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Post by ben on Nov 5, 2014 21:06:42 GMT -6
Alliteration aside, one of my MK-U47's is not switching patterns. I'm kind of a noob on trouble shooting these things. Where should I start? I don't know if it's the switch or something else.
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Post by svart on Nov 5, 2014 22:21:39 GMT -6
The MK-47 has a relay on the inside of the mic that connects the front and back skins. Take the body off, plug the mic in and switch the pattern switch to see if the relay is clicking.. That would be test #1.
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Post by tonycamphd on Nov 6, 2014 1:25:36 GMT -6
and be VERY CAREFUL, high DC voltage!
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Post by jeromemason on Nov 6, 2014 3:35:57 GMT -6
Yeah please be careful.... there could be as much as 150v near that maybe more.... I'm not familiar with that exact mic, but those 47's use some juice and there's a lot of it right around that area.
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Post by Deleted on Nov 6, 2014 6:14:10 GMT -6
Most probably it's the relay. Check like svart proposed.
Highest voltage as of the specs of Max' design is 160V DC, which is sufficient to give a deadly shock (>60V is already "problematic", no matter how much electrical power...). So you better have good ears and stay away far enough with your skin...stay safe.
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Post by svart on Nov 6, 2014 7:46:05 GMT -6
Also, I thought about it some, and the relay might be a reed type relay, which you probably won't hear much of a click, so do it where it's really quiet.
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Post by ben on Nov 6, 2014 10:26:58 GMT -6
Yeah, I learned the hard way the other day that the PSU packs a jolt. Luckily, it was unplugged lol.
The relay works. To be sure, I connected the other PSU, and the mic body works fine. Both mic bodies test fine with the good PSU. So, It must be something in the PSU? It sounds like the broken PSU still trips the relay, just no pattern change.
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Post by Deleted on Nov 6, 2014 10:41:09 GMT -6
So,
can you...with all caution...measure the DC voltage with the apparently faulty psu at the test points, where it reads "160V" in Max's schematic? (isolated crocodiles or so...)
What's the real voltage there?
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Post by ben on Nov 6, 2014 11:22:33 GMT -6
So, can you...with all caution...measure the DC voltage with the apparently faulty psu at the test points, where it reads "160V" in Max's schematic? (isolated crocodiles or so...) What's the real voltage there? The only test point I see is the B+. It reads 109 (should be 105) without the mic attached. Would that be enough to cause a problem? Any other test points? |
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Post by Deleted on Nov 6, 2014 11:42:00 GMT -6
D'oh,
thank you for asking back - i looked up a wrong schematic on my harddrive...
But OK, nevertheless - check the voltage B+ *with the mic attached*...
Maybe the error in the psu can be tracked down to a voltage change while having the actual load.
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Post by jeromemason on Nov 6, 2014 11:48:16 GMT -6
B+ is the voltage that is sent to the microphone, are you sure it's supposed to only be 105v? If the is 160v stated on the schem0 then I would think b+ would be up there.
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Post by ben on Nov 6, 2014 11:51:12 GMT -6
with the mic plugged in, it goes to 67v. The mic works fine in cardioid though. No change when I switch patterns. I'm going to check the schematic later today. Maybe I have a wire out of place on the 7 pin.
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Post by Deleted on Nov 6, 2014 12:52:18 GMT -6
OK,
i want to clarify...
160V - this was my error.
B+ pin should read 105V to ground. A few volt more or less are not that critical.
Pattern pin should read 48V or 0V to ground when switched.
That's what i read from the correct schematic.
Both voltages readout ***WITH*** load/mic attached.
67V B+ is pretty low, may be the problem.
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Post by svart on Nov 6, 2014 13:03:19 GMT -6
You are correct, it is the power supply it sounds like. With the MK47 and it's variants, the B+, 105VDC is initially measured WITH the 2.4K (2.3K on schematic) load to ground but NO mic plugged in. The unit is USED without the 2.4K load in circuit. That 2.4K resistor is only there for testing the power supply and calibrating it's output without the mic.. So I'd make sure the 2.4K is not connected when the mic is used. That could cause your halving of voltage on the B+ if you doubled the load..  |
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Post by Deleted on Nov 6, 2014 13:35:40 GMT -6
If the mic switches patterns with another psu and generally works, the reed relais is definitely working, i would take it for granted that the mic itself is OK...check contacts/pins are correctly done on the psu and make sure that the load resistor for measuring purposes is switched out like svart wrote. With a bit of luck, it's a simple error easy to fix.
