Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 15, 2012 18:38:44 GMT
OK guys I am going to need everybody's help with repairing and upgrading my mono amp/s. About a year ago I tried to replace the red led on my left amp with a cool blue one to match my V2. I touched something I shouldn't have and there was a bang. It has taken me about a year to pluck up the courage to try and figure out how to get inside the damn thing. I now have it stripped down and the first thing I noticed there are two internal fuses. Fingers crossed they had blown. A continuity test confirmed both fuses had indeed blown. This is my first problem - looking at the fuses the only markings I can read are: 250v 5S8A Sun? they are 20 x5 mm. picture below. And the fuse holder if it gives you any clues? Can anybody suggest a replacement fuse because a quick look on the web revealed nothing with those numbers / markings. I don't even know what rating they are apart from 250v. All help appreciated.
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Deleted
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Post by Deleted on Sept 15, 2012 19:01:23 GMT
You need 8A/T (T stands for Time Lag) or slow blow.
Now the real question is did they blow because you accidentally shorted the rectified AC or did you destroy the amp which blew the fuse.
check the 4 diodes in the bridge rectifier. Each diode should measure about 0.6V forward and something (or nothing) in reverse. If 1 or 2 measure 0 Ohm replace it.
Measure Ohms between the + and - of the rectifier. You should see a 'short' 0 Ohm that slowly increases in value. Now reverse the meter wires and you should see a negative value going though zero and back up again. If that always stays very close to 0 Ohm the amp itself is knackered (output devices and God knows what else) If it measures O.K. and the rectifier measures O.K. pop in new fuses and light the thing up.
If the fuses fail again with a flash... you will need some help.
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 16, 2012 11:12:37 GMT
You need 8A/T (T stands for Time Lag) or slow blow. Thanks Frans, I will take it one step at a time. I have found some fuses at the correct rating, but I am confused because there are 3 types - (35 / 80 / 200 breaking capacity @ max voltage) which one would you recommend? I cannot see any diodes anywhere near the bridge rectifier? I have got to go out now but I will post a picture later. Chris
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Post by Deleted on Sept 16, 2012 11:36:49 GMT
You need 8A/T (T stands for Time Lag) or slow blow. Thanks Frans, I will take it one step at a time. I have found some fuses at the correct rating, but I am confused because there are 3 types - (35 / 80 / 200 breaking capacity @ max voltage) which one would you recommend? I cannot see any diodes anywhere near the bridge rectifier? I have got to go out now but I will post a picture later. Chris Hi Chris The attached links should give you some idea of what you require. www.jaycar.com.au/productView.asp?ID=SF2233 (32(L) x 6(Dia.)mm) www.jaycar.com.au/productView.asp?ID=SF2121 (20mm x 5mm) If you were to look inside of a bridge rectifier you would find four diodes arranged something like this: Attachments:
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 16, 2012 15:31:08 GMT
Thanks Alex. I think I understand now, the diodes make up the bridge rectifier - that's why I cant see any (Yes?) I am posting a picture of it anyway and maybe you can tell me where I need to take the measurements. Thanks for the link about the fuses but it does not really answer my question about the (35 / 80 / 200 breaking capacity @ max voltage)
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Deleted
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Post by Deleted on Sept 16, 2012 16:33:32 GMT
a simple 8A/T fuse will do. 80V is enough.
