xerxes
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Post by xerxes on Nov 15, 2006 22:15:40 GMT
The Corda Headamp-1 build is well under way: More picturesBar the case, the mains and the input RCAs it's pretty much there. The build went pretty smoothly; the Welwyn RC55Y resistors were a bit tricky to fit as the body of the resistor is a fraction longer, perhaps a millimetre, than the PCB holes are spaced apart. The body of the large 5w resistor was also too large to fit in the space between the adjacent components, but other than that, no problems. Many thanks to the sponsors of this project, Mike and Rick, for their generous donations.
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Post by PinkFloyd on Nov 15, 2006 23:15:22 GMT
beautiful workmanship xerxes! superb looking job indeed. That resistor will fit but you'll have to bend the legs a bit: or, even better, fit the 220nF under the board : Looking great xerxes!
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Post by PinkFloyd on Nov 15, 2006 23:20:15 GMT
By the way, you're probably on top of the connections but, if not, here you go:
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xerxes
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Post by xerxes on Nov 15, 2006 23:56:06 GMT
Thanks Mike,
With regard to the big 5w resistor, I had already installed the little 220nF cap that's immediately behind it, so there' was no room to move it back. I only orderered the exact number of caps required and I've already snipped the excess lead off, so I can't really de-solder it and mount it laid over on its side undeneath the board.
The leads of the 5w resistor just about reach through the holes in the board, so it should be OK. ;D
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rickcr42
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Post by rickcr42 on Nov 16, 2006 0:13:26 GMT
not that there was even a hint of doubt on my part but this hammers home that not only was "sharing the wealth" the right move but the recipient of the board the right choice.Call it Karma or destiny,whatever,the board was meant to go where it is with the proof being the rapid project start and forum sharing. I had it for months and did nothing.Owen for a couple of days yet is close to an actual amp. Damn nice job man.You are definately an asset around here in the backwater of audio DIY electro-erotica (or is that "asset" without the "et" ? Or is that maybe a slip being more self descriptive than witty ? Hmmmmmm..........may need to think on this with some hallucinegenic assistance.......where is that tree carver dude....... )
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xerxes
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Post by xerxes on Nov 16, 2006 0:43:17 GMT
I've been itching to build something "from the board up" for some time, so when it arrived I got cracking. I'm itching to hear it as well, so provided the op-amps turn up, I should finish it tomorrow. I was a bit worried that I might make a bit of a pigs ear of the soldering, but I seem to have picked up the knack easily enough; all the joints are nice and shiny and "volcano shaped". Having built this, in the future I definately won't be put off building something that is only available as a board or kit and not as an assembled module, although I might give the stuff with lots of tiny surface mount components a miss.
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rickcr42
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Rest in peace my good friend.
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Post by rickcr42 on Nov 16, 2006 1:24:27 GMT
Cool can't wait to read the review
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Post by PinkFloyd on Nov 16, 2006 16:30:30 GMT
x2 and it also looks like he's actually soldered the buf-634 in and not hammered them into position excellent stuff! What are you going to house her in Owen?
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xerxes
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Post by xerxes on Nov 16, 2006 17:25:44 GMT
The LM6171s, in the right package this time, turned up today, so all will be revealed very shortly.
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Post by PinkFloyd on Nov 16, 2006 18:47:12 GMT
The LM6171s, in the right package this time, turned up today, so all will be revealed very shortly. Nice one man, can't wait to see it
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xerxes
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Post by xerxes on Nov 16, 2006 20:27:06 GMT
The good news is, I've finished: More PicturesThe bad news is, it doesn't actually work. I get power, there's a feint "bong" through the headphones when I switch it on and the led lights up, but I can't hear the music etc. In fact it's completely silent, even with the volume turned all the way up, not a sound. What could I have done?
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rickcr42
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Post by rickcr42 on Nov 17, 2006 0:40:31 GMT
First-make sure you are getting a proper voltage/polarity out of the regulators.If the power is not right nothing else will be
Second-recheck your solder flows around the heavy metal parts like jacks,volume pot,etc.
Third-if the above two check out try tapping the signal at the output of the opamp (befor the buffer stage)and sending that to your cans
all about process of elimination and that begins at the power source which in turn leads to the likely suspects then on to the twilight zone shit,step ;D
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xerxes
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Post by xerxes on Nov 17, 2006 0:55:10 GMT
Hi Rick, All the solder joints should be good, I checked them very thoroughly as I added the components. Looking at the circuit diagram: The fact the the LED light would suggest that everything up to there is OK, yes? I guess the buffers are the main area for suspicion, these were the most awkward things to solder. Could I have overheated them? How would I go about checking them with a multimeter? I've been looking at the circuit diagram for the BUF634s, the pins are from left to right: BW | Vin | V- | V0 | V+ Would I be correct that I should have: +15v betwen V0 and V+ -15v between V- and V0 ?
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rickcr42
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Rest in peace my good friend.
