amadork9 Posted December 14, 2010 Share Posted December 14, 2010 Hello I just bought a very clean GFA585LE with no signs of leaking caps and was wanting to change them before they do and upgrade to better components theres a company that offers this service but I was looking to save and do some of it myself it myself. Here is what they offer, Install high quality audio grade capacitors and low noise metal film resistors in working driver, output stage, and power supply circuits for greater musical clarity. Areas targeted for improvement include the input circuitry, feedback loop, output stage biasing, driver/output stage/power supply bypassing, EMI protection. They also state they use Rubicon black gate capacitors, I searched on ebay for these and couldnt find them, is there something as good I can use and what would be the values?Check DC offset, check and adjust bias, before/after modification extended listening tests. Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted December 14, 2010 Share Posted December 14, 2010 That's a very nice amp. I find the bass to be superb. The amp is not that old, so I would not start changing caps. That said, there are bypass caps on the power supply caps that for some reason take a real beating. They could be replaced, and I agree checking the bias and DC is always a good idea. As for the other mods (which are expensive), I would not bother. The 585 sounds quite good as is, so there is no reason to mess with it (it may actually decrease its value). If you are bent on doing this, you may want to add bypass caps on some of the existing caps (eg, input, feedback). How experienced are you on this sort of thing? Congratulations on a getting an excellent amp. What will you be using it with? Quote Link to comment Share on other sites More sharing options...
cyclonecj Posted December 14, 2010 Share Posted December 14, 2010 I have one of these amps & replaced trhe caps a few years ago myself. Getting the circuit board out was a slight problem, but I was able to do the whole job within about 2 hours. Amp has been working excellent since then. Quote Link to comment Share on other sites More sharing options...
djk Posted December 14, 2010 Share Posted December 14, 2010 "The amp is not that old" About 20 years old, all the small electrolytics should be replaced. These amps are known to have leaky electrolytics that can damage the circuit board. It is worthwhile to replace the power supply bypass caps after about 7~10 years. I have seen two year old Rockford Fosgate amps blow their bypass caps clean off the board, the ripple current is quite high. See page 7 for Blackgate. http://percyaudio.com/Catalog.pdf My first choice for the supply bypass caps would be 33F/160V, second choice 47µ/100V. Quote Link to comment Share on other sites More sharing options...
amadork9 Posted December 16, 2010 Author Share Posted December 16, 2010 That's a very nice amp. I find the bass to be superb. The amp is not that old, so I would not start changing caps. That said, there are bypass caps on the power supply caps that for some reason take a real beating. They could be replaced, and I agree checking the bias and DC is always a good idea. As for the other mods (which are expensive), I would not bother. The 585 sounds quite good as is, so there is no reason to mess with it (it may actually decrease its value). If you are bent on doing this, you may want to add bypass caps on some of the existing caps (eg, input, feedback). How experienced are you on this sort of thing? Congratulations on a getting an excellent amp. What will you be using it with? Yes compared to my mc7270 bass is more controled yet still deep especially with my cornscala's with no damping material inside the cab resonances were out of control with the mc7270 probably due to its low damp factor (30) not sure that i need damping material now also the 585 seems to have more detail the mc7270 seemed rolled off but was smoother sounding. Yes the power supply caps ill look into. no i dont have experience but ive built xovers and very mechanically inclined so maybe, i wont do it unless im sure i can. Is black gate good? I will be using it with McIntosh MX-130, Sound Shaper ss-525x, Cornwall ll mod to Cornscala, PH800/K55M and ALK AP12-500 ES-5800 Quote Link to comment Share on other sites More sharing options...
