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Old 28th December 2004, 03:13 PM   #1
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Unhappy Need help with linn Valhalla repair

I've got a LP12 (somewhere 1985 model) that stopped turning.

All symptoms are similar to the ones as described in this old post (copy form the audio asylum):

Yes, there are two items which experience failures that you can service yourself and fairly easily. Does the led in the switch light up? If so then the following is most likely the problem and it will just leave the motor vibrating or turning verrrry slowly. With the table plugged into the mains VERY CAREFULLY (enough voltage in there to end you listening career) measure the output to the motor between the red and blue wires, it should be between ~85 to 90+vts a/c (as I recall), depending on if you have the zener diode update. The large P/S caps will fail over time, just measure the each of the two them across the board for 160vts, if less they need to be replaced. The other field readily field serviceable failure will require a Valhalla repair kit from Linn which consists of the necessary parts. I don't remember the price. This failure is noted by blown fuses and a related triac and resistor. Hope this helps.


So I followed the instructions to repair it and replaced the capcitors with new ones. But the problem remainded the same.
The voltages were 139VTS with the old capacitors and 140 with the new, os hardly any difference. This was in line with the output voltage on the rectifier which was 280V (SHouldn't that be 311??)

Output voltage on blue connection was 35V/50HZ and on the red 28V/50HZ

I found the schematics of this board and have attached them.
I also tried to figure out how it works, but I'm to electronically ignorant to understand this so I was hoping to get some help over here.

The schematics say: RV1 to be set to 85V+/- 1V. But when I measure that I only find 6 volts or so so this might indicate what is wrong.


Does anybody have some suggestions how to proceed?
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File Type: pdf valhalla_diag_l.pdf (29.7 KB, 639 views)
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Old 28th December 2004, 06:12 PM   #2
nghiep is offline nghiep  United States
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Check out this post from Audiogon. http://forum.audiogon.com/cgi-bin/fr...1140&read&3&4&
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Old 30th December 2004, 01:34 AM   #3
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Local Linn Dealers do not supply the repair kit separately. They only want me to have the TT brought in for repair and asking repair prices more than I paid for the deck.

I tried to get the kit form hifi-repairs.com but got no response on my email.

any other suggestions?
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Old 30th December 2004, 05:22 PM   #4
EC8010 is offline EC8010  United Kingdom
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I've just been looking at the diagram. U3 and X1 are a crystal oscillator. U5a and b are dividers that divide the frequency of the crystal down to 50Hz (or possibly 60Hz). U2a buffers the square wave leaving the dividers. U2 b and c are 12dB/octave low pass filters that remove the higher harmonics of the square wave to leave a sine wave. U2d and associated transistors form a high voltage amplifier to drive the motor.

Unfortunately, there is no isolation transformer, so this circuit is extremely dangerous to test. I wouldn't dare poke around in it without it being connected via an isolating transformer.

What you could usefully do is to print out the diagram, disconnect the Valhalla and leave it to discharge for at least 15 minutes, then go through and determine the value of each component and mark them on the diagram. If you then take the marked-up diagram to an engineer he/she will have a decent chance of being able to fix it. The circuit isn't rocket science.
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Old 31st December 2004, 09:05 PM   #5
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Quote:
The schematics say: RV1 to be set to 85V+/- 1V. But when I measure that I only find 6 volts or so so this might indicate what is wrong.
I think that's 85vac at the output.

What happens at the output when you adjust RV1?

Take huge care, an isolation transformer is really necessary for safe working. It's possible to work with an oscilloscope in differential mode, but really not recommended.

Paul
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Old 2nd January 2005, 08:51 AM   #6
LFM is offline LFM  Canada
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Default Valhalla repair

Eric, I just repaired the Valhalla board for my LP12. I changed the electrolytic capacitors and it still wouldn't work. The motor just sat there and vibrated. The switch LED lit. I was about to give up on it but decided to give it one more try. I reheated the solder joints for the new electrolytics just to make sure they were good. While I was at it I decided to add a little solder to the resistor joints that get so hot. I checked and resoldered a couple of joints where electrolytics attach to the board elsewhere . One in particular looked like it had broken away from the trace. I put things back together and away it went. It has been working perfectly for a couple fo months now. It was running slightly fast. I compensated for this by wrapping the platter with 2 turns of black electrical tape. I read about this trick at the Audio Asylum. There is no way to adjust speed with the Valhalla board. Give this a try. If that switch LED is working this will probably work. Good Luck!
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Old 2nd January 2005, 01:16 PM   #7
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Thanks for all the comments,

I only measure 37 volts at the output, so that's way too low.

I've got a reply from Hifi-repairs who sells at kit containing all parts that wear on the walhalla board. At a very reasonable price.

For the time being I've made a Naim Armageddon clone. This might be one of the easiest DIY projects around.

It took a 3*55VAC / 550VA transformer 2 resitors to lower te voltage to about 90V and 2 capacitors for the phase shift.
And sonically I can't find anything wrong with it.

But I still prefer the convenience (and resell value) of the valhalla.
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Old 8th January 2005, 12:12 AM   #8
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Quote:
It was running slightly fast. I compensated for this by wrapping the platter with 2 turns of black electrical tape. I read about this trick at the Audio Asylum. There is no way to adjust speed with the Valhalla board.
Speed adjustment on the LP12 is achieved by tilting the motor. You should find the setup manual on the web with a search.

Wrapping the inner platter in tape seems a good way to damage the performance.

Paul
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Old 8th January 2005, 08:26 AM   #9
LFM is offline LFM  Canada
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Thanks for the tip Paul. I did play with the motor height and tilt after I reassembled. The belt was climbing too high and rubbing against the plastic part that prevents the belt from derailing. I will drop the belt further. Thanks again
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Old 9th January 2005, 09:48 PM   #10
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Smile Got it fixed

It turned out that Paul and LFM were both right.

I double checked all joints on the board, and all joints around 2 resistors that get very hot (judging from the color of the board around it) were basically barely, connected. It was not easy to get it soldered again, i needed to make scrathes on the pcb layer to get a firm connection.

After taht I was able to get the motor running if I gave it a sweep, it wouldn't start by itself. But adjusting RV1 fiexed that.

Thanks for the advise.
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