PV LTD 400 Problem

Bob Snelgrove · Post by **Bob Snelgrove** » 25 Sep 2011 12:24 pm

Guys

Every time I turn it on, I get a LOUD popping, crackling noise that sounds like it's going to wipe out my beautful old EV speaker. After power up all is well. Could the power switch need to be cleaned?

I have to unplug the speaker now for fear of destroying it!

thx

bob

Mike Wheeler · Post by **Mike Wheeler** » 25 Sep 2011 1:03 pm

If it's never been done, it's probably time to have a tech do a cap job and give it a good checkout. The LTDs are old enough that capacitors and resistors can be out of spec enough to cause your problem.....or even a meltdown.

More specifically, if the power supply filters have become leaky it can cause an imbalance in the power amp +/- DC rails, causing the pop you describe...and it can eventually blow you speaker if ignored.

I'd advise a good amp tech soon.

Paul Sutherland · Post by **Paul Sutherland** » 25 Sep 2011 1:07 pm

I'm not an expert on electronics, but I've heard many times that solid state amps can blow up instantly if there is no load on the amp. When you unplug the speaker (while the amp is still turned on) you are taking the load off the amp. I wouldn't do what you have described.

Bob Snelgrove · Post by **Bob Snelgrove** » 25 Sep 2011 1:40 pm

Mike Wheeler wrote:If it's never been done, it's probably time to have a tech do a cap job and give it a good checkout. The LTDs are old enough that capacitors and resistors can be out of spec enough to cause your problem.....or even a meltdown.

More specifically, if the power supply filters have become leaky it can cause an imbalance in the power amp +/- DC rails, causing the pop you describe...and it can eventually blow you speaker if ignored.

I'd advise a good amp tech soon.

Actually, I just did a Sarno assisted cap job!

I'm going to deoxit the pots just in case.

thx

bob

Bob Snelgrove · Post by **Bob Snelgrove** » 27 Sep 2011 5:58 am

Bump hoping Brad can chime in here!

Mike Wheeler · Post by **Mike Wheeler** » 27 Sep 2011 3:51 pm

Just for the record, it's tube amps that can be damaged by not having a speaker load while turned on. Solid state amps won't be harmed at all by not having a load.

However, with solid state, it's a bad idea to plug or unplug the speaker while the amp is on.....because there's a risk of accidentally shorting the amp's output, and that would be fatal.

Bob Snelgrove · Post by **Bob Snelgrove** » 27 Sep 2011 4:08 pm

Mike Wheeler wrote:Just for the record, it's tube amps that can be damaged by not having a speaker load while turned on. Solid state amps won't be harmed at all by not having a load.

However, with solid state, it's a bad idea to plug or unplug the speaker while the amp is on.....because there's a risk of accidentally shorting the amp's output, and that would be fatal.

Would having the volume down help?

bob

Richard Sinkler · Post by **Richard Sinkler** » 27 Sep 2011 10:10 pm

Just for the record. every Peavey amp I have owned (Session 400, Session 500 and my NV 400) have all made large popping noises when turning on. I have been told not to worry. The DDT compression will keep the speaker from melting and flying across the room. Many Peavey users I know call this "The Peavey POP". It helps to turn down both the pre and post gain controls prior to turning the amp on.

Bob Snelgrove · Post by **Bob Snelgrove** » 28 Sep 2011 5:53 am

Richard Sinkler wrote:Just for the record. every Peavey amp I have owned (Session 400, Session 500 and my NV 400) have all made large popping noises when turning on. I have been told not to worry. The DDT compression will keep the speaker from melting and flying across the room. Many Peavey users I know call this "The Peavey POP". It helps to turn down both the pre and post gain controls prior to turning the amp on.

Richard

This is an original LTD, no compression!!

I'm talking a room clearing, ear popping sound

bob

Richard Sinkler · Post by **Richard Sinkler** » 28 Sep 2011 10:55 am

Like I said, all my Peaveys have had a "room clearing, ear popping sound". I am sure my original Session 400 didn't have DDT, but the speaker never blew out. When Ken Fox updated my NV400, it was making that popping sound and I was told not to worry.

Maybe Ken will see this, or pop him an email.

Bob Snelgrove · Post by **Bob Snelgrove** » 28 Sep 2011 12:45 pm

Richard Sinkler wrote:Like I said, all my Peaveys have had a "room clearing, ear popping sound". I am sure my original Session 400 didn't have DDT, but the speaker never blew out. When Ken Fox updated my NV400, it was making that popping sound and I was told not to worry.

Maybe Ken will see this, or pop him an email.

Neither my original session 400 or this ever had anything but a soft pop when powering up.

Mike Wheeler · Post by **Mike Wheeler** » 28 Sep 2011 6:54 pm

Turning the volume down might help, but that depends on what is causing the pop in the first place...is it before, or after, the volume control.

I repaired a lot of 400 model amps back in the 80's and early 90's in my Gnashville shop, and they all had a modest pop when turned on, but it wasn't very loud. What you describe, Bob, is absolutely not normal at all. There is one, or more, component(s) failing somewhere. We could guess which one it is 'till the cows come home.

The only way to make it stop is to have a good tech go through it and find the problem.

Richard Sinkler · Post by **Richard Sinkler** » 28 Sep 2011 7:38 pm

Also, what is loud to one may not be considered loud to another. Like I said, All my Peaveys (and one's I have borrowed or used in a backline)have had a power on "pop". I seem to remember that the pop is due to the switch not actually interrupting the AC line, but switching is done through a triac causing the pop. I could have misunderstood this.

Have a qualified tech look at it. If he finds that these Peaveys shouldn't make that pop, let us know, as there are a lot out there that do.

