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Old 23rd July 2007, 11:59 PM   #1
meepers is offline meepers  United States
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Join Date: Oct 2005
Default Punch 800.2

So I got this amp about 4 years ago, had it pushing a boston pro 12.5 4 ohm. it took all of 3 months for my sub to totally stop working. voice coil was FRIED. so i figured I just over ran the sub. Changed it out with another 12.5 4 ohm. this one lasted about 3 weeks, I had the gains turned way low on the amp, and xo set at 85h. after it toasted the second sub I started to suspect the amp. I changed it over to full range speakers. At low volume, it sounds like the speakers are hanging up, the sound is scratchy, and muted. if I turn the volume up to a normal listening level, the sound improves greatly. with the gain set at about 1/3 getting a clean 4v signal from my line driver, I every thing sounds great. and then... the magic smoke leaves the drivers.. I opened the amp, everything looks great. no burnt traces, no signs that anything was ever over heated or abused.

anyone have an idea what might be causing this to kill speakers? For a big amp I am really pleased with its output when it works properly, and makes one hell of a sub amp. I would love to fix it as it was quite pricey in its day, and I have a matching 250 for it as well. any fosgate guys know where to start? I can pop it open for board revisions or to test whatever with my dvom. I dont have a scope.
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Old 24th July 2007, 12:13 AM   #2
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Disconnect your RCAs and speakers , then turn on the amp and read the DC voltage at the speaker terminals 10.0 Milli-volts or less is pretty much Ok .
It sounds like you will have like 48 to 58 volts at your speaker terminals if so your amp has blown outputs and needs to be serviced
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Old 24th July 2007, 01:39 AM   #3
meepers is offline meepers  United States
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I cant say I was surprised to see you were the first person to anwser :P out of all the post reading I do in this forum, you have to be one of the best resources here. I am going to throw her on the test bed and I will post the results shortly.
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Old 24th July 2007, 01:54 AM   #4
meepers is offline meepers  United States
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ok. first off, I lied. its the 800a4. readings as follows.

LF 5.7 mv
RF 5.1 mv
LR 12.9mv
RR 36.9 VOLTS

Houston, we have a problem.

So I am guessing I could use it as a 2ch amp no problem? hehe..

what would I need to look at for replacement now that I have retarded voltage at one channel?
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Old 24th July 2007, 02:42 AM   #5
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Well, you got a three channel amp there meepers lol lol lol

I was sure you had a rail voltage coming out of something there just by the description of the amps SQ. That and the fried Voice coils.

Most All Rockford's fail there outputs in this exact way of passing the power rails to the speakers and producing very nice smoke rings lol lol lol

For what they charge for their amplifier products they could and should have engineered speaker protection relays inside all of there amplifier products, especially there Class D stuff Whew!!! you ain't seen nothing till one of those unload into a voice coil Who-Wee now thats some fireworks

Thank you for your very kind comments, I try to be helpful when possible. I have been doing this a very long time. There a several other people here that I am proud to post with though, as they also have a vast amount of knowledge to share also. I am just glad they let me in to hang around with them as they are some very smart folks in their own right.


Ohm out your output fets in the bad channel, They are gonners my friend, and I would replace everyone of them in that channel. You also have to worry about the driver section of SMD components in front of the bad outputs.
This is a HESHA based amplifier so you must remove the outputs from there MESHA panels. I use special tools unlike the RF techs which use a 150 watt soldering iron mounted on bench press.
I chose to use a Professional rework station, But I have less than 1% failure or my rework of these and my panels look original when I get done.

You can see by the DC readings the good channels have low DC offset on the output, The week one has 12 Milli-volts which tells me that channel has been artificially aged and the damage is displayed as DC offset over 10 milli-volts DC, Anymore and I would say it needs to be reworked also as it is headed around the bend on you already.
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Old 24th July 2007, 03:00 AM   #6
meepers is offline meepers  United States
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yeah this forum is a great place and alot of knowledge amongst the members. and unlike most other forums I am or have been a part of, there is very little of people going at it. I still need more practice at the putting things together, but I am quite skilled at taking things apart.

I wish I would have realized there was a problem before having a $400 dollar amp kill $500 in speakers. And I REALLY wish I would have sent it in when it was under warrenty.

Once I pull the cover off, what chips should I check out? Like I said, I couldnt see anything that looked smoked when I took it apart the first time. I can post up pics once its apart as well.
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Old 24th July 2007, 03:07 AM   #7
meepers is offline meepers  United States
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oh yeah, I did not think about the smd components. grr. I am guessing since I ran the rear channel bridged that it would be a good idea to rework both rear channels and not take a chance. I just dont want to drop 200 bucks into this amp to have someone else fix it if I can do the work myself. But I know smd is not a strong suit of mine.

I will pull the case back off and start probing around and see what is gone for sure.


Thanks again for taking the time.. Its way appreciated, and I hope by learning more, I will be able to help others in the future.
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Old 24th July 2007, 03:26 AM   #8
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I post elsewhere also, and I am going to state part of a ongoing post I have made at length elsewhere.

4 Channels amps running bridged for bass line, IS NOT a good idea.

Why and How, I come to this conclusion:

In every 4 channel amp there is a single power supply that is big enough to run all 4 channels to full power at any given moment.

Now armed with this info, does the following make sense to you

When operating a 4 channel bridged to 2 channel it is possible to OVER drive one of your channels and pass 4 times the normal power through that single channel. And if you do pass 4 channels worth of power through that single channel, HOW long do you think it will handle that excessive power level before it goes South on you and possibly taking out your expensive speakers with that single channel being driven way past its Safe Operating Area SOA for short???


If you funnel 4 lanes of traffic down to one lane what happens if the cars don't slow down ???

I have repaired more 4 channel amps than any other type of amplifier, and when I question my clients they were all running them bridged < 25 years of answers in 25 seconds >

I would treat yourself to a new amp and let the four channel either rest or sell it broken on e-bay, Tell the truth when your selling it, but there are a lot of better ways to run a sub then with a 4 channel amp.

I hope this makes sense and helps you to make the best decision for yourself and your stereo
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Old 24th July 2007, 03:32 AM   #9
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RF amps are always dieing together with a speaker. I respect them a lot, but for this only reason I'll never connect another RF amp to my nice components and a sub
Check resistance between pins of big 3-legged MOSFETS soldered to MESHA board along the amp sides. 4 FETS per one channel
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Old 24th July 2007, 03:51 AM   #10
meepers is offline meepers  United States
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yeah, I hear ya. I figured this was going to be a good work horse amp. I have an A404 in my car running the front stage, And I have an A300 that I need to repair for the sub. I have been running a super old school Radion 150 watt amp to my 10" in my car.

There are a hand full of fets that are getting no readings. I dont want to just run it as a 2channel amp and risk another set of speakers, I rather replace it with another art series or a PC2150 just for sub duty. After taking a look in side, the soldering required for anything but the fets *and I know its usually more then that* is way beyond what I am equipped for. and I am a bit concerned about the mesha boards as well, I would hate to break one. What do you think a competent repair shop would charge to repair? and what is the amp worth? I wish I would have kept my BD1000.

Thanks for all the input. but its sad to say, this one is beyond my skill level for solder and testing.
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