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Post by tonycamphd on Nov 6, 2014 14:43:02 GMT -6
that power supply puts out 396vdc uloaded!!! at least that's what i remember measuring!  |
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Post by ben on Nov 6, 2014 16:45:07 GMT -6
You are correct, it is the power supply it sounds like. With the MK47 and it's variants, the B+, 105VDC is initially measured WITH the 2.4K (2.3K on schematic) load to ground but NO mic plugged in. The unit is USED without the 2.4K load in circuit. That 2.4K resistor is only there for testing the power supply and calibrating it's output without the mic.. So I'd make sure the 2.4K is not connected when the mic is used. That could cause your halving of voltage on the B+ if you doubled the load.. Yes, without the 2.4k, the voltage was well over 200v. I checked the wiring against the pictures and everything seems to be wired properly. If the relay is tripping, then that means the pattern switch is probably ok? What else could the problem be? |
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Post by ben on Nov 6, 2014 17:11:40 GMT -6
Checked the pattern switch with a continuity meter and it seems to be switching fine.
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Post by svart on Nov 6, 2014 17:13:02 GMT -6
Ok, but you said that with the mic connected it was only 67V.. Which means that you have too much load from the mic. When the mic is connected you should have roughly 105V.
But you also said that the mic on another power supply works fine. Can you measure the B+ on the mic while connected to the other supply?
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Post by ben on Nov 6, 2014 18:23:16 GMT -6
The "Broken" supply is 105v with the test resistor, 285v without and 106v with the mic hooked up. The 67v was with the test resistor still in place.
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Post by ben on Nov 6, 2014 18:47:28 GMT -6
I think I figured it out. It seems that the pattern switch is not grounding properly. I'm going to try to fix that, but just so I know, should the B+ voltage be 105 WITH the mic as a load, or without?
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Post by ben on Nov 6, 2014 19:15:27 GMT -6
ok, so I fixed the ground and it didn't fix the pattern issue. I pulled apart the other PSU and made sure that both were wired exactly the same and they are. Tested both mics with both PSU's and the mic bodies work fine with the working PSU. Now I'm stumped.
Thank for taking the time to help guys. I should have learned how to do this stuff a long time ago. Better later than never!
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Post by tonycamphd on Nov 7, 2014 1:08:31 GMT -6
I think I figured it out. It seems that the pattern switch is not grounding properly. I'm going to try to fix that, but just so I know, should the B+ voltage be 105 WITH the mic as a load, or without?with |
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Post by Deleted on Nov 7, 2014 3:33:47 GMT -6
ok, so I fixed the ground and it didn't fix the pattern issue. I pulled apart the other PSU and made sure that both were wired exactly the same and they are. Tested both mics with both PSU's and the mic bodies work fine with the working PSU. Now I'm stumped. Thank for taking the time to help guys. I should have learned how to do this stuff a long time ago. Better later than never! OK, so we try to track down, where the problem is. 1. If both mic bodies work correctly with one PSU, the mics are alright. 2. The pattern switch does only one thing. It puts zero or 48V to the pattern pin. This switches the reed relay in the mic body. 3. If you have B+ of 105V with the mic connected or the load test resistor switched in, everything is nice with this. 4. If you only have one pattern with one PSU, it has to be something wrong with the voltages on the pattern pin of the PSU. Triple check. Drink a cup of coffee. Triple check again. (That's the way i often fix those "D'oh" Homer type of errors.....) There definitely is something to fix, and if there is something to fix, you can fix it. Take your time. |
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Post by ben on Nov 7, 2014 6:22:19 GMT -6
ok, so I fixed the ground and it didn't fix the pattern issue. I pulled apart the other PSU and made sure that both were wired exactly the same and they are. Tested both mics with both PSU's and the mic bodies work fine with the working PSU. Now I'm stumped. Thank for taking the time to help guys. I should have learned how to do this stuff a long time ago. Better later than never! OK, so we try to track down, where the problem is. 1. If both mic bodies work correctly with one PSU, the mics are alright. 2. The pattern switch does only one thing. It puts zero or 48V to the pattern pin. This switches the reed relay in the mic body. 3. If you have B+ of 105V with the mic connected or the load test resistor switched in, everything is nice with this. 4. If you only have one pattern with one PSU, it has to be something wrong with the voltages on the pattern pin of the PSU. Triple check. Drink a cup of coffee. Triple check again. (That's the way i often fix those "D'oh" Homer type of errors.....) There definitely is something to fix, and if there is something to fix, you can fix it. Take your time. I found a bad resistor!!! Woohoo!!! Sure enough, no 48v, so I followed the path on the PCB and found that the 12k resistor is bad. Off to Radio Shack later today, and I'll keep you posted  |
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