Bob Snelgrove · Post by **Bob Snelgrove** » 30 Sep 2011 7:33 am

Here is an update from an email I sent to Brad:

"Hi Brad,

Finished the cap job a while back and am thrilled, especially with an
EVM-15L speaker.

I was having a problem just recently when I turn on the amp, a really LOUD,
crackling, popping sound. So loud that it sounded like it could damage the
speaker.

This was only on power up, after that the amp was fine.

I pulled out the chassis to check the power switch and deoxit the pots.
When I got it on the bench, I noticed that the third from the left 100 ufd,
gray cap ( Yellow circled)

had broken off from the board; both leads. I guess this must have happened
when I removed the chassis to check the switch etc. Not sure how it
happened so I had my wife solder the leads to the leads still soldered to
the board.

So I plug it in and the sound is very soft and dull and when I turn the
sensitivity up, the vol. went down and vice versa. On top of that when I
went to make sure we got the polarity right one of the soldered leads broke!"

So now I'm worse off. At least before, it sounded great after the initial pop.

What would cause the sensitivity control to work backwards aside from the low volume/tone problem?

thx

bob

Keith Currie · Post by **Keith Currie** » 30 Sep 2011 3:34 pm

My NV 400 makes a pop when turned on and always did but it does help to turn the reverb down when I turn it on.

Ken Fox · Post by **Ken Fox** » 1 Oct 2011 1:57 pm

You can unplug the Molex connector from the preamp board to the power amp board and check again. If the pop is there it is not from the preamp. That would narrow it down to the power amp board. If it is gone when disconected there is possibly an issue with the preamp board. Beyond that it is tech time to trace the problem out.
I am no longer doing any solid state amp repairs, only the "intense mods" in my shop on working steel amps.

Bob Snelgrove · Post by **Bob Snelgrove** » 1 Oct 2011 8:17 pm

Ken Fox wrote:You can unplug the Molex connector from the preamp board to the power amp board and check again. If the pop is there it is not from the preamp. That would narrow it down to the power amp board. If it is gone when disconected there is possibly an issue with the preamp board. Beyond that it is tech time to trace the problem out.
I am no longer doing any solid state amp repairs, only the "intense mods" in my shop on working steel amps.

Thanks, Ken

I wish I still only had the pop problem. After removing the chassis, finding or breaking a preamp 100 uFD Electrolytic cap lead, resoldering it, the amp is lifeless, low volume no tone, reverse action on the sensitivity.

Good news, I guess is now the pop is gone $:\$

bob

Richard Sinkler · Post by **Richard Sinkler** » 2 Oct 2011 1:22 am

What a bummer Bob. This may sound harsh, but a few on here have said that the pop you hear is pretty normal. Man, I hope you figure out the problem and get your amp back up and running.

Bob Snelgrove · Post by **Bob Snelgrove** » 2 Oct 2011 6:14 am

Richard Sinkler wrote:What a bummer Bob. This may sound harsh, but a few on here have said that the pop you hear is pretty normal. Man, I hope you figure out the problem and get your amp back up and running.

Any PV repair shops in the south bay?

thx

bob

Ken Fox · Post by **Ken Fox** » 2 Oct 2011 10:23 am

Probably cost you around $20.00 to send from a FedEx locatioon to Peavey in Meridian,MS (if you pack it). Considering their expertise and low labor rate (around $55.00/hour) I think you would be money ahead.

Bob Snelgrove · Post by **Bob Snelgrove** » 2 Oct 2011 11:31 am

Ken Fox wrote:Probably cost you around $20.00 to send from a FedEx locatioon to Peavey in Meridian,MS (if you pack it). Considering their expertise and low labor rate (around $55.00/hour) I think you would be money ahead.

That looks like the plan, Ken.

I was just at the studio and checked the molex connectors.

What is strange is that when I turned the volume all the way up and the sens, all the way down, it sounded pretty darn normal and loud.

thx

bob

Richard Sinkler · Post by **Richard Sinkler** » 2 Oct 2011 2:20 pm

That sure is a strange problem. I believe any Peavey dealer that does repairs, also is an factory authorized repair station. Guitar Showcase is probably one. Guitar Center is a Peavey dealer, but I'm sure they do repairs or how good they would be. I would probably follow Ken's advice and send the chassis to Peavey.

Bob Snelgrove · Post by **Bob Snelgrove** » 4 Oct 2011 6:03 am

I talked to Grant at PV repairs and he told me to check the pots tightness to the front chassis. Said a bad or loose ground contact could cause the sensitivity pot to act in reverse and cause the loud pop.

The pots were all very loose but sadly tightening them didn't make any difference.

I'll pull the preamp board and check the solder connection next.

bob

Ken Fox · Post by **Ken Fox** » 4 Oct 2011 7:57 am

I have to disagree with Grant, but I have seen too many of these. They do not use the front of the chassis as a ground plane. The contact is made via the circuit board. I have seen a bunch of these pots not soldered well (early production runs only). I had 3 pots fall out of a board when I took it out of the chassis on a very early model. Later model were much better (wave soldering was greatly improved later, it seems.

Bob Snelgrove · Post by **Bob Snelgrove** » 4 Oct 2011 8:07 am

Ken Fox wrote:I have to disagree with Grant, but I have seen too many of these. They do not use the front of the chassis as a ground plane. The contact is made via the circuit board. I have seen a bunch of these pots not soldered well (early production runs only). I had 3 pots fall out of a board when I took it out of the chassis on a very early model. Later model were much better (wave soldering was greatly improved later, it seems.

Next step pull the board today!

Thanks, Ken!

bob

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