lidl e Posted July 6 Share Posted July 6 So like a volume pot that goes 1-10 would be called a linear pot. Is that correct? What do you call a pot that has a detent in the middle and goes from 1 in the middle to 5 and -5. Dors that make sense? Like a blend pot i guess? Specifically a tone pot that boost or cuts Cheers, lads. Quote Link to comment Share on other sites More sharing options...
SamIAm Posted July 6 Share Posted July 6 (edited) As I understand it ... The term linear is one that describes how the pot resistance changes relating to its position (Its taper) , the following is roughly how it works. A center detent pot has a physical notch or dimple such that when it is moved to the centre position you get that little 'click' to indicate such, the electrical behaviour of the pot remains the same. A common blend control is actually two pots with a single control shaft, as you turn the signal going through one pot increases whilst the other one decreases. I believe a centre detent pot used to boost/cut requires some more electronics behind it (commonly active electronics) to achieve that effect. Sam x Edited July 6 by SamIAm 4 Quote Link to comment Share on other sites More sharing options...
lidl e Posted July 6 Author Share Posted July 6 3 hours ago, SamIAm said: As I understand it ... The term linear is one that describes how the pot resistance changes relating to its position (Its taper) , the following is roughly how it works. A center detent pot has a physical notch or dimple such that when it is moved to the centre position you get that little 'click' to indicate such, the electrical behaviour of the pot remains the same. A common blend control is actually two pots with a single control shaft, as you turn the signal going through one pot increases whilst the other one decreases. I believe a centre detent pot used to boost/cut requires some more electronics behind it (commonly active electronics) to achieve that effect. Sam x Cheers. So i need to specify a centre detent pot! It is an active preamp 1 Quote Link to comment Share on other sites More sharing options...
3below Posted July 6 Share Posted July 6 Are you replacing an existing pot? It could be logarithmic or linear either side of the detent. Are there any legible identity codes on the pot? If not you have four possible ways forward. 1. Ask the manufacturer what pot is fitted, 2.Search the internet for a schematic or clone schematic which might show the pot type, 3. Make some basic measurements, using a multi-meter and determine if the pot is log or lin, 4. Buy a log and a lin centre detent pot. Try them both and see which you like. What preamp is it? the BC collective wisdom may know the answer to your question. 2 Quote Link to comment Share on other sites More sharing options...
lidl e Posted July 7 Author Share Posted July 7 13 hours ago, 3below said: Are you replacing an existing pot? It could be logarithmic or linear either side of the detent. Are there any legible identity codes on the pot? If not you have four possible ways forward. 1. Ask the manufacturer what pot is fitted, 2.Search the internet for a schematic or clone schematic which might show the pot type, 3. Make some basic measurements, using a multi-meter and determine if the pot is log or lin, 4. Buy a log and a lin centre detent pot. Try them both and see which you like. What preamp is it? the BC collective wisdom may know the answer to your question. It's this fella. Treble boost from a 90s ibanez BII preamp Any way i can tell what i need? Quote Link to comment Share on other sites More sharing options...
3below Posted July 7 Share Posted July 7 (edited) A quick search does not find any schematics for a BII pre-amp. However, this circa 2008 looks promising https://www.talkbass.com/threads/fyi-ibanez-sr480-preamp-schematic-jpg-pdf.455174/. The pot values are shown as 50K Ohms. I would imagine that the amp designs would not have changed much in that era, you could look which IC is fitted - TL062? On the treble pot board, can you see what value the capacitor has on the side, and what colour code and hence resistance the resistor is. This will help confirm that it is the schematic above. The best answer would be to desolder the pot and then measure the resistance across the two outer legs. Edited July 7 by 3below Quote Link to comment Share on other sites More sharing options...
SamIAm Posted July 7 Share Posted July 7 This schematic claims to be for that EQ and it shows a 20K pot. https://everycircuit.com/circuit/5314341701681152/active-2-band-bass-guitar-eq- Also, this post has some more info https://www.talkbass.com/threads/1990-ibanez-sr1000-wiring-help.1089289/post-16157750 Sam x 1 Quote Link to comment Share on other sites More sharing options...
Count Bassy Posted July 7 Share Posted July 7 What does the writing on the side of the pot say? 1 Quote Link to comment Share on other sites More sharing options...
lidl e Posted July 7 Author Share Posted July 7 Cheers, all! Will open itnup and take better oics when i get home in a few. I thunk this might be the circuit? https://everycircuit.com/circuit/5314341701681152/active-2-band-bass-guitar-eq- Does that say 20k or 50 k? Quote Link to comment Share on other sites More sharing options...
3below Posted July 7 Share Posted July 7 Those appear to be 20K, 19.8K + 0.2K. 1 Quote Link to comment Share on other sites More sharing options...
