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Post by sometrolls2 on Aug 16, 2007 23:41:48 GMT
I just replaced the 327/337 transistors on top board( V1 Xcans), this removed a distortion/small bass problem, but has started a left channel buzz. I know the solution to the new problem has been posted before and have looked and looked.
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Post by PinkFloyd on Aug 18, 2007 19:52:14 GMT
I just replaced the 327/337 transistors on top board( V1 Xcans), this removed a distortion/small bass problem, but has started a left channel buzz. I know the solution to the new problem has been posted before and have looked and looked. Hmmmmmm...... how loud is the buzz? is it quite loud or a low level buzz? You've obviously swapped the valves around to rule them out I assume? A buzz on one channel can indicate a few things, by far the most common (and almost impossible to locate at first) is the quad phono socket... the ground legs that attach to the PCB have a tendancy to break after a while (with all the ins and outs) and the only way to find out if this is the case is to desolder the quad phono socket and check the legs, don't rely on a continuity test here, actually remove it and inspect.... if one of the legs is broken in two there is your culprit. I'm assuming your amp has got new caps on the PSU board? if not, are any of them bulging or showing signs of distress? I have found that replacing old caps on the PSU board can get rid of hum. Also check the headphone socket, pull the jack out slightly, does it still hum? before I type screeds of stuff it would be best if you explain exactly what you have done to the amp, what the initial fault was that led to the 327/337 being replaced and how would you explain the hum..... ie: low level, loud etc. etc. Is the hum only at noticeable at zero volume levels and not too noticeable when you listen to music or does it hum even with music being played? Have you swapped your interconnects over to establish they are ok? Have you connected right to left and left to right from your source to ensure it's ok? If not, then best to check these things. |
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Post by sometrolls2 on Aug 18, 2007 23:59:41 GMT
I fitted the caps set and that was fine, then did diodes and left a blob that made a connection that should have not been there, I think is was D1 and the non polar. Found that and corrected it and installed some regular slow diodes, but it had created a distortion problem which is associated with bass.
So changed tubes and problem still there. On PSU board replaced non-polar cap and caps by the regulators, problem stll there. Replaced transistors and now have buzz which is loud with no signal but does disapear behind the music somewhat. However previous loss of bass corrected. Replaced jack with Jalco, and buzz still there.
Also tried using output as input, which does get a signal to the headphone jack, same noise; Swapped tubes; swapped phono leads around; had source turned off.
The soldering on the phono sockets looks like new. I assume something broke and is now partially working, with the thing to replace after the transistors being the regulators( have spares), and then onto the lower board. TR2 does have a spare hole/pad, I could be getting a contact between that and the other legs, its very hard to see, I wondered which transistor and regulator was for the left channel. Could that TR2 pad just be removed?
I could change all the PSU caps as I have spares, but don't really want to do that as a first resort. If the jack is pulled out when powered up, I get violent crackling sound down the phones.
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Post by PinkFloyd on Aug 19, 2007 10:35:56 GMT
Maybe it looks like new but have you physically removed the phono block to check the ground leg hasn't broken? Believe me this DOES happen.... please check it, it's easy to do.
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Post by sometrolls2 on Aug 19, 2007 19:54:24 GMT
Phono inputs removed and they look fine, it has a ground leg for each channel and they both look fine. Changed the regulators and the buzz has dropped an octave and is clearly stronger at lower volumes than higher. I have some Russian EBs coming, so that should let me test with tubes that are definitely working.
I already have Samwha caps that could be used to replace the PSU board polars, after that I dunno.
Could this kind of signal be tested for using a multi meter?
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Post by PinkFloyd on Aug 19, 2007 20:27:44 GMT
I missed that bit. So you fitted a new set of caps and all was working perfectly correct? You then fitted the UF4007 diodes, powered the amp up and noticed this buzzing / hum? You then noticed that there was excess solder on one of the diode pads that was bridging to a pad it shouldn't be correct? Have you checked that all the diodes are the correct way round? ie: the silver band on the diode body corresponds to the black band on the PCB? One thing's for sure, whatever the problem is, it is isolated to the PSU board so go over that board with a fine toothcomb. Before you replace anything else double and triple check everything is the right way round. Then go around every pad you have touched and heat them up till the solder melts (with a hot soldering iron) and feed in a small amount of fresh into each joint until it flows like water. Could be the DC filtering is compromised by a dry joint somewhere. Believe me, when you do find the culprit you'll kick yourself...... 9 times out of ten it's either a dry joint or or a pad that "looks" good but has actually parted company with the track. I assume you have already done a continuity test from pad to pad to establish there are no breaks? It could be a number of things but chances are it's a simple thing like a dry joint or a pad that has a hairline crack between it and the track. Don't worry though, it won't be anything major..... just a case of finding the culprit and I bet you a pork pie it's not component failure  |
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Post by sometrolls2 on Aug 19, 2007 21:05:08 GMT
Fitted ultra fast diodes, with blob, then sound became thinner with distorted bass.
