XR600B fuse blown

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rmm
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Re: XR600B fuse blown

Post by rmm » Wed Feb 09, 2011 7:54 pm

Found a shorted output transistor (SJ6357), so there's hope I'll be able to bring this thing back to life even with my lack of experience. My local supplier has an NTE replacement, but I did see Enzo's advise against these, which I intend to follow.

My question to anyone is this: Testing across Base and Emitter in any of these once back in the circuit read like a short, meaning my diode setting beeps even though I have pulled the shorted transistor out. Is this normal? which is why I had to take all out to be able to find the shorted one? Just wondering if I need to keep looking for shorts.

Thank you
-Ruben

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Enzo
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Re: XR600B fuse blown

Post by Enzo » Wed Feb 09, 2011 10:45 pm

Call customer service at PV and get the scematics for your unit.

In fact, look on the circuit board of the power amp. On the solder side it should tell you what model power amp board it is. Probably either 400B/G or 400BH. Then do a search here, because I think we have posted both of them several times. They are almost identical, but use the right one so we don;t confuse part identifiers.

In circuit there is a 1 ohm resistor between base and emitter, so it looks shorted to your meter. You have to remiove them to be sure. But usually it is a short from collector to emitter you find.

SJ6357 is a PV house number, and they no longer use that number system.

Go to the3 schematic request section here, and one of the stickies I believe is the Peavey master semiconductor cross reference. Download it.It will tell you that the SJ6357 is in reality an MJ15003, current PV part number for that is 70484140. The MJ15003 can be had from most large parts houses like Allied or Mouser. Yes, please don;t use the NTE.

See all those large rectangular cement resistors? They are 10 watts each, and have very low resistances like 1 ohm and 0.33 ohm, and even a couple 0.1 ohm. Make sure none are open. I know your meter can;t tell the difference between 1 ohm and 1/10 ohm, but open is no problem for the meter. The resistors will either be open or OK, they won;t be "wrong" in value.

rmm
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Re: XR600B fuse blown

Post by rmm » Thu Feb 10, 2011 8:05 am

The amp is a 400B/G.

Mouser does not have MJ15003(obsolete), but has plenty of MJ15003G - same thing right?

Enzo, what a fountain of knowledge you are thank you so much for your advise. While we are at it please correct me if I am wrong, but fuses on this unit need to be fast active and not slow blow. Right? My ceramic fuse was not marked and did not see any other indication on that anywhere else.

I did get the materials to build a "Light bulb limiter", which I read about here, and will use it in my tests once I get all parts in. Thanks everyone for your help. Before this the most "advanced" job I did was bias my 62(or possibly 61) Fender Concert Amp.

Cheers!
-Ruben

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Enzo
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Re: XR600B fuse blown

Post by Enzo » Thu Feb 10, 2011 6:18 pm

You will run into this on a lot of transistors these days.

Because of the European RoHS rules, they have to remove all the lead from parts. They even use lead-free solder... yuck.

The transistor is an MJ15003. The G on the end means "green" as in ecologically good, as in lead-free. The parts are the same, just the G ones will not have lead-bearing solder tinned onto the legs.

A lot of companies use G, and some others use PbF. Pb is the chemical abbreviation for lead, and the F is for free, so PBF also just means lead-free.

Here in the USA, we are not bound by the RoHS rules, but the parts makers don;t want to make two types, so they all have swung over to the green side.

Unless a fuse label says slow blow, or time delay, then assume common fast blow type fuses.

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Re: XR600B fuse blown

Post by Marty McCann » Fri Feb 11, 2011 9:50 am

Enzo wrote:You will run into this on a lot of transistors these days.

Because of the European RoHS rules, they have to remove all the lead from parts. They even use lead-free solder... yuck.


Here in the USA, we are not bound by the RoHS rules, but the parts makers don;t want to make two types, so they all have swung over to the green side.
While not "bound" by RoHS (some pronounce it Row house) here in the US, we are bound by the Consumer Product Saftey Commission. The CPSC does regulate the amount of lead in products, but not to the more stringent degree of European RoHS. In Europe they have RoHs, RoHSII, and REACH rules for manufacturing. China and Korea have their own versions.

Electronic parts today are made for Global distribution, so the manufacturers have to toe to the most stringent codes in order to compete.

And yes most circuit boards today are lead free to comply with RoHS. If you want to read something scary as an electronics tech Enzo; Google "Tin Whiskers". As a result of this phenomenon, our products are simply not going to have the longevity of years past.

rmm
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Re: XR600B fuse blown

Post by rmm » Fri Feb 11, 2011 7:44 pm

The Old XR600 head lives!!

