Speaker sounds blown

[amptech]

or cpc...cricklewood electronic if your in england..

 

[Perry Babin]

Not ebay. Too many counterfeits. Mouser and digi-key are some of the best/easiest to deal with of you only need small quantities.

 

[amptech]

if there the same spec..use them.

 

[RubberSalt]

Normal I'd do ebay, but after reading that basic repair guide, I remember counterfeits. Couldn't remember where to order from.

Digikey is real fast for us here, so probably place order there.

I need to look at the output transistors, highly doubt they are shot, but never know.

 

[amptech]

just a quick check with the dmm will show if the done...b-c-e if short bin them!

 

[amptech]

some o/p's are Darlington device's or standard transistor type's cross check them with data sheet before hand.

 

[amptech]

check the emitter .22 ohm 5 watt emitter resistor's for o/c.. but start work on the psu and get that up and running..then move towards the amp stage. do u have circuit schematic?? this would give a quick track round the amp and save some service time.

 

[RubberSalt]

No I don't output transistors are f9540n, and irf450n.
(l for left, m for middle, r for right)
Channel 1 gives readings for f9540n LM:.1ohm, LR:1ohm, MR:.3ohm
Channel 1 gives readings for irf450n LM:2ohm, LR:.9ohm, MR:1.2ohm

Channel 2 gives readings for f9540n LM:1.7m ohm, LR:+2m ohm, MR:79k ohm
Channel 2 gives readings for irf450n LM:79k ohm, LR:.+2m ohm, MR:+2m ohm

.... Shorted/open power fets cause mis readings on o/p transistors?


Oh yeah, this mm is a pos harbor freight. I'm going to be picking up a night for $25 at a pawnshop. Had 1 that I left in my car. For a summer >.<

 

[amptech]

post a photo of the amp on here...so we can see the insides

 

[amptech]

if need be remove the o/ps one at a time for checking...that way your get better reading.

 

[Perry Babin]

IRF540?

Ch1 needs new output transistors.

 

[amptech]

yep!

 

[RubberSalt]

 

[Perry Babin]

Did you see the open trace?

 

[RubberSalt]

yup

 

[RubberSalt]

Over here at work, brought the Sony amp in. It's a "xm-7527". This amp lights up the over current when trying to power it on.

Channel 1 shows a short on 1 of the transistors, fs70smj 2 .

 

[Perry Babin]

I didn't think they were still available but pacparts indicates that they may be able to get them. They're $40 each.

 

[RubberSalt]

I wonder if there is any replacements... $40 each and 2 needed. Sounds like I'm going to reading a crap ton of datasheets lol

 

[RubberSalt]

FS70SMJ-06

They look like they could be close enough as a replacement. Main difference I see is the capacitance is about 2k pico F less and the rise takes A little longer, but the fall is a little shorter

 

[RubberSalt]

It looks like there is a -28v and a +28v rail in this amp.

Datasheet comprisons: fs7osmj-02
fs70sm-06

Long story short: -02. -06
Vdss. 100v. 60v
Ciss. 8200pf. 6540pf
Coss. 1150pf. 1640pf
Crss 600pf. 790pf
Td(on). 54ns. 95ns
Tr 140ns. 195ns
Td(off). 830ns. 290ns
Tf. 350ns. 210ns