Linndrum recap job - problems with two values

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DUAL-Chris
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Linndrum recap job - problems with two values

Post by DUAL-Chris » Sat Jun 11, 2016 9:27 pm

Hello,
my name is Chris and I'm new at this board. I love vintage hifi and the songs of my youth in which old synths are used.

My plan is to buy a Linndrum. (LM-2, this is incorrect I know)
By the way, how much will I have to pay for a version without midi interface? Or, what is a good price nowadays?

The problem mentioned above is because every vintage device or set I want to use daily has to undergo a recapping job. I do this because I tested several caps of 35 year old equipment and all the caps had only 50% of the former value resulting in a hum, distortion or malfunction.

So before I buy the drum, I studied service manuals and pictures from inside the Linndrum.
I've come very far but a few things I have to know before I'm sure to have all the parts listed.
I see some parts are hardly to get and I wanted to have them here to be sure I can do the job.

1. The big 27,000 µF cap. Which voltage is necessary and is it screwed to the board or soldered? Is it 10 mm pin distance if soldered? What is the maximum height?

2. The 10 uF axial caps which are located on the drum board. Which voltage is necessary here?

Thank you very much,
Chris

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madtheory
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Re: Linndrum recap job - problems with two values

Post by madtheory » Sat Jun 11, 2016 11:06 pm

Voltage doesn't really matter as long as it is the same or more than the original part. Caps are very easy to get in all
ratings, so it wouldn't be a show stopper to not know the values in advance. Plus you should only replace the ones that have failed. 35 years is an average, and capacitance has a wide error margin which is taken into account in the circuit design. So don't replace unless it's actually leaking or causing problems. It's too easy to damage rare ICs by recapping wildly nilly.

And what's "incorrect" about an LM-2?

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Re: Linndrum recap job - problems with two values

Post by DUAL-Chris » Mon Jun 13, 2016 12:08 pm

madtheory wrote: And what's "incorrect" about an LM-2?
That the Linndrum's factory name isn't LM-2, but only Linndrum. It was the second drum from manufaturer Linn and it did follow after the LM-1 but the name is not LM-2.

You are right, capacitors are available in all sizes and values. But the big 27,000 µF is not, definately. Ok you get 27,000 caps but they are to long. The Linndrum's 27,000 has to be short because the 2nd pcb is above it.

I don't want to start the search for this rare thing if I have the drum here and to see then that it has a two week delivery time, that's all.

Best wishes,
Chris

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Re: Linndrum recap job - problems with two values

Post by madtheory » Mon Jun 13, 2016 12:54 pm

OK what dimensions should the cap be? You can usually get a modern cap that is smaller in physical size. Volumetric efficiency has improved since the Linn was made.

Or you could upgrade the entire PSU:
http://www.synthcity.nl/powersupply/linnpsu.html

Or buy a plugin emulation instead (it's really very good):
http://www.alyjameslab.com/alyjameslabvlinn.html

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Re: Linndrum recap job - problems with two values

Post by dstrength » Mon Jun 13, 2016 7:32 pm

It's a screw thread mounted cap. This is what you want:

http://www.mouser.com/Search/ProductDet ... 303U16BA2B

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Re: Linndrum recap job - problems with two values

Post by dstrength » Mon Jun 13, 2016 7:41 pm

Some other things you might want that I usually have to order when restoring a LinnDrum:

Slider Caps - Mountain Switch 10TB002 (black)
http://www.mouser.com/ProductDetail/Mou ... ujXLji4%3d

Battery: Power-Sonic 3.6v NiCd - PCBM-3.6
http://www.mouser.com/ProductDetail/Pow ... uC7JLEs%3d

1/4" Jacks: Switchcraft RN111PC
http://www.mouser.com/ProductDetail/Swi ... uqY95MY%3d

I also make and sell replacement wood side panels:
http://www.gmusynth.com/collections/woo ... ide-panels

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Re: Linndrum recap job - problems with two values

Post by recordbot » Thu Jun 16, 2016 12:17 pm

I sold my Linndrum a year or 2 ago (I still have the box!)

all I can say is you're a brave man who is willing to take on a challenge, can't recall many people who have dealt with years of linndrum use not constantly interrupted by maintenance, it's just a problematic design, machine is very sensitive to both temperature and humidity, OS fritzing out was the most common issue,

I sold mine for 2 grand with a midi kit, I was assuming they were worth 400 bucks for years, I got cool sounds out of it and when it worked it was a super cool rhythm box, but ask techs and explain whats happening with your unit and many will say "yeah it's a linndrum" or "I don't work on linndrums"

I would say stability wise the linndrum is approaching polymoog territory .

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