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Old 22nd April 2007, 07:09 PM
Mark Mark is offline
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Default (Another) Newbie Builds a KEL84 (Part 1)

Hi,

Newbie post. I’ve recently finished a KEL84. I’ve been reading the forum regularly for a while, and it seems there is some interest in ‘how was it for you’ kit building stories, so here’s mine.

The kit arrived with no squashed corners or tyre marks. There were no damaged parts when I opened it. It had been well packed by WD. There were a number of small items missing that Andy at WD supplied First Class post next day. The instructions were not as good as I expected. They have a number of errors and inconsistencies, and they refer to parts that are no longer supplied (e.g. the tape switch). This is confusing for a newbie, and not what I expect for what I assume to be an entry-level kit.

The main irritation with the instructions was the lack of any photographs. It’s like doing a jigsaw puzzle without the picture ! A lesser irritation was the sub-optimal build sequence, which meant I had to install and remove hardware three or four times in different sequences because it blocked access to something else. WD assures me this isn’t the standard they expect either, but has been inherited from WAD, and they’ll fix it as soon as they get time. The ever-helpful Andy at WD was also able to answer all my questions in a series of what seemed like daily calls over a period of a week. As others have already found out, they are nice people to do business with.

I was surprised at the amount of ‘bodging’ and finishing required. I had to saw off part of a piece of plastic on the top the Mains TX so the holes in the chrome cap would align with the bolts holes in the TX. I also had to drill out one tab hole and all eight diode holes in the PCB because they were too small. I think all this has been previously posted by others on the forum. The selector switch spindle was too large for the hole in the knob, so I also had to drill out the knob. Finally, if you fit the anti-rotation pin of the selector switch in the hole in the chassis, and line up the knob with the text on the front panel, the flat on the spindle for the grub screw is 180 degrees away from where it should be !

Picky/cosmetic niggles include the Mains TX bolt heads that won’t sit flat on the top of the chrome caps, and the six holes in each cap of which only four are used.

In contrast to the hardware, the PCB is a dream – well laid out, well labelled and plenty of room. WD supplied the resistors and other components in separate plastic compartments with component value labels that made it even easier. I was able to blitz the board in an afternoon.

The grey single core PTFE insulated screened cable supplied is no doubt ‘sonically superior’, but I found it a pain to work with. If you grip the grey outer with your left hand and pull the stripper on the signal core with your right hand, the cable stays unstripped, and the grey outer sheath slides down the cable. I also kept breaking the small number of very fine conductors after I had soldered them, because of the number of times I had to bend them out of the way and untangle them to solder up the selector switch. A bit embarrassing when I’ve been stripping single and twin core screened cable for 25 years making up cables for PA systems without a problem ! I gave up in the end, and bought the no doubt even more sonically superior relay switched input board. That went together easily – although de-soldering the phono spigots to get them clean enough to go through the PCB was a pain until I worked out a novel technique (!). Heat the spigot with a soldering iron until the solder melts then blast it with a compressed from an air duster using the narrow bore tube supplied (make sure you shield the area around to catch the molten solder, and wear eye protection !).

The two-colour LED appears to be a recent addition. It’s welcome as a simple check that the heater supplies are working to at least one valve, but it still feels like an add-on that hasn’t quite been thought through when it comes to attaching the LED to the front panel. I have shrink-wrapped (sorry, heat shrinked) mine per the instructions, but it wouldn’t push into the hole in the front panel. However, after leaving it a week at gas mark 6 inside the chassis I was able to push it in easily. Perhaps the long term heating makes the heat shrink softer.

That's my 5000 characters for one post. Part 2 plus pictures to follow.
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Old 22nd April 2007, 07:13 PM
Mark Mark is offline
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Default (Another) Newbie Builds a KEL84 (Part 2)

(Following on from Part 1)

Anyway, I finally got to switch-on time over a month later (minus 10 days out of the country on business). I fitted my 78p worth of 8 ohm 7 Watt dummy load resistors (Maplin), switched on at the amp, plugged in and finally switched on at the wall (so I was as far away as possible in case anything exploded !). The LED went green, then orange and all the valves lit up. I waited a few minutes for smoke, or something to start melting, but all was well, so it went straight to the lounge for music. Instant problem – very loud right channel, but I was so desperate for music I temporarily cured it with a 20dB L pad attenuator I had to hand.