amadork9 Posted December 16, 2010 Author Share Posted December 16, 2010 "The amp is not that old" About 20 years old, all the small electrolytics should be replaced. These amps are known to have leaky electrolytics that can damage the circuit board. It is worthwhile to replace the power supply bypass caps after about 7~10 years. I have seen two year old Rockford Fosgate amps blow their bypass caps clean off the board, the ripple current is quite high. See page 7 for Blackgate. http://percyaudio.com/Catalog.pdf My first choice for the supply bypass caps would be 33F/160V, second choice 47µ/100V. Power supply caps are those on the output pcb assembly? I think it shows 47uf/160v capacitors electrolytic, I downloaded the schmatic and did not see the power supply board. thanks ken Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted December 16, 2010 Share Posted December 16, 2010 "..... Power supply caps are those on the output pcb assembly? I think it shows 47uf/160v capacitors electrolytic, I downloaded the schmatic and did not see the power supply board. thanks ken ...." The cap DJK is referring to (47uF) is the bypass cap (for the PS cap). The suggestion is to replace all the small electrolytic caps, including this PS bypass cap. You may also want to replace the PS caps (the big cans). The PS caps may be expensive, you might want to check with Apexjr to see if he has any. I would be less worried about using fancy caps at this point. If you want to go the next step and bypass some of the other caps with small film caps, then go over and get some advice at DIYAUDIO. Make sure you have a schematic available when you do this. Very important: if you are not comfortable with electronics (eg, have trouble identifying the PS caps, or do not know how to safely discharge a PS cap), then have a more experienced friend help you. There are high voltages lurking in the power supply, even when the amp is turned off. This is not a joke, but we have no idea what your background is with this stuff. Quote Link to comment Share on other sites More sharing options...
amadork9 Posted December 17, 2010 Author Share Posted December 17, 2010 "..... Power supply caps are those on the output pcb assembly? I think it shows 47uf/160v capacitors electrolytic, I downloaded the schmatic and did not see the power supply board. thanks ken ...." The cap DJK is referring to (47uF) is the bypass cap (for the PS cap). The suggestion is to replace all the small electrolytic caps, including this PS bypass cap. You may also want to replace the PS caps (the big cans). The PS caps may be expensive, you might want to check with Apexjr to see if he has any. I would be less worried about using fancy caps at this point. If you want to go the next step and bypass some of the other caps with small film caps, then go over and get some advice at DIYAUDIO. Make sure you have a schematic available when you do this. Very important: if you are not comfortable with electronics (eg, have trouble identifying the PS caps, or do not know how to safely discharge a PS cap), then have a more experienced friend help you. There are high voltages lurking in the power supply, even when the amp is turned off. This is not a joke, but we have no idea what your background is with this stuff. How do you safely discharge a PS cap? i registered with diyaudio and couldnt find any pics on how to discharge. thanks ken Quote Link to comment Share on other sites More sharing options...
amadork9 Posted December 20, 2010 Author Share Posted December 20, 2010 I have one of these amps & replaced trhe caps a few years ago myself. Getting the circuit board out was a slight problem, but I was able to do the whole job within about 2 hours. Amp has been working excellent since then. Are the potentual leaking caps on the input board? did you replace the bypass caps on the power supply and/or on the input board? Quote Link to comment Share on other sites More sharing options...
djk Posted December 20, 2010 Share Posted December 20, 2010 All the small electrolytics have the potential of leaking, only the big computer grade ones don't leak. Use a 100R/2W resistor in series with a wire with an aligator clip on one end and a test prod on the other for a cap dischage aid. Most any high-quality caps will replace the stock ones. I don't spend for Black Gate, I use Panasonic, Elna, Nichicon. Quote Link to comment Share on other sites More sharing options...
amadork9 Posted December 21, 2010 Author Share Posted December 21, 2010 All the small electrolytics have the potential of leaking, only the big computer grade ones don't leak. Use a 100R/2W resistor in series with a wire with an aligator clip on one end and a test prod on the other for a cap dischage aid. Most any high-quality caps will replace the stock ones. I don't spend for Black Gate, I use Panasonic, Elna, Nichicon. I know this is gonna sound green but which kinda caps i order, polar, aluminum, bipolar, radial 105 or 85 degres 10ml x20ml +/- ? Quote Link to comment Share on other sites More sharing options...
djk Posted December 23, 2010 Share Posted December 23, 2010 Replace polar with polar, non-polar (or bi-polar) with like, 105°C first, 85°C if you can't get 105°C, radial to replace radial, axial to replace axial. You can use higher voltage, higher capacitance, both within reason and size limitations. Quote Link to comment Share on other sites More sharing options...
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