allenf
250+
tangled up in blue
Posts: 287
|
Post by allenf on Nov 28, 2007 17:46:50 GMT
Hi All. I secured a v2 off the bay. This one has been repaired by Musical Fidelity in Jan and Feb 2007 with new valves and transistors according to the check lists I have. And they fitted a purple led while they were in there  At some point the valves have been swapped to Ei ECC88, and the amp sounds great. I opened it up after 3 hours "soak test" and everything was barely warm to the touch  But is that amount of scorching on the pcb normal for a v2  |
|
|
|
Post by PinkFloyd on Nov 28, 2007 18:09:59 GMT
Hi All. I secured a v2 off the bay. This one has been repaired by Musical Fidelity in Jan and Feb 2007 with new valves and transistors according to the check lists I have. And they fitted a purple led while they were in there At some point the valves have been swapped to Ei ECC88, and the amp sounds great. I opened it up after 3 hours "soak test" and everything was barely warm to the touch But is that amount of scorching on the pcb normal for a v2 That's a tad excessive (the scorching) and usually you'll find it may scorch directly beneath the transistors. I've seen scorching at those points before but never to that degree. As long as the parts have been replaced and the amp is working fine and not running as hot as toast everything should be A OK. It would be interesting to see what the PCB tracks look like any chance of a picture of the underside of the PCB? Looks like diode, a couple of the resistors and transistor on the PSU board may have gone tits up at some stage. Mike. |
|
allenf
250+
tangled up in blue
Posts: 287
|
Post by allenf on Nov 28, 2007 18:29:47 GMT
Fast reply Mike - cheers! I'm emailing you now about modding |
|
|
|
Post by hooograa on Dec 4, 2007 6:47:38 GMT
I had the same thing happen to my V2 in the same place (burnt all the resin leaving charred fibers under the mosfets, power regulator and resistors). I had to reconstruct the PCB tracks with component leads too. I found that if any of the tracks had lifted they would add hum to the background and distortion to the high end. If your handy with a soldering iron look for loose components if you find any gently scape the lacquer off the track and add solder or a component lead and solder. Two years down the track and it sounds better than ever thanks Pinkie. David
|
|
allenf
250+
tangled up in blue
Posts: 287
|
Post by allenf on Dec 4, 2007 9:45:43 GMT
Cheers David, mine's on its way back from the Grotto having had a generous sprinkling of the magic Pinkie dust  |
|
allenf
250+
tangled up in blue
Posts: 287
|
Post by allenf on Dec 5, 2007 12:30:08 GMT
 Mike has done the caps and diodes, headphone socket, pot and knob mod, and cleaned up the Musical Fidelity repair job from the meltdown. I can say for sure that having been powered up (standard wall wart supply) for just an hour or so the amp sounds much cleaner and less euphonic (tubey) than pre-modded, a very natural extended balance with perfect left-right placement and a HUGE headstage that tapers out from centre without any gaps. Nothing is exaggerated in any way, it is just a really nice sound that doesn't sound "detailed" but IS detailed and layered. The amp's noise floor is very low - silent in fact. There is no induced interference from a 2.5G mobile phone, nor laptop screen refreshes or hard drive activity, the kind of stuff that plagues my Little Dot valve amps. For reference I also have to hand a Little Dot 2, a Little Dot Micro Tube with the 4 x 634 buffers and Vishay resistors, an early Supermacro V1 with 627 and 634 opamps, a standard Go-Vibe V5, an Xtra X-1, and headphone outs on my Cyrus 1 Mk 2 and Audiolab 8000S. Source is Foobar 2000 on my laptop playing red book CD via usb-audio.de ASIO to a headroom Micro DAC. Thank you Mike! We are not worthy  |
|
mrarroyo
Been here a while! 
Our man in Miami!
Posts: 1,003
|
Post by mrarroyo on Dec 5, 2007 21:57:25 GMT
I had a Little Dot Micro Tube just like yours allenf! It was a sweet little unit specially for under $200. But the MF X-Can V2 is IMO superior.
|
|
|
|
Post by PinkFloyd on Dec 5, 2007 22:45:22 GMT
Hi Allen, Glad she arrived safely and happy you like the sound, pleease do give her a good while for the caps to form and then the magic really will start to happen A few pics of the guts:  Nichicon Fine Gold on board  Pana FM / FC, EVOX and UF4007 ultrafast diodes  ALPS 50K pot, purple LED and Jalco pro headphone socket  Front panel   Let us know what she sounds like after a week or so Allen. All the best. Mike. |
|
leo
Been here a while!
Team wtf is it?
Posts: 3,638
|
Post by leo on Dec 5, 2007 23:58:30 GMT
Very nice!
Wouldn't mind having a listen to one of the modded X-cans, I've only heard somebodys stock units of the V2 and V3
|
|
mrarroyo
Been here a while!
Our man in Miami!