So went back to a new set of regular diodes and the problem was still there, so I assume that something had been damaged. Changed tubes and still there. Changed PSU transistors and the whole thing shifted to buzz/hum on left channel, yet the distortion+thinness problem seems to have gone.
Changed regulators and noise is a little more controlled, so maybe that needed doing anyway.
Will start on resoldering and pad investigation with the top board.
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Post by PinkFloyd on Aug 19, 2007 21:49:50 GMT
Good move |
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Post by sometrolls2 on Aug 20, 2007 6:32:33 GMT
Found a the track lifting and damaged by caps 12/11, used a big solder blob and a spare diode leg to bodge a fix and it is 90% better, from unuseable to a problem with very quiet sections. Those caps get knocked when removing the 5 pin connector, so probably just accumulated damage to their track. I'll replace the the Panasonics 35/1000 with spare Samwha 25/470 and try connecting the legs directly.
An odd thing is that with no signal as the volume is turned way up the hum/buzz moves around the soundstage, is this revealing an issue with the pot?
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Post by PinkFloyd on Aug 20, 2007 20:40:08 GMT
Found a the track lifting and damaged by caps 12/11, used a big solder blob and a spare diode leg to bodge a fix and it is 90% better, from unuseable to a problem with very quiet sections. Those caps get knocked when removing the 5 pin connector, so probably just accumulated damage to their track. I'll replace the the Panasonics 35/1000 with spare Samwha 25/470 and try connecting the legs directly. An odd thing is that with no signal as the volume is turned way up the hum/buzz moves around the soundstage, is this revealing an issue with the pot? Ok, that's solved that problem. As I said earlier, things to look out for are pads that have parted company with the track.... you've found one such pad and it's now 90% better. Now go over the PSU board again and see if you can find any other solder joints which need attention. I assume you've got the amp back in it's enclosure when listening? If not there will be a slight degree of noise due to RFI,as soon as you put the boards back in the enclosure it will disappear. Mike. |
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Post by sometrolls2 on Aug 21, 2007 5:21:38 GMT
Its not solved as such, I have a marantz CD player so I can turn the player volume down, XCans volume up and in the interim get by. I've ordered a solo and psu and intend to compare that with the modded XCans and keep the winner for the best part of a decade, with the expectation of selling the defeated XCans; so I really need to get the thing working properly.
The pad and track by C12 is totally gone, and soldering cap legs together and then cap leg to diode hasn't improved things further. Is there some track replacement stuff that can be layed, painted, drawn, stuck etc?
Also get change in buzz when I touch the front panel or bare volume control - a grounding issue?
Does it seem plausible that the non-polar caps would be damaged by a short circuit of some kind due to the blob?
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Post by PinkFloyd on Aug 21, 2007 9:22:50 GMT
Tell you what, send me the PSU board and I'll sort it up for you.
Mike.
(PM me)
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Post by sometrolls2 on Aug 22, 2007 3:16:41 GMT
Thanks will do, I'll sort out the packing and anything worth sending with it some.
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Post by PinkFloyd on Aug 22, 2007 9:12:31 GMT
Thanks will do, I'll sort out the packing and anything worth sending with it some. Please don't send me your entire systen.... just the boards |
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Post by sometrolls2 on Aug 22, 2007 19:14:05 GMT
I will, but was going to bundle whatever relevant spares I have as a form of wholey inadequate appreciation. And maybe even a really good pork pie.
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Post by PinkFloyd on Sept 15, 2007 15:14:31 GMT
What a friggin' MESS man!! WTF were you using to solder with...... a fckin' branding iron?? No, you didn't. You fitted a BC 237 and a 32725 and not only that you fitted the 32725 where a 33725 should have gone. I have fitted new BC33275 & BC32725 in their correct position. Your next monumental cock up was to fit two 7815 regulators instead of one 7815 and one 7915. Left channel buzz?? I'm surprised this contraption worked at all! Lifted pads under mammoth BLOBS of solder, wrong components in place..... an absolute disaster zone man! This is no way to solder!  Firing huge blobs of molten solder onto a pad is going to do nothing but harm and will be covering up problem areas like pads parting company from track (which has proven to be the case) I bloody well hate going over these bodge ups as you can never get the boards "looking good" again once someone with a branding iron and three ton of molten solder has been at it Fortunately I've managed to get it to sound good again and your hum is gone and she's firing on all four cylinders. I'll leave her on test for a few hours and get her back to you on Monday  |
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