Cartridge failiure
Im having a right nightmate at the moment trying to locate a fault. Iv'e built a op-amp phono stage, well a kit anyway thats worked fine for a couple of year's or so i thought!
On a couple of occasions iv'e had one channel of the cartridge go down..ie no sound at all..when iv'e switched on..and Len gregory's MM mkii are expensive to say the least.
Im having a right nightmate at the moment trying to locate a fault. Iv'e built a op-amp phono stage, well a kit anyway thats worked fine for a couple of year's or so i thought!
On a couple of occasions iv'e had one channel of the cartridge go down..ie no sound at all..when iv'e switched on..and Len gregory's MM mkii are expensive to say the least.
Sorry i forgot this bit...
My pre amp is passive diy home brew, which has a selector switch made up of three wafer's. One for channel and the other operates a row of blue led's, just so i know what's in use ie cd,tuner, phono..etc...
Could it be that DC from the led wafer nearest to the phono input is some how tracking across, and feeding back through the phono stage into the cartridge, bearing in mind that only one channel blows.
My pre amp is passive diy home brew, which has a selector switch made up of three wafer's. One for channel and the other operates a row of blue led's, just so i know what's in use ie cd,tuner, phono..etc...
Could it be that DC from the led wafer nearest to the phono input is some how tracking across, and feeding back through the phono stage into the cartridge, bearing in mind that only one channel blows.
Hmm.... failure of either 15 volt regulator that supplies the OPA137 could cause a DC presence on the input connector.
Much more likely IMO is some intermittent short circuit.
Another thought is intermittent SCR latchup occuring on the OPA137 during power-up. C23 and C24 (10uF) are for ripple rejection, but also cause slow power-up. If they are not the same value, ie one has dried up, it could cause a problem. Also, check to see that the power wiring is identical between channels.
Hugo's idea of input caps sounds good to me, but don't make them too big
Much more likely IMO is some intermittent short circuit.
Another thought is intermittent SCR latchup occuring on the OPA137 during power-up. C23 and C24 (10uF) are for ripple rejection, but also cause slow power-up. If they are not the same value, ie one has dried up, it could cause a problem. Also, check to see that the power wiring is identical between channels.
Hugo's idea of input caps sounds good to me, but don't make them too big
Actually, there are parasitic SCR's (or thyristors, as we call them here) all over the place in any integrated circuit with a semiconductive substrate, and almost all IC's have a semiconductive substrate. Some IC's have more sensitive SCR's than others, though. Some of the SCR's are connected straight between the positive and negative supply lines and can cause the IC's to self-destruct in seconds when the power supply is powerful enough.
About 20 years ago I had an Ortophon cartridge. Can't recall the number, it was quite expensive for me in that time, around €200. It broke just a few weeks after the warranty period. I went to the shop and they told me that the warranty period was over. So I bought a new one, I was fairly happy with the sound. About nine months later the cartridge broke again, same problem, one of the channels died. Again I went to the shop and this time I had more luck with the warranty. The man told me it would take a couple of weeks to get things fixed for me. After a few weeks I phoned the guy but no one answered. It turned out the man had stopped his business, and retired. I never got the problem solved. Much later I heard that those cartridges had a production problem and most of them get broken within the year or so.
/Hugo
/Hugo
Linn and MM mkii
Thanks guy's
I've thought about contacting White Noise, as Alan quite correctly spotted the design. However i thought the prob was with the cartridges at first, as both two Music makers have gone and a linn K9
So thats what 's kind of bugging me..as it worked fine on my old Myryad int amp..but now plays up on my Willams Hart system. Its a shame because im missing vinyl replay, and not to blow Len Gregory's trumpet to much, but his MM mkii is one of the best carts around, plus he's a top bloke.
Im also thinking of building the Williams Hart phono stage..should'nt cost too much as iv'e got most of the bits for one anyway. And it goes hand in hand with most of the other kit's from that range.
Thanks guy's
I've thought about contacting White Noise, as Alan quite correctly spotted the design. However i thought the prob was with the cartridges at first, as both two Music makers have gone and a linn K9
So thats what 's kind of bugging me..as it worked fine on my old Myryad int amp..but now plays up on my Willams Hart system. Its a shame because im missing vinyl replay, and not to blow Len Gregory's trumpet to much, but his MM mkii is one of the best carts around, plus he's a top bloke.
Im also thinking of building the Williams Hart phono stage..should'nt cost too much as iv'e got most of the bits for one anyway. And it goes hand in hand with most of the other kit's from that range.
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