[Dan Kolton]

Frank,

Is it possible for me to modify (increase) the delay time of the relay in the Ultra Pre-amp by changing something simple like a resistor?  I'm referring to the relay that connects the output to the power amp after the pre-amp warms up.

[avahifi]

Dan, does your preamp have the first generation Ultra EC three board plus small relay board circuit set, or the new one piece everything on one mother board circuit set?

In either case you can change the time delay by changing one resistor value.  The current value is 150K ohm (a small resistor standing on end on the small separate relay board on the first generation Ultra EC, or laying down at the edge of the board behind the 14-pin logic chip on the new mother board.

Making the resistor bigger will cause a longer time delay, smaller a shorter delay.  For example, the solid state units use a 50K resistor providing a 5 second delay.  The 150K resistor provides approximately a 15 second delay for the hybrids and tube units to allow for more initial stabilization time.

Regards

Frank Van Alstine

[Dan Kolton]

Frank,

You implemented the Ultra in my old T7 chassis before the new chassis was out.  I assume from what you told me that it doesn't have the single board, but I've not yet looked inside.  I further assume that each additional 50k is worth 5 seconds more delay.

Thanks very much for the info.  I asked on the Circle thinking that it might be info useful to others.

[avahifi]

In general you are correct.  15 seconds should be adequate though.

Frank

[Dan Kolton]

Frank,

I timed from turn-on until I heard the relay engage.  It was 12 seconds instead of 15.  It'll be a while until I've time to pull the cover and look at the resistor, but I think I'll install a 200 ohm just for safety.  Were you, perhaps, using a smaller resistor early on?  Also, what other specs. should the replacement have?

Thanks,

[avahifi_lj]

Hi:

The actual time will vary a bit due to variations in all the parts used in the mute circuit.  I assume you were talking about using a 220K Ohm resistor (or something close), and not a 220 Ohm resistor.  Pretty much any 1/4 Watt resistor close to the value you want will work.  Note that the board is double sided, so be careful when removing the old resistor -- you don't want to lift the foil traces.  You will also need a pretty fine tip on the soldering iron/pen.

Larry

[Dan Kolton]

Thanks Frank,

Of course I did mean 200k.  Is there room to cut the lead and install a 50k or so in series?  That way I'd have no problem lifting the foil.

[avahifi_lj]

Hi:

The resistor sits on end with one side mounted flush to the board.  What I would do is clip the wire from the top side of the resistor.  Using a fine tip soldering pencil (iron) heat the solder pad and remove both the old resistor body and wire.  Install the new resistor by heating the solder pads and then insert the resistor leads.  You will need to alternate heating of the two pads until the new resistor is fully inserted/seated.  Note that the solder pads and traces are pretty small.

Thanks

Larry

[Dan Kolton]

Thanks Larry.  Sorry I didn't notice that the previous reply was from you, not Frank.