[Grumpy_Git]

Right my shiny case has arrived, all my calipers and rulers are hidden in storage somewhere  so two quick questions.

1) would a 1 inch sheet metal punch be a good size for making the cutout for the valve sockets or would something smaller be better?

2) would a 12.5mm punch be suitable for the RCA socket cutouts? again, would something bigger/smaller be better?

Thanks all.

Nick.

[andyr]

1) would a 1 inch sheet metal punch be a good size for making the cutout for the valve sockets or would something smaller be better?

2) would a 12.5mm punch be suitable for the RCA socket cutouts? again, would something bigger/smaller be better?

Thanks all.

Nick.

1.  1" hole is perfect for the tubes.

2.  12.5mm hole is too big for RCA sockets - you need 3/8".

Hehe ... how're you gonna do the IEC hole? 

Regards,

Andy

[Grumpy_Git]

Cheers Andy

Its cut and has an iec supplied   

or use one of the many square punches available? I used a Dremel on the 55N.

I've just found my GK1 assembly instructions (thought I'd chucked them!) and Hugh suggested 1/2", hmmm!?

Nick.

[andyr]

I've just found my GK1 assembly instructions (thought I'd chucked them!) and Hugh suggested 1/2", hmmm!?

Nick.

Mmmm, all I can say is ... I just drilled 4 RCAs for my new amp cases and I used 3/8" bits.  Maybe it depends on what RCA sockets you use - so go buy some and measure the hole required to clear the isolating inserts?

Regards,

Andy

[RonR]

Gents,

Could this be a difference between the GK-1EL, GK-1M and GK-1R?

Cheers,

Ron.

[andyr]

Gents,

Could this be a difference between the GK-1EL, GK-1M and GK-1R?

Cheers,

Ron.

Possibly, Ron ... although an RCA is an RCA is an RCA! 

Regards,

Andy

[AKSA]

Hi Ron,

Nah, the holes are all pretty much the same as I recall - the M and R versions used block RCA pcb mount thingies, and the half inch hole, 12.7mm, was to clear the earth contact so that sig earth and chassis earth could be brought to one star point to avoid earth loops.

Hope this helps,

Cheers,

Hugh

[RonR]

Andy,

You're not using the Hugh-supplied RCA blocks, are you?

That would explain it.

Cheers,

Ron.

[andyr]

Andy,

You're not using the Hugh-supplied RCA blocks, are you?

That would explain it.

Cheers,

Ron.

Correct.   

Regards,

Andy

[ginger]

Nick,
Do you have minimal circuit design skills or have access to someone who does.

If so then running your rotary selector switch in "functional parallel" to the push button switches is possible.

If (as I beleive they probably do) the existing select lines have pull up resitors to +5V and the microprocessor senses the momentary connection to 0V when a momentary action switch is pressed
THEN.

The trick is to run the select lines back to the rotary selector switch. On the common you need 2 circuits, one effectively acting as a trigger input to some logic and the other as a pulsed contact closure output.

Because the rotary switch is break before make the common will momentarily dip to 0V as you change switch selections. Guarantee this dip with a pull down to 0V resistor off 10 times the value of the pull ups on the select lines on the existing board (so as to not upset the existing logic). Use this momentary dip to 0V to trigger a monostable IC like a 74HC221 which has a pulse time set to say 100ms. This 100ms is the contact debounce and settling time for the switch to settle to its new position. Use the output of that monostable to trigger a second monostable with similar pulse time. The second monostable output connects 2 places, 1 - back to the 1st monostable to prevent it from retriggering during the second monostables pulse time AND 2 - to the base of a NPN transistor connected across the switch common pull down resistor (collector to the switch common, emitter to 0V) so that with the transistor switching on you are effectively providing a 100mS contact closure to the new select line.

A 74HC221 is a dual mono so all this can be done with 1 IC, 1 transistor and a handful of resistors and capacitors. It will run off the existing boards 5V rail and can be built on a small piece of "matrix" board.

This should work.

If this went "over your head" then probably best not to mess with it. If it made sense why not give it a whirl.

BUT remember he usual commercial caveat you see on most gear:
Messing with the circuit voids your warranty

Cheers,
Ian

[Grumpy_Git]

Ian

cheers for this, I can cope im just slow and will have at it soon.

Right now I'm DIYing the kitchen, sigh, home ownership is a bugger.

Nick.

[Tinker]

Thanks for your great suggestion, Ginger.  Earlier I think I (flippantly) suggested a trigger circuit using a 555 timer.  Ginger's suggestion is more elegant, easier to construct and should work well.  The GK1R does indeed employ pull-up resistors.  Also, the typical debounce time of pushbutton switches is at least a few ms, so I put a ~20ms debounce circuit into the design to prevent false triggering. The 100ms time constant suggested by Ginger ought to be more than adequate for reliable operation.  The PSU for the GK1 has power to burn, and can easily power this circuit too.

And although this should work well, as Ginger said, caveat experimentor.

Cheers,
   Ben.