Rockford 551S Schematic Request

[Jat40]

If anyone has a schematic for a Rockford 551S, please email to stoneytay@bellsouth.net.

I got this amp and the only thing I found bad was Q204, Q205, R224, and R225. Replaced them and the amp is drawing to much current. I have 5V on the 320s5 with only remote and ground connected, outputs look OK, not shorted, no open resistors that I can find, but there is something pulling hard to ground.

Thanks for the help,

JT

[1moreamp]

Have you tried the Rockford tech site below:

Rockford Corporation Technical Library CD

[seankane]

Originally Posted by Jat40

If anyone has a schematic for a Rockford 551S, please email to stoneytay@bellsouth.net.

I got this amp and the only thing I found bad was Q204, Q205, R224, and R225. Replaced them and the amp is drawing to much current. I have 5V on the 320s5 with only remote and ground connected, outputs look OK, not shorted, no open resistors that I can find, but there is something pulling hard to ground.

Thanks for the help,

JT

What are the readings from the gate (left leg) to the source (right leg) on all the output transistors with a meter while they are still in the circuit? This wont be able to detect a leak but it will detect if they are shorted. Also I have been getting alot of amps in lately with the bias pots cranked all the way up (clockwise). I think people see these as extra gains and mess with them. Try turning them all the way counterclockwise and see if your current draw goes away. Please post the readings...

[Jat40]

All read 5.4m, in diode mode, 0.6