hello guys, ive been trying to fix a cyrus power amplifier and on 1 corner of the pcb board underneath its gone black with heat, there 4 transistors that i wanted to swap for new ones but needed to make sure there the same spec, heres what they say on them, 48ag lm7915ct, its more the first row of numbers/letters im concearned about i was thinking this was the makers identification mark?, the other is ph3d bd136, the amp displays a yellow green flashing light when power is applied,any help would be appreciated, thanks guys
transistor identification
- Thread starter mozmax
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hello, thanks for replying, so does this mean i have to find out who the manufacturer is before i buy them to make sure there the exact same spec?, thats gonna be a pain more thn likely because theres not much info on them, i was thinking the one that says ph3d might be a philips?, ile have to do some more research on google no doubt, thanks again
AUD101
Parsley The Lion!
Not necessarily so, unless Cyrus has commissioned a semiconductor manufacturer to specially make unique devices for their products etc.
This is a possibility, but I am not sure - other forum members maybe able to confirm.
Reputable semiconductor manufacturers are: Fairchild, NXP/Philips, ON-Semi, STMicroelectronics, Sanyo, Texas Instruments (Ti), Toshiba etc
...and always buy them from reputable retailers: Digikey, Farnell, Mouser, RS etc
In your initial post you stated there were 4 "transistors" - you quoted two devices [LM7915CT & BD136] - What are the other two? - Is the Cyrus still working with these components?
Also if possible please post a few pictures of the part of the PCB you describe as "gone black with heat" and the 4 "transistors".
hello, ive tried to take a pic its hard to see from this side of the pcb, the black is underneath but look closely in the corner of the pcb and you should see it, thanks for helping, regards
mozmax
ps the cyrus isent working, the person i bought it off said he was listening to it one day then the next time he switched it on it just flashes yellow green light
mozmax
ps the cyrus isent working, the person i bought it off said he was listening to it one day then the next time he switched it on it just flashes yellow green light
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I suspect you'll find the opposite semiconductors are not the same as the LM7915CT and BD136. You're looking at the power supply section of the unit, the LM7915CT regulator sets the negative voltage, and the BD136 may be either a pass transistor or part of the regulator circuit. Conversely, the similar device pictured on the left lower is likely the LM7815xx positive regulator and the upper left is likely a complementary part to the BD136.
Even though the area may be "burned", what are you doing to troubleshoot the problem (ie, measuring or testing)? Changing transistors and voltage regulators without checking to see if they failed or what else may have caused them to fail is not an effective way to solve this.
Even though the area may be "burned", what are you doing to troubleshoot the problem (ie, measuring or testing)? Changing transistors and voltage regulators without checking to see if they failed or what else may have caused them to fail is not an effective way to solve this.
petehall347
the brandy coffee man
you really need to find out why its in protect .
check dc offset first before the relay .
the outputs seem prone to going on cyrus amps .
check dc offset first before the relay .
the outputs seem prone to going on cyrus amps .
hey... thanks for the help so far, heres some pics of the other 2 transistors, you was right there not the same, im just in the process of looking for me old multimeters,not used them in a while, i just thought it would be a good start to replace them because of how hot they have been, plus there only cheap, thanks guys
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Yep, the MCT7815 is a Motorola part, and I think the LM7915 appears made by National Semiconductor. Most of these are pretty generic so as long as you get a good pair made by a reputable manufacturer you should be good, assuming they actually need replacing. Some added heatsinking could be helpful. Same for the BDxxx.
Common problem?
heres some info i found on the net
The Standby light flashing GREEN/YELLOW
? This indicates an overload condition in at least one channel. If the problem is of a temporary nature (for example excessive volume setting), normal operation will resume after ten seconds. If the fault indication
persists, there may be a problem with the loudspeakers or their connections. In this case, switch off the power at the rear of the Cyrus Power and disconnect the speaker cables from the rear panel. If the fault indication has now cleared when power is re-applied, check the loudspeakers, cables and plugs carefully for loose strands of wire which
may be causing a short circuit
ive found me multimeter, could anyone run threw checking the dc offset, never done out like that before, thanks guys
The Standby light flashing GREEN/YELLOW
? This indicates an overload condition in at least one channel. If the problem is of a temporary nature (for example excessive volume setting), normal operation will resume after ten seconds. If the fault indication
persists, there may be a problem with the loudspeakers or their connections. In this case, switch off the power at the rear of the Cyrus Power and disconnect the speaker cables from the rear panel. If the fault indication has now cleared when power is re-applied, check the loudspeakers, cables and plugs carefully for loose strands of wire which
may be causing a short circuit
ive found me multimeter, could anyone run threw checking the dc offset, never done out like that before, thanks guys
petehall347
the brandy coffee man
was on early ones as there wasn't any short circuit protection .. maybe there is with this one ?
petehall347
the brandy coffee man
which model is it ?
petehall347
the brandy coffee man
it should have a model number ...
example xpa
example xpa
petehall347
the brandy coffee man
show us a picture of front and rear and a pic with all insides ..
in the meantime try pulling one fuse at a time from main board and power up to see if it comes out of protect .
we can maybe narrow it down to left or right channel that way .
in the meantime try pulling one fuse at a time from main board and power up to see if it comes out of protect .
we can maybe narrow it down to left or right channel that way .
petehall347
the brandy coffee man
looks better known as cyrus mbloc ..
am struggling to find a service manual for it .
i see cyrus has owner manual .
just noticed the wire doesn't look right behind the main fuse .
also looks like one of the channel fuses has been changed at some point .
am struggling to find a service manual for it .
i see cyrus has owner manual .
just noticed the wire doesn't look right behind the main fuse .
also looks like one of the channel fuses has been changed at some point .
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