Hi,

I have now removed and tested all larger transistors, you were right, no presuming!- one of the 2SC5200's is broken.

Also both of the smaller transistors (A1306 8F and C3298B 8A)  and a tiny one (2n 5551 y114)  that were soldered to the board and on the heat sink have gone too.

Am i right in thinking i will need to replace these smaller components before putting in one pair of the larger ones and starting to test as shown below?

while im ordering components is there anything else i should look at testing based on what has blown?

Hey, thanks again for all the help so far,

Can anyone help me further?


Ben

Hi guys,

Sorry for the delay.

Have now got a working multimeter,

The figures were the same for each type of large transistor
NPN's showed;  Base-Emitter and Base-Collector - 030 in both directions- and C-E as continuous (bleeped)

PNP's showed; B-E 265 both directions, B-C - 050 in both directions - and C-E as 300 both ways

I presumed that meant they had all blown: i took one of each out to test, but they are fine, so i presume this is just due to the rest of the circuitry (not sure if it is worth removing and testing all of them?)

Similar for the bridge rectifier figures made me think it was gone so removed this, but again tests fine off the board.

I have had a look at my leads for the speakers, they look fine except one of the 'male' ends is a little loose where it is riveted. Doesn't look like it could short, but could make an intermittent connection - I will swap the plug before i connect them - If i ever get it working!

You said to have a poke around the power supply, What else do i need to look at?

Thanks a lot,

Ben

These are some more close up pics

Many thanks

 Thanks,

I thought the small brown mark on it was that it was burnt out - shows its worth double checking

I have realised that i missed out that the fuse has gone, and goes within 1 second again if i use a new one so i cant hear the relay click, or measure any voltages- am i right in thinking this was 'presumed' and that when measuring voltages etc, it should be using the light bulb limiter and a fresh fuse?
If so i will measure all of these voltages when i have made the limiter
(there are in fact 6 0.5 resistors, 2 47 and one 2k)


If the transistors are the black boxes attached to the heat sink (all with three legs) then there are
6 large ones:
    - 3x ' Toshiba 25A1943'
   - 3x  ' toshiba 25c5200"
5 smaller ones ( only 4 on heat sink - 2 of which directly soldered to board 2 on wires )
A1306 8F
C3298B 8A
2x   F    215     TIP 41C ( one not on heat sink)
F    151   TIP42C

There are also many normal looking cylindrical flat sided ones such as
S8050    d-143 and   C9013   H-212

Please let me know if the attached pics are any better and if i have missed any other questions...

Many thanks

( I may need to do a few posts, it doesnt seem to like posting what i have written with loads of attachments)

Wow! Thanks so much to all of you!

I have tried to take some pictures but my camera is not the best (only on the phone), If they are not good enough please let me know and i will try and borrow my brothers SLR.

This is the picture of the ceramic resistor that looks charred. -




My multimeter was low on batteries so I have re-checked this and it NOW seems to show a resistance of 2000 ohms which would match the 2k on it, so either this is not the problem or could it still be intermittent?

The rest of the pictures i have taken are here
http://s248.photobucket.com/albums/gg172/BencraigT4/Broken%20PA%20amp/

There is another circuit board behind the front panel, though I guess this isnt the cause of the problem

It stopped working at a wedding, was not on full power, but i was not in the room at the time, so dont know if anyone 'tampered' with it whilst intoxicated!

Thanks you all so much! - Did not expect this much support at all!

Hi, an amp of mine has stopped working. A carlsbro marin 8400

I have found a ceramic resistor looks blown and the multimeter confirms this

The resistor is a rx27 5w 2k

2 questions,

1) I can't find the correct resistor, would a 2k2 be ok?
2) are other components likely to be blown as well, or is a single fault like this common?

Any help greatly appreciated,

Many thanks, 

Ben