Why the Peavey PV1200 PA amplifier blew a channel
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- Опубліковано 14 сер 2021
- Pulled the bad parts and determined the possible cause of why the amp blew up.
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Email: johnaudiotech@gmail.com
Thank You! - Наука та технологія
Hi everyone! Sorry for not posting up a video last week. I was under pressure to get work completed. I did find clips from a couple months ago that I forgot to finish, so here you go...
Not always you have the ability to make videos all the time.
No problems for me. I do not stop watching your channel.
Hello. why does the Class-d amplifier get so hot after 30 minutes when you only connect the power supply?
The L15D I have is 40 degrees same with many class-d I have!
Is thete a lot of noise going through transistors or ic. which creates heat? This is filtered out at the speaker output.
We used Peavey amps in the first job I worked after college. They were used for driving railway track circuits during calibration and testing, and I remember them blowing up on a regular basis.
This is a bad design like many Peavey products. This one didn’t take into account thermal expansion of the heat sink.
You mean thermal expansion of the transistors. There's no doubt the thermal strain caused eventual fatigue failure at the soldered pin joints due to secondary stresses; these would have been mitigated by the use of sockets. This is one reason why BGA joints also fail in CPUs, GPUs and APUs (X-Box 360, Sony PS3 et al); again mitigated by the use of sockets.
These TO3 transistors are not supposed to be soldered. They should be installed on sockets, in which the leads can slide due to expansion when they heat up.
I agree sockets are a better solution.
But many amps like-again, the Adcom GFA-555-use this type of arrangement with no issues. The difference is the transistors are hand-soldered, using copious amounts of solder. You're supposed to actually let the solder blob up a bit, instead of a smooth tapered fillet as one would normally do. This works fine actually, I have worked on dozens of GFA-555's and never had an issue with that. I did see a couple failures where the solder wasn't blobbed up thick enough.
These were just run through the wave soldering machine, leaving a thin fillet that of course stresses over time.
Also possible the aluminum they are using has too much thermal expansion in the Z-axis. Metallurgy fail.
@@phloodpants You are correct regarding hand soldering using copious amounts of solder. I have three power amps here that I built over 20 years ago in that way and they are all fine.
They should be soldered point to point, separate from the PCB.
TO3 transistors don't stress when they are screwed to heatsink ?
@@phloodpants Interesting that they have proved to be reliable in the GFA555. I've had a few issues with older TO-3 sockets not making good contact after 30 years, so I guess it's really a case of picking the lesser of the two evils. I do wonder if using a modern PCB with plated through-holes would stop the issue with solder joints cracking on TO-3 transistors.
I suppose it's also one more reason why companies have moved to TO-3P packages for most big transistors.
Nice analysis!
Nice work John!
Hello John, Very interesting, a good way to learn how to diagnose a failure, an old Peavey Amp. Garage bands probably liked them because they were cheap, at least in the 70's. Glad your doing well, I hope your Brother is too. Busy with work and working on the house, interior make over and light remodel, catching videos as I'm able. It's been a hot Summer, over 30 days so far where the temperature was 90 degrees or more. June 28th, Portland International Airport (PDX) was 116 degrees, a record. Your channel is always still of interest to me, Thank you. All the Best from Oregon, Cass.
Hi Cass. My brother is cancer free which is a miracle. It has been hot and humid around here. 116 Deg is insane! Hottest I've ever witnessed was 104.
Just an idea:
Why not sell the working board online as a replacement part.
And then modify the damaged one.
TO3 sockets as mentioned in other posts is a great idea. But what would also help is a two layer PC board with plated through holes. As you can see this is a cheap single layer PC board using a lot of wire jumpers and the power transistors only have a surface solder connection versus a minimum 0.062 soldered through hole. IMO, there is no excuse today not to use 2 layer boards. In fact some PC board shops I deal with don't even do single layer boards anymore. If you submit one, they will put pads on both sides plated through so there is no cost savings on a single layer board. You can still find single layer boards in cheap consumer electronics but a product such as shown here deserves better.
the first thing i would do to test the opamp is to pull out the "working" one from the other side and compare resistance measurements between the pins on each one
Tkanks!!
Amps like these are used on-top-of or near speakers. You still must then solder in the sockets, and while you solved the thermal expansion problem, you have introduced "vibration induced distortion". A properly engineered PCB with thru hole plating and large solder pads on both sides of the PCB would solve this issue, provided the heat sinks were increased in size(thicker=less expansion).
I highly disrespect them based on their appearance on Undercover Boss. They convinced a wonderful, hardworking, employee to turn down a far better job offer, pretending to care for the camera, and then laid him off and sent the factory to China. We aren't talking about investors. We are talking about the father that started the company and his son. That being said their equipment is generally sub par. They work but tend to sound terrible.
I agree and it wasn't just him it was pretty much all of the employees were screwed over by father and son.
"the father that started the company and his son" ... actually step son, but the apple still didn't fall far from the tree. Both are uncaring a-s-s-holes IMO.
