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Author Topic: U87 switch deck hell  (Read 2799 times)

duskb

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U87 switch deck hell
« on: February 25, 2016, 04:12:53 pm »

I'm in a predicament. I have a 70's 87 that became the unfortunate recipient of a stick hit and the entire switch deck crumbled like a potato chip. I contacted Neumann and sent them an image of the broken part and they sent me a new one. Of course, as fate would have it, once I installed the capsule on the new deck it didn't work right. I then took the mic to Charlie Bolis who informed me that the deck Neumann sold me is of a new design (it uses magnets and a PCB instead of the old leaf switch/lever design) and can't be retrofitted to work on the old mics, at least not without a ton of custom work and risk.

Has anyone run into this problem and come up with a workable solution?
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Dusk Bennett
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Award Winning Engineering
www.duskbennett.com

klaus

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Re: U87 switch deck hell
« Reply #1 on: February 26, 2016, 02:04:03 am »

The information you received is erroneous. Neumann's current replacement switch assembly for your 1970's U87, which now uses softer plastic that is resistant to drying out and crumbling, is easily installed and guaranteed to work.

The fact that glass-embedded, magnetically activated reed switches have superseded the old mechanical contact switches is not relevant, as the whole head assembly comes completely assembled, with the new mechanism and new (magnetic) switch actuators fitted.

Please ask an experienced Neumann microphone tech what exactly does not work in your setup. (I just installed one of these for a customer's 1971 U87, so I can attest that the replacement part works without issues).
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Klaus Heyne
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mbrebes

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Re: U87 switch deck hell
« Reply #2 on: February 26, 2016, 03:41:59 pm »

If you need someone else fairly close by to take a look at it, I am in Northridge and am very familiar with the old U87's.
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Vertigorecording

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Re: U87 switch deck hell
« Reply #3 on: February 26, 2016, 11:50:29 pm »

I was given a basket case that didn't work by Dusk, hoping I could figure it out. I did think that the switching was wrong but after finally taking a good look at it, the whole thing was wired wrong. The backplates were improperly connected and after tracing things out against an old crumbled one that I had on hand, I realized that the switches were not the problem and the wiring was causing the problems in the patterns.

Lesson learned. Start from square one when presented with a Frankenstein. I gave the erroneous info to Dusk but I fixed it all this evening. The new one works fine without modification, as Klaus stated. My bad. I do not consider myself an inexperienced Neumann tech.
-Charlie
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klaus

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Re: U87 switch deck hell
« Reply #4 on: February 27, 2016, 01:16:23 am »

I do not consider myself an inexperienced Neumann tech.

Nothing of the kind expressed or inferred. Glad it all worked out.
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Klaus Heyne
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duskb

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Re: U87 switch deck hell
« Reply #5 on: February 27, 2016, 04:25:56 am »

I was given a basket case that didn't work by Dusk, hoping I could figure it out. I did think that the switching was wrong but after finally taking a good look at it, the whole thing was wired wrong. The backplates were improperly connected and after tracing things out against an old crumbled one that I had on hand, I realized that the switches were not the problem and the wiring was causing the problems in the patterns.

Lesson learned. Start from square one when presented with a Frankenstein. I gave the erroneous info to Dusk but I fixed it all this evening. The new one works fine without modification, as Klaus stated. My bad. I do not consider myself an inexperienced Neumann tech.
-Charlie

Charlie is right. I gave him a mic that I swapped the deck out on and the wiring contacts were laid out differently than I had on the original device. Apparently my understanding of the schematic was wrong and it burned both myself and Charlie.

Fortunately he persevered and fixed it for me. Nothing lost nothing gained and in this case I learned some valuable info.

Thanks for the help guys.
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Dusk Bennett
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Award Winning Engineering
www.duskbennett.com

klaus

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Re: U87 switch deck hell
« Reply #6 on: February 27, 2016, 03:08:39 pm »

Now, imagine, our politicians were adopting the same basic decency when they disclose making mistakes. What a wonderful world it would be...

Thank you!
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Klaus Heyne
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radardoug

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Re: U87 switch deck hell
« Reply #7 on: February 27, 2016, 03:43:44 pm »

Charlie, can you enlighten us a bit more? Was it that the wires in the new head came out in a different place to what you expected? Was the wiring in the body standard?
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klaus

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Re: U87 switch deck hell
« Reply #8 on: February 27, 2016, 04:50:43 pm »

Though I am not Charlie, I have a good idea, speaking from recent experience what the issue may be:

The replacement heads have four unmarked stand-off columns to where you are supposed to solder the four capsule wires- front and rear diaphragms, and front and rear backplates.

Proper wire lead-out designations are not found on any circuit diagram, and only through continuity tests between each stand-off column and the (documented) contact pins at the bottom of the head assembly can you assign the right wire to the correct stand-off column.

Now, back to Charlie...
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Klaus Heyne
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Vertigorecording

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Re: U87 switch deck hell
« Reply #9 on: February 27, 2016, 06:26:37 pm »

Yes, Klaus is right about problem number one. What goes where?

For whatever reason, (all the junk….I mean treasures …..we keep around instead of throwing out!) I have a "potato chip" version, deteriorated, yellow plastic KK87 with a K87 still attached. Because it is completely fragile, decayed and broken apart, I literally have an "exploded" view of what goes where. From that assembly I was able to determine which pins were the front and rear backplates.

After that, the front and rear diaphragms. The front backplate was the tricky part since accessing it on three different capsules is done at least two (maybe three) different ways. The new K87 capsule has a big 'ole lug to solder to when connecting the front backplate, and the rear backplate is connected by the capsule mount screw.

On the oldest K87, the rear backplate was connected by a screw on the FRONT of the capsule that leads to the rear backplate connection. It is insulated. The front backplate makes its connection via the saddle mount. That, I believe was the heart of the confusion. The backplates were mis-wired and mis-identified. Quite an adventure!
-Charlie
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duskb

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Re: U87 switch deck hell
« Reply #10 on: February 29, 2016, 01:55:44 am »

Now, imagine, our politicians were adopting the same basic decency when they disclose making mistakes. What a wonderful world it would be...

Thank you!

I agree. In this case I attempted to figure out the repair myself because I knew in the back of my mind Charlie could bail me out if I got stuck. Any 'mistake' I made would ultimately be part of my 'education' on my employers part. Admittedly they have paid a lot to my reeducation fund over they years but they have profited occasionally from it as well.

I think most politicians either don't have the balls to try what I do or they realize there is no Charlie to call on once they get in over their head. :)

I am a lucky man somedays.
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Dusk Bennett
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Award Winning Engineering
www.duskbennett.com

radardoug

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Re: U87 switch deck hell
« Reply #11 on: February 29, 2016, 02:35:34 pm »

I was presented with a U67 once with the comment it sounded bad. The present owner had bought it very cheap because it sounded bad. The capsule had been wired in backwards, because the 67s have the wires swapping sides. [KH: on U67 heads, the lead-out wire for the front diaphragm connects somewhat illogically to the rear of the capsule's base.]

Good for the new owner, bad for the previous owner!
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