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Reply With Quotecan you post the schematic?
I've got a broken down CS400 amp and have already got the right schematics, thanks to Mrs. Google who's being a great help in this matter.
The power board, possibly even both, appears to be broken, the fuse had been blown, at least one of the .33 Ohm resistors become quite hot. I'd driving the amp for test purposes through a simple bulb to prevent further damage.
I have a few questions: There is a red and brown cable running to the driver board. A "device", fixed to the cooler, is connected there as well. This "device" is broken in pieces, what could that be ?
There are transistors installed "2N3773" and "MJ15020", the schematics refer to 6357 or 6344, are these replacements ?
can you post the schematic?
Here it is.
No, this is not the one I have, my amp has only NPN transistors on the power board. I'll upload the schematics later this week since I'm on business trip.Originally Posted by Jazz P Bass
The "device" I'm referring to appears to be "CR12", this looks like a few diodes plus a resistor. It is connected to the power board but the connector itself runs to the driver board with red and brown wires. However, I've already got one channel to work fine, the other one has this broken "diode - transistor" thing which I don't know what it is and what is does - or should do.
It's been a long time since I have seen one of these and they changed over the years. The device you are talking about could be a thermistor on the heat sink or a stacked diode. If it is a stacked diode it will appear on the schematic as several diode junctions in series and can be substituted by rectifier diodes in series using the the number of junctions in the schematic. You can call Peavey you know. They are usually very helpful, even with old stuff, and probably still stock the part.
Thanks, I'll contact Peavey, let's see whether they can help.
Jazz, that is the newer "wind tunnel" style CS400. He has the original one.
Go to the Schematics Request section of this forum, and one of the sticky threads near the top is the Peavey semiconductor crossreference. You can look up those SJ6344 or SJ6357 types and find their MJ150xx equivalents.
CR12 is a dual diode (two junctions in series), the resistor is a separate part. Those dual diodes are Peavey type 13886. You can get them direct from Peavey, I do. You could screw around coming up with something to put in their place, but it is so much easier to just use the exact part in the first place.
I'll add the schematic here below.
The dual diode is part of the bias circuit, it is mounted on the heatsink to thermally track. During test, you can replace it with a piece of wire - yes, short right across it. That will let you determine if anything else is bad. The resulot of deleting that dual diode will be increasede crossover distortion but the amp channel will also run cooler.
The two power amp channels are independent, and you can disable either one by pulling the four-wire molex connector to the main power transistor board.
Education is what you're left with after you have forgotten what you have learned.
Thanks Enzo, thats quite valuable info ! The schematics are the right ones, thanks as well. Let you know when the second channel works too.
Aha, I am not going crazy, we DO have two threads going for this repair. Let us pick one and let the other one die.
Education is what you're left with after you have forgotten what you have learned.
O/k.
I'll bite.
What the heck is a 'wind tunnel' amp?
It means that the amp is aerodynamically stable up to its full rated output!
Enzo's referring to the heatsink design. It has one of those fan cooled "wind tunnel" heatsinks.
The original CS400 and CS800 had solid metal fronts. There was a fan in the rear, and vent holes on the lid to allow air flow.
Newer designs had the large vent grille on the front panel, and the fan on the rear. The heat sinks formed a tunnel through the middle of the amp. COmpare the front panel pcture in these owner manuals.
Original
http://www.peavey.com/assets/literat...0_c_series.pdf
Extra Crispy... I mean wind tunnel
http://www.peavey.com/assets/literat...s/80300990.pdf
Education is what you're left with after you have forgotten what you have learned.
The original CS400 and CS800 had solid metal fronts. There was a fan in the rear, and vent holes on the lid to allow air flow.
Newer designs had the large vent grille on the front panel, and the fan on the rear. The heat sinks formed a tunnel through the middle of the amp. COmpare the front panel pcture in these owner manuals.
Original
http://www.peavey.com/assets/literat...0_c_series.pdf
Extra Crispy... I mean wind tunnel
http://www.peavey.com/assets/literat...s/80300990.pdf
Education is what you're left with after you have forgotten what you have learned.
Gotcha on the wind tunnel.
Thanks.
I new there was something familiar there.
I worked on one 2 weeks ago.
Hm, do we have two forums and two threads ? I'm confused ... or cause confusion myself ... let me suggest to let this one die, there was one famous word from Mr. Highlander about only one ...
Just had time to check the one, working channel. One bit concerns me, if it is working at high power on 8 Ohm speakers, the transistors become quite hot very quickly and the entire cooler as well ( as it should be). After a while the temp switches cut the power which I consider ok. I checked and all transistors become hot quickly, so all are working. The sound is ok, no distortion. but the clipping LED is on at high load.
Q: Do these amps really become that hot ? Remember there's only one working channel at present, how hot will it be if both channels are working ? The + / - Voltage is on 61 V, on high load it is at about 51 V (+/-).
Just a question....how do we all get one of those fancy Enzo-double-postalizers? I am jealous, when I post, only one single measly post is seen. When Enzo posts he gets an automatic repeat in case no one paid attention the first time....
All right, the problem is clearer now, the channel I'd thought working perfectly turned out to have a faulty driver board. After, lets say 4 minutes, the power reduced to 51 Volts and the transistors on the power board became hot. I swapped the driver boards and all is perfect. The faulty driver board always starts good but after a few minutes it fails again. Do you have an idea what this could be ?
Is it getting hot with no load? Be sure the thermal tracking diode mounted on the heatsink is working. If it is open, it will cause a higher voltage difference on the bases of the driver/output transistors and they will get hot from conducting almost the full cycle, sort of AAB class.
Measure the voltage drop across the emitter resistors to see how much current they are really dealing with. Try shorting that thermal diode stack and see if it cools down. If it does, the driver is probably OK.
It's an annoying quirk of the latest version of the forum software - depending on what browser you're using, the phase of the moon etc., posts will sometimes be duplicated
Although in the case of Enzo's posts, most people could benefit by reading them twice
"Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"
Thanks to my holidays I had a few minutes aside gardening ... there is one driver transistor on the driver board broken, B-C short cut in both directions, spare parts ordered. Now I'm off for a few days in the UK, so long and thanks for your help so far.
Yeah, I try to think to delete those. It is annoying. I hit POST and it sits there thinking. After a time it asks me if I really want to leave the page. When i say yes, it takes me back to the forum, but leaves two posts. Other times I try to post, and it warns me I have to wait 28 more seconds before posting "again." Not sure what to do about it, since I am computer illiterate.
Education is what you're left with after you have forgotten what you have learned.
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