Can you tell me or recommend, where to buy this peavey cs3000 Circuit Board, because it just burn. I can see the model was P2500AMP on the board. Thanks
Hola John, saludos desde Guatemala
Peavey amplifier is the best amp yet like crow and QSC. I have 15 of them 2000 watt and works great. You just need high end equipments like preamp for good sound.
Yeah, that's way under-spec'd on the number of parallel output transistors for running 600W into 2 ohms. For a typical example, the Adcom GFA-555 is about 350W x 2 into 4 ohms, not sure how much more into 2 ohms, but much less than the PV anyways... and it's also sporting four pairs of output transistors. The PV is fan-cooled at least, but nah, that only goes so far. They are cheaping out hard there.
The number of transistors isn't unreasonable. Look inside some other PA amplifiers, and you'll see similar numbers of transistors. Heatsinking is definitely on the anemic side though, so it can't do 600W into 2 ohms for long. The trick with professional amps is that they tend to have pretty good VI limiters and (sometimes) peak limiters, which helps to stop them from self-destructing if things go wrong. Home amps (like the Adcom) generally don't have much in way of protection.
Doing the math, each transistor has to handle about 4.3 amps RMS. That may be pushing it a little when it comes to DC SOA, but this isn't DC (lowest is about 20 Hz), and each transistor is only handling the 4.3A for half of the cycle. That's not unreasonable for most TO-3 transistors that got used in big amplifiers.
There were some Peavy fans, but overall, they were middle of the road in respect. Some of their products were sort of doomed to fail, like this one. It is probably worth fixing to sell but only marginally so.
If you don't know why the voltage was chosen, don't change it. There are multiple reasons to choose a higher output voltage than just power.
There was a time when those JRC4558 ICs commanded such a price it prompted a reissue of the chips. Supposedly the new ones are made with the original masks. I'm not sure if they are exactly the same though. The originals came in Tube Screamer overdrive units. Do a web search on Tube Screamer JRC4558 and you'll see a lot of discussion about it. I made a distortion box with a really old JRC4558 and I'd have to say there's something to the legend.
4558 was introduced in the mid-70s and has always been a very common IC. They are essentially just two 741s (from the 60s) on one chip in a plastic case. I don't think there is much difference between the different variants in sound. And to my ears, they sound absolutely fine. You even find them in high-end equipment from the 70s through the 80s.
I ran pro sound in the early 80's. Peavy equipment, either creating sound - guitar amps, mixing consoles, etc. - or reproducing sound - speakers - they all had a very harsh sound. They were heavy. However, they were descent quality for their price and they were made in the USA. We moved away from the brand, over time. I would not expect any of the components to be on sockets, because these amps were routinely subjected to extreme vibration and impact, in daily transportation. I guess they could have been in sockets and tacked down with caulk...
The cs800x is a great amp.
Hi how are you sir I like your video I wanted to ask you a question what output transistors were used in this amplifier that cost $8 I would like to know the part number's printed on the case of the PNP and the NPN output transistors. Thank you in advance for answering my question❤✌️💯😁
Re the Peavey image - in the '80s they did a lot of business selling high power clean solid state amps to pedal steel players, and fully outfitting the P&W scene. This made people associate them with conservatism. They have made awesome "big iron" classic style valve guitar amps for decades, and their 6505 is considered top rank in high gain guitar amps.
Peavey built a full tube guitar amp which was a terrible design. They used an opamp to create the negative bias voltage. When the opamp died, bias voltage went to zero volts all four el84's red-plated and took out themselves and the output x-former.
In working condition the amp goes for nigh on 1000 bucks....
What a waste of money
Wow, that not enough heat sink area to keep the out tranies in SOA at such large supply voltage rails. With larger heat sink +/- 50V, the board would make good sub amp. What are the out transistor in this amp - the MJ15003/4 (23/24) can take a lot of beating if well cooled.
If you still have that board and are looking to get rid of it, I’d happily pay you for it. I blew a channel of my PV1200 and can’t be bothered to buy the parts for it, but I’d happily buy a working board just for the convenience.
Yes I still have it. You can have it if you pay the shipping. The board is untested but the output components and drivers check to be okay using my meter. If you really want it, email me at the gmail shown in the description (typing links here seems to block messages sometimes).
Peavey amplifiers were excellent for what they cost, but they were always a cheap amp when they were new. Their power supplies and cooling tended to be a little on the anemic side for the amplifier power ratings, and occasionally they would cut corners when it came to physical construction. So it's not a Crest 8001, but it also wasn't priced like one.
Hello. could you answer me one thing? why does the Class-d amplifier get so hot after 30 minutes when you only connect the power supply?
The L15D I have is 40 degrees. same with anyone else I have!
There is a lot of noise going through transistors or ic. which creates heat? This is filtered out at the speaker output and the coil gets hot even if you do not connect the speaker
The type of ferrite used in the coil may not be ideal for the switchmode frequency of the amplifier and it gets warm due to eddy current losses.
@@JohnAudioTech Thanks. what about transistors and class d ic. Gets hot only with power suppky in? all the way up to 40 degrees
@@JohnAudioTech I think the copper wire inside the coil is undersized and that there is a lot of noise that is filtered away! There may be high frequency noise.
cant beat old peavey guitar amps at least!
