Help diagnosing a problem - V69

[Fab4ever]

I wonder if you could help me. I have a new V69 I bought (over eBay). I have it in right now, but I have been getting an annoying distortion, kind of a crackling noise, even when no one is singing or speaking into the mic. I have tried changing each cable, and there's no change. I have plugged another tube mic into the exact setup, same power supply and same cables thru the same channel in my RNP, and there's absolutely no crackling.

I am afraid it's something in the mic itself, but I wonder if I"m overlooking anything. Any ideas?

Fab

 

[c7sus]

Could be moisture. Is it humid where you live?

Try putting the mic under a 100watt lightbulb for about 20 minutes or so.

Also, store your mics in ziplock baggies with dessicant.

 

[Rev E]

I had the same problem with my (former) V69. I'm not sure exactly what was wrong. I believe it was a power supply issue. I ended up having taking it back to Sam Ash to be sent to Marshall for repair. They fixed it. And after about 5 weeks, it worked fine after that ... that is until I sold it and bought a U195.

 

[Marik]

Fab,

If, as C7sus has already suggested, drying out the capsule does not help, next suspect would be tube. If you have some spare 12AT7, or even better 6072, try to replace the tube. Be carefull, though, the socket is held by rubber ring, so hold firmly the ring (and socket) and lightly swing the tube pulling it out.

 

[Fab4ever]

Thanks guys. I will try drying out the mic ... it is very humid where I live. I was thinking about putting a 6072 in there anyway - that is, before I even got the mic, so I likely will do that.

The guy I bought it from seems willing to deal with Marshall for me, if it comes to that. I'll try drying the capsule first. Thanks again.

Fab

 

[Fab4ever]

Couple follow up questions:

Dessicant - is that the little baggie that comes inside some things that's supposed to dehumidify them? Where would i get that?

6072 - Will any 6072 fit? And, as I've never changed a tube in a mic before, does the tube slide straight in and out, rather than screwed like a lightbulb?

Sorry for the newbie-esque questions, and thanks!

 

[DJL]

Quick tube tip... if and when you change the tube, don't touch the tube with your fingers... the oil from your hands is not good for the tube... use a tissue or something.

 

[Han]

Couple follow up questions:

Dessicant - is that the little baggie that comes inside some things that's supposed to dehumidify them? Where would i get that?

6072 - Will any 6072 fit? And, as I've never changed a tube in a mic before, does the tube slide straight in and out, rather than screwed like a lightbulb?

Sorry for the newbie-esque questions, and thanks!

That little baggie is called 'a sachet of silica gel' and it is to absorb the humidity in a small airtight space. If you put it in the open, it will be saturated within ten minutes and won't work at all.

I've bought a box with 100 10gram sachets somewhere in England, do a Google search for silica gel.

 

[Fab4ever]

Thanks for all the help. I did heat the mic up under a lamp for a half hour or so, but it still buzzed. I have contacted the seller and hope he will help me... if not I'll contact Marshall and see what kind of a company they are. I'll let you guys know what happens.
Meanwhile, I've ordered some desiccant packs, now that I know what they are, and will keep them with my mics whenever they're stored.

Fab

 

[Han]

The lifetime of a tube is limited, it may be four months or fourty years, or anything between.

It happened to my Neumann after some two and a halve years, the same noise, as if there's a storm coming. It got worse after the tube got warmed up.

When the tube was swapped for a new one it sounded like new, the tube alone costed three times a V69 though, duh!

 

[Marik]

Couple follow up questions:

Dessicant - is that the little baggie that comes inside some things that's supposed to dehumidify them? Where would i get that?

6072 - Will any 6072 fit? And, as I've never changed a tube in a mic before, does the tube slide straight in and out, rather than screwed like a lightbulb?

Sorry for the newbie-esque questions, and thanks!

Fab,

I heard you can pruchase these silica packs in photo stores...

Yes, any 6072 will fit. I personally prefer GE 5 star, if you can find it. However, in V69 design you probably won't hear much difference as it uses feedback in order to give less gain and not to overload output FET circuit.

BTW, I forgot to mention, to change the tube, first, you will need to unscrew the socket from the body--there are two screws on the sides--you cannot miss them. Yes, the tube easily slides in and out.

<Quick tube tip... if and when you change the tube, don't touch the tube with your fingers... the oil from your hands is not good for the tube... use a tissue or something.>

DJL,

Here I would not worry too much. Although this is true for high current application like power amplifier output stage, where tubes work with much higher currents and get pretty hot (sometimes, esp. in class A amps, really very hot). For a lot of different reasons (noise, longevity, temperature in enclosed body, etc) mics use low (about 0.5-1ma) currents, so they don't get hot and oil from the fingers won't burn. Anyway, I always touch tubes in mics and never ever had any problems.

 

[DJL]

Marik, I make it a habit not to touch any tubes... but thanks just the same.

Silica pack tip... when they trun color and stop working... you can dry them out in an oven... slowly and at a low temp... when it's dried out it will change back to the orignal color.

 

[darrin_h2000]

It does remove the markings from NOS mullards but other than that theres no harm...Id avoid touching the contacts for the obvious reasons.

 

[chessrock]

I think there might be a moral to this story somewhere, but I can't exactly think of it . . .

 

[Rev E]

Before I ended up sending it back to Marshall, someone at the store also suggested the tube. I bought a new one and changed it out... same thing. It was a power supply issue with me. I bet it's the same for you, but you should try the tips that others have suggested. Seriously, your problem sounds exactly like mine with this same mic.