Relay problems? Not sure

[dscottguitars]

I set up an amp I am building with the relay components for channel switching available from Hoffman.  I double checked to make sure the connections are correct and the negative is floating-not grounded.  I turned on the amp and have these issues, but not sure that it's in the relay circuit.

1.)  Volume controls-all new- are very scratchy, I have a gain, volume and master and all three are effected.

2.)  Voltage readings on the relay circuit are: 

6.37v AC on the source-good
1.1+v AC  and  2.7v DC on the positive side of the bridge-input of 5v regulator
~.5v AC  and ~.6vDC on the output side of the 5v regulator going to the diode and relay switch

I tried connecting the negative line with by touching the wires together-the switch is not hooked up yet-and nothing happens.  Channel one is still on and channel 2 doesn't respond.

All the voltages on the plates of the tubes are what I expect.  The power amp is separated from the preamp and that works great-quiet as a church mouse with the master pot not scratchy.

Thank you,

Daniel

[sluckey]

1.1+v AC  and  2.7v DC on the positive side of the bridge-input of 5v regulator
~.5v AC  and ~.6vDC on the output side of the 5v regulator going to the diode and relay switch

That's not good. How much voltage do you have across that 4700µF cap?

[plexi50]

1.1VAC on the 5 volt regulator input? Could a diode in the 6.3Vac bridge be backwards. Or the 4700 cap polarity is wrong

[dscottguitars]

One problem eliminated!  The scratchy pots.  It was a bonehead move:  forgot a coupling capacitor on channel 1 tube V2.

But the relay switching is still not working.  I connected the two wires that would go to a switch and channel one is still on.

1.1VAC on the 5 volt regulator input? Could a diode in the 6.3Vac bridge be backwards. Or the 4700 cap polarity is wrong

The bridge is the one from Hoffman's parts and it's one unit, so the diode backwards shouldn't be.  The cap is correct also.

How much voltage do you have across that 4700µF cap?

The voltage across the cap: (somewhat confused here, but one meter lead on the pos side and the other on the neg side)  ~7.5v DC (didn't check AC)  And 2.62/-2.62v from the pos/neg to ground.

Which one is correct when you say voltage across the cap?

And when I check the voltage using one meter lead to each of the wires to the switch there is 4.98v DC

Connect them together and there is 2.7v with one lead on the connected wires and the other to ground.

I also updated the schematic to reflect to coupling cap and the first part of the preamp that didn't show up.

Should I get both AC and DC voltage in that relay circuit?

I have 2.7v and -2.7 volts on the pos/neg sides of the bridge-respectively.  But still ~.64v on the diode-pos and neg side of the relay.

Thanks for all the input...

Daniel

[sluckey]

The relay power supply is floating. That means it ain't referenced to chassis ground at all. Sure, you may read some voltages in reference to the chassis, but they will all be bogus. All relay power supply voltage readings should be made in reference to the negative side of the bridge, or the negative side of the filter cap. Nothing else matters.

With that in mind, the ~7.5dc you measured across the 4700µF filter cap is OK. That becomes the input to the regulator chip. Leave your black meter lead on the negative end of the 4700µF. That's your reference point. Now place your red lead on the output terminal of the regulator chip. You should read +5Vdc. What does your meter say?

[dscottguitars]

Hi Steve,

I got 4.98v/ close enough to 5 for me.  But the relay does not switch channels.

[dscottguitars]

The diode I am using on the relay switch is a 1N5408, the same ones I use in the power supply.  It's a 3 amp version.  Could that make a difference?

[dscottguitars]

Looking at the relay tips page, I see the note: "It can be confusing when you look at the diagram on top of the relays which is actually the bottom view."

I think I have this backwards.  Could that be it?  I definitely flipped it over and matched the positive side of the top to the same side on the bottom.

[sluckey]

The diode 'may' be installed backwards. Disconnect one end of the diode. Does the relay click now when you short the switch wires? If so, reverse the diode.

The diode cathode (banded end) must connect to the + side of the relay.

[dscottguitars]

Thanks Steve, that was it.  I switched the diode around and the pos/neg leads and the relay switches between channels.

 

[guitardude57]

Depending on which relay you use, power polarity can be OK with the scheme,
or backwards from it. which I found with one of my builds.  Glad it was just the diode.
Also, a 1N4007 is plenty for the diode.