Valhalla board tech question

Posted by: rp on 02 July 2001

Hello,
I intend to recap my valhalla board, it's Vout is a little low. Hopefully shotgunning all the electrolytics will solve it without getting to into it. What I can't figure out is how to disconnect the ribbon wire that connects the power switch to the board. What holds it into the black plastic terminal on the board? Is it just a force fit? Is there a clip somewhere? Soldered somehow? It's a strong fit so I don't just want to start tugging hard on it. It's hard to get a good look at it since of course I'm underneath the thing looking up with a flashlight etc.
Anyone been here before. Any advice will be greatly appreciated.
Posted on: 02 July 2001 by MarkEJ
I have a Valhalla board which I'm in the process of building into an external box. Even with the board outside any box at all, there is no obvious way of disconnecting this cable. The connection at the board end looks like it should just unplug, possibly after first releasing some sort of hidden "sqeezer" clip on the top of the connector block, but it's more obstinate than any similar connector I've ever encountered, and I'm used to taking laptops apart...

If anyone else knows better, I'm obliged to them.

Best;

Mark

(an imperfect
forum environment is
better than none)

Posted on: 02 July 2001 by dave simpson
Hi Guys,

Simply grasp the cable near it's union with the connector and "pull" it out gently.

Reverse procedure for re-connection. Oh yeah , big tip, *WHILE* removing cable for the first time note which "side" of the cable is up or down relative to the top plate. You'll find one side is distinguished by a shiny appearance at cable's end and the other side isn't. Make sure you re-attach the cable with this orientation correct or the platter won't turn (btw, no damage is done if you get it wrong).


hope this helps,

dave

Posted on: 02 July 2001 by rp
Gotta love it - in what other hifi world but the flat one can you to get all your esoteric questions answered. What I want to know from MEJ is how you got your board out? The switch snaps in from above, the board is inside - if you couldn't get the ribbon out of the connector, how'd you do it? Cut the ribbon? As for me I'm going to try the force method before I try the needle method only because I like to spend as little time as possible underneath the kitchen table working up through the expansion slot with a camping headlamp on my head!
Posted on: 03 July 2001 by MarkEJ
rp:

I got the board from someone who'd swapped their Valhalla for a Lingo. The dealer took it out -- so it must be detachable! Should have thought of this -- I don't have an LP12 so it didn't occur to me eek

Dave: (with many thanks!)

quote:
Simply grasp the cable near it's union with the connector and "pull" it out gently.

I assume you mean "Pull" in a direction parrallel with the plane of the board, rather than perpendicular to it?

Best;

Mark

(an imperfect
forum environment is
better than none)

Posted on: 03 July 2001 by Rico
quote:
I assume you mean "Pull" in a direction parrallel with the plane of the board, rather than perpendicular to it?

Corrrrrrrecto. Thumb and forefinger on each side of the ribbon - slides out easily enough.

Rico - all your base are belong to us.

Posted on: 03 July 2001 by Sproggle
quote:
I intend to recap my valhalla board, it's Vout is a little low

As I understand it:

The LP12 motor runs best at a lower voltage than the Valhalla provides. The Valhalla needs the extra voltage to provide enough torque for start-up. The Lingo starts at Valhalla voltage but drops to its normal voltage as soon as the platter reaches a constant speed - when less torque is needed.

If this is so then, all else being equal, a Valhalla with normal voltage might sound worse than one with slightly low voltage...

--Jeremy

Posted on: 03 July 2001 by Andrew L. Weekes
I'd tend to agree with Jeremy, all things being equal.

The valhalla takes in mains voltage and rectifies it directly, one of the reasons it's a nasty thing to poke fingers near eek

The rectified mains is used as the raw supply from which the output amplifiers work. These amplify the generated AC for the motor drive. The only thing that's likely to cause a drop in output voltage is the drive level to the o/p stage.

I'd be far more concerned (in terms of degraded sound) by problems in the accuracy of the phase shift to drive the motor, which is derived from the main generated AC signal.

One day I'll produce a proper circuit diagram, but it's a bloody horrible PCB to follow!

Andy.

Andrew L. Weekes

Posted on: 03 July 2001 by Andrew L. Weekes
I'd be grateful for any results from your 'remote valhalla' experiment.

I want to do this with mine, when I have time, as I feel certain it will be better as far from the Prefix as possible.

From my initial investigation it may be possible (via a change of crystal) to operate the board at 45RPM, although start-up torque may be a problem.

Anyone got an old Valhalla board they're willing to donate to me for a sensible fee?

Andy.

Andrew L. Weekes

[This message was edited by Andrew L. Weekes on WEDNESDAY 04 July 2001 at 09:30.]

Posted on: 03 July 2001 by Ron The Mon
Andy,
Here in the states, Linn dealers have Valhallas
mounted in clear acrylic(outboard) with the same
connection to LP-12 as lingo to do direct
comparisons. I have compared LP-12s with internal
Valhallas to this and can hear NO difference. I use Naim MM phono boards in my LP-12 (ala Prefix) and assumed the hum was from the Valhalla but actually it was from the motor!! Make sure in your case it is the Valhalla before proceding. If not I would advise a Lingo or Armageddon.

