thirdstone Posted May 14, 2008 Report Share Posted May 14, 2008 Hi Guys I have managd to damage the VBC trim pot on the circuit board. I need to replace it but I do not know the value. Please speak upm if you know. Kev Quote Link to comment Share on other sites More sharing options...
psw Posted May 15, 2008 Report Share Posted May 15, 2008 The sustainer circuitry is always been kept under wraps...so I don't know the value. However... Usually there is a marking...something like 103 for instance (from recollection is 10k ohms)... Otherwise, you can use a multimeter to measure the resistance at it's maximum (between the outer ends of the internal strip that the wiper (centre pin) travels on). Different trim pots have different formats and sizes so without a photo...etc... Also, these commercial boards are often difficult to solder and desolder so take great care...best to find someone who has the right equipment as over heating for instance with an inappropriate iron can easily burn out a component further down the line or damage a track on the circuit board. Generally, a trim pot is an easier component that others to work with though as it is big enough to handle, but often the board is fragile or may have multilayers that can easily be damaged... Hope that helps... pete PS...someone who can mend computer boards and such would have the skills...but with care you may be ok...how did it get damaged in the first place, what is the form of this damage? Quote Link to comment Share on other sites More sharing options...
thirdstone Posted May 15, 2008 Author Report Share Posted May 15, 2008 The sustainer circuitry is always been kept under wraps...so I don't know the value. However... Usually there is a marking...something like 103 for instance (from recollection is 10k ohms)... Otherwise, you can use a multimeter to measure the resistance at it's maximum (between the outer ends of the internal strip that the wiper (centre pin) travels on). Different trim pots have different formats and sizes so without a photo...etc... Also, these commercial boards are often difficult to solder and desolder so take great care...best to find someone who has the right equipment as over heating for instance with an inappropriate iron can easily burn out a component further down the line or damage a track on the circuit board. Generally, a trim pot is an easier component that others to work with though as it is big enough to handle, but often the board is fragile or may have multilayers that can easily be damaged... Hope that helps... pete PS...someone who can mend computer boards and such would have the skills...but with care you may be ok...how did it get damaged in the first place, what is the form of this damage? Thanks for the reply. The trim pot fell apart when I was adjusting it , simple as that. I was pretty pissed off. I have soldered in a 250K pot which has the thing back up and running.,in fact its given me the oppotunity to have the control accessable on the guitar. The trim pot did have some numbers on them so based on what you said about the code I'll have a look. I hope I have not thrown it out. Cheers ...Kev Quote Link to comment Share on other sites More sharing options...
thirdstone Posted May 24, 2008 Author Report Share Posted May 24, 2008 I have thrown it out. If anyone can post a photo of the rear side of a sustainer cct board I could figure out what the value is. please help an old fella. Kev Quote Link to comment Share on other sites More sharing options...
psw Posted May 25, 2008 Report Share Posted May 25, 2008 Thanks for the reply. The trim pot fell apart when I was adjusting it , simple as that. I was pretty pissed off. I have soldered in a 250K pot which has the thing back up and running.,in fact its given me the oppotunity to have the control accessable on the guitar. The trim pot did have some numbers on them so based on what you said about the code I'll have a look. I hope I have not thrown it out. In this previous reply I thought you had come to a workable solution...but you actually do want the trim pot...ok... I don't think you will have a lot of joy with the pic or details of the sustainer board, I have been running the sustainer thread for a while and close up pics and details have not been forthcoming.... Not to worry, you seem to suggest that with an external 250k pot the thing works, so use a trim pot of that value (it is probably overlarge for it's function). If you think laterally, a pot sweeps from near zero ohms to the value of the resistor. So, if the value was 10K or 100K as is often the case in active circuits, then somewhere low down in the 250K range you will have that value, who knows, maybe you will have less or more control! As it is a 'set and forget" trim pot, once you have it set where you want it, it doesn't really matter what the value of the pot is, as it is the sweep of the pot that determines it's actual resistance. You may find that if the 250K is set very low down that a trim of 100k or less is more appropriate, but as I say it probably doesn't really matter. The thing is to try and find a trim pot to match the size of the original, but I am sure you will find something that works... hope that helps, I think it might... pete PS...once you have the thing out, perhaps you could take some photos and such of the board for other's to research...hint, hint (for instance, there appears to be some kind of mystery transformer on the board of the fernandes, amoungst other things like chip numbers and such....) Quote Link to comment Share on other sites More sharing options...
thirdstone Posted May 26, 2008 Author Report Share Posted May 26, 2008 Thanks for the input Pete. Yes I did get the cct working with a 250K pot, but it’s too large a value. I have replaced it with a 50 K pot in the hope of finding its sweet spot. Then I can measure the value and replace with the appropriate board mounted trim pot. I can’t believe that on the entire WWW there are no photos of the cct board. I will post one soon on this site. As far as making one, I thought about that but really apart from the thrill of doing it yourself I can’t see the point when they are not over expensive( apologies to beer broke students). I might , however spend way too much time and money making an under achieving Tube amp in the future. Quote Link to comment Share on other sites More sharing options...
thirdstone Posted May 28, 2008 Author Report Share Posted May 28, 2008 Here are some photos front Back with missing trim pot Quote Link to comment Share on other sites More sharing options...
psw Posted May 28, 2008 Report Share Posted May 28, 2008 Ah....the mysterious transformer....what does that do!!!! This is great to see, thanks for the pics though the mystery still remains. I dare say that if you got as good a pic from a new one, your value would be solved. For instance, if I recall right, the one marked 203 stands for 20 with three zero's, 20,000 ohms, or 20k which would be an expected value in an active circuit like this (over 250,000 or 500,000 in a passive guitar circuit). 50K is closer to the mark I would suspect and if set right, will be any value lower down to zero(ish) as I earlier pointed out, so will function just as happily. As far as making one, I thought about that but really apart from the thrill of doing it yourself I can’t see the point when they are not over expensive( apologies to beer broke students). I might , however spend way too much time and money making an under achieving Tube amp in the future. Very sound and something I have tried to communicate. The DIY sustainer project is not primarily about making it cheaper (although this could result from the work) but to explore the whole thing and perhaps make it better. Both sustainiac and fernandes have good products more highly developed. Ah...but in your second sentence you reveal what drives the interest in such projects. You would endeavor to venture in the difficult and expensive DIY valve amp area despite very good tube amps available in the marketplace and designs developed over years (far more than has been expended on sustainer technology). That is not a criticism, but an observation of where your interest lies and in your comments you acknowledge that which is good to see. Far and away, most people who would like a sustainer should get one of these...those who want to explore, develop or create such things...well that is why you may wish to DIY. Plenty of good guitar's about, but people all over this board still have a desire to make their own, often to remarkably similar vein to what is already available and at a higher "cost". (I am no different, I just 'built' a telecaster!). There are still quite a few mysteries in this... there is what looks like a black painted vertical board through the circuit (along side the switches). There is nothing like black paint to pique ones imagination and desire to know what it does or how one could do something similar....hmmmm thanks pete Quote Link to comment Share on other sites More sharing options...
Leppard84 Posted March 25, 2009 Report Share Posted March 25, 2009 I have thrown it out. If anyone can post a photo of the rear side of a sustainer cct board I could figure out what the value is. please help an old fella. Kev I looked at your board pics, and your missing the vibration control (VBC) right? That's marking was 104, so 100K-ohms. And a thank you to you as well. I broke my gain control one which your pic clearly shows as 503. Hope it helps, and thank you! ToNy Quote Link to comment Share on other sites More sharing options...
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