Mystery circuit

[Nickeroo]

My first post here, greetings to all.

I bought an electric guitar from Ebay. It has had an aftermarket circuit board installed. I am thinking it might be an onboard preamp, but I am guessing in the dark, as I haven't got much electronics knowledge beyond simple soldering of pickups/switches.

Here are some pictures:











I identified the two chips as:

MC1458CP1

and

NE571N


I attached a 9V battery to the battery clip and the diode lit up, then faded out. I think on off is controleld by a DPDT switch on the guitar. I think the cirucit may be an onboard preamp connected to the single"active pickup" which is itself powered by a 9V battery.

Perhaps someone can suggest what the circuit does? I can take more pictures if needed.

I would be very grateful.

Thank you.

[Frank Berry]

Looks to me like it might be a low powered transmitter .... wireless guitar.

[Nickeroo]

Hmm! To be honest, when I saw the Ebay auction, that WAS my first thought, as it is quite a big circuit. Is there a way I could test that out to see if it is a wireless?

[jerluwoo]

Looks to be tuned rf circuit to me. Will most likely need something that operates at the same frequency stamped on the crystal (silver can on the far right in pic 2) to test it.

[Frank Berry]

Originally posted by jerluwoo
Looks to be tuned rf circuit to me. Will most likely need something that operates at the same frequency stamped on the crystal (silver can on the far right in pic 2) to test it.

... or a multiple of the frequency stamped on the crystal.
I'll bet it operates in the 174MHz VHF band.

[lineup]

NE570,NE571,SA570
is one Compandor.

Can both compress and expand dynamic range.
Just as guessed, this chip is often used radio communication circuits.
Probably: Compress -> Transmit -> Expand in receiver

http://www.nxp.com/acrobat/datasheets/SA571.pdf

The SA571 is a versatile low cost dual gain control circuit in which either channel may be used as a dynamic range compressor or expandor. Each channel has a full-wave rectifier to detect the average value of the signal, a linerarized temperature-compensated variable gain cell, and an operational amplifier.
The SA571 is well suited for use in cellular radio and radio communications system, modems, telephone, and satellite broadcast/receive audio systems.

[Peng]

NADY had a 101GT wireless system. These could be the insides of the transmitter. If so , it should be easy to get the info from NADY i suppose...


grtz,
Peter

[Nickeroo]

Wow, my first guess may have been right then!

The only reason I thought it may have been the wireless is that the dude from Night Ranger has an internal Nady, and they looked kind of similar in their size.

The number on the silver thing says:




T191.300 (I think)


So I'd need a box that recieves the righ signal to test?


Re: the LE diode not functioning, would that be a problem do you guys think? It went on when I put the battery in and then faded instantly.

[Nickeroo]

Actually I think the LED is ok. on the Nady 201, the LED goes on briefly to indicate the conenction was made. The LED on all the time means battery is drained.


Many thanks to all you guys and most especially Pen/Peter for offering a probable name for the circuit!

[lineup]

If you have not Nady 101 Wireless Receiver
you may search eBay for it.

I would not use wireless.
I would remove that circuit.
And use a good Guitar Preamplifier (with your favourite effects) + shieded guitar cable with plugs.

One small Battery Amplifier ( 9VDC or 2x9VDC alkaline ) in your guitar to drive the cable.
And one PreAmp with 'fuzzing effects' at Power Amplifier input.

We have a special forum for Guitar Preamps and other Musical Instruments.
diyAudio Forums > Top >Other Stuff > Musical Instruments
Of course, for 'fuzz box' circuits you may also Browse our Tube Forum.
I both these forums are topics with links to good guitar circuit ideas.
Such circuits that are not too difficult for DIY Do-It-Yourself.

Here is one link collection for Guitar Circuits:
ePanorama.net - Guitar effect boxes
from the good site
ePanorama.net - Audio Circuits Page

Regards
Lineup Audio Circuits