HK 430 Noise, RCA cables?

[vondy]

So tried some new cables thanks to jimjimbo, nice cables but noise is still there. Opened her up and cleaned the pots, fuses, etc. Everything looked clean to begin with.

 

After further exploration, here is what I've noticed. Each driver makes a sound when the HK is turned on. Tweeter makes a hiss, mid a deeper his, woofer a hum. Nothing on the amp itself seems to alter the noises be it volume, input, etc. Doesn't matter if anything else is connected to the amp or not. The only difference is when cables are connected to the Aux input the high frequency hiss gets a bit crackly.

 

I've tried a different outlet, same thing. The outlet it usually resides on is on a dedicated circuit anyway with a Brick Wall surge protector.

 

Now this is me with my ear right up on the speaker, step back and you hear nothing.

 

Maybe these older amps are just not dead silent and it's normal?

[HDBRbuilder]

To at least SOME extent, you are experiencing what happens when the signal to noise ratio is high, but there is no signal going thru the amp to the speakers...so the amp just has the noise to send to the speakers.  Make sense??

 

As for the crackling, hum, and such...take the receiver and have it tested to find out what the problem is.

 

In my own experience, I have found that CLEANING the fuse connections, and ensuring the fuses are all fast-blow of the same brand and type and the correct rating...tends to often be the one MAJOR thing that gets overlooked in cleaning.  THERE ARE LOTS OF FUSES IN THE H/K 430, some of which you probably don't even realize WHERE they are until you run into them...they are not only under the hood, and on the rear panel, but also you need to remove the chassis bottom plate to find the rest of them!...and most people don't even think about that area, unless they are techs who have the wiring schematic to go by.

 

I once had something weird going on with my stereo...this happened years ago...and I finally just got up and opened the receiver up everywhere I could...come to find out some kind of SMALL spider had gotten inside of it and its tiny little babies were hatching out of the egg case and running around all over the place inside of the receiver...some of them getting fried in the process...so, every time I hear somebody say something is wrong with a piece of equipment , I tend to WANT to ask: "Is anything LIVING inside of it?"

[mike stehr]

2 hours ago, vondy said:

Maybe these older amps are just not dead silent and it's normal?

 

It may be normal to hear some slight hiss with your ear right next to a tweeter, but hums and crackles indicate other problems.

When you had the receiver refurbished, did the unit have the capacitors replaced? Like the power supply caps, or the numerous smaller caps in the unit? Did he re-bias the amplifier circuit after refurbishing?

If you have a DMM, maybe check the DC offset at the speaker terminals. The amount of DC at the speaker terminals should be millivolts or microvolts. If either side is over a volt, there is a problem.

[vondy]

When I had it refurbished I told him I wanted it brought back to original specs so I assume he replaced anything that should have been. The only details I can find are form an old email where he said the initial cost covers "three power supplies and main amp."

 

How many fuses are in this? I saw two inside and three on the back. I did not look under the main board but seems weird they would hide any under there.

 

I can check the voltage at the speaker terminals.

 

My knowledge of the internal workings of these electronics is very limited. 

[jimjimbo]

I would highly recommend following Andy's advice.  Take off the bottom panel and look for fuses.

[vondy]

14 minutes ago, jimjimbo said:

I would highly recommend following Andy's advice.  Take off the bottom panel and look for fuses.

Yeah just looked at the Service Manual, there are 8 total, 3 underneath. I'll clean and replace

[HDBRbuilder]

One more thing, if the H/K was an "international model" it may have the switching under the hood or outside on the rear panel for voltage/cycles...it will either be a switch type set-up OR it COULD be a plug which is turned and re-inserted according to the diagram(normally on the plug as an arrow) showing the voltage/cycles for the country you are in when you use it.  This is also a connection that needs to be cleaned during the cleaning process.  The H/K 430 was hands-down the largest selling receiver of its time, and minor changes were made throughout its lifetime without making model changes...none of which affected the performance, but changes nevertheless.  It went from screw speaker-wire connections to spring-loaded, for example (and it is mighty hard to fit all those copper strands from lamp cord type speaker wire into the tiny hole provided on the spring loaded connecters!)...with this, in itself often being a problem...since it takes ONLY one little strand touching the connection next to it to jack things up involving what you are hearing through your speakers.

 

Three power supplies replaced????...and main amp?....I don't get it!  Looks like a lousy way of telling you what was replaced to me.  Pretty much everything used on them back when they were being made is still available today.  The tech guy should have been more specific about what he did...and if he had to re-solder anything, since a bad solder when replacing parts can often cause problems, even if it "checked-out OK" right after the item replacement was finished...and sometimes just carrying the unit home can cause those problems to begin.

 

I really hope this/these issues can be solved, because it is a shame that you are having them!  that unit is a SWEET unit if working properly!

 

I had to get a number of output transistors replaced once in a different H/K unit and two of the replacement ones were bad, but it took the amp to warm up a few times during usage before the problem occurred indicating the issue was with the replacement parts...even though everything checked out OK before it left the tech's place.

[vondy]

This was a fellow forum member who did the work. There was no official itemized repair sheet or anything.

 

Was he referring to the caps related to the power supplies and main amp? I didn't think he actually replaced those parts.

 

The amp sounds great! I don't think this is causing any issues as far as listening to music goes. If it is it's on a level I can not hear. The hiss/hum does not increase with volume.

[HDBRbuilder]

Turn everything off, then unplug the receiver power cord without letting the plug go, flip the plug over so that when you plug it back in, the opposite prongs are going back into the holes opposite of the way they were when you pulled the plug. Sometimes it is the simplest of things that solves the problem of hum and such.  Actually that is normally the FIRST thing that SHOULD be tried.  If it is worse plugged-in that way then go back to the way it was before.  Those old-style plugs can be inserted either way.