see post # 7 for correct measurement points
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Crispy
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Post by Crispy on Sept 16, 2012 18:04:28 GMT
a simple 8A/T fuse will do. 80V is enough. measure in the diode setting of the meter. red pin on AC (lower left) and black pin on AC (lower right). What are your measurements? (WITHOUT ANY FUSES) measure in the diode setting of the meter. black pin on AC (lower left) and red pin on AC (lower right). What are your measurements? (WITHOUT ANY FUSES) Cheers Frans I will get some fuses ASAP. I have taken the two readings above without any fuses. red pin on AC (lower left) and black pin on AC (lower right) The reading was = random numbers then settled at 1 black pin on AC (lower left) and red pin on AC (lower right). The reading was = 533 I will give you the other readings as soon as I receive the fuses. Chris
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Post by Deleted on Sept 16, 2012 18:16:22 GMT
Hi Chris, Sorry for being a bit unclear on the measurements. All measurements should be taken without the fuses. The last 2 can ONLY be taken without fuses otherwise you would simply be measuring the secondary of the trafo and would always show a 'short' for the measurements. with 1 you mean the same 'value' as the one you get when nothing is connected ? I (now) think the AC markings on the PCB are NOT from the bridge rectifier but intended for the wiring this calls for other measurements. I was a bit hasty... sorry. (thanks Chris, the other Chris.. that is, as I had made a little mis and hope I am not taking the piss for this Chris) Top left is +, top right is AC, bottom left is AC and bottom right is - (as in standard bridge rectifiers) measure in the diode setting of the meter. red pin on + (top left) and black pin on AC (top right) and on AC (bottom left). What are your measurements ? measure in the diode setting of the meter. black pin on + (top left) and red pin on AC (top right) and on AC (bottom left). What are your measurements ? measure in the diode setting of the meter. red pin on - (bottom right) and black pin on AC (top right) and on AC (bottom left). What are your measurements ? measure in the diode setting of the meter. black pin on - (bottom right) and red pin on AC (top right) and on AC (bottom left). What are your measurements ? measure in the diode setting of the meter. black pin on - black pin on - (bottom right) and red pin on + (top left). What are your measurements? measure in the diode setting of the meter. red pin on - black pin on - (bottom right) and black pin on + (top left). What are your measurements? measure in the diode setting of the meter. red pin on AC (top right) and black on AC (bottom left). What are your measurements? (WITHOUT ANY FUSES) measure in the diode setting of the meter. black pin on AC (top right) and red on AC (bottom left). What are your measurements? (WITHOUT ANY FUSES)
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 17, 2012 7:51:19 GMT
Hi Chris, Sorry for being a bit unclear on the measurements. All measurements should be taken without the fuses. The last 2 can ONLY be taken without fuses otherwise you would simply be measuring the secondary of the trafo and would always show a 'short' for the measurements. with 1 you mean the same 'value' as the one you get when nothing is connected ? I (now) think the AC markings on the PCB are NOT from the bridge rectifier but intended for the wiring this calls for other measurements. I was a bit hasty... sorry. (thanks Chris, the other Chris.. that is, as I had made a little mis and hope I am not taking the piss for this Chris) Top left is +, top right is AC, bottom left is AC and bottom right is - (as in standard bridge rectifiers) measure in the diode setting of the meter. red pin on + (top left) and black pin on AC (top right) and on AC (bottom left). What are your measurements ? measure in the diode setting of the meter. black pin on + (top left) and red pin on AC (top right) and on AC (bottom left). What are your measurements ? measure in the diode setting of the meter. red pin on - (bottom right) and black pin on AC (top right) and on AC (bottom left). What are your measurements ? measure in the diode setting of the meter. black pin on - (bottom right) and red pin on AC (top right) and on AC (bottom left). What are your measurements ? measure in the diode setting of the meter. black pin on - black pin on - (bottom right) and red pin on + (top left). What are your measurements? measure in the diode setting of the meter. red pin on - black pin on - (bottom right) and black pin on + (top left). What are your measurements? measure in the diode setting of the meter. red pin on AC (top right) and black on AC (bottom left). What are your measurements? (WITHOUT ANY FUSES) measure in the diode setting of the meter. black pin on AC (top right) and red on AC (bottom left). What are your measurements? (WITHOUT ANY FUSES) No problem Frans. New measurements are: red pin on + (top left) and black pin on AC (top right) = random numbers then as nothing connected and on AC (bottom left). = random numbers then as nothing connected black pin on + (top left) and red pin on AC (top right) = 542 and on AC (bottom left). = 539 red pin on - (bottom right) and black pin on AC (top right) = 504 and on AC (bottom left). = 537 black pin on - (bottom right) and red pin on AC (top right) = random numbers then as nothing connected and on AC (bottom left). = random numbers then as nothing connected black pin on - black pin on - (bottom right) ? ? I took the measurement as below black pin on - Red pin on - = 003 and red pin on + (top left). = random numbers then as nothing connected red pin on - black pin on - (bottom right) = 001 and black pin on + (top left). = 254 red pin on AC (top right) and black on AC (bottom left). = as nothing connected black pin on AC (top right) and red on AC (bottom left). = as nothing connected Phew that took some working out, so god knows how you do this all day
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Deleted
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Post by Deleted on Sept 17, 2012 8:48:27 GMT
Ah yes.... another quick copy paste thing without paying real attention. Should have been: measure in the diode setting of the meter. black pin on - (bottom right) and red pin on + (top left). What are your measurements?
