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  #11  
Old 16th November 2016, 09:01 AM
bob orbell bob orbell is offline
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Default Re: Another WAD KEL84 Rebuild

Quote:
Originally Posted by Phil Y View Post
Just a quick one, what does PWBA stand for?
(I know Alan is referring to the PCB)

Phil.
Or it could stand for "Peter W Belt Ahrrrrrrrrrg"
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  #12  
Old 16th November 2016, 10:17 AM
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Shane Shane is offline
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Default Re: Another WAD KEL84 Rebuild

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Originally Posted by John Caswell View Post
Hi,
Absolutely no reason why you cannot use the Pre 3 relay input PCB, just mount it on short 20SWG wires soldered to the phono sockets. This reduces the wiring "mess" drasticallyAlso mount the relays in standard DIL IC sockets.

John
Why didn't I think of that? 😳 Especially since I mounted my vero-board version that way! I did manage to incorporate relay switching of the tape monitor loop, which simplifies the signal cabling a little, but if you don't need the monitoring facility you could use the redundant hole in the front panel to mount the tri-colour LED that the new board has connections for.
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  #13  
Old 16th November 2016, 02:16 PM
bob orbell bob orbell is offline
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Default Re: Another WAD KEL84 Rebuild

There has been post and pictures of the relay PCB on here some time ago being fitted to WAD kit as John has suggested, please don't ask me where, but it may be under AMP'S WAD. BOB
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  #14  
Old 17th November 2016, 09:22 PM
snowman_al snowman_al is offline
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Default Re: Another WAD KEL84 Rebuild

Well the humming transformer is fixed.

As mentioned previously, I made a thin plastic gasket to go between the core and the top cap. I bought 4 longer bolts, 55mm, and some half (or locking) nuts. These I fitted under the transformer and nipped the bolts up just tight enough to stop the cap 'buzzing.

The remaining hum is when the bolt(s) touch the chassis. The mounting holes in my chassis were only just large enough for the bolt to go through. It was all but impossible to position the transformer without a bolt touching the chassis, so:

First I opened the holes up to 6mm so I could fit the hard plastic spacers to the chassis. I tried this configuration and it is very quiet, but still needed the under chassis nuts to be 'critically' tightened to get to a low level.

Next I tried four soft grommets in the holes. I had to open them up to 7mm this time. This needs the under chassis nuts to be changed for 'nylock' types as you only need to pinch the grommets a little. And its silent...

To ensure the transformer is earthed, I fitted a star washer on one of the clamp bolts and an earth lead under the chassis to the mains input socket earth.

I have included a few pictures here: https://goo.gl/photos/d6PHZjjv3C6PDCm67

Alan
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  #15  
Old 17th November 2016, 10:42 PM
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Phil Y Phil Y is offline
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Default Re: Another WAD KEL84 Rebuild

Glad to hear you have it sorted Alan.
That is basically exactly what I did with mine except for the top cap which, as far as I can recall, didn't cause any problems.

Phil.
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  #16  
Old 21st November 2016, 08:38 AM
snowman_al snowman_al is offline
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Default Re: Another WAD KEL84 Rebuild

Well a small packet arrived on Saturday morning, a new main board and a relay board kit. Many thanks Matthew. Time to strip the chassis down...

No real difficulties fitting the relay board. Just note it is not symmetrical so plan the drilling of the 4 holes carefully. I aligned it with the centre line of the existing holes and a couple of millimetres from the chassis side.

I wanted the board to be closer to the frame so I cut the spaces down to 15mm. That in turn needed the 47 ohm resistor to be re-positioned. In its normal vertical location it could just touched the bottom RCA socket. I have re-positioned it to the side and mounted horizontally.

The only other small change I made was to mount the output cable pins on the track side of the board. This allows me to change the cable at any time without removing the board(!) and also made installation easier as I only had the switch cable and supply wires to deal with.

For the rest I just followed the supplied instructions. Alan

Pictures here: https://goo.gl/photos/kVox4oY2yPg5uwKz6
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  #17  
Old 26th November 2016, 10:17 AM
snowman_al snowman_al is offline
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Default Re: Another WAD KEL84 Rebuild

I've been waiting for a few parts to turn up this week, so have been tidying the hardware and making sure everything fits...

First I had to drill another mounting hole in the new board to match my older chassis. (I had not noticed this was different until I had already mounted several components.)

Then C4 fouled the selector switch. So I had to cut the (now) unused lugs of the switch and lay C4 over a little. Just enough room...

Refitted the Zobel parts and the output transformers.

Finally made up a daughter board for the Schokkty diode bridge and Pi filter out of vero board.

Some pictures here: https://goo.gl/photos/jyW6oYN9ep77Tee59

Alan
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  #18  
Old 26th November 2016, 10:39 AM
bob orbell bob orbell is offline
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Default Re: Another WAD KEL84 Rebuild

Looking good Snowman, strange about the centre hole being in the wrong place, when I fitted a new WD PCB in my WAD KEL 84 all the holes matched. I also had to bend over C4 to miss the switch. BOB
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  #19  
Old 26th November 2016, 10:47 AM
Chris Chris is offline
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Default Re: Another WAD KEL84 Rebuild

Very neat work..
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  #20  
Old 27th November 2016, 07:10 PM
snowman_al snowman_al is offline
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Default Re: Another WAD KEL84 Rebuild

Thanks for the comments and advice everyone.

Most of my parts order arrived yesterday, so I finished populating the board today.

I finally rejected the Jensen capacitors. As Phil Y suggested in a previous post, they measured fine on a capacitance test, but lost their charge in less than a minute at 300 volts... (Polys were still charged nearly a day later. Ouch!)
I used higher voltage rating and 105 degree caps for the electrolytic replacements.
Nothing too bijou for the resistors, I just Mills for the cathode bypass and a few Takman resistors, the rest are carbons or metal films that were to hand. I doubled the wattage of the original 100k and 27k load resistors though.

I could not resist 'making sure it still worked', so a very quick 'lash up' and now have sweet music again.

https://goo.gl/photos/8qTRsmbjbyM8NufM8

Need to tidy everything up next and replace the volume pot.

Does anyone know what I can remove the printed lettering from the front panel with? I was going to remove the 'source/tape' switch from the panel, but that left a hole, and I could not bring myself to fit a LED. I might wire it to the selector switch feed so it would become a 'mute' switch.

I think I might just let it play a bit longer for now though...
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