jaycar response 2x150 blown

[wrxer]

hi guys, i am blown away by this forum, it is awesome for you to be sharing info and help the way you all do.
and that has prompted me to seeking advice on a jaycar response 2x150 car amplifier, it is my mates amp, and i said i would like to try and fix it for him. he said that it didnt work and he took it to the repair shop ages ago and cant remember how much it was to fix it
When i went to power it up, i got a big bang and it smelt burnt, even though i only plugged in the earth and b+. on opening the box after, i found the burnt smell was a cooked transistor P55NE06, however i think just replacing this one would be pointless.
from looking around this forum and others, it seems i should replace all 8 of these transistors with STP80NE06-10 and on the board is the spots for another 2, and i should fill these spots as well with the transistors and bits to make them work.
to my untrained eye, the rest of the board looks fine and unburnt.
i am a newbie to electronics, however i have built several electronics kits, and am a very competent motor mechanic. i have not got a scope, but i do have a dmm and solder irons big and small.

what else can i look at to see if it is worth throwing money at to fix?
what else do i need to do, for you guys to help me fix it?
is it likely that replacing the trannys will fix it?

regards jack

[Perry Babin]

Please post a photo of the amp board.

[wrxer]

Originally Posted by Perry Babin

Please post a photo of the amp board.

i am a week away from home, i will take a pic then, cheers

[wrxer]

Hi all, attached are the board pics.
Attachment 251829
If we look at the unclamped P55NE at Q14, we can see that it is cooked, also Q12 looks only slightly better.

Please note that when i join my multimeter leads together on the 200ohm scale i get a reading of 0.2ohm.

When I put my multimeter on B+ and Earth i get 0.7 ohm (200ohm scale).
When I test the unclamped P55NE at Q12, Q14 and Q16, I get:
leg 1-3: 0.8ohm on 200ohm scale
leg 1-2: 0.3ohm on 200ohm scale
leg 2-3: 0.7ohm on 200ohm scale
When I test at the clamped P55NE at Q11, Q13 and Q17, I get
leg 1-3: 0.263ohm on 2k scale
leg 1-2: 0.264ohm on 2k scale
leg 2-3: 0.7ohm on 200ohm scale

From reading other topics it seems i should be replacing all 6 of P55NE. They seem a little hard to find although STP55NF06 are plentiful.
Are the STP55NF06 suitable replacement for the STP55NE06, or are there better choice (maybe STP80NE06)?
p55ne,p55nf,p80ne.zip

Should I install extra transisters and gate resistors and links at the blank places near Q15 and Q16?

Attachment 251830
If we look at the second attached picture, we can see some board discolouration near R401, it easier to see on the photo than real life. It seems to be from ZX1 which is right next to RX8, I think this might be a Zener Diode.
Do I simply replace ZX1 or does something else cause this to blow?

Regards Jack

[seankane]

Neither of your attatchments are viewable. What file format are you trying to upload them in? It says it is an invalid link. Are you uploading them with the manage attatchments option in the post? Its down below the text box a little ways.

[wrxer]

Attachment were too big, sorry.

Hi all, attached are the board pics.
SAM_0094.JPG
If we look at the unclamped P55NE at Q14, we can see that it is cooked, also Q12 looks only slightly better.

Please note that when i join my multimeter leads together on the 200ohm scale i get a reading of 0.2ohm.

When I put my multimeter on B+ and Earth i get 0.7 ohm (200ohm scale).
When I test the unclamped P55NE at Q12, Q14 and Q16, I get:
leg 1-3: 0.8ohm on 200ohm scale
leg 1-2: 0.3ohm on 200ohm scale
leg 2-3: 0.7ohm on 200ohm scale
When I test at the clamped P55NE at Q11, Q13 and Q17, I get
leg 1-3: 0.263ohm on 2k scale
leg 1-2: 0.264ohm on 2k scale
leg 2-3: 0.7ohm on 200ohm scale

From reading other topics it seems i should be replacing all 6 of P55NE. They seem a little hard to find although STP55NF06 are plentiful.
Are the STP55NF06 suitable replacement for the STP55NE06, or are there better choice (maybe STP80NE06)?
p55ne,p55nf,p80ne.zip

Should I install extra transisters and gate resistors and links at the blank places near Q15 and Q16?

[wrxer]

If we look at this second attached picture, we can see some board discolouration near R401, it easier to see on the photo than real life. It seems to be from ZX1 which is right next to RX8, I think this might be a Zener Diode.
Do I simply replace ZX1 or does something else cause this to blow?
SAM_0095r.JPG
Regards Jack

[Perry Babin]

The board is discolored due to heat stress. This is common on amps that use such simple voltage regulators but the Zener diode (at the end of the resistor) should be checked. Sometimes a defective zener can cause greater heating than there should be.

What is the value of the gate resistors for the power supply FETs?

[wrxer]

Thank you for your prompt reply.
SAM_0096.JPG
All the resistors at R35, R37 and R41 measure at:
R35: 14.5
R37: 14.5
R41: 14.5
All 200 ohm scale.

SAM_0097.JPG
However the resistors on the other side measure:
R36: 46.1
R38: 46.1
R42: 46.1
All 200ohm scale.

I am pretty sure these are the gate resistors.
The resistor colours are Yellow, Blue, Black, Gold.

[Perry Babin]

They are 47 ohm resistors. You can use a wide range of FETs in the amp. I suggest using the originals but if they're not available, you can use IRFZ44s, IRFZ46s, IRFZ48s IRF3205s would probably also work.

You need to check the PNP transistors that are driving the FETs as well as each of the individual gate resistors.

You also need to check the output transistors to confirm that none have failed.