1977 Ibanez 2700 EQ issue

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Author Message Psychoacoustic Username: Psychoacoustic Registered: 06-2006 Posted on Tuesday, July 11, 2006 - 8:23 pm:    I recently bought and took delivery of a beautiful 1977 2700 and man is she sweet! However, there is a slight hum when plugged in and a MASSIVE hum when the active eq is engaged. Does anyone have any advice for me on how to fix this? I would think it might just be a grounding problem because when I touch the output jack the hum almost completely goes away. Any help would be greatly appreciated - I want to play this guitar with my band but the hum is making it near impossible. Thanks! Jimih Username: Jimih Registered: 04-2006 Posted on Wednesday, July 12, 2006 - 3:48 am:    Hey I just want to congratulate you with it ! Got one myself. Take care of it , it will be worth a lot of dough in the future, besides just being unic as it is. And the electrics..yes it sounds like wire that needs to be reset. Just open it and look. It should be a no-brainer Psychoacoustic Username: Psychoacoustic Registered: 06-2006 Posted on Wednesday, July 12, 2006 - 2:03 pm:    Thanks Jimih! I actually got it from Scott Praegitzer. I would say its a 9/10 condition and just plays beautifully. This is my first foray into the vintage Ibanez world, but I can feel more purchases coming soon! heh heh Thanks for the advice - I'll look for the wire inside the cavity. Jimih Username: Jimih Registered: 04-2006 Posted on Thursday, July 13, 2006 - 3:28 am:    Hehe Im so poor right now. Just bought a Fender Strat Japan in Gold Finish(the neckserial says its from 95 but cant seem to find the model ANY where. So if anyone knows anything about it. Plz reply. I think it might a replaced neck ? ), with a Seymor Duncan pu in the neck position. Damn its awesome ! But now it stops with the buying for a long time , unless I come to some money. I got a Guild jazzguitar, an Ibanez Custom, a handbuilt Acoustic ( a Hopf); a seagull s6 acoustic and my new Fender. That should cover the sound range :-) Please Lord send more money ;-) And yes Scott seems like a nice guy so well done ! Jimmi Jimih Username: Jimih Registered: 04-2006 Posted on Thursday, July 13, 2006 - 3:32 am:    Also got an ESp Surveyor bass from the eighties, very rare too ;-) Psychoacoustic Username: Psychoacoustic Registered: 06-2006 Posted on Thursday, July 13, 2006 - 11:17 am:    Still have not been able to solve this problem. I opened the cavity and pulled the battery, but now after I put the battery back in there is no sound but when I turn the volume pot I get MASSIVE squealing. This is very odd... Any help here would be appreciated. I seriously doubt the average guitar tech will know about these active electronics. Ibanezfreak1960 Username: Ibanezfreak1960 Registered: 03-2004 Posted on Thursday, July 13, 2006 - 12:54 pm:    Psycho, what are you running it through and have you tried a different amp, cable, outlet ect.? Phatphred Username: Phatphred Registered: 03-2006 Posted on Thursday, July 13, 2006 - 2:27 pm:    If the solder joints to the pots, and jack and switches (tritone and toggle) are sound, it is likely that there is a problem either with how the printed circuit board connects to the wiring harness, or in the components on the printed circuit board itself. However, before looking at the components (the integrated circuit, capacitors, coils, diode etc) check the PCB itself for any dry solder joints or break in the tracks. As I have said elsewhere, a local radio repair shop should be able to fix a fault with the PCB. Mine even had the integrated circuit in stock! Remember, this is not rocket science, PCBs have got an awful lot more complicated since the late 70s. A circuit diagram will help you and/or the repairman. I haven't come across a schematic for the Artist Custom 2700, but I suspect that the circuit for the Musician MC400/500 of the period will be identical. This should help: http://www.noahjames.com/vintagepage/mc500wir.jpg I also have these images, also courtesy of the great Jim Donahue: Hope you don't go blind looking at these diagrams or get your fingers burnt on that soldering Phatphred Username: Phatphred Registered: 03-2006 Posted on Thursday, July 13, 2006 - 2:37 pm:    Sorry about the doubling. I have other diagrams which would not upload which I can e-mail if you mail me. Jim_donahue Username: Jim_donahue Registered: 04-2004 Posted on Thursday, July 27, 2006 - 9:35 pm:    These EQ's had a Hiss on the treble boost, but what you have seems to be different. The op amp in there is a 4558, sometimes these blow and will cause the problem you are talking about, if you can't find a 4558 you can replace it with a TL062. On many of the later models they used Diodes on the jack, usually if the EQ does not work this is 90% the problem. Can you define the problem a little more? Jim Psychoacoustic Username: Psychoacoustic Registered: 06-2006 Posted on Wednesday, August 02, 2006 - 10:18 pm:    Thanks Jim for the info. I actually fixed most of the problem using the schematic Phatphred provided. She is running pretty sweet now with only a bit of hiss when I really crank the gain on the active EQ. Yes, the treble does increase the gain a bit but i usually have that completely rolled off anyway so its no biggie. I can say that these guitars are REALLY nice. I have been playing it without the EQ engaged most of the time and just love the tone from the pickups - very P-90ish with a lot of single coil type sparkle.

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