Posts: 1,003
|
Post by mrarroyo on Dec 6, 2007 0:01:34 GMT
leo if you move to the USA or GB you could borrow one from me or Mike.  |
|
leo
Been here a while!
Team wtf is it?
Posts: 3,638
|
Post by leo on Dec 6, 2007 0:09:37 GMT
leo if you move to the USA or GB you could borrow one from me or Mike. Soon as I get some spare cash I may just buy one and get one of Mikes kits. |
|
XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
Posts: 5,689
|
Post by XTRProf on Dec 6, 2007 1:54:32 GMT
Hi all, If the PCB and tracks are scorching for certain areas, can also consider a mini computer fan, with power tapped from the PS rail internally, fanning the affected part. Of course, you have to drill some holes in the casing for the draft to come in. I'm not sure whether this will cause motor noise picked up by the amp circuit. But, if AC, this could be a problem. Do it only when you know what you are doing, btw. |
|
allenf
250+
tangled up in blue
Posts: 287
|
Post by allenf on Dec 6, 2007 8:25:13 GMT
I had a Little Dot Micro Tube just like yours allenf! It was a sweet little unit specially for under $200. But the MF X-Can V2 is IMO superior. I know Miguel, partly based on your and jamato8's recommendations on the Buy-Fi I bought it! The Micro Tube IS quite a nice unit for the price, especially good at driving the Alessandro cans at low volumes (though it does do "Loud" but not "Scale" alas..). And the Little Dot 2 is quite fun too. The V2 is in a different league. I feel I have come full circle. My first decent cans were HD650s. They lasted about as long as it took to buy some Grado SR80 love and got sold. I then got the Alessandro MS2is and sold the Grados. I then bought the Beyer DT770 PRO 80 ohm and DT990 PRO 250 ohm. I then bought the Equation Audio RP21s (thanks to Miguel and his mods again ) and sold the DT770s. This chain of events occurred over a three year period, and I OUGHT to be happy with the DT990s (which I really like), but I have a hankering to go back to the HD650s as I hear they work extremely well with the X-Cans (and will complement my Alessandros which are keepers for life). Gratuitous moody Aluminium knob shot (pinched off my Go-Vibe):  |
|
allenf
250+
tangled up in blue
Posts: 287
|
Post by allenf on Dec 6, 2007 8:29:24 GMT
Hi Allen, Glad she arrived safely and happy you like the sound, pleease do give her a good while for the caps to form and then the magic really will start to happen A few pics of the guts: <images of superb workmanship snipped> Let us know what she sounds like after a week or so Allen. All the best. Mike. That's great work there Mike, Thank You. After Xmas I'll be back for a Little Pinkie PSU.. Cheers. |
|
allenf
250+
tangled up in blue
Posts: 287
|
Post by allenf on Dec 19, 2007 20:05:33 GMT
Bumping this thread with some updates. I work from home 4 days a week and listen to the "headphone rig" while working, at low to medium volume for 4 to five hours in the morning and an hour or so in the evening. I am trying really hard not to get all enthusiastic and FOTM with myself about my modded V2, but I'm obviously not trying hard enough ;D I can't add anything more to what I've already said previously in this thread apart from noting the lack of ear fatigue after a good session with the DT990s, the V2 is really good at that. As a stopgap until I order a Little Pinkie PSU I bought an inexpensive 12v AC 3000mA psu from my local Maplin: www.maplin.co.uk/Search.aspx?criteria=l54br&source=15&SD=YUnfortunately this supply has created a heat issue, I'm paranoid about this - see thread title The standard wallwart power supply tests @ 13.1V unloaded and gets really hot but the V2 itself runs barely warm, just enough to tell it is switched on. The Maplin supply tests @ 14V (which doesn't drop under load, tested) and runs moderately warm but the V2 gets noticeably much warmer on standby, hot enough to warrant investigation. So I opened up the V2 and could smell those new caps burning in..  The valves & caps were not hot enough to burn your fingers (and not as hot as my Audiolab 8000S which has been left switched on more or less continuously for 12 years and runs very hot for an idling SS device) but hot enough to halt the experiment until I have done the case vent mods that Mike has described elsewhere. Which is a shame as I could detect sonic benefits with the new psu, specifically a reduction in clutter with really congested musical sections. I'm wondering how and why an extra volt or so could make such a difference to the standby temperature, maybe the extra voltage is immaterial but the higher capacity psu is allowing the amp to draw more current on standby or something..? |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Dec 19, 2007 23:44:38 GMT
allenf
You have just found the main problem with having a much higher rated transformer of that type. Don't use it if you don't want valve life shortened considerably, and other components
stressed. 14Volts is far too high ! Ventilation should already be adequate when using a
transformer of the correct ratings. If you know what you are doing, it may be possible to reduce the filament voltage with a series diode or a higher value series resistor in the filament circuit. The extra HT voltage may even be a small bonus. Mike should be able to give you more specific advice.
SandyK
SandyK
|
|
