single input kel84

[Greg.]

Hi Brian,

Thank you for your very kind words. I have no doubt the amp will continue to improve with time. Now it is time to simply enjoy the music

Greg

[colin.hepburn]

Yes Brian enjoy the music
A job well done Greg

[chambers67]

Just thought I would do an update of my adventures with my WAD KEL84, older version with the chrome carry handles. Following the advice of forum members, it got me thinking that I should actually get to grips with the build instructions! After pulling the pcb and carefully testing each resistor and capacitor, and being confident that all was well, I got the amp up and running. It sounded reasonable, but with hardly any power. I had made the conscious decision not to test the valve voltages at that stage.
Instead, I thought that perhaps some parts were testing fine, but not necessarily working as they should and rather than replacing a part at a time, I would replace some of the resistors, all the coupling caps and the two 1000uf electrolytic and see what happens. Scientific, eh? Well, with the level of my knowledge, it was the way forward. This is a list of the things done. All the following resistors were substituted with Takman and Tkd metal film types.
Replaced R10 and R11 100k uprated to 2w.
R12/13/14/15 (27K) uprated to 1w.
R28 220K 2w.
R1 2.2K 2w.
R24/25/26/27 (270R) 1w.
The Ansar coupling caps where replaced with orange drops and the two electrolytics, with Elna Silmic II.
Without exception, I found that all the component leads were of a larger diameter. Not being armed with a Dremel, I ground down a miniature slotted screwdriver and used it as a reamer. In retrospect, on certain components, I could have snipped off the existing leads and soldered to them. Not sure if this would have been recommended, but it would have been kinder to the pcb. A number of tracks had lifted and on two bits, I had to fashion wire “bridges”. Oh, and the wiring tabs broke off the choke, necessitating a not very pretty job involving some old capacitor leads.
Greg had kindly donated cable to be used for the feedback connections, as well as some useful advice, when I met up with him to take delivery of the KEL he had brought back to life. I also found that if, as recommended by Greg, the leads are better soldered with the tinned leads verticall rather than wrapped around the tabs, I had to extend a few leads, then employ heat shrink tubing as insulation. My soldering has improved, but not a lot, despite my ordering some low melt silver solder, recommended by Greg. Nice stuff.
Anyway, with the pcb in situ and all connected, I proceeded to switch on and began testing the valve voltages. I was met with a faint smell of plastic and an alarming voltage at one of the ECF80 pins. I quickly switched off. After a lot of searching around, I noticed that the red lead on the left pcb had moved, touching the outer lead on one of the large Srague capacitors. Removed and re-sited, hoped that I had’nt cooked anything.
Luckily all voltages, including choke and front panel side of R38, were all within tolerance. Connected up and switched on, I now had a centrally focussed stereo image and appreciable volume, even at low levels. Still has some time before it reaches its optimum, but even as it is, its sounding very nice. I have ordered some nice chrome/brass control knobs from Matthew Snell to replace the plastic ones (also wanted the chrome tx covers, but a bit pricey for me at the moment).
I realise that my blanket approach to the problems with this amp means that I am not sure which component/s were responsible for the faults. But .... pleased as punch, I am.

[Greg.]

Well done Brian. Seems you have a great outcome

I'm currently working on your speaker cables, juggling the task with some of my own stuff. I'll be in touch soon.

Greg