Kel84 input oddity

[John Caswell]

Apologies not really necessary, we can all be smart after the event, except of course for me who is smart all the time Yeah right talk to my Ladywife bout that!

John

[John Caswell]

On the relay point. The new relay board from Matthew is a Plated Through Hole (PTH) type, so if you wish it can be but with the relays (only the relays mounted in DIL sockets on the opposite side to the components so they are easy to get to and replace/rempve for fault finding.

John

[Calorgas]

Yes as you've correctly guessed I did have the amp powered off when I 'probed the inputs'.

I'll plug it back in and repeat the test this evening. So speakers attached, volume down, but all sources disconnected so that I have access to the inputs, turn on, measure inputs as described in post 18.

(I think that open circuit (on my cheapo meter 'sinometer' MS8230B) is displayed as '1' but no doubt I will find out when I'm doing it)

If I really do need to get the switch out afterwards to check the indexing, is it safe to push the caps out of the way i.e. bend the wires over, or would that put too much pressure on the solder joints? I have no problem looking at the switch as I'm familiar enough with them, but am just afraid of creating a new issue in the process.

[John Caswell]

One of the common problems I have had with the input selector switch is overzealous soldering causing the solder tags/contacts to melt the plastic and short out to each other.
No, there shouldn't be a problem, just do it carefully and make sure none of the component wires are touching each other/anything else. Re the meter, to check what is says when something is o/c, just power it up on an Ohms range, then with the probes touching each other see what it shows, ditto with the probes not touching each other - simple as that!

John

[bob orbell]

Originally Posted by snowman_al

Arrrh,
Apologies, I was not aware the relays switched the inputs to ground when not powered. No schematic is my only (lame) excuse.
Sorry again Calorgas for the confusion.

No offence meant Al, as John said, we all can and do make mistakes, I purchased a new Harley Davidson in 1992, wot a mistaker to maker soon got shut of though, it got nicked. Bob

[Calorgas]

Originally Posted by snowman_al

Sorry again Calorgas for the confusion.

No worries, in fact the more I repeat all this the better the chance of me remembering something of it in the future

There's still a glimmer of hope that with everyone's help I might be able to resolve this here, which would be very satisfactory!

[Calorgas]

The results are in from the powered up probing:
Input 1 selected, 1 open, 2,3,4,5 short
Input 2 selected, 2 open, 1,3,4,5 short
Input 3 selected, 3 open & 4 open, 1,2,5 short
Input 4 selected, 4 open & 3 open, 1,2,5 short
Input 5 selected, 5 open, 1,2,3,4 short

So I guess that confirms the wiring problem.

[bob orbell]

Input 1-2 and 5 correct, 3 and 4 not so, I must think about this in the morning. Bob

[snowman_al]

I'll try again...

Unfortunately the test has only confirmed what the fault is, the operation of positions 3 and 4 are some how 'joined'.

It is difficult to see the PWB from the pictures, so please check there are no solder blobs / bridges / hairs joining the tracks shown in the picture with a *. They are the tracks that switch the relays in positions 2, 3 and 4. The picture shows the board in the same orientation as your pictures. Look at the bottom left corner just above the out put transformer.



If you find nothing wrong there, then you will need to get access to the switch.

I am assuming the switch wiring is Red for position 3 and Green for position 4?

[Calorgas]

Ok good that's a check I can easily do, I'll have a close look this evening after I finish work and report back on the state of the board.
I'm pretty sure that it's Red for position 3 and Green for position 4 at the switch, but will re-check that too.

Cheers, Dave