Issue with PG Ti series amp: cut out at high volume

MEGA · Post by **MEGA** » Mon Aug 09, 2010 10:18 am

Hi all. Been a while.

I have two PG Ti 500.4 amps running a set of JL XR650CSi speakers each.

So the left amp has started cutting out at approximately 40% volume. It will always be fine below this volume and almost always fail above it. IT will come back in for a second, half a second, 5 secords sometimes. But then out again. IE out for 7, in for half. Out for 10. In for 1. At random.

IF I drop it back to 40-45% volume then she runs perfectly again.

I *think* it could be a failing transistor. Any ideas about this? And how would we detect which one it is?

I actually have a spare donor 500.4 which I can use for parts. But I have no idea where to start. (It died for another reason.. But the transistors and most parts should be fine)

I have a good audio guy. But it's a big risk to savage a board if this could not be the problem... ? Could it be anything else?

PS. I am in UK. So links to US repair centers etc aren't going to save me here ...

Massive thanks for any feedback on this one!

Post by **kg1961** » Mon Aug 09, 2010 11:30 am

i would look at the wire going to the sub some times if there is a lose stran of wire touching the basket or another v coil this would cause the amp to shut down

eulogious · Post by **eulogious** » Mon Aug 09, 2010 1:23 pm

How do your caps look? They could be going out, that's why it's random...

tonym · Post by **tonym** » Mon Aug 09, 2010 1:44 pm

check the rca's..they might be comin off....I had the same issue with mine a week ago...was the rca's(gold part)

Post by **kg1961** » Mon Aug 09, 2010 2:20 pm

also if you don't have the power.. (wire 4gauge battery alt that can handle the amp ect) the amp can go to a hard clipping and shut down

MEGA · Post by **MEGA** » Mon Aug 09, 2010 11:49 pm

kg1961 wrote:i would look at the wire going to the sub some times if there is a lose stran of wire touching the basket or another v coil this would cause the amp to shut down

Issues with this post in order:

1. Your avatar makes baby jesus cry from his crotch
2. XR650 speakers are not subs. They are components
3. The 500.4 is not a sub amp.
4. Like I said the amp is fine below a certain volume, consistently. And goes out above it. A simple wiring issue would not cause this

But honestly, excusing me being a sarcastic so and so I do appreciate all feedback so cheers anyway.

MEGA · Post by **MEGA** » Mon Aug 09, 2010 11:50 pm

kg1961 wrote:also if you don't have the power.. (wire 4gauge battery alt that can handle the amp ect) the amp can go to a hard clipping and shut down

I run 0 gauge throughout the car. And only one of my 3 amps has this symptom.

So again no..

MEGA · Post by **MEGA** » Mon Aug 09, 2010 11:51 pm

tonym wrote:check the rca's..they might be comin off....I had the same issue with mine a week ago...was the rca's(gold part)

Interesting.. This would cause the amp to cut at only a certain volume do you think?

I'd like to hear more from this point. drop another reply if you can?

MEGA · Post by **MEGA** » Mon Aug 09, 2010 11:51 pm

eulogious wrote:How do your caps look? They could be going out, that's why it's random...

Caps? You mean capacitors on the board of the amp? Does the amp have capacitors??

dontlookatme · Post by **dontlookatme** » Tue Aug 10, 2010 1:24 am

MEGA wrote:
eulogious wrote:How do your caps look? They could be going out, that's why it's random...
Caps? You mean capacitors on the board of the amp? Does the amp have capacitors??

Epic fail

Yes open ur amp and take pics for us

MEGA · Post by **MEGA** » Tue Aug 10, 2010 1:30 am

Sorry. I know what a capacitor is. I was making sure the OP wasn't suggesting a power cap etc in my wiring setup. Obviously that couldn't cause the problem. Because the issue is specific to one of the 3 amps in the setup.

I'm not sure if I need to further explain the issues that the amp is having though. It is failing under specific circumstances. It has not fully failed.

Meh.

dontlookatme · Post by **dontlookatme** » Tue Aug 10, 2010 1:41 am

The more detailed pics the better we can help u

eulogious · Post by **eulogious** » Tue Aug 10, 2010 5:19 am

MEGA wrote:
eulogious wrote:How do your caps look? They could be going out, that's why it's random...
Caps? You mean capacitors on the board of the amp? Does the amp have capacitors??

Yes, the caps on the board. PG is KNOWN for having problems with the caps in the amps when they get old. PG must have bought a pallet of bunk caps back in the day and didn't realize it until they were already having problems. So yes, check your caps as this is a known issue. The ti amps are quite as bad, but still do have this cap problem. When caps start to fail, it's very hard to tell, besides the funky behaviour with the equipment they are in. There are time when it's blatantly obvious that a cap failed (caused a fire, liquid on the board, the boards getting' eating by the liquid, the cap itself bulging), then there are times you can't tell at all.

So I would take the cover off and inspect the board and then throw up some pics of the board. That way we can see what you are seeing, and will make it a little easier to spot things as well.

I would recommend replacing all your caps anyways, if you want to keep the amp for a while. Once the caps are replace, you will easily get another 10-15 years out of the amp, so it's worth the effort. It will also narrow down your problem, if it doesn't fix it. I believe there is a how to in the "how to" section of the forum that tells you what you need to do to replace the caps, if you don't know how to.

dvnt88 · Post by **dvnt88** » Tue Aug 10, 2010 5:30 am

Have you checked the connections to you x-overs and the x-overs themselves? I ask as the 1st set of the comps I had (bought them right when JL released them years ago) like yours did the same thing and found out it was a component in the x-over that was the intermittent problem, which JL replaced at no charge, just my 02c.

eulogious · Post by **eulogious** » Tue Aug 10, 2010 5:36 am

I would also say check your RCA's like tonym said. You wouldn't be the first to have problems with the RCA's. Tonym and str3etwarrior both have had problems with RCA's just recently, so checking those guys would be a good call I would think. Street's problems was that it took about 10 min for the amp to "warm up" and play at full volume. Ended up being the RCA's...

Post by **stipud** » Tue Aug 10, 2010 6:52 am

How have you set your amp gains? Its very possible that 40% on your volume dial is exceeding the power output of the amplifier, sending it into clipping, and causing it to turn itself off.