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  #1  
Old 31st May 2022, 11:43 AM
misterc6 misterc6 is offline
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Default KEL84 XL Integrated final testing problem

I'm in the final stage of testing my self-build KEL84 XL. I’m getting continuity from the first five roundels on each channel back to the potentiometer. The circuit diagram of the relay board is not included in the information pack so I’m not sure what should be happening with the ‘Tape Out’ roundels, surely they must be connected to the buffer resistors on the relay board and have no continuity to the potentiometer. Is that correct?

Malcolm
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  #2  
Old 31st May 2022, 01:21 PM
Richard Richard is offline
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Default Re: KEL84 XL Integrated final testing problem

Hi, it sounds as if you may be testing the switching connections without the amp powered up.
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  #3  
Old 31st May 2022, 02:43 PM
misterc6 misterc6 is offline
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Default Re: KEL84 XL Integrated final testing problem

Hi, no it's fully powered up. The manual says "check for continuity between the roundels on the Relay Switch Board PCB around the phono socket centre pins and the volume control potentiometer as you select each input in turn. This will verify that the RSB is working correctly. Make sure that you check both channels." I highlighted the word input.

The KEL84 XL that I'm building has six pairs of RCA sockets on the rear panel, five of them are signal inputs, all of which have continuity to the pot, but the sixth is 'Tape Out" It's probably me being pedantic, but once I solder up the roundels to the input sockets it becomes harder to undo if I need to investigate further.

I have everything else done, valve voltages measured, front panel on, indicator glued in, base plate on. I just need to know if I need to test the Tape Out roundels before I solder up all the roundels.
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  #4  
Old 31st May 2022, 02:58 PM
snowman_al snowman_al is offline
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Default Re: KEL84 XL Integrated final testing problem

Maybe a picture helps?
If the OPL and OPR connections are the inputs to the volume control (pins 3) then adding RR1 and RR2 buffer resistors connects the 'roundels' to the OPL and OPR lines and hence to the volume control.
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File Type: jpg IMG_6249-002 (1).JPG (162.5 KB, 20 views)
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  #5  
Old 31st May 2022, 03:47 PM
misterc6 misterc6 is offline
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Default Re: KEL84 XL Integrated final testing problem

Thanks Al,

So all the 10 input roundels are connected directly to the pot when selected by the relays switching, but the two tape out roundels are connected permanently to the potentiometer through the value of their buffer resistors, is that correct?
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  #6  
Old 31st May 2022, 04:01 PM
snowman_al snowman_al is offline
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Default Re: KEL84 XL Integrated final testing problem

I do not have a KEL84 anymore, so only have the pictures I took when I did mine, but that is how I see it.

Perhaps it has been worked out so which ever input is selected, you can record via the OPL and OPR lines through the buffer resistors to tape out? Without the need of another switch (Tape / source) which the original KEL84s had.

Perhaps some one else could confirm my understanding?
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Last edited by snowman_al; 31st May 2022 at 04:14 PM. Reason: Tape source switch.
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  #7  
Old 31st May 2022, 04:32 PM
misterc6 misterc6 is offline
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Default Re: KEL84 XL Integrated final testing problem

I’m pretty sure that’s how it works. There’s a 6 core cable from the relay board to a Lorlin switch. On the front panel the inputs are labelled - phono, CD, tuner, aux, tape and mute.

I was using the 200R (buzzer) range on my meter, The tape buffer resistors are 1k, I’ve changed the range to 2k and I’m reading 1k from the tape roundels to the pot. I guess that means all is well.

Many thanks for your help.
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  #8  
Old 31st May 2022, 05:27 PM
misterc6 misterc6 is offline
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Default Re: KEL84 XL Integrated final testing problem

All done and sounding sweet and powerful at the same time.
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