Hi! A friend have this Rel Storm sub, which started to make strange sparkling noises. As can be seen from the enclosed picture, at least one component have been on fire. There are not many parts, so it should be possible to get it up and running again. It would be nice to have the circuit diagram, but probably not necessary. At least it would be nice to know the type and value of the burnt component. I don`t know the status of the semi conductors, but most seem as common types. Maybe except for one of the output transistors, which is labelled MLP120. I didn`t find any data for it. The other is a N-channel MOS with P/N BUZ900, which I can find several places. A bit expensive though..
Gunnar
Gunnar
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Real fire storm in a amp is suggesting bad design... I guess is something like hitachi / maplin basic schematic with latheral mosfets, but something in the implementation is not done well or smething abnormal happened?
Not sure what happened, except that my friend heard noises, and the smell from burned electronics..
Strange, I can`t even find a picture other than the one I have here. I don`t know what the burnt component is/was..
Looks like a resistor to me.
Probably around 5 watt.
The track side suggests maybe something like a bleeder or ground link.
But I have been known to be wrong before 🙂
Probably around 5 watt.
The track side suggests maybe something like a bleeder or ground link.
But I have been known to be wrong before 🙂
REL may tell you what the resistor value is, but they won't give you a schematic. The outputs are mismatched, which tells me one was previously replaced. The BUZ900 is used in later amps, but doesn't look original.
Looks like board traces burnt too.
Personally not worth fixing, as REL amps are badly under-built, and not a paricularily good design.
Looks like board traces burnt too.
Personally not worth fixing, as REL amps are badly under-built, and not a paricularily good design.
Thanks!
You think the MLP120 is not original? I saw a post on a different site (Polish? used Google translate..) that had the same amp, and also the same MLP120 transister. I did a search and it seems the the BUZ905 is complementary to BUZ900. So far I don`t know if the transistors are bad. Also found an old post in an uk forum (see REL Loudspeaker Repairs) that used 10N20 and 10P20 as replacement transistors. The burnt resistor(?) ALMOST show on the picture from that uk forum..
You think the MLP120 is not original? I saw a post on a different site (Polish? used Google translate..) that had the same amp, and also the same MLP120 transister. I did a search and it seems the the BUZ905 is complementary to BUZ900. So far I don`t know if the transistors are bad. Also found an old post in an uk forum (see REL Loudspeaker Repairs) that used 10N20 and 10P20 as replacement transistors. The burnt resistor(?) ALMOST show on the picture from that uk forum..
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Sorry about the off-topic but dang what year is that keyboard from? Looks to be part of the earth/case grounding circuit.
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The Key Tronic, hihi, don`t know how old it is. I like it much better than the flat, almost no response keyboards..
I'm betting that resistor is simply a low value 5 watt say 1- 10 ohms non critical since it is the ground lift from circuit ground to case.
removed most transistors and el.lytic capacitors. One of the output transistors, BUZ900 was shorted between D and S. Found no other problems so far. The powersupply seems ok. The capacitors values are a bit low, but my meter is rather simple. Measure at 120Hz. Found new output transistors on eBay. Didn`t find the original(?) MLP120, but found the BUZ900, and complementary BUZ905. There is no DC-offset adjustment on the amp. Maybe a DC-servo? Really few parts on the board.
Check your Ebay transistor BEFORE you fit them.
The middle pin of a Lateral mosFET is the SOURCE.
Whereas the middle pin of a Vertical mosFET is the Drain.
For a To3 device, the case is the Source of a Lateral mosFET.
The middle pin of a Lateral mosFET is the SOURCE.
Whereas the middle pin of a Vertical mosFET is the Drain.
For a To3 device, the case is the Source of a Lateral mosFET.
Thanks!
Exactly what I hoped for 🙂 I got the replacement output transistors from China, and have reinstalled everything, except this resistor. REL was helpful, and tried to help, but couldn`t identify the resistor on the diagram.. The person I was in contact with could perhaps have asked somebody else...
Exactly what I hoped for 🙂 I got the replacement output transistors from China, and have reinstalled everything, except this resistor. REL was helpful, and tried to help, but couldn`t identify the resistor on the diagram.. The person I was in contact with could perhaps have asked somebody else...
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