1983 Linn Sondek LP12 turntable Valhalla power supply overhaul - UK Vintage Radio Repair and Restoration Discussion Forum

howard · 10th Mar 2011, 4:03 pm

Hello again,

I bought this Linn Sondek LP12 turntable back in 1983 when it was still sensibly priced. This one came with the Nirvana upgrade to the suspension, and the Valhalla power supply which unfortunately expired 16 years later. The local Linn dealer insisted that Valhalla power supplies were not repairable and as I was quoted £240 for a new one (more than the entire turntable cost in 1983 !) I settled for the cheaper Basik power supply but since then the Linn never sounded quite as good. I know now that I had been misled as all Linn dealer manuals are now readily available on the web, and Linn did supply a Valhalla repair kit in 1999 for around £12, which contained a new KAB1000 1000 volt bridge rectifier, a 40 ohm Surge Guard thermistor and a new 1 amp fuse with full fitting instructions, and it would only have taken around 30 minutes to repair it. Even though I have a large LP collection, thereafter I lost interest in the Linn and stuck to CDs. Recently though I noticed a lot of Valhalla boards, working and not working, turning up on Ebay and eventually I grabbed a working one complete with switch.

Ron Bryan checked it over and it was still working, so what causes these power supplies to fail so often ? They are susceptible to mains surges, the bridge rectifier can short out internally when there is a surge, a 47 ohm resistor burns out at the same time and the fuse blows. Eventually Linn fitted a Surge Guard thermistor in place of the 47R resistor and a 1000 volt rated KAB1000 bridge rectifier which prevented premature failure of the board but there are undoubtedly loads of the earlier boards still in use.

So before fitting the Valhalla board which is around 20 years old, it was overhauled to ensure that it continues to work for some time to come and the 47R (R1) resistor was replaced by a Rhopoint SG240 thermistor (£1.67 + VAT from Rhopoint Components). A new Vishay KAB1000E 1000 volt bridge rectifier was acquired (£0.97 + VAT from Farnells) but not fitted as the original is fine. A couple of 15k ohm resistors (R2 and R3) resting on the board which get very hot and had caused the fibreglass underneath them to turn black were also replaced with a couple of Welwyn W22 7W 15k ohm wirewound resistors (£3.35 + VAT for 5 from Farnells) mounted away from the board. The overhauled Valhalla board (and matching switch) was fitted into the deck on new standoffs (99p a pack on Ebay) and it works well.

If you are thinking of fixing a Valhalla board, don't touch any components or track when it's connected to the mains ! Also handle it with care, ideally use an anti-static mat and wrist straps to avoid damage to the chips.

The Linn Sondek LP12 is an excellent sounding deck even with a modest Linn LVX arm and A&R P77 cartridge fitted, and it's good to have it back in its original spec. However I don't recommend that anyone goes and buys one secondhand due to the very high cost of original spare parts, "upgrades" and specialised maintenance by Linn dealers. There are much better value turntables around which work as well and are far less troublesome.

My thanks to Ron who fitted the new components.

Howard

10th Mar 2011, 5:05 pm

Anything is fixable, good job of not giving into a dealers spin. A question, how does a power supply whose job is only to spin a motor make a turntable sound 'better' or 'worse'?

howard · 10th Mar 2011, 5:40 pm

Quote:

Originally Posted by merlinmaxwell

...... A question, how does a power supply whose job is only to spin a motor make a turntable sound 'better' or 'worse'?

This turntable produced a different and not so good sound after its 1999 overhaul and the fitting of a Basik power supply. Whether that was down to the cheaper power supply or the new springs fitted at the same time I don't know but I felt happier the way it sounded before. I didn't suggest that the deck sounds better now with its Valhalla power supply reinstated, the deck is long overdue for an overhaul anyway so I'm looking out now for a free "Linn clinic" checkover with correct setting up of its suspension but it won't be upgraded further.

Howard

dseymo1 · 10th Mar 2011, 6:15 pm

Quote:

A question, how does a power supply whose job is only to spin a motor make a turntable sound 'better' or 'worse'?

I think the idea is that it produces a more accurate sine wave than typical mains, correctly phased, thus reducing 'cogging'. There are claims of reduced dynamic wow, but how that is achieved without increasing torque, I don't know. Since the motor used by Linn is nothing special, I don't know how valid such claims are.

10th Mar 2011, 4:03 pm	#1
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	1983 Linn Sondek LP12 turntable Valhalla power supply overhaul Hello again, I bought this Linn Sondek LP12 turntable back in 1983 when it was still sensibly priced. This one came with the Nirvana upgrade to the suspension, and the Valhalla power supply which unfortunately expired 16 years later. The local Linn dealer insisted that Valhalla power supplies were not repairable and as I was quoted £240 for a new one (more than the entire turntable cost in 1983 !) I settled for the cheaper Basik power supply but since then the Linn never sounded quite as good. I know now that I had been misled as all Linn dealer manuals are now readily available on the web, and Linn did supply a Valhalla repair kit in 1999 for around £12, which contained a new KAB1000 1000 volt bridge rectifier, a 40 ohm Surge Guard thermistor and a new 1 amp fuse with full fitting instructions, and it would only have taken around 30 minutes to repair it. Even though I have a large LP collection, thereafter I lost interest in the Linn and stuck to CDs. Recently though I noticed a lot of Valhalla boards, working and not working, turning up on Ebay and eventually I grabbed a working one complete with switch. Ron Bryan checked it over and it was still working, so what causes these power supplies to fail so often ? They are susceptible to mains surges, the bridge rectifier can short out internally when there is a surge, a 47 ohm resistor burns out at the same time and the fuse blows. Eventually Linn fitted a Surge Guard thermistor in place of the 47R resistor and a 1000 volt rated KAB1000 bridge rectifier which prevented premature failure of the board but there are undoubtedly loads of the earlier boards still in use. So before fitting the Valhalla board which is around 20 years old, it was overhauled to ensure that it continues to work for some time to come and the 47R (R1) resistor was replaced by a Rhopoint SG240 thermistor (£1.67 + VAT from Rhopoint Components). A new Vishay KAB1000E 1000 volt bridge rectifier was acquired (£0.97 + VAT from Farnells) but not fitted as the original is fine. A couple of 15k ohm resistors (R2 and R3) resting on the board which get very hot and had caused the fibreglass underneath them to turn black were also replaced with a couple of Welwyn W22 7W 15k ohm wirewound resistors (£3.35 + VAT for 5 from Farnells) mounted away from the board. The overhauled Valhalla board (and matching switch) was fitted into the deck on new standoffs (99p a pack on Ebay) and it works well. If you are thinking of fixing a Valhalla board, don't touch any components or track when it's connected to the mains ! Also handle it with care, ideally use an anti-static mat and wrist straps to avoid damage to the chips. The Linn Sondek LP12 is an excellent sounding deck even with a modest Linn LVX arm and A&R P77 cartridge fitted, and it's good to have it back in its original spec. However I don't recommend that anyone goes and buys one secondhand due to the very high cost of original spare parts, "upgrades" and specialised maintenance by Linn dealers. There are much better value turntables around which work as well and are far less troublesome. My thanks to Ron who fitted the new components. Howard Attached Thumbnails Last edited by howard; 10th Mar 2011 at 4:20 pm.

10th Mar 2011, 5:05 pm	#2
Guest Guest Posts: n/a	Re: 1983 Linn Sondek LP12 turntable Valhalla power supply overhaul Anything is fixable, good job of not giving into a dealers spin. A question, how does a power supply whose job is only to spin a motor make a turntable sound 'better' or 'worse'?