measure in the diode setting of the meter. red pin on - (bottom right) and black pin on + (top left). What are your measurements?Anyway those tests were done correctly so no need to measure again. It seems the bridge rectifier is still O.K. If it is O.K. in reverese voltage remains to be seen but figure it will be O.K. It appears as though there is no hard 'short' in the output stage but that doesn't mean the amp section is O.K. as one of the output devices could still be broken. Be sure the pins of the replaced LED doesn't make physical contact with the front panel. The measured 254 could be (doesn't need to be) something to worry about. 2 options: Put in some fuses, switch on the amp with the mains cord disconnected ... duck (take cover) ... and plug in the mains lead. Flashing fuses means: ah well... let's get it repaired or dump it. Fuses O.K. means: check if the amp still works. You could probably also pre-check the output devices (depending on if it's discrete or not) in this case pictures of the output devices mounted on the heatsink are needed.
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 17, 2012 14:46:56 GMT
Anyway those tests were done correctly so no need to measure again. It seems the bridge rectifier is still O.K. If it is O.K. in reverse voltage remains to be seen but figure it will be O.K. It appears as though there is no hard 'short' in the output stage but that doesn't mean the amp section is O.K. as one of the output devices could still be broken. Be sure the pins of the replaced LED doesn't make physical contact with the front panel. The measured 254 could be (doesn't need to be) something to worry about. 2 options: Put in some fuses, switch on the amp with the mains cord disconnected ... duck (take cover) ... and plug in the mains lead. Flashing fuses means: ah well... let's get it repaired or dump it. Fuses O.K. means: check if the amp still works. You could probably also pre-check the output devices (depending on if it's discrete or not) in this case pictures of the output devices mounted on the heatsink are needed. Thanks Frans, it looks like I may get away lightly with my little mis-hap (fingers crossed) The output devices that are on the heatsink are pictured below and there are exactly the same amount on the other side of the board. The LED is not connected at the moment because this what caused the problem in the first place. My own stupid fault, I assumed the output to the LED was 12v and it obviously wasn't, so as soon as I switched the amp on it blew the LED. It was when I tried to measure the output voltage to the LED that I touched something with one of the probes of the multimeter and there was a bang I think it read something daft like 77 volts before the mishap? I have taken the old LED to bits and found a resistor with the numbers ER74 - 5K6J, So I probably need a new one to replace that for the new LED? Pic below. Chong if your reading this - I may need to borrow one of your ex army helmets just in case ;D ;D
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Post by Deleted on Sept 17, 2012 18:09:46 GMT
The 5k6 will probably still be O.K. I reckon the LED is connected to the + power supply and runs through the 5k6 to ground. Simply measure it if it reads 5k6 it's O.K. a 13mA led current is somewhat high though. If I were replacing the LED I would use a higher value resistor. For a blue LED I would use a 22k, perhaps even a 47k resistor. 77V is quite likely if the amp were rated around 300W (or 200W with an under-dimensioned transformer ). For a 200W amp one would expect around 60 to 65V if the trafo is over-dimensioned. Checking output devices: measure each MAG1832 on the diode setting. red lead on centre pin and black lead on the most right pin. and.. black lead on centre pin and red lead on the right pin. If any of the devices reads close to 0 Ohm (probably in both directions) that one is defective. If all devices read something (and different in the reversed direction) it will be quite safe to mount the fuses and light it up. Judging from what happened the amp will probably be O.K. and you simply shorted the reservoir caps.
