Ppi pc1400

[mike49504]

I just recieved another one of theese amps in for repair its missing alot of parts off the board.

power supply fets are missing which i believe are IRFZ44's

Outputs are missing Which i think are TIP35's and 36's

The next parts are missing wondering if someone knows what parts belong in theese locations

Q12
Q13
Q15
Q16
Q72
Q73
Q75
Q76

Theese locations are between the outputs

Any help would greatly be appericated

 

[mike49504]

If this helps theese are the parts that are missing

 

[Perry Babin]

2SA1011 and 2SC2344. The 2SAs drive the TIP36s.

 

[mike49504]

Ok its been awhile since i took this amp apart.

Wondering do the tip 35's go in closet to the power supply fets or do the 36's?

 

[Perry Babin]

The 36s are nearest to the supply.

 

[mike49504]

Ok thanks.

Next questions is how do i tell where the 2sa and 2sc parts go.

Drivers for the outputs since all 4 spots on both sides of the amp are showing continuity for the tip 36 pads

 

[Perry Babin]

The 2SAs go near the TIP36s.

 

[mike49504]

Ok im putting this amp back together.

My question is do i still have a problem with this amp.

With no outputs in the amp The readings i get between the pads are.

For both Tip35's and Tip 36's

From pads

1-2:9.31 k ohms
1-3:16.9 ohms
2-3: 9.12 ohms

This is the mono version of this amp.

Wondering do the readings look ok or does it apper to have another problem?

 

[Perry Babin]

less than 10 ohms from 2-3 is likely to be a serious problem. Are you sure that you don't have any defective outputs?

 

[mike49504]

The outputs are removed from the amp right now so are the 2sa1011's and 2sc2344's .

The reading i posted are from the pads on the board.

When i got this amp in it had blown outputs and blon power supply fets.

So im wondering what i might check next to find the problem

 

[Perry Babin]

Are you sure it's 10 ohms and not 10 k or M ohms?

 

[mike49504]

from pads 1 to 3 on the board i have 16.1 ohms not kohms or not mega ohms

From pads 2-3 i have 9.91 Kohms

 

[Perry Babin]

10k ohms may be normal. I've never had any reason to remove the outputs and measure the resistance between those terminals. It shouldn't be a significant problem as it would be if it were 10 ohms (as you initially indicated).

 

[mike49504]

I cant get this amp to power up now

The voltages on the SG3525 are
1:0.14
2:2.60
3:0.1
4:0
5:0
6:3.80
7:0
8:4.95
9:6.09
10:0
11:0
12:0
13:13.45
14:0
15:13.45
16:5.22

Voltage on power supply fets IRFZ44's

1:0
2:13.90
3:0

Any ideas what this might be?

 

[Perry Babin]

It appears that there is no oscillator. That's typically only caused by a defective IC, a missing/defective timing capacitor or an external fault (solder bridge, etc). The components connected to pins 5 and 7 would be the areas where you'd need to look for problems.

 

[mike49504]

Ok if i need to take a pic i will .

I noticed on the bottom of th amp there is a orange thing with a stripe around it. To me it looks like a diode its between the 2sa and2sc parts.

wondering if that a diode if so do you know what i could use in there 1 is cracked in half.

 

[Perry Babin]

If it's on the edge of the board, it's a thermistor. They are used in several ways (bias compensation, thermal protection and fan control). You'll need to replace it if it's broken.

Which one is cracked (R1, R2...)?

 

[mike49504]

R3 is broken.

 

[Perry Babin]

On the photos I have, the 3rd thermistor is labeled R250. If it's the one between the audio drivers, install a shunt on the JPx for that channel so that the bias circuit is bypassed.

I don't think that that can effect the IC's oscillator.

 

[mike49504]

I think the Ic is bad like you said I tapped on it a sec real lightly and tryed powering the amp back up and now it draws excessive current. Ill try putting a new one in and see what happens