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 12:56:44 GMT
You make me laugh Chong, bring it on
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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 13:02:00 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 Thanks for trying to explain Alex, but that lot just went straight over my head
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Deleted
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Post by Deleted on Sept 22, 2012 19:11:03 GMT
Hi Chris,
Try to see if you can source those transistors. I figured you would like have destroyed (at least) 2 transistors. Those were the 2 best ones out of the bunch (I figure thermal runaway due to lack of heatsinking) Those that measure 0 Ohm are defective. The other 4 you can mount back in there. Mount them back in the CORRECT place.
Now measure in the amp as done before (rectifier and transistors) Place new fuses (I expect them to have blown again) If all comes back as before the misrey atrated, fire up the amp and see if it works (for a brief period of time) If it does you order new transistors (preferably all 6 new ones) and fit those. test again (shortly) and put it back in it's case.
Chances are (but not necesarily so) that the drive transistors also have gone belly up. In this case the fuses might blow again and it will be more difficult to repair (without a schematic)
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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 23, 2012 19:22:41 GMT
Hi Chris, Try to see if you can source those transistors. I figured you would like have destroyed (at least) 2 transistors. Those were the 2 best ones out of the bunch (I figure thermal runaway due to lack of heatsinking) Those that measure 0 Ohm are defective. The other 4 you can mount back in there. Mount them back in the CORRECT place. Now measure in the amp as done before (rectifier and transistors) Place new fuses (I expect them to have blown again) If all comes back as before the misrey atrated, fire up the amp and see if it works (for a brief period of time) If it does you order new transistors (preferably all 6 new ones) and fit those. test again (shortly) and put it back in it's case. Chances are (but not necesarily so) that the drive transistors also have gone belly up. In this case the fuses might blow again and it will be more difficult to repair (without a schematic) Hi Frans. I think I have managed to find the transistors that I need, but if you don't mind could you double check them for me. If I am correct they are TO-264 and it took me hours to find them, although it did help when I found an old Magnatec PDF file about the MAG2013. The PDF had this data: VCBO Collector – Base Voltage –200V VCEO Collector – Emitter Voltage –200V VEBO Collector – Base Voltage –5V IC Collector Current –15A IB Base Current –1.5A PC Collector Power Dissipation 150W TJ Junction Temperature 150°C And these are the ones that I think are suitable replacements; they have exactly the same dimesions. uk.farnell.com/magnatec/2sa1943-0/transistor-pnp-2-21f1a/dp/1218390?Ntt=1218390uk.farnell.com/magnatec/2sc5200-0/transistor-npn-2-21f1a/dp/1218389?Ntt=1218389When you say mount them back in the CORRECT place I assume you mean 1832 on one side of the board and 2013 on the other, and not in the same places that they came out of? If I am reading this correctly I mount the 4 good ones and measure the amp again, replace the fuses (which had blown) and if all readings are OK fire up and see if it works. The question is will it work with only 4 transistors in place and which four mountings on the board do I use? Also just out of curiosity have you any idea why there are two empty transistor mounting spaces on each side of the board? The transistors were a right PIG to get out and I managed to lift 3 pads on the top side of the board - is this a problem? See pic This pic shows one of the pads still attached to one of the transistors; can you buy replacement pads to fit in? The underside of the board is OK. Is this known as a double sided PCB board and do you have to solder both sides? Fingers crossed I haven't trashed the drive transistors. Sorry for all the questions Frans.
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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 23, 2012 19:28:06 GMT
Alex, I have just spent hours looking for replacement Transistors and I think I now understand what you were trying to say, I think it may have finally sunk into my thick skull Thanks again.