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Post by rickcr42 on Nov 17, 2006 2:21:44 GMT
in thse days of PB/No PB parts,leaded/lead free solder regular technique and visual inspection may not be enough. To check for bad joints try using an ohm meter to see if you in fact have a good connection (zero ohms or damn close to) or a reading in the ohms range which signals a high resistance contact hence a cold or cavitated joint. Place the red probe right in the RCA jack "hot" thentest for zero on the pcb trace leading from it for your test point. For the volume pot clip to the 1K resistor on the input filter circuit (cap/R/Cap) and the 2K2 series resistor leading to the opamp "+" input and with power OFF rotate the pot.If the ohms readin varies you are good to go Do both the above for each channel one at a time. Next if that checks out hold the pcb up to a bright light and look "through" the board to see if there are any solder bridges or missed connections.you would be surprised how much a back lit pcb exposes that is easily missed with top viewing/top lit if all the above check out disconnect the OPAMP SIDE of the 100 ohm resistor between the opamp and the buffer and gently bend it straight up. Now comes the fun part : Test A-The Opamp :AMP OFF !Use a jumper wire (spring loaded probe tip clip wires would be nice but likely you have none ) from the opamp output pins,both L and R to an off board TRS jack (headphone jack),connect the common ground of the jack to any available pcb ground point,power up then listen.If this checks out then the buffer is the problem Test B-The Buffer :Amp OFF !Connect a jumper wire (again spring loaded probes are a real help here) directly to the jack side (where the 47K input Z load set meets it) of the 2K2 resistor (This is effectively a straight wire connection to the input jack) then the other end directly to the 100 ohm buffer input resistor you previously disconnected at one end from the pcb.This bypasses ALL circuitry between the input and the buffer.Power up and listen.If it works the problem is before the output stage,if not likely the actual output jack has a problem or the power supply is not right. This process of elimination is kinda sorta how we did it in the old days but then we used (and I still do ) and signal injector and mini amp/speaker hooked to the output to trace an audio circuit from back to front so would inject a signal to the input of the output stage and if we get "tone" work backwards to the input until we get silence which identifies exactl where the signal is being blocked hence the bad stage I assume you are getting +/-15 volts of course and that the problem is common to both channel AND that the test source is a known good source AND the interconnects have been checked out AND the test cans work...........
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Post by PinkFloyd on Nov 17, 2006 11:54:21 GMT
Neither did mine first power up and it was those buffers not adhering to the pads that was the problem. Probe from each of the buffer legs (on top of the board) to the next component along to ensure you've got continuity.... just because the solder joint "looks" good doesn't mean it is good with these bastards, in fact I got so fed up with them I ended up smashing f**k out of them with a hammer ;D
Failure to fire up can be attributed to a lot of things and usually the last thing you look at..... 8 times out of ten I've found it to non amp related such as dodgy inteconnects, shagged headphone cord etc. so, as Rick says make sure everything is going "in" to the amp as it should. Get a magnifying glass and double check each and every joint and track...... you mention a "thump" at turn on, I assume you have checked the DC offset before plugging the phones in??
Check the offset by turning your multimeter to the DCV range and probe between ground and left (at the headphone socket pads) and ground and right.... the reading you should be getting is a few millivolts and not a few volts so if your meter doesn't show anything when set on the 200mV range crank her up to 2V or 20V and see if you get a reading.... if there are VOLTS at the output then we can probably have a better idea what's causing the problem.
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Post by PinkFloyd on Nov 17, 2006 13:25:08 GMT
Also, are you sure you got the right switch for the crossfeed, the right headphone socket etc.? Probably a minor thing here xerxes and when you find it she'll fire up no probs
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Post by PinkFloyd on Nov 17, 2006 22:14:52 GMT
What's happening xerxes? keep us updated! You haven't gone at it with a hammer, yet, have you?
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Nov 17, 2006 22:15:13 GMT
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Post by PinkFloyd on Nov 17, 2006 22:17:08 GMT
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Nov 17, 2006 22:24:36 GMT
What's with this cross-posting crap Mike ? I am in the middle of responding,hit "post reply" and find what ? that some other knucklhead beat me to the same exact point is what !!!!!!!!!!! this shit will NOT be tolerated bucko ;D
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Post by PinkFloyd on Nov 17, 2006 22:35:32 GMT
What's with this cross-posting crap Mike ? I am in the middle of responding,hit "post reply" and find what ? that some other knucklhead beat me to the same exact point is what !!!!!!!!!!! this shit will NOT be tolerated bucko ;D It's called fastest finger on the button, wisest arse (ass) pips not so wise arse at the post, tortoise beats hare......... just one of those things Rick, I can't help being cool and classy and hitting the nail on the head with one suave and sophisticated blow of the hammer..... Fastest finger on the button.... the colonel does fast chicken, I do fast finger.
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Nov 17, 2006 22:39:18 GMT
called "finesse" dude.I am more a "Hit it with a friggin' Sledgehammer" single blow and done with it type a guy myself
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Post by PinkFloyd on Nov 17, 2006 23:38:19 GMT
called "finesse" dude.I am more a "Hit it with a friggin' Sledgehammer" single blow and done with it type a guy myself You run the risk of destroying your entire keyboard with a sledgehammer. The "fastest finger" technique is not only keyboard friendly, it also delivers an almighty payload without having to resort to brute force.... quite amazing what a finger in the right place can achieve
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Post by PinkFloyd on Nov 17, 2006 23:50:28 GMT
Enough of making light of Owen's "failure to start" hiccup. Owen, I've been there quite a few times and you will get her up and running. Duff components are pretty rare these days (especially the ones you've got on board) so it's 97% possibility it's either a wrong value in a wrong place or a dry joint / short somewhere.
I can't remember any abnormalities or secret jumpering of the PCB when I put mine together, so no gremlins with the PCB itself, pretty much plug and play....................... apart from the buf 634 which just didn't want to make contact with the pads. By the way, the Buf 634 I sent you should accept solder easily they were part of the second batch I ordered.
Times like this all I can say is "good luck" finding the gremlin as it's impossible to diagnose something unless it's in front of you (even then, sometimes hard) Look for the least obvious and you'll probably find the culprit.
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rickcr42
Fully Modded
Rest in peace my good friend.
Posts: 4,514
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Post by rickcr42 on Nov 17, 2006 23:50:34 GMT
wouldn't be the first time WHAMMO !Keyboard toast plus a trip to Office Max
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