Output transistor question

hey I have an aiwa cx-nmt50 system. Cant find specs on it anywehre but I do know the output transistors if someone could approximate output power from the complimentary sets. The main channels are as follows : B1625 and D2494 ( front left/right channels)
the center channel amp has these transistors on it : D2061 and B 1370
the rear channels I'm assuming are single ended because I can only find one complimentary pair? Their the same as ther center channel amp transistors. Also on the same board ( all the surround channels are on one board) is one option that says "BTL" (bridge tied load) but is apparently not used. What could that be for?
 

dimitri

Member
2002-10-17 3:45 pm
retired

clem_o

Member
2005-06-14 6:34 am
Manila
do a google on your transistors, you should be able to find some specs on them. Add a "2S" as a prefix, and keep the characters together.

To be sure, you'll need the actual supply voltages and the number of output pairs to get an idea of dissipation and current capability per amplifier. Regardless of what the calculations turn out to be, it will probably be on the 'optimistic' side since most AV amplifiers are current-starved via the power transformer - generally incapable of keeping all channels running at full rated power.
 
no idea........ugh this brings us to the not having a mm again......:( dont ask.

anyways, the caps are 50 volt and 25 volt, the transformer has 125 volt 5 amp and 10 amp outputs on it. I think theres an on board rectifier on the ciruit boards, but seeing the 50 volt 3300 uf caps the voltage cant be high.I'm guessing all thr tranny is is an isolation transformer? :confused:
 
It sounds similar to a system i recently repaired. There is the master amp for front channel which uses the Sanken darlingtons, and the left and right rears use some small TO-220 ROHM devices (I didnt check them as they all worked - the fault was with the cd player)

The BTL amplifier is probably for the centre speaker and from what I could work out it was a VERY low power chipamp on the pcb.

It'll be something like - front 30W, rear 10W, centre 5W
 
ThSpeakerDude88 said:
hey I have an aiwa cx-nmt50 system. Cant find specs on it anywehre but I do know the output transistors if someone could approximate output power from the complimentary sets. The main channels are as follows : B1625 and D2494 ( front left/right channels)
the center channel amp has these transistors on it : D2061 and B 1370
the rear channels I'm assuming are single ended because I can only find one complimentary pair? Their the same as ther center channel amp transistors. Also on the same board ( all the surround channels are on one board) is one option that says "BTL" (bridge tied load) but is apparently not used. What could that be for?


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as jaycee has said, "It'll be something like - front 30W, rear 10W, centre 5W"

another way to look is by the value of the rail voltages! also the filter caps will give you some clues!
 

clem_o

Member
2005-06-14 6:34 am
Manila
"160W total power" means all channels combined output, I don't know if the spec means peak or rms.

30x2 + 10x2 +5 = 85Wrms total. Usually the peak power is 2x the rms power rating, so I'd say that's about right!!

Do yourself a favor and get a MM, even an inexpensive one is good enough for most jobs, and I think you'll be much happier!

Cheers!
 
It will mean "Music Power" which is peak power + whatever figure comes into your head first.

As for the CD laser, yeah, I tried that and it improved things, but the constant skipping was only 100% cured by a new laser. The new laser looked much higher quality (sealed trimpot for example) than the factory one it replaced.
 
well mine wasnt skipping per se, it just plain wouldnt read cds. It would spool em up looking for the cd but it would put it back down and move on to the next ones and do the same. LOL would yall quit it with the multimeter thing!! :p I reallllyy cant afford one right now, as soon as I get a job that will be the first thing I get- after new floor boards, seats redone, gas tank, brakes, exhaust etc. in my falcon. :p


I've found that if you tripple check yourself on everything you dont mess up usually, and its fine if you have lower voltage circuits. I wont start messing with higher than 30 volts voltages untill I get a multimeter, stuff such as my tube radio. I just make sure I do everything right the first time and if I do something wrong theres consequences! If I break something I trace the problem out and I've learned from the experience :)

btw thanks for the power ratings. I wasnt sure on what that guy said about the 85 watts because he didnt say it was RMS. Duh on my part :xeye: I see that manufacturers tend to rate their RMS at very high THD levels....dont you even get me started on that :smash: ... but 1% THD @ 160 watts sure is a lot less than other companies with 10% THD slapped on their RMS ratings. Aye, all that means is that the system can do say 100 watts continuous with ten percent of the signal distorted without hurting the equipment, but being horrible to our ears, doesn't it?! sorry, you got me started :p ANYways, is it possible that the peak is slightly higher than the 160 watts it states or is that about it ?
 
This is all very pathetic as the speakers it comes with are rated as follows: Front left/right : 80 watts per channel music power,
Rear: 40 watts each music power ( yeah only because you have capacitors in line with the positive side to cut any bass that 40 watts of might destroy!!)
Center: 30 watts music power ( see above for reason why the speaker that should be rated higher than the rears because the main sounds in a movie come out of it is rated lower)
 
'Music Power' ratings are about as clear as reading your future by looking at tea leaves... Anyway it does give you 'some' idea of the true rms power rating of the amplifier's channels, which will be significantly less than the 'music power' rating!

BTW, have you ever had a look if there's a line fuse? If its connected to the primary side of the power transformer you can get a good idea of how much the transformer can really dish out; the amplifiers' combined power can't be above the transformer's capacity - check the fuse ampere rating and multiply by your local line voltage...

Cheers!!
 
I think it was a 125 volt 5 amp or 10 amp , cant remember which.Still, thats enough to dish out what, 625 watts?? the secondary's say 125 volt 5 amp and 10 amp on the board. So I dont think the system is starved of mains power. Unless they dropped the voltage to a ridiculously low voltage after rectification.
 
Can't use the secondary as basis, since you can't measure the voltage output of the secondary. The manufacturer will silk a 125V, 5A fuse for the secondary simply because yopu can't specify (purchase) a fuse of similar rating with a lower voltage! :)

Its possible also to estimate the transformer power rating based on the size and heft of the unit (i.e. eyeballing) but it takes experience...