Subsequent tests with a continuity tester showed I’d connected the right channel signal to the wiper of the pot instead of the end of the track. Most of the voltages were within 1% of spec. One of the EL84 amplifier voltages was 9% out, which is fine, but the two ECF80 splitter valves were a different story. One was 13 to 17% over or under on three voltages, which is borderline when the target maximum is 15%. The second was 30% over or under on the same three voltages. I swapped the splitter valves over, and found the 30% error problem ‘followed the valve’. WD replaced the valve. The voltages for the replacement were all well within spec except for one which was on the limit at 15% over. I see Jake and the Dog recently commented on these.

WAD also sent me a couple of ‘used’ ECF80s FOC. These were even worse than the valve I returned, with voltages 40 to 50% off spec ! Any comments on variations in ECF80s ? What does a 50% off spec ‘aP’ and ‘gT’ voltage do to the sound ? The ‘stock’ ECF80s supplied are marked ‘EI Yugoslavia’.

So what does the amp sound like ? In a word - great. I immediately noticed lots of tight, rich, sonorous bass, and no TX or speaker hum (which seems to have plagued others). The only thing left is to tidy up inside the chassis, which is where I would welcome some help, because there are no ‘here’s one we made earlier’ photos in the instructions. Which cable should be twisted and which ones left untwisted ? What’s the best cable routeing ? Should the feedback cables go straight from front to back or around the side ? Has anyone got a neater arrangement for the resistor and capacitor across each pair of speaker terminals ? Is there a better route for the power supply cables to the relay input board ?

So if anyone is still awake after all that, here’s a couple of photos of the inside. Jake and the Dog did such a good job with photos of the outside recently (showing the latest World Designs front panel rather than the old WAD design) I won’t bore you with any more. Comments welcome – on fixing the LED, tidying up or anything else.

IMG_0336.jpg

IMG_0337.jpg
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Old 22nd April 2007, 07:45 PM
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john & Jake the dog john & Jake the dog is offline
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Default Re: (Another) Newbie Builds a KEL84 (Part 2)

Hi Mark,
I placed my feedback cables under the Pcb tucking them under the front edge of the board then running back straight to the speaker posts.
Your resistor/cap position is better than mine.
I had to be brutal with the Mains transformer plastic to get the cap to fit.
I've asked Nick for a price on some more bolts which I will shorten and drop in the vacant holes.
I have "tensioned" the LED wires so that it springs into the hole. I suppose a drop of araldite would complete it.

Regarding the voltages If you look at my post some of mine are miles out, no-one has commented officially but they can't be right.
I wonder about the effect on the sound.

Did your selector switch tally with the markings. I'm sure I've wired the selector switch correctly, only cd and radio, as it is numbered.
With the Knob missing I put the selector on the second click (CD) and fixed the knob.

This has selected radio and if I back off a click it selects CD. No more clicks left so unable to select phono If I wanted to.
No problem as I only use cd and Radio, I've just moved the knob.

cheers
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Old 22nd April 2007, 08:03 PM
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david counter david counter is offline
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Default Re: (Another) Newbie Builds a KEL84 (Part 2)

Quote:
Originally Posted by john & Jake the dog View Post

Did your selector switch tally with the markings. I'm sure I've wired the selector switch correctly, only cd and radio, as it is numbered.
With the Knob missing I put the selector on the second click (CD) and fixed the knob.

This has selected radio and if I back off a click it selects CD. No more clicks left so unable to select phono If I wanted to.
No problem as I only use cd and Radio, I've just moved the knob.
you can adjust the switch to give from 1 position to 6 positions by moving the metal ring
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Old 22nd April 2007, 08:10 PM
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john & Jake the dog john & Jake the dog is offline
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Default Re: (Another) Newbie Builds a KEL84 (Part 2)

Hi David,
That'd be right, could do that but I was interested to know whether other owners had the same problem as it seems a bit of a waste numbering the tabs if the selector then selects the wrong inputs.
Being another valve newbie I thought there was a major problem when no sound was forthcoming on switch on, it was the switch that was out one click.
cheers
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  #6  
Old 23rd April 2007, 12:31 AM
richardcooper2k richardcooper2k is offline
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Default Re: (Another) Newbie Builds a KEL84 (Part 1)

i too have experienced a degree of frustration when building a kit which has changed from the instructions or doesn't go together quite right; so i have had to improvise. (i havn't built any WAD or WD kits)
but the upshot of this has been when i have got the thing finished, i have experienced a greater satisfaction as i feel i have made a greater amount of input into my creation !
sometimes when i have had to improvise i havn't been absolutly sure my solution works as well as the origional plan would have. this has caused dissatisfaction. but on balance the extra satisfaction i have had from solving the unexpected problems has outweighed this
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