Relay Question on PS Audio 200c

[Pure_Brew]

I'm curious about my relay, and I apologize in advance for my newbishness. This is part of my quest to track down all the mech noise and be rid of most of it once and for all.

I have a PS Audio 200c, and from what I read from another poster, not only the power transformer, but the relay in the amp can also be a cause for mechanical noise (which he swapped out to good effect with a SSR). This is an Magnecraft W199AX-9.
Here's the specs on it if this helps, and it appears to be available.

Contact Rating
40 A
Contact Configuration
DPST-NO
Contact Materials
Silver Alloy
Maximum Switching Voltage
600 V
Switching Current at Voltage (AC, Resistive)
40 A at 277 V 50 / 60 Hz
Switching Current at Voltage (DC, Resistive)
40 A at 28 VDC
Switching Current at Voltage (Pilot Duty)
A600
Minimum Switching Requirement
1 A at 12 VAC


Specifications
Nominal Input Voltage
120 VAC 50/60 Hz
Coil Resistance
290 Ohm
Cover Style
Open Style
Weight
227 to 312 G


Coil Characteristics
Operating Range - % of Nominal (AC)
85 to 110 %
Operating Range - % of Nominal (DC)
80 to 110 %
Average Consumption (AC)
10 VA
Average Consumption (DC)
4 W
Drop-out Voltage Threshold (DC)
10 %
Drop-out Voltage Threshold (AC)
10 %


Performance Characteristics
Electrical Life (UL508), Operations at Rated Current (Resistive)
100000
Mechanical Life, Unpowered
1000000
Operating Time (Response Time)
30 ms


Environment
Ambient Air Temperature around the Device - Storage
-40 to +85 °C
Ambient Air Temperature around the Device - Operation
-40 to +55 °C
Connection
8 AWG
10 mm²
Terminal Tightening Torque
7 to 9 in lb
0.8 to 1.0 N·m


Would it be smart to just replace it with the same thing, which I can't imagine would hurt since its like 24ish yrs old, or should I use a solid state relay, and if so, can anyone suggest an alternative?

Thanks in advance

[fotios]

Looking at the site of Magnecraft, i have to say that this relay is a real monster of power and of excellent quality. In the picture it appears as open type. Why this PS Audio amplifier uses this power relay? Because its mains switch is very small (push button) for decorative reasons? I have seen this practice in many Crown amplifiers. You are suspicious that it causes mechanical noise. Are you sure for this? Have you checked in which condition are the power contacts? Are worn-out? If yes, then you have to try a clean-up of contacts with a fine sand paper, but very little to not remove except the dirt and the gold plating of contacts. You can use white spirit to make a wet cleaning of contacts as well. From experience in power plants, power relays which connect heavy inductive loads to the mains, have a life of up to 5 years as much. Then must be replaced.

[fotios]

I have to add some comments yet.
This type of powering-up of mains x-former with a relay, it is an old fashioned method.
Of course, the issue it is the appearance of the front panel of amplifier. For decorative reasons, we use a small push button type switch for powering-up the device. But the mains switch simply it passes the mains voltage in a current limiting circuit. This circuit is composed from a large NTC thermistor which limits the inrush current during the charging of reservoir capacitors of power supply. A timing circuit of, say, 0.5 sec activates then a power relay which shorts the thermistor. In this manner, neither the contacts of switch or of relay are heavy loaded. This method offers two benefits; the good control of inrush current and the possibility of using a small mains switch instead a big and ugly rocker switch.

[Pure_Brew]

Hi,
I suppose that it uses this relay for it's benefits as you described. I believe that this design takes all the work out of the switch itself. I'm not 100% sure about the noise, but It would cost me only around $20 US to get a new one, and after 20 years in service (everything appears original) it might be good to change.

It's a big relay for sure, and this amp is rated to output 200wpc(4ohm) 400wpc(8ohm) and 1000wpc into a 1.5ohm load.

I'm sure the power transformer hums, but if they are both making noise it is a bit hard to tell, since the transformer is so much closer to the top cover, and they relay/trans are right next to each other. This may or may not be a sensible explanation, but if the noise is louder on the relay side of the transformer, then the mechanical noise is summing to a gain. Likewise if the sound is uneven or even quieter on the relay side, then the generated noise could be there but out of phase to a point, causing some cancellation . Of course I am pondering this and I could be completely wrong, since I suppose the lamination hum could be uneven as well.

I wonder if I should just take the relay out of the amp and use some heavy jumpers to power everything up and see what occurs then?

Thanks.

[fotios]

Originally Posted by Pure_Brew

I wonder if I should just take the relay out of the amp and use some heavy jumpers to power everything up and see what occurs then?

This is correct. If i were in your place, i would have done this experiment already.

Regs
Fotios

[Pure_Brew]

Makes sense. I've never worked on an amp before, proceeding with caution...

[Pure_Brew]

Another question before I proceed. After checking around a bit more, it looks like I should drain the power supply caps. These are 4 big 10000uf 100v capacitors. It's hard to get at the leads, but I can get at the common ground bus bar that is attached to all 4, and also wraps around and is attached to the main chassis. I can also get to the individual copper buses coming off each cap.

My question is, can't I just use a lamp with a 100w lightbulb to bleed these off? I could clip leads to the lamp and throw the switch as the final connection.

Thanks

[Pure_Brew]

Update: I did swap this magnicraft with the identical. They both make a mechanical noise.
The transformer has been vacuum dipped, cured and re-inforced. The transformer tech stated that the transformer wasn't noisy at all. The tech that just recently looked over the amp agreed that the coil in the magnicraft is a little noisy.

So, can anyone suggest a solid-state relay that I could possibly use in place of this?

Thank You

[tiefbassuebertr]

Originally Posted by Pure_Brew

Update: I did swap this magnicraft with the identical. They both make a mechanical noise.
The transformer has been vacuum dipped, cured and re-inforced. The transformer tech stated that the transformer wasn't noisy at all. The tech that just recently looked over the amp agreed that the coil in the magnicraft is a little noisy.
So, can anyone suggest a solid-state relay that I could possibly use in place of this? Thank You

check out therefore this thread:
The ultimate Inrush Current Limiter Solution for large Toroidal Transformers

An other possibility is the modify of the relais coil driving: use DC instead AC and you will no longer observe any buzzing effects at the relais coil.
Ask there about the suited DC voltage:
Magnecraft
191 Waukegan Rd, Ste 206
Northfield, IL 60093-2743
Phone: (847)441-2526
Fax: (847)441-2522
Email: relays@magnecraft.com
Then you must a rectifier, suited resistor and capacitor to create a DC voltage about an easy way.

[Pure_Brew]

Thanks I missed this reply. I actually ended up building a DC supply for the relay which turned out to be 100% non-evasive drop-in. Works like a champ.
Swappin' Mech Power Relay for Solid State

I also installed a pair of CL-60's ala Pass layout. 1 on each pair of windings. This was simple since all I had to do is replace the jumpers with the thermistors on the terminal block.