Relay power supply and wiring. Will it work?

[Tdale]

I'm attaching a picture of a circuit I'm planning to use.

I copied some from Bob's layout, and found some on the web.

The circuit I found on the web, show that the left corner of the bridge should be grounded, but in bob's layout, it's not grounded.

Will my power suppy work?

And will my foot switch arrangement work? I'm planning to use a normal 3-pin XLR.

[Luthierwnc]

You didn't show your grounds. You want the FWBR and regulator to be grounded at all times. The relay grounds are all you want on the switches.

Put a diode in reverse parallel on the relay hot and ground to prevent flyback.

Do you have any LED's to tell you when the thing is on? They will need power as well.

Skip

[Tdale]

Does it have to be grounded?

Look at this:
http://www.patmedia.net/bob-ingram/DClo ... Layout.jpg

I can't see any grounding in the 5V power supply?

Tommy

[Luthierwnc]

Evidently not. I still like the idea of having that cap fully charged. Have a look at this link for some switching ideas:

http://www.lynx.bc.ca/~jc/relaySgl200dpi.gif

This also addresses how to light up an LED with the footswitch. The original schematic in the SchematicHeaven file also shows a grounded power supply. In this case, it is a voltage doubler but all of the power conditioning components are grounded. The only component that isn't is the relay itself.

sh

[Tdale]

I'm adding a led, just need to use a 4-pin xlr... I didn't bother to draw it.

I'm no expert on electronics, so I didn't know that a cap doesn't charge fully, without being grounded....

Bob said that when he grounded his supply, it hummed...

Tommy

[Bob-I]

Correct, do NOT ground the relay supply, and put that reverse bias diode across the coils.

Looks right to me.

[Tdale]

Not sure about which way is reverse... should the "arrow" of the diode symbol point towards the "+" of the rectifier bridge?

Tommy

[Luthierwnc]

Guess I could have kept my mouth shut. If Bob has a proven system and you have the parts, do what he says. The band on the diode is the same as the arrowhead on the schematic. In this case, you want the band towards the hot side of the relay.

That said, the attachment is the way I do it. Being both cheap and lazy, I use a common switchcraft stereo jack and ground it on the back of the amp. All the other grounds are on a main buss wire. I've used this on four amps and never had a hint of noise.

sh

[d95err]

Correct, do NOT ground the relay supply, and put that reverse bias diode across the coils.

Interesting. I'm planning to install a channel switch relay in an amp I've built. It's cathode biased, so basically I have three options on referencing the relay voltage: Ground, Power Tube Cathodes or Isolated.

Could you explain some more about the advantages/disadvantages of isolating or grounding the relay circuit?

[Bob-I]

Guess I could have kept my mouth shut. If Bob has a proven system and you have the parts, do what he says.

Well... I'm not the guru, I just had noise when I grounded mine. If you're worked without noise, then maybe I should revisit this.

That said, the attachment is the way I do it. Being both cheap and lazy, I use a common switchcraft stereo jack and ground it on the back of the amp. All the other grounds are on a main buss wire. I've used this on four amps and never had a hint of noise.

sh

Interesting, it looks exactly like my schematic except I used 5V. I wonder why I got noise and you didn't.

I've been using isolated stereo switching jacks. By connecting the non-switched side to the relays, and the switched side to the front panel switches, the panel switches are disconnected when the footswitch is plugged in. Simple and effective.

[Bob-I]

What resistor did you use in parallel with the LED?

[skyboltone]

Hey Bob:
Check this out. Series not parallel though. If you want parallel, take the answer and insert the parallel value that provides the same voltage drop. The same site has a calculator for multiple diodes and a cheat sheet for diode voltages. I have several hundred LEDs of various colors and descriptions that I got at a swap meet years ago. This formula seems to work.

http://led.linear1.org/1led.wiz

Dan

[Luthierwnc]

Bob, I'm not sure but somewhere (here or maybe the GearPage) I read that some folks didn't like having the relays on the mains transformer. I use a separate transformer. The resistor on the red LED is 48 ohms and the one on the green is 120 ohms. It is just enough resistance to light the LED but it has an independent signal to ground so the relay trips. In the case of the amp I'm finishing, the 12v line is also the indicator light supply for the D-lator switch so it needs to be available without a relay.

BTW, until tonight, I used a DPDT stomp switch for the OD. It is in a two switch Hammond box. The boost is just SPST. The OD switch has the feed for the OD and another for the boost in parallel with the stand-alone boost switch. I built the HRM first. Since both tone stacks muddy the sound, I rigged it so hitting the OD would turn them both on but the boost could be used independently. I'm using the same stomp box for the Hybrid now so I went back to the usual method. I've got wide feet so I can get them both with one step.

Have a look at the JC Malliet link I mentioned earlier. Those same pages have been up there at least nine years. Except for AGA, Ampage and a couple sites like his, there wasn't much else back then. He's got a lot of good (and independent) information on Fenders, Marshalls and assorted mods. Useful stuff.

D95ERR - I'm afraid I can't give you much help. There are a couple things to consider: On scratch amps, I've always made my own aluminum chassis'. They seem to have a lot fewer ghosts, parasitics and ground loops. The originals were built out of Bassman chassis' and there is a lot of spare room in those to keep signal, supply and heater wires away from each other. In my case, a high density build is likely to be an unsuccessful prototype.

sh

[Tdale]

Guess I could have kept my mouth shut. If Bob has a proven system and you have the parts, do what he says. The band on the diode is the same as the arrowhead on the schematic. In this case, you want the band towards the hot side of the relay.

That said, the attachment is the way I do it. Being both cheap and lazy, I use a common switchcraft stereo jack and ground it on the back of the amp. All the other grounds are on a main buss wire. I've used this on four amps and never had a hint of noise.

sh

Looks nice.

is it a separate transformer? It says 6V on the primary... what voltage is the secondary?

Could you explain a little about the resistors in paralell with the LED's..Are they there to give the right voltage for the led? Doesn't it affect the voltage for the relay coils?

Tommy

[Luthierwnc]

The transformer is a Radio Shack 12v model. The supply circuit is quite compact. If you blow up the “guts finished.jpg” in the “Hybrid Build in Progress” thread, you can see assembly next to the large filter caps. I bolted a TO-3 case regulator on the underside of the board. There are four holes in the board to accommodate the regulator; two small ones for the terminals to stick out and two big ones to hold the case (which is also the ground and heat sink). An enclosed FWBR is bolted on the top. The secondary wires are soldered directly to the legs of the rectifier. The output is bent over and tied to the input of the regulator and a 1000 cap. The output of the regulator is tied to another cap and the relay supply wire.

Here is where it gets a little tricky. The caps are tied together on turrets and to a ground wire underneath the board. That wire has a terminal lug soldered to the end along with a pigtail going to the buss. The FWBR ground is bent into a loop and positioned directly over the mounting hole. From the bottom of the board, here is how the sandwich is made: 6/32 bolt, lock washer, terminal lug with grounds, regulator, board, FWBR, FWBR ground leg, metal nut. All of the grounds in the supply are together at that point and tied to the buss wire with a single lead. It takes about 1.25” of real estate on the main board.

The parallel LED is an idea I got off the JC link. Most of the time you see them in series. The resistor slows up enough juice to light the LED but not enough to collapse the coil field. I like it because if the LED fails, I can still get my solo in.

sh