I think they must have soldered the transistors first, then tightened the screws and popping the pins through the solder.
More likely that unit had a hard life in the back of a van with no suspension. Going from bar to bar.
@@1pcfred Yep, those guys can be rough on their audio gear!
Thermal cycling would have done this. At the transistors heat up the legs will expand slightly, stressing the solder joints. Over a number of thermal cycles the solder will crack.
The PV line of amps were the entry level or cheap amps. The CS series was much better.
La serie PV es económica muy delicada esos power
I'm a fan of yours sir😁
If you have enough time,,Can you check and review an OCL amplifier from online shop,,
It is a Stereo OCL amp with 18-25volts CT supply with Tip2955 & Tip3055 as output transistor.thank you sir
Electronic and audio amps hobbyist from Philippines ❤️❤️
From time to time, I have watched your channel.
Usually, you have some decent content and you explain things well enough.
I used to have a sound company a coupla decades ago and used only the best amps and speakers (Crown amps and JBL - exclusively).
Nothing wrong with Peavey. Your 'expert friends' aren't so well informed. The specs are decent, even tho this particular amp is the budget variety; as they scrimped on the heat sinks - admittedly.
You could do far better with your gear if you fixed it and spend a few dollars in order to do it. I've seen some lesser amps on your channel - for sure. lol! I think your test speaker cabs are a huuuuge joke. Y'know; the ones with the piezo tweeters? Ha! You might spend a few bucks and put some decent drivers in those cabs and diy a custom x-over network for them. Perhaps even reinforce the wood and severely dampen the cabs - to boot.
That would be worthwhile project also, and should help you grow your YT brand in the process.
With that PV1200 and some speakers that are worthwhile, you could VASTLY improve your bench so that you could enjoy it as well as have something to use to measure against future project amps.
Just some thoughts . . .
Peavey slaughtered my village. ☹
You must be from Meridian, Mississippi? The company's original home town...
Fix it ! And give it away to someone who need it , a local band , music shool etc
Seen a few band riders with NO PEAVEY on them.
Pv series are crap products,CS range are legends,i still own CS1000X and CS800X going strong as new with all parts original,but well looked after!!! And my PV 2000 i throw it in the bin 2 years ago,it was a timer bomb!!
Cold solder joints is the death of all electronics,i opened my Crown Macrotech 2400 amplifier recently and half of the outputs where in the air basicaly....plus the bias was out of range as hell.....now imagine to run this amplifier in 2ohms load for 1hr.......booooom and bye bye...so i spent half day and i resoldered all the connections from a to z in outputs boards and restore the bias,now my MT2400 is as strong,stable and good as new.
Forgot to mention that i also replaced the thermal compound ,checked the psu main filter caps,and give the driver board a proper clean,the next inspection will be in about 2-3 years from now.
I just looked up the Peavey CS series amps and they do appear to be very well built.
@@JohnAudioTech They really are,pv series look like jokes compare to cs series.
But i prefer lateral mosfet over all,have a look at ASHLY FET 2000m,ASHLY FTX 2001 Series 3 and the H&H M900 if you wanna see proper Hi-Fi monsters.
It not liked as much because the way they rate the amplifier is always miss leading the brands people like are brand that rate there amplifier close to specs at least in car audio and most people in home audio
If you build garbage for 30 years people start to disrespect you. People want 6L6'S, EL84'2 ect. not TDA7294's or chips alike powering their guitar amplifiers. Not that I don't likeTDA7294's they have their place. It's just not in a guitar amplifier.
I need all transistor number peavey2000 all.
Good Lord I put bigger heatsinks on my 40W amps, MUCH bigger.
Forced airflow makes a TON of difference, like an order of magnitude.
@@SianaGearz Indeed it does, but in a home music system (my 40W amps) fans are about the last thing you want. Still, it would take hurricane-level airflow to cool 600 Watts with those puny heatsinks.
I find that every Peavey “PV” series amplifier were all true lemons. I’ve blown out several of these and removed my fair share, and reconed many drivers because of these damn things.
Not a fan of Peavey.
You gotta ask yourself why there are no vintage Peavey amps around. They just don´t last that long. It is crap aimed at amateurs and first time buyers.
For the money Peavey is ok.
Fix it
Don't you miss sneackers?..... i do and a lot..... interesting that you did not tried to have another cat
When the owner is ready, the cat will appear. That is the way of cats.
Of course I miss Snickers. It has been hard starting my day or returning home with him not here to greet me. People grieve and recover in different ways. With this and other things going on in my life, I need some down time. I'll get another cat sometime in the future. I'm in no rush.
Yoooo it’s Carlos “DestroyerX” from the DIYAudio days. Never shy away from being inappropriate, do you?
@@envisionelectronics Carlos is kind of special. He's not trying too be inappropriate, or trying to make some one feel bad, just a little different than most of us. You sort of have to forgive him his Brazilian nature.
So now you know why don't have a good reputation ... NEVER socket a tansistor if you want it to be reliable !!!!!.