3below Posted July 7 Share Posted July 7 (edited) 59 minutes ago, 3below said: A quick search does not find any schematics for a BII pre-amp. However, this circa 2008 looks promising https://www.talkbass.com/threads/fyi-ibanez-sr480-preamp-schematic-jpg-pdf.455174/. The pot values are shown as 50K Ohms. I would imagine that the amp designs would not have changed much in that era, you could look which IC is fitted - TL062? On the treble pot board, can you see what value the capacitor has on the side, and what colour code and hence resistance the resistor is. This will help confirm that it is the schematic above. The best answer would be to desolder the pot and then measure the resistance across the two outer legs. Looking at your images confirms it is not the above circuit, the treble capacitor on your board is C6, on the schematic it is C3. Must look more closely at the evidence in future Having said that there is no reason why the RC combination in that circuit could not have been used in other preamps. Edited July 7 by 3below 1 Quote Link to comment Share on other sites More sharing options...
lidl e Posted July 7 Author Share Posted July 7 56 minutes ago, 3below said: Those appear to be 20K, 19.8K + 0.2K. Does that mean the pot is 19.8 and the little black thing is .2? Quote Link to comment Share on other sites More sharing options...
lidl e Posted July 7 Author Share Posted July 7 52 minutes ago, 3below said: Looking at your images confirms it is not the above circuit, the treble capacitor on your board is C6, on the schematic it is C3. Must look more closely at the evidence in future Having said that there is no reason why the RC combination in that circuit could not have been used in other preamps. Cheers, bud. I dont know any of this! Quote Link to comment Share on other sites More sharing options...
3below Posted July 7 Share Posted July 7 (edited) 4 hours ago, lidl e said: Does that mean the pot is 19.8 and the little black thing is .2? The little black thing with a stripe is an electrolytic capacitor. The pot (in the model circuit) is 20K. The best bet is to de-solder the pot and remove it from the little board. You will have to do this anyway to replace it, de-solder braid and or a solder sucker are useful. Get a multimeter (a cheapie 10-12 Euro one will do), and measure the resistance between to two outside terminals (legs). Edited July 7 by 3below 1 Quote Link to comment Share on other sites More sharing options...
Count Bassy Posted July 7 Share Posted July 7 In most cases the value of the pot , and its characteristics are written on the side of the pot itself. Unless the company are being deliberately awkward. 1 Quote Link to comment Share on other sites More sharing options...
lidl e Posted July 7 Author Share Posted July 7 1 hour ago, 3below said: The little black thing with a stripe is an electrolytic capacitor. The pot (in the model circuit) is 20K. The best bet is to de-solder the pot and remove it from the little board. You will have to do this anyway to replace it, de-solder braid and or a solder sucker are useful. Get a multimeter (a cheapie 10-12 Euro one will do), and measure the resistance between to two outside terminals (legs). So that's a cap like on my fender basses. Like the .047 The little PCB is just a design choice? One could achieve the same idea without it? Quote Link to comment Share on other sites More sharing options...
3below Posted July 7 Share Posted July 7 51 minutes ago, lidl e said: So that's a cap like on my fender basses. Like the .047 The little PCB is just a design choice? One could achieve the same idea without it? Yes and yes, although the PCB makes the construction simpler / neater / easier than point to point wiring when you are manufacturing thousands (or more) of the preamp. Stating the obvious, when you re-build it you will solder the new pot onto the PCB. 1 Quote Link to comment Share on other sites More sharing options...
tauzero Posted July 7 Share Posted July 7 1 hour ago, 3below said: Yes and yes, although the PCB makes the construction simpler / neater / easier than point to point wiring when you are manufacturing thousands (or more) of the preamp. Stating the obvious, when you re-build it you will solder the new pot onto the PCB. Which is also a reminder that you need a pot with PCB mounting terminals in the same orientation: and not one with solder terminals or right-angle terminals 2 Quote Link to comment Share on other sites More sharing options...
lidl e Posted July 7 Author Share Posted July 7 So it does look like it is a 20k. Does the 17 C on the other side mean anything? Can you tell what value the cap is from these pics? Quote Link to comment Share on other sites More sharing options...
lidl e Posted July 7 Author Share Posted July 7 10 hours ago, SamIAm said: This schematic claims to be for that EQ and it shows a 20K pot. https://everycircuit.com/circuit/5314341701681152/active-2-band-bass-guitar-eq- Also, this post has some more info https://www.talkbass.com/threads/1990-ibanez-sr1000-wiring-help.1089289/post-16157750 Sam x I was looking at that EMG BTS as i think that is basically the same as this Ibanez BQ-II. But when icgot the bass back, it sounds so good, i want to try and get this one sorted. It does have EMG pickups. Quote Link to comment Share on other sites More sharing options...
itu Posted July 8 Share Posted July 8 17C may be manufacturer's date code or similar. 20 kohm is clear. Other alphabets are non standard, as there are many different ways of telling things: "A" may be "audio taper" i.e. logarithmic, but it can also be linear. That C6, you took a picture from the other side only which says 85 degree centigrade. This is the max temp it works. The numbers on the other side tell the parametres needed. 1 1 Quote Link to comment Share on other sites More sharing options...
Count Bassy Posted July 8 Share Posted July 8 I didn't know this, but it seems that: "G taper is reverse audio till midpoint and regular audio after that" and "a linear should work, but the control won't "feel" the same". 1 Quote Link to comment Share on other sites More sharing options...
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