Pre II heater current

[Bizzie]

I've just bought some russian 6N1P valves to use in my MF Xcans and they sound pretty good even with out burning in so I was thinking of trying in the Pre II to see how they sound in that. The problem is the heater current draw is higher at 550-650 ma and I dont know if the PSU II will be able to cope with the extra load does anyone know if it will be OK.

[prince of darkness]

The PSU II heater windings are rated at 9v,2A,in order to power a 6922 and three ECC83's, so should have no problem (especially if you're not using a Phono II as well).

[Bizzie]

Thanks Prince
I will be using Phono II as well though but I'm so impressed with these valves that I really want to give it a try they seem to be a real bargain I bought 10 for £15.84 including P+P and think that they sound as good if not better than the Mullard ecc88's that I took out of the Xcans and they've only had a few hours burn in.

[John Caswell]

Hi all,
The PSUII uses a 78S05 3 pin regulator which is rated at 2A, however on its heatsink in PSUII it is running near to thermal shutdown. I strongly recommend that it is removed off the PCB and heatsink and bolted down to the chassis base using a standard TO220 insulating kit. Its leads can be extended quite safely up to 6"/150mm without problems and it will run a lot cooler.
I have had this problem on several KLPP1s and this has cured it.

John aka Dr John

[Bizzie]

Originally Posted by John Caswell

Hi all,
The PSUII uses a 78S05 3 pin regulator which is rated at 2A, however on its heatsink in PSUII it is running near to thermal shutdown. I strongly recommend that it is removed off the PCB and heatsink and bolted down to the chassis base using a standard TO220 insulating kit. Its leads can be extended quite safely up to 6"/150mm without problems and it will run a lot cooler.
I have had this problem on several KLPP1s and this has cured it.

John aka Dr John

Hi John
I thought that the heatsink fitted looked quite large and up to the job but don't want to create any problems with the regulator so I am prepared to follow your advise.
Does it matter where the regulator is bolted to the chassis and can you tell me where to get the insulating kit.

[John Caswell]

Hi Bizzie,
Generally I get them from Farnell and RS but pm me with an address and I will put a couple of sets in the post along with screws etc. and a drawing of how to do it.
You can bolt the regulator where you like but I tend to put is as near the PCB connections as is sensible. There is no reason why it cannot be under the PCB as long as the leads are long enough

John aka Dr John

[Bizzie]

Thanks for the offer John but after I asked the question I had a look and got some from Rapid they sell them in packs of 10.