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 19, 2012 20:03:23 GMT
The 5k6 will probably still be O.K. I reckon the LED is connected to the + power supply and runs through the 5k6 to ground. Simply measure it if it reads 5k6 it's O.K. a 13mA led current is somewhat high though. If I were replacing the LED I would use a higher value resistor. For a blue LED I would use a 22k, perhaps even a 47k resistor. 77V is quite likely if the amp were rated around 300W (or 200W with an under-dimensioned transformer ). For a 200W amp one would expect around 60 to 65V if the trafo is over-dimensioned. Checking output devices: measure each MAG1832 on the diode setting. red lead on centre pin and black lead on the most right pin. and.. black lead on centre pin and red lead on the right pin. If any of the devices reads close to 0 Ohm (probably in both directions) that one is defective. If all devices read something (and different in the reversed direction) it will be quite safe to mount the fuses and light it up. Judging from what happened the amp will probably be O.K. and you simply shorted the reservoir caps. Cheers Frans. I checked all MAG1832 devices and they were all OK, so I put in the fuses, took cover and fired her up. PHEW it powered up no problem. It then took me about an hour to pluck up enough courage to try the amp out in my system with music going thought it. What a relief to hear Norah Jones wafting out of the speakers. So far so good. Now back to the LED. I tried the above with an old red LED and the 5.6k resistor that checked out OK. Time to try the blue LED with the 5.6k resistor - I did not do this when I originally tried the blue LED. As soon as I turned the amp on it blew. see pic. It looks like it has blown a fuse rather than a resistor in the wire? The LED I am using is as follows: Forward voltage 9.v - 14v Wave length 460-463-466 View angle 25 degree Luminous Intensity 10000mcd The LED takes it's power from the leg of this resistor and then to ground. The transformer is a Toroid International TI-65634 and the power amp is rated at 200w. The toriod is 100mm in dia x 70mm in height and weighs a ton, if this helps. Would this resistor do the job or could you recommend one that is suitable as there are so many with different values it is mind boggling. uk.farnell.com/multicomp/mccfr0w8j0473a20/resistor-carbon-film-47kohm-125mw/dp/1128112Thanks again Frans.
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Post by Deleted on Sept 19, 2012 20:11:19 GMT
For LED's only one thing is important...the mA rating. judging from the high luminance of 10cd ! that's awfully bright ! I would limit the current to 2mA as to not burn out your retina when looking at the amp. 77V/0.002A=38k5 so a 39k resistor (0.5W) will be O.K. If it is still too bright go for 82k If you want it brighter go for 22k (1W) the 5k6 is a much too small value for high-efficiency LED's unless you want to light the room with it.
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 20, 2012 7:32:35 GMT
For LED's only one thing is important...the mA rating. judging from the high luminance of 10cd ! that's awfully bright ! I would limit the current to 2mA as to not burn out your retina when looking at the amp. 77V/0.002A=38k5 so a 39k resistor (0.5W) will be O.K. If it is still too bright go for 82k If you want it brighter go for 22k (1W) the 5k6 is a much too small value for high-efficiency LED's unless you want to light the room with it. You are right Frans they are awfully bright ;D. I put a 68k resistor in line to calm it down to the brightness I want in my V2 & X PSU which is already 12V. Should I use a different value and only put one resistor in to try and get the same brightness? Cheers.
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Deleted
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Post by Deleted on Sept 20, 2012 10:08:24 GMT
a few resistors in series doesn't hurt. This way it might be easier to adjust the brightness.
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XTRProf
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Pssst ! Got any spare capacitors ?
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Post by XTRProf on Sept 20, 2012 13:28:24 GMT
Ah, Chris, good to see that your amp is A-Ok again. Btw, why use high brightness LED? Use the normal ones will be better as that blue is not only better looking than the high brightness pale blue but also it will have a pleasant brightness For Your Eyes Only. You can get one from Pinkie. I'm sure Pinkie will be kind enough to help you on this if you cannot find one. Anyway, the normal brightness one needs 2 to 3 VDC for the best flicker free colour. Ar, Sheena Easton for you ..............
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XTRProf
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Post by XTRProf on Sept 20, 2012 13:46:17 GMT
I also saw the "Upgrade" now. Don't forget to change the bridge rectifiers to one of Schottky or fast but soft recover type. Frans and Alex will be able to advise you on this although on different wavelenghts. Also, change the E-Caps to "audiophile" grade ones like Pioneer Audio, Elna Audio, Panasonic FM or FC, etc if on a "budget". If cost no object, Elna Cerafine or Silmic, Mundorf, etc since BG is already dead. Hmm........., audio and power power too to OCC copper or OCC silver if cost not object for the last. Again, there will be nuclear reactions on this.