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Post by Deleted on Sept 23, 2012 21:29:01 GMT
Those are the ones I would use as a replacement, good find. When you say mount them back in the CORRECT place I assume you mean 1832 on one side of the board and 2013 on the other, and not in the same places that they came out of? You have removed 3 MAG2013 and they came out of the PCB. Simply mount the 2 good ones of those 3 back where they originally came out of. When you solder MAG2013 in the positions where MAG2813 came from it'll blow for sure. So... 2013 on the side they came out of and leave 1 position open. and... 2813 on the side they came out of and leave 1 position open. If I am reading this correctly I mount the 4 good ones and measure the amp again, replace the fuses (which had blown) and if all readings are OK fire up and see if it works. correct The question is will it work with only 4 transistors in place and which four mountings on the board do I use? It SHOULD work, just don't play it loud and use a speaker you do not value too much. Mount the 2 (on each side) on 2 of the 3 positions you lifted them from. Doesn't matter which ones. Also just out of curiosity have you any idea why there are two empty transistor mounting spaces on each side of the board? They probably designed it for four transistors but found 3 was more than enough. The transistors were a right PIG to get out and I managed to lift 3 pads on the top side of the board - is this a problem? Nope, the business end of the PCB (traces) is on the bottom. Only if you have traces on the top AND bottom side of a device you will need to solder on both sides when the internal bushings are gone. This pic shows one of the pads still attached to one of the transistors; can you buy replacement pads to fit in? The underside of the board is OK. Is this known as a double sided PCB board and do you have to solder both sides? Not needed, see remark above. Fingers crossed I haven't trashed the drive transistors. Lets hope they still are O.K., totally depends on HOW the transistors internally broke down. This is the only reason (mounting 4 back) to easily see if more damage has been done. If the amp works with 4 devices switch off and replace all of these transistors with the ones you selected (3 of both types) Make sure the PNP is replaced by the PNP devices and the NPN with NPN devices.
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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 24, 2012 20:50:05 GMT
Frans, I have mounted the transistors back in the board and taken new readings: MAG 1832 1. 495 & 143 2. 634 & 153 MAG 2013 1. 107 & 398 2. 109 & 393 And the new Bridge Rectifier readings: red pin on + (top left) and black pin on AC (top right) as nothing connected and on AC (bottom left). as nothing connected black pin on + (top left) and red pin on AC (top right) 535 and on AC (bottom left). 532 red pin on - (bottom right) and black pin on AC (top right) 498 and on AC (bottom left). 530 black pin on - (bottom right) and red pin on AC (top right) as nothing connected and on AC (bottom left). as nothing connected black pin on - Red pin on - 003 and red pin on + (top left). as nothing connected red pin on - black pin on - (bottom right) 000 and black pin on + (top left). 259 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 Do you think it is safe to mount the fuses and fire up
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XTRProf
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Pssst ! Got any spare capacitors ?
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Post by XTRProf on Sept 25, 2012 1:26:40 GMT
Chris, now is the time! Rope-a-dope, left-right jabs and finish off with a right and left cut and finally the "machine-gun" KO punches like IP man, the Sifu (Master) of Bruce Lee when he was younger and before he took shelter in the US, here: Don't go for round 3 ................ The video is a REAL heroic reenactment for the Chinese during the Japanese occupation of China, btw ...............
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Post by Deleted on Sept 25, 2012 5:58:12 GMT
The only 'strange' reading might be the red one, in reverse one can measure schottky protection diodes (I think). Still ver well possible the drivers have been damaged as well. This is not appearant from the measurements.
I hope you bought a box of fuses !
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Post by Deleted on Sept 25, 2012 6:23:24 GMT
Personally, I would be soldering some relatively low value PW5 resistors across some of the blown fuses, and using them to help limit any further damage during testing.(NOT on the AC input side, but after the rectifier bridge)
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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 27, 2012 16:23:36 GMT
Hi Frans, I have been busy but I finally got around trying the amp, it fired up 1st go without blowing the fuses. PHEW . I then tried it for about 30seconds with some music playing through a cheap speaker, and all seems well? Thanks a Million man. As this thread is repair and upgrade, I need to order some transistors to repair this amp, so while I am at it I may as well order some upgrade parts for both amps, but need a little advice first. Could you please advise me on upgrading the following components: Electrolytic Capacitor values, do I replace these caps with the same values or would there be better SQ with higher values? If yes what values would you recommend? Same with these Blue caps Same with these Red Caps
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Post by Deleted on Sept 27, 2012 19:34:48 GMT
Good to hear it is still working.
