Pre2 relay input switching PCB

[RobHolt]

Peter, I agree that fresh designs are the way forward and that you shouldn't be hampered in any way by the constraints of the old kit.

Your approach is perfectly reasonable IMO. If the parts used in the new kits, eg some of the boards and transformers are made available there are plenty of use who will use our own initiative and mod our existing products as we see fit. This is the best compromise IMO - gives some room for existing users to tweak while not holding back the new stuff.

[John Caswell]

Hi all,
In reply to Lord's friend's comment
In his typically blunt way, he said:
"Frame relays just move the problem from the front to the back panel."
"Reed relays (vacuum sealed), can't corrode but you can't have any AC on the switching voltage."
Not so, modern relays are hermetically sealed in an inert (Nitrogen usually) atmosphere and usually have gold/palladium/silver contacts or a combo, and bifurcated contacts to boot. All PO approved relays are good for at least 100,000 operations without failure. Far far better than a rotary selector switch but not as cheap of course!

John aka Dr John

[Rupert]

Peter,

Thanks for your earlier reply re upgrading from series II to III. Lets be honest, my hope that this might be possible was purely self interested, but I am sure many will have wished/thought the same. It is good to know that you have even considered this possibilty. I have no doubt the fresh start, with new products, is the right way to go. If there are any spins offs, such as relay fitting, that can be retro fitted, I've no doubt they would be welcome.

I'll leave the relay thread to run.

Rupert

Originally Posted by John Caswell

Hi all,
In reply to Lord's friend's comment

Not so, modern relays are hermetically sealed in an inert (Nitrogen usually) atmosphere and usually have gold/palladium/silver contacts or a combo, and bifurcated contacts to boot. All PO approved relays are good for at least 100,000 operations without failure. Far far better than a rotary selector switch but not as cheap of course!
John aka Dr John

Thanks again John, I'll pass on the modern correction!
He also scoffed at the idea of a lowish cost PCB + relays, as he'd apparently had to pay £5 each for Frame relays when he built his stuff. (He is an Electronica recording artist who built a lot of his own gear 'back in the day'.)
I'll remind him that a decade or so has passed.

Any comment on the hazards of AC on the switching voltage?

[John Caswell]

Hi all,
Well you don't want AC on the control voltage to the relay coil as it can cause it to "chatter". Current consumption of modern relays is pretty low so it would be reatively easy and safe to run off the DC heater supplies, all that woeuld be required would be a suitable coil voltage, probably 9V for for 6.3V heaters. With regard to using the new relay PCB in PreII I am pretty sure it can be installed using say 20SWG wire links between the phonos and the PCB (s).
My own relay board is Vero plus wire links plus some Omron relays I bought at a rally for 50p ea and I run mine off a 12V supply. Works a treat and saves on coax wiring to boot

John aka Dr John

[little eddy]

Will the relay pcb fit any of the other WAD amp steelwork such as the Kit88?

[petercom]

No idea as I don't know the dims between the sockets of the KIT88.

The dimensions of the sockets for the WD88VA are 19mm centres between L & R and 16mm centres between each pair. There are six pairs of sockets in one row.

Pre2 has two rows of sockets, five pairs on top, five pairs underneath.

I would imagine the WD88VA is the closest you will get, but you may have to run short wires between the phono sockets and the PCB if the sockets spacing is not the same.

[John Caswell]

Hi Little Eddy,
Yes you can fit it BUT it will require short Tinned Copper wire links between the phono sockets and the PCB. Also bear in mind that it is a 4 input plus tape loop PCB, however the tape loop can be wired as a 5th input with a bit of wire juggling. Its main advantage is it gets rid of that glorious buggers muddle of coax input wiring and that poor input switch

John aka Dr John