loweringthetone Posted February 2, 2012 Share Posted February 2, 2012 (edited) A Soundgear SR800 from 1987. Wiring has not been tampered with and Im trying to diagnose a non working tone circuit. The bass control pot has stopped working, and the treble pot acts as another volume control. Anybody know anyone near Nottingham who could diagnose the problem ? ALSO on these instruments, each pot has a small PCB attached with a couple of capacitors and resistors. Anyone know why ? Is it because the pickups are low impedance ? or is it to adjust the tone ? FINALLY - Id love to teach myself, anyone know a good book on guitar circuits ? Any help would be much appreciated Edited February 2, 2012 by loweringthetone Quote Link to comment Share on other sites More sharing options...
icastle Posted February 3, 2012 Share Posted February 3, 2012 Well the problem could be a number of things but the favourite (albeit without being able to see it) is going to be the solitary IC mounted on the small board to the rear of the volume control. I'm picking that because, unless one of the interconnecting wires has failed, the chances of a passive component failing are much lower than a semiconductor failure. Unfortunately all I can find is a rather crude wiring diagram without component values so I'm not certain how easy it is to get a replacement IC. The SR800 is an active bass and all Ibanez have done is split the active circuit into three modular sections instead of the more usual single board with a pile of wires running to it. Quote Link to comment Share on other sites More sharing options...
loweringthetone Posted February 3, 2012 Author Share Posted February 3, 2012 Thanks icastle for the response. Youre right I think, the wiring seems undisturbed and the other components are very clean - the bass has hardly been out of the house since new Im told. The IC is a JRC 4558D which is thankfully still available cheaply on ebay (£1.20 each). Its the same chip as in a Tubescreamer I understand and no doubt in other Ibanez basses. I've ordered a few - should arrive in a week or so. Now if I can find a man who can solder ICs safely ..... Many thanks again for your help Quote Link to comment Share on other sites More sharing options...
icastle Posted February 3, 2012 Share Posted February 3, 2012 (edited) [quote name='loweringthetone' timestamp='1328301524' post='1525316'] Thanks icastle for the response. Youre right I think, the wiring seems undisturbed and the other components are very clean - the bass has hardly been out of the house since new Im told. The IC is a JRC 4558D which is thankfully still available cheaply on ebay (£1.20 each). Its the same chip as in a Tubescreamer I understand and no doubt in other Ibanez basses. I've ordered a few - should arrive in a week or so. Now if I can find a man who can solder ICs safely ..... Many thanks again for your help [/quote] 4558's are really common, the electronics version of Magnolia emulsion paint. If it helps, I'm in NW Leicestershire (about 10 mins from M1 J21) - if you can get the bass down to me at a mutually convenient time then I can solder a new IC in for you in a couple of minutes - with a 100% BassChat discount of course, provided you provide the IC. PM me if you want to go down that route. Edited February 3, 2012 by icastle Quote Link to comment Share on other sites More sharing options...
loweringthetone Posted February 7, 2012 Author Share Posted February 7, 2012 You are a gentleman sir. Huge thanks. Ill be in touch when they arrive .....from Hong Kong ! Quote Link to comment Share on other sites More sharing options...
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