I've had this one while. The electrics don't work, and I'd love to get it workibg .... but... I don't know what it is supposed to do!
I messaged Hugh Manson about it a few years ago, he said he would look at it but life got in the way, and now he has retired.
I know a decent electronics chap who fixes up old hi-fi and the like so my plan is to get it over to him to see if he can reverse engineer the circuits. But you lot know everything - so long as I don't want to buy a car I reckon it's worth a shout out to the hive mind.
So here goes, I'll let the pictures do the talking:
1. Front. 3x brass knobs, jack socket, Line of 3 micro switches (3 way / 2 way / 3 way), 2 other micro switches (2 way / 3 way). blanked off micro switch hole (no idea if ever had anything in it). 2x KA Rainbow humbuckers.
2. circuit in situ. It is powered by 2x 9v batteries
3. Flip side.
There appear to be 2x chips in there and what could be 5x trim pots (?), the fifth one is to the side of the microswitch on the right. These are accesible from the top side with a small screwdriver slot on each pot.
Pots are corroded, middle one more than the other two. They spin ok.
On the left of picture, next to the 2x micro switches see 3x holes and a green cap? That corresponds to the filled in hole on the front. Could have been original switch but the board didn't look like it had ever been removed but I will never know.
No sound with fresh batteries but I can get a faint clean signal if I wiggle the jack in the socket.
Hugh said he remembers doing something that resembles this but he only saw pictures of the top of the board. Could be EQ, power stage or one of his first attempts at building effects in (so probably some sort of fuzz circuit). My other Manson has switches but no circuit. That has phase and coil splits so imagine these feature as well.
Where to start? If it's gash then I'll rip it out and put something else in there (suggestions?). If nothing else something for us to chew fat about.
Ok - over to you lot, what's the prognosis doc?
Comments
Pot switch cleaner? Do that for everthing then you'll need a multimeter: start by checking voltage from the battery is going in ok, continuity on the pots, continuity on the input from pickups and output signals from preamp but after that it's a case of inserting audio and tracing where it fails within the circuit. Google circuit tester.
If none of this sounds familiar take it to a repair person. Someone who fixes pedals or amps can handle it.
The larger chip looks like a quad opamp and the smaller one is likely a dual opamp. These provide the gain and the resistors and caps form filters which is how the EQ is manipulated.
Any electronics guy can repair this as it's very basic stuff but if you want to have a go yourself start by reseating that opamp in it's holder. Clean all pots and switches. Look at the solder joints and redo any bad ones. Then make sure you have volts on the opamps. I would expect the 2 batteries form a dual supply so 18V between the opamps + and - pins but 9V with respect to ground.
That switch that is missing/blanked has been bypassed/hardwired underneath.
The socket looks pretty corroded. I'd start by spraying switch cleaner into it and working a jack in and out to clean up the contacts. Then apply switch cleaner to all the switches (and work them back n forth). As has been said, remove and reseat the Op Amps (the legs can get corroded - and the action of removing them and refitting can scrape that off). Then try again...
The function of the micro lever switches might be discernible if the connections between their contacts were known.
https://www.andybaxterbass.com/products/1982-manson-merlin-bass-mahogany