but it'll do for now until I'm appropriately educated! ]

With this item, I am a total ignoramus & there is no point in trying to imply otherwise. So, the overall objective of this thread is to try to gain as much relevant info as possible. Yes, I did do a search on the www, but found nothing that met my need: hence, this thread.

One burning issue is this: which way does the ribbon cable from one pcb connect to the other? A glance at the attached photos 1 & 2 explains that Q. I suspect that photo 2 is the correct arrangement, but confirmation - or otherwise - would be much appreciated. When this item was passed to me, the two PCBs were indeed joined. A few hours later, after my friend had departed, I picked it up and "Whoops!" The aforesaid ribbon cable came adrift .

All the above will do for a 'starter'; any useful info provided will be much appreciated.

Al. / Oct. 26th.

[Refugee]

You should be able to follow the earth track to give you the orientation.

[peter_sol]

I expect you are aware that it is a preamp and EQ unit.

[Skywave]

Err, no: I wasn't so aware - as I said, I know nothing about this item and have zero experience of such things. But your comment has helped: Thank you.

Al.

[Skywave]

Originally Posted by Refugee

You should be able to follow the earth track to give you the orientation.

Thanks - sometimes the most obvious things get overlooked. But as I said, I know absolutely nothing about these sorts of things and although it is small and doesn't appear overly complicated, my total & absolute ignorance when faced with such things tends to make me feel a bit intimidated, so clear reasoning then goes out of the window! It also doesn't help that this is for a friend - and I do owe him a favour. However, I'm sure that patience and perseverance will win the day - it usually does.

Al.

[joebog1]

Can you give me the model of the guitar please ?.
I do have some circuitry available.

Joe

[Diabolical Artificer]

As mentioned it's a very simple 5 band EQ and preamp to boost/tweak OP from a pizzo pick up. As Ref says follow the ground and power for the little LED/sw. Connecting it the wrong way won't do any damage, but to be sure power it up first time with a current limited bench supply.

Andy.

[stevehertz]

I have been performing guitar setups and repairs for 50 years. First off, I would be sceptical of that PCB being given to me in isolation and deemed faulty. I'd want to see and test the complete guitar to check each and every component in the chain ie from pickup to output jack being fully functional. I'm talking from experience here, sadly you just cannot trust other people's diagnosis. I'm a qualified electronics engineer as well as my luthier skills and tbh I would baulk at being handed a relatively complex piece of electronics with disconnected ribbon cables, no information and someone else's faulty diagnosis plonked on it. I'd say I cannot fix it and hand it back. On the other hand you seem a very helpful guy and I wish you the best of luck 'fixing' it. I wish I could help rather than offer my experience based negative comments.

[JonSnell]

In my experience, there are three main reasons for these pre amps to fail;
1/ Not been used for a few years and the electrolytic capacitors degrade/dry out.
2/ Scratchy pots, a good clean with contact cleaner and lubricamt can usually fix that.
3/ The piezo cell is faulty or has a break in it. Not repairable. Replace the strip.

This assumes the obvious; battery and connections etc.

The board has a pair of dual op amps, 4558 style. One is responsible for the tone controls and the other is a basic pre amp.

Information is usually available on the gargler. If you google the guitar model number or pre amp model number there should be information out there.
Have fun.

[llama]

If the ribbon cable "let go" that easily I'd suspect that most of its wires were already fractured due to metal fatigue. Without connecting it back up, I'd put a battery and series resistor on likely-looking points where the edge connector goes and get that LED to light up. Then you'll know the polarity and likely connections. My replacement would be a section of flat, flexible ribbon cable - just trim back the intervening wires you don't need.

You are lucky that all the components are conventional, not SM.
Graham

[Uncle Bulgaria]

I agree with stevehertz - in my experience with guitars it's the bits in contact with the user that fail. Loose connections in jacks or fractured wires (lots of the switches and jacks get loose through use and rotate, stressing the wires inside).

My Uher experience tells me that the ribbon cable could be problematic if it's solid core. I spent ages tracking a fault that turned out to be an intermittent connection inside a ribbon cable. As llama says, check them out!

I sympathise with not knowing where to start as I would have no theoretical idea of how the circuit worked, but I'm sure you can understand the circuit now people have said what it is.

I bet it will turn out to be a basic continuity fault rather than something esoteric at the component level!

[Skywave]

Thank you, everyone! All helpful, constructive comments read, understood & noted: based on all of that, the investigation will continue. This is an initial 'just for now' type post: further posts will follow ASAP, hopefully embracing a positive outcome.

Al. / Oct. 27th.

[Skywave]

Originally Posted by joebog1

Can you give me the model of the guitar please ?.
I do have some circuitry available.

Joe

Thanks Joe, but I do not have the guitar & do not know the model. I only have the parts as described.

Al. / Oct. 29th.

[Skywave]

Following the advice in post #2, q.v., which I carried out, I have decided that for now I have gone as far as I am prepared to go. I will now arrange for it to be returned to its owner and await the result.

Al. / Oct. 29th.