Just finished slapping that thing together after I replaced a shorted output transistor and it works! Of course the real test will be the 4 hour gig tomorrow. I’m bringing extra fuses and a back-up PA head.

Thanks Marty, Steve, and Enzo for your all your help, advise, and words of confidence.

Cheers!
-Ruben

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Enzo
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Re: XR600B fuse blown

Post by Enzo » Fri Feb 11, 2011 8:17 pm

Oh brother, well aware of tin whiskers. It is like new stuff is built with cancer inside.

rmm
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Re: XR600B fuse blown

Post by rmm » Sun Feb 13, 2011 2:36 pm

Used the old XR600 head last night since replacing the shorted transistor and it did just fine - not a problem.

Thanks everyone!
Ruben

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SemperFiSound
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Re: XR600B fuse blown

Post by SemperFiSound » Sun Feb 13, 2011 3:29 pm

Excellent news and good on you for getting that gal up and running again.
Cheers,
Steve
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pawleep
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Re: XR600B fuse blown

Post by pawleep » Mon Feb 01, 2016 11:15 am

trying to figure out why mine only has 2 p600d diodes on pwr transistor board?
thanx P
Lee Thistle wrote:XR600B with 400BH amp update: I unplugged the red and orange transformer wires, and the unit powered up. The power-on bulb did not light though, and there was a tiny hum from the transformer(could hardly hear it). My bulb limiter didn't light at all. It did not blow the fuse. TRANSFORMER IS GOOD, right ? Then I took the boards out and tested the FAT (as Enzo calls them) diodes by the filter caps. One of them is shorted for sure. I did the test with them all still soldered in, and only one reads 0 in both directions on my meter/diode tester. Then I did a quick check on the power transistors while still soldered in. None seem to be shorted. Then I checked the 2 small transistors on the amp board (with small heat sinks). No shorts there either. SOOO should I unsolder the power transistors anyway and bench test them ? Or just replace that rectifier diode and give it a try ? I emailed Peavey a couple of days ago for a schematic but no reply yet. The number on those rectifier diodes is...P600DG18710. Anyone know a generic number for it. We have a decently stocked shop here so I might get it locally ?

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Enzo
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Re: XR600B fuse blown

Post by Enzo » Mon Feb 01, 2016 6:02 pm

because you only need two, one across each set of output transistors. Note the part is wired in reverse bias, it is there to clamp transient voltages. They RARELY fail. I don't think I have seen even a single one of those fail in the last 30 years working on Peavey gear.

If you measure one that seems like it is shorted while it is soldered to the board, it is a LOT more likely one of the output transistors is shorted emitter to collector. The diode is parallel the transistor, so a shorted transistor makes that diode read like it was shorted.

I am sure they do fail once in a while, but very rarely.

Look at your 400BH schematic to the right of the output transistors.

pawleep
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Re: XR600B fuse blown

Post by pawleep » Mon Feb 01, 2016 6:41 pm

one transistor was bad, and a 47 ohm resistor too
thanx enzo
Enzo wrote:because you only need two, one across each set of output transistors. Note the part is wired in reverse bias, it is there to clamp transient voltages. They RARELY fail. I don't think I have seen even a single one of those fail in the last 30 years working on Peavey gear.

If you measure one that seems like it is shorted while it is soldered to the board, it is a LOT more likely one of the output transistors is shorted emitter to collector. The diode is parallel the transistor, so a shorted transistor makes that diode read like it was shorted.

I am sure they do fail once in a while, but very rarely.

Look at your 400BH schematic to the right of the output transistors.

Lee Thistle
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Re: XR600B fuse blown

Post by Lee Thistle » Mon Jun 03, 2019 6:22 pm

Hello Peavey Folks: Yes, it's been almost 10 years since you helped me with that XR600B rectifier issue. The XR600B still works and gets used quite regularly. These days it is only used at practice, no more outside gigs. I have another issue. The XLR inputs are getting loose. If I touch a mic cable that's plugged in I get a loud crack sound. Most likely loose solder on that front board. I get occasional slight distortion from my speaker horns. I think it may be the loose solder joints vibrating because the amp sits on top of the horn with the mid under that. That's what I hope and not bad horns. QUESTIION Are those XLR inputs accessible to re-solder ? It's been 10 years since apart.

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Enzo
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Re: XR600B fuse blown

Post by Enzo » Mon Jun 03, 2019 8:02 pm

Sure they are, you have to pull the panel and get at the solder side on the rear. A few screws and...

Lee Thistle
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Re: XR600B fuse blown

Post by Lee Thistle » Tue Jun 04, 2019 7:39 am

Thanks Enzo.....Good to chat again. I'll take it apart and have a look.

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