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 21, 2012 15:55:58 GMT
Checking output devices: measure each MAG1832 on the diode setting. red lead on centre pin and black lead on the most right pin. and.. black lead on centre pin and red lead on the right pin. If any of the devices reads close to 0 Ohm (probably in both directions) that one is defective. If all devices read something (and different in the reversed direction) it will be quite safe to mount the fuses and light it up. Frans, if you have read my review of the Aune T1 you will know that I have problems with my amp again. It is probably down to my own stupidity that I tried to listen to the T1 through my speaker system with the amp out of it's case. see pic The first track I played lasted almost to the end of the track when it popped and the amp felt very warm, probably because the heat sinks were not attached to the case? So I decided to re-check all the MAG1832 output devices (are these transistors?) The result of all 6 of them: 1. 001 & 001 2. 001 & 001 3. 000 & 000 4. 000 & 000 5. 001 & 001 6. 001 & 001 Judging by what you said the last time, I think I have trashed the lot, if so could you please advise me of a suitable replacement. Do I need to check the SML BUZ 9006P I think the board says FET? I also re-checked the Bridge rectifier with far different results to before, so I have probably trashed that as well, if I have could you please advise me on a replacement. Results: red pin on + (top left) and black pin on AC (top right) 506 and on AC (bottom left). 539 black pin on + (top left) and red pin on AC (top right) 543 and on AC (bottom left). 540 red pin on - (bottom right) and black pin on AC (top right) 505 and on AC (bottom left). 538 black pin on - (bottom right) and red pin on AC (top right) 544 and on AC (bottom left). 541 black pin on - Red pin on - (bottom right) 000 and red pin on + (top left). 001 red pin on - black pin on - (bottom right) 000 and black pin on + (top left). 001 red pin on AC (top right) and black on AC (bottom left). 1434 black pin on AC (top right) and red on AC (bottom left). 1370 I cannot see anything obviously wrong otherwise like anything burnt out, is there anything else I need to check. I don't know if the replacement fuses had anything to do with it, I doubt it but I could only get 200v breaking capacity instead of 80v at short notice. Cheers Chris
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Post by Deleted on Sept 21, 2012 16:13:04 GMT
You better had used the heatsinks. They were there for a reason....
It appears at least 2 transistors are blown.
action: Desolder all of these transistors and measure them individually. You might also have damaged the transistors that drive the power devices.
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Deleted
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Post by Deleted on Sept 21, 2012 21:20:23 GMT
You better had used the heatsinks. They were there for a reason.... It appears at least 2 transistors are blown. action: Desolder all of these transistors and measure them individually. You might also have damaged the transistors that drive the power devices. In addition to that from Frans , you should also confirm that they are all actually that device type, and that half of them aren't MAG2013
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XTRProf
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Post by XTRProf on Sept 22, 2012 7:24:48 GMT
Oh dear, Chris, you must put back everything before you continue testing your revived amps as Frans had written. There is a reason for the heatsinks. Yeah, I know you might have been got carried over after the amps had been dead for a while and enjoying the amps singing again. Well, round 2 diagnostic. Ting!
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 22, 2012 12:34:38 GMT
In addition to that from Frans , you should also confirm that they are all actually that device type, and that half of them aren't MAG2013 Bloody hell Alex, are you Psychic, how did you know that half are Indeed MAG2013. I don't know how many times I have looked at them and never noticed the difference even when de-soldered. You and Frans are walking encyclopaedias of electronics and I really appreciate both your help as I know zilch about electronics but enjoying learning. ;D The amp was dead in my eyes anyway so I might as well learn from it so I don't make the same mistakes when I upgrade my other mono amp to match.
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Post by Deleted on Sept 22, 2012 12:53:04 GMT
Hi Chris When you use + and - supply rails, the devices used in the output stage are complementary NPN and PNP types of transistors, or N-channel and P-channel FETs. Years ago they used all devices of the same type, (usually NPN), with a single supply rail and a big output coupling capacitor. Regards Alex
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Crispy
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"Done me wrong," it's the same old song" - forever
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Post by Crispy on Sept 22, 2012 12:54:57 GMT
Sorry Frans, I was just a bit too eager to try the Aune T1 through my system and although the heatsinks were attached to the transistors they were not dissipating heat through the case - I honestly thought they would keep cool enough with all the fresh air around them? WRONG Never mind, like I said to Alex the amp was dead in my eyes before this so back to square one. The new readings for the transistors are: 1. as if nothing connected MAG 1832 2. as if nothing connected MAG 1832 3. 000 & 000 MAG 1832 4. as if nothing connected MAG 2013 5. as if nothing connected MAG 2013 6. 000 & 000 MAG 2013 BTW what is the difference between the two just out of curiosity? of course in layman's terms please. Thanks again. Chris
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