I have not been able to find some decent (and accurate) schematics for this amp. As far as I can see (a guess, but educated) it uses polar capacitors in the input stage and perhaps also in the feedback side. Can not say for sure though.
If it were my amp or design I would change those for either bipolar (electros) or non polar caps when the values are available. Perhaps an increase in value. Given the 5Hz -1dB spec it is highly unlikely there will be more bass extension, as in the V2 e.t.c. where it is severely under dimensioned and a change there will most defenitely lead to sonic improvements.
Also I cannot recommend to enlarge caps as I cannot tell where they are and what they do or if it adviseable.
For the more magic parts I am not your guy (religion prohibited so to speak), perhaps others can sprinkle that around.
I don't know how old the caps are and if they have been 'warmed' for long periods (does the amp run fairly warm/hot normally ?) and what the temp range is (85oC ?) If old (> 15 years) a replacement of some caps may be recommended.
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XTRProf
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Pssst ! Got any spare capacitors ?
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Post by XTRProf on Sept 28, 2012 11:33:45 GMT
Chris, Don't "upgrade" the caps all at one go. Replace the large ones first and then later go for the smaller ones. So I recommend a 3 stage "upgrade". First, large e-caps. Second, smaller e-caps. Third, all those film caps to PP or Teflon. As Frans had written, if you can find PP or Teflon film caps that are affordable to you to replace the e-caps that will be the best as film caps don't deteriorate with heat as fast as e-caps. More or less can use forever for the film caps. Also, the PP or Teflon also sound better. A personal guarantee from me! Favourite affordable "high-end" PP is Wima for many DIYers. Evox or Rifa also have PP. So if you do it in a 3 stage upgrade way, you will be able to hear for yourself whether there is any sonic improvement and be wiser nevertheless with this "upgrade". How big an e-cap you can "upgrade" to will be very dependent on the surge current the rectifiers and traffo secondary can supply. Too much surge current from the big caps, the bridge rectifiers and traffo secondary will suffer with long term reliability problem. A safe bet is 1.5 times the values from current values. I don't expect any designers will have a safety factor less than 1.5. Safety factor is the margin over what the component or circuit is designed for. Most important. Get something that can fit your PCBA space whether you "attack" the situation from top or bottom of PCBA. Also, be reminded that most e-caps are directional ie you have to see the -ve sign on the e-caps before you take them out. Put the "upgrade" in the same orientation when you solder back onto the PCBA. Else, you go back to army time bomb squad! Arghhhhh, round 3 ting? If you are know the amp sonic character VERY WELL before the upgrade, I'm very confident you will hear the difference (for better or worse ) with a new set of caps "upgrade".
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Post by Deleted on Sept 28, 2012 11:39:19 GMT
Consider upgrading 1 monoblock (in steps or at once) first and the other block AFTER you have completely modified the other one. This way you have some comparative possibilities.
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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 30, 2012 18:11:22 GMT
Consider upgrading 1 monoblock (in steps or at once) first and the other block AFTER you have completely modified the other one. This way you have some comparative possibilities. Frans, that's what I intended to do. I have just ordered the parts so hopefully over the next week or so I will repair and upgrade this amp. I decided to play safe and keep exactly the same values of caps, but of a higher 105 degree. The larger PSU caps are on order so I will have to wait till middle of Nov before they arrive. I will keep you posted. Thanks again.
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Crispy
500+
"Done me wrong," it's the same old song" - forever
Posts: 631
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Post by Crispy on Sept 30, 2012 18:20:20 GMT
Put the "upgrade" in the same orientation when you solder back onto the PCBA. Else, you go back to army time bomb squad! Arghhhhh, round 3 ting? ;D ;D ;D ;D No Way man, not going there[/size] ;D ;D ;D ;D Chong, I will PM you about the Hunger games as I am having a bit of bother with drop-box - will let you know when it get's sorted
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XTRProf
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Pssst ! Got any spare capacitors ?
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Post by XTRProf on Oct 1, 2012 6:54:12 GMT
Eh, what's wrong with your Dropbox? It's always in the Windows Explorer almost at the top on the left pane. Don't need to login into Dropbox website. Enjoy your upgrade! Actually, 1.5X is a very safe bet from experience.
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Crispy
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"Done me wrong," it's the same old song" - forever
Posts: 631
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Post by Crispy on Oct 1, 2012 16:19:44 GMT
Eh, what's wrong with your Dropbox? It's always in the Windows Explorer almost at the top on the left pane. Don't need to login into Dropbox website. Chong, I was having problems logging on to drop-box, it would not recognise my password. That is now sorted. The main reason I can't send you them straight away is that my allotted 2.5GB of space is full, I am sending my brother in Australia some TV programs to watch, but as soon as he has got them I will upload you them. Chris
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Crispy
500+
"Done me wrong," it's the same old song" - forever
Posts: 631
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Post by Crispy on Oct 5, 2012 19:38:01 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 Alex, I think I need your hep again Could you please tell me whether the Mag 1832 are PNP or NPN because I forgot to write it down I was soldering in the replacement PNP transistors uk.farnell.com/magnatec/2sa1943-0/transistor-pnp-2-21f1a/dp/1218390?Ntt=1218390 me on the Mag 1832 side when I had a horrible feeing that I had soldered them on the wrong side I have tried find out this information everywhere on the net but cannot find it - I must be tired. Thanks Alex. Chris
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Post by Deleted on Oct 5, 2012 20:02:07 GMT
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Post by Deleted on Oct 5, 2012 21:14:42 GMT
Click on the provided data sheet and check that the pinout and lead spacing is the same as the one being replaced.You also need to check the mounting hole location and width are the same,The complementary device is the PNP 2SA1943. I will look further after early supermarket shopping Alex
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Post by Deleted on Oct 5, 2012 21:53:41 GMT
Don't know if this is any help? Syd
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Post by Deleted on Oct 6, 2012 1:00:29 GMT
I have checked the data sheets for the 2SC5200 that Chris linked to . The 2SC5200 is a pin for pin replacement for the MAG1832, and I would expect that the 2SA1943 with the same case would also be a pin for pin replacement for the MAG2013 too.It may be advisable though to replace all of the existing MAG devices to be on the safe side.2SA1302 and 2SC3281 are other possible alternatives. The 2SA power devices are PNP types, and the 2SC power devices are NPN types. 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 Oct 6, 2012 12:59:24 GMT
I have checked the data sheets for the 2SC5200 that Chris linked to . The 2SC5200 is a pin for pin replacement for the MAG1832, and I would expect that the 2SA1943 with the same case would also be a pin for pin replacement for the MAG2013 too.It may be advisable though to replace all of the existing MAG devices to be on the safe side.2SA1302 and 2SC3281 are other possible alternatives. The 2SA power devices are PNP types, and the 2SC power devices are NPN types. Alex Thanks Alex, that has just confirmed my worst nightmare - I soldered the three new 2SA PNP (Mag 2013 replacement) where the Mag 1830 should be. It is a good job I checked with you first, at least I can de-solder them and put them in the correct place. Lesson learnt - don't try to do things when you are tired. BTW I did buy new replacements for all six transistors, I suppose I was in a rush to fit them in Thanks also to Chris and Juke for your input.
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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 Oct 25, 2012 15:11:13 GMT
Just a quick update. Mag NPN 2SC5200 in place, also Wima 4700uf & Panasonic 220nf polyprops. Welwyn 1w 39k resistor for blue LED in place. More Wima polyrops in place. All electrolytic caps replaced with same value 105 degree Rubycons. Just awaiting some Panasonic 6800 PSU caps to arrive from back order, then it can be tested and hopefully it will be singing out the music again
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