KEL34 making safe to work on

[willslenco]

Decided to strip all the mods out and pretty much start from scrstch.

As I mentioned in earlier post that this was a prototype build, well on stripping it down I've found that the board is slightly different to supplied kits, finalised version has altered ground routes hence the "star" ground implemented on valve base side and a couple of broken tracks. It also does not have a fuse holder and uses a fused IEC instead, plus valve bases are given better wiring arrangements.

[willslenco]

Originally Posted by Richard

Hi Will, yes the advice often given here is to build an amp as standard then change something if you can see a reason to.

Some "mods" are electrical and can be tried for logical reason, others are flavourings offering a different mix of musical colourings and presentations.

If any work for the listener then they are worthwhile but most are incremental "icing on the cake".

Popping in the packaged rectifiers will be a neat and reassuring way of restoring the amp. Better diodes and the pi filter do offer a small electrical improvement but it may not be a priority in the system.

Different coupling caps often give a noticeable change in sound despite having similar electrical values. I too tried the Ansars yours has fitted and liked their detailed sound but missed the easy-going sound of the original Rodenstein MKT1813 polyesters. A good alternative are the 0.47uF 630V orange polyesters supplied by Matthew for the WD88VA or the Soniqs SAX,
http://www.world-designs.co.uk/capacitors.htm

Hi Richard

Thanks for the advice, I have ordered all new caps (a mixture of Nichicons (KX,FW,KZ), Clarity Caps (SA , ESA) and a couple of OEM polystyrene), and new rectifiers, along with 2w ecc82 anode resistors, to bring this back to a 'standard' build, which I'm pretty sure I will be happy with driving my LS3/5as.

Yes I've always been surprised the difference caps and resistors can make, I've built a lot of opamp based phono stages over the years and have played with lots of different caps to 'voice' them.

[willslenco]

A question which probably has a simple answer but I don't know it. The KEL34 components list specifies quite a number of 0.66w resistors, as far as I can see these are not available now (except in SMD form), yes I know I can just use 1w items (I'm assuming .5w wouldn't be safe?) but were .66w really a thing and why/when did they disappear?

[Richard]

Hi Will, A quick look at the parts list for Kel34 and the following ones;

Kel34 1998 small resistors are 0.66W

Kit88 2000 small resistors are 0.66W

Kit34 2001 small resistors are 0.5W

Kit6550 2001 small resistors are 0.5W

so it looks like there was a change in supply/availablity or rating change.

1W carbon are still available so I’d go with those where yours says 0.66W

[willslenco]

All the replacement parts have arrived.

[Chris]

Hi Malcolm, that bundle of components will keep you busy for a while, did you buy all from the same supplier.

Chris.

[willslenco]

Originally Posted by Chris

Hi Malcolm, that bundle of components will keep you busy for a while, did you buy all from the same supplier.

Chris.

Hoping to get on with it today, they were mostly from Hifi Collective but the retifiers off ebay.

[bob orbell]

they were mostly from Hifi Collective, - that was expensive then . Bob

[Greg.]

Originally Posted by bob orbell

they were mostly from Hifi Collective, - that was expensive then . Bob

Not more expensive if you look at the broader picture. DIY repairs as well as being pleasurable are very cheap compared to a dealer or electronics engineers charge. Allows for the purchase of higher quality components from the likes of HiFi Collective, some of which are becoming increasingly difficult to source in small quantities. Furthermore, with Nick Lucas (HFC) being the original WAD employee who probably posted out this kit many years ago, there is a certain satisfaction in putting money into his pocket rather than the big industrial suppliers.

[willslenco]

Spent a good few hours yesterday stuffing the board and putting it all back together. Fired it up and most voltages were ok... except no heater voltage to the 6AU6s. Checked back and nothing reaching the heater wires, tried to check the rectifier but ended up frying it :ropies_pullhair: The board was real messy in this area due to previous owner installing the off board rectifiers so I checked continuity and it seems there must be a break in track (although I did check it prior to reassembly).

Didn't fancy stripping everything out again so cut the rectifier out and wired up a different one off board to check again. All good now although the heater voltage is a bit low and 6AU6 anode & ECC82 cathode voltages are rather high.

Connected a sound source (speakers were already attached) and it is playing rather nicely.