Valhalla board tech question
Posted by: rp on 02 July 2001
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.
If anyone else knows better, I'm obliged to them.
Best;
Mark
(an imperfect
forum environment is
better than none)
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
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
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)
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.
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
The valhalla takes in mains voltage and rectifies it directly, one of the reasons it's a nasty thing to poke fingers near
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
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.]
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
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
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
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.
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
Pay close attention when replacing C1 as it is soldered on both sides of the board.
Cheers,
Jim Cash
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.
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
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
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