Ron The Mon

Posted on: 04 July 2001 by Andrew L. Weekes
The primary motive for remotely mounting the Valhalla was to gain access to it for modification / improvement. I guess hum fields are low since there's no transformers involved.

The biggest problem is the engineering a reasonable connection internally in the LP12, Linn want an arm and a leg for the Lingo PCB / switch ass'y.

What to Naim use for an Armageddon?

Andy.

Andrew L. Weekes

Posted on: 04 July 2001 by Andrew L. Weekes
quote:
because I like to spend as little time as possible underneath the kitchen table working up through the expansion slot with a camping headlamp on my head!

Cool!

Sounds a lot safer than my technique of balancing it between two chairs, whilst lying on my back!

Does anyone know where I can purchase small amounts of the 'Dexion' type tubing (square section tube, that can be joined by moulded plastic inserts, i.e. right angles etc.).

This would be the simplest way to manufacture an LP12 jig, something I've been wanting to do for years.

Andy.

Andrew L. Weekes

Posted on: 04 July 2001 by rp
quote:
The LP12 motor runs best at a lower voltage than the Valhalla provides. The Valhalla needs the extra voltage to provide enough torque for start-up. The Lingo starts at Valhalla voltage but drops to its normal voltage as soon as the platter reaches a constant speed - when less torque is needed.

This is how the PS worked in my old Axis. The PS is pretty fancy looking for an economic table and probably a fair match for the Valhalla and it offers 33/45 rpm switching. Wonder why Linn didn't scrap the Valhalla and offer a new board based on this. Maybe they didn't know where to put the heat sink. Maybe they were worried it would work too well and people would skip the Lingo.

Posted on: 04 July 2001 by Ron The Mon
rp,
Years ago I asked Bill Miller (who designed both power supplies) why the Axis technology wasn't in the LP-12 and he said the Axis power-supply, complete with heatsink, cost less to make and didn't sound as good as the Valhalla!! To make the Valhalla equivilent of the Axis PS would result in an outboard power-supply three times the size of the Valhalla!! And at the time Linn's market research showed that existing LP-12 customers wouldn't pay for an outboard supply.
FWIW, he did hint at the fact that the Valhalla did sound slightly better when mounted externally though he advised against it because of safety issues. However, after hearing for myself that the Valhalla sounds about the same in or out of the LP-12, I chalk that up to the fact that most LP-12s nowadays are on better stands(SO was the standard back then) which improve the turntables mechanicals, and Valhalla(and Prefix).

Ron The Mon

Posted on: 20 July 2001 by jcc
Just a quick note FYI. Depending on the vintage of your valhalla, the large caps (C1,2,18) may not be current spec. The correct caps are 33uf 350v. These will work on any age valhalla.
Pay close attention when replacing C1 as it is soldered on both sides of the board.

Cheers,
Jim Cash

Posted on: 22 July 2001 by rp
quote:
The correct caps are 33uf 350v. These will work on any age valhalla.
Pay close attention when replacing C1 as it is soldered on both sides of the board.

I simply used Mouser Xicon 47/250 caps since Mouser is easy to deal with, cheap, and the caps were the same physical size and axial. I would have liked to use something nice like a Panasonic HFS or a Nichicon Muse but alas they don't make the needed value. I think that Linn was more interested in raising the V rating more than dropping the capacitance (which really makes little sense). My guess is that they couldn't find off-the-shelf 47/350 axial caps that would fit the boards and that they certainly weren't about to redesign them just for this. I doubt there is any noticeable sonic difference between 33 and 47, and the 350V will be more reliable, but since I can fix this myself I don't really care that I used the 250V ones. And yes I did notice that one cap is soldered on both sides - those clever little Scottish devils!
I haven't checked but it turns out my board may have the zener mod, which I just found out about. Next time I'm in there I'll look. This this might be the reason for the voltage being lower on one side.
BTW I think the soundstage sounds a little bigger with the new caps.

Posted on: 22 July 2001 by Milan
Andrew,

Dexion still trade. Try www.dexion.com and you can find a local stockist. These would be better than Dexion direct as they prefer to deal with warehouse type stuff.

Most good hardware/DIY places should sort you out some pre punched galvanised angle though.

Regards

Milan

Milan

Posted on: 23 July 2001 by Andrew L. Weekes
I'm going to contact some more of the distributors once I've calculated exactly how much I require.

The type I'm after is 'Speedframe' the few distributors I've looked at so far are only interested in massive quantities, I only need a couple of lengths.

It's the ideal system to use if you cannot weld, and I should be able to acheive something near-identical to the real Linn jig using it.

I'm not having any ghastly angle iron in my house (apart from the Mana under the LP12!).

Andy.

Andrew L. Weekes

Posted on: 26 July 2001 by jcc
quote:
I haven't checked but it turns out my board may have the zener mod, which I just found out about. Next time I'm in there I'll look. This this might be the reason for the voltage being lower on one side.

Probably not, the correct output voltages for the valhalla are: 85v +/- 1v on the red leg, 75v on the blue.

The 'new' spec for the large caps seems to help initial start up of a LP12 more so than anything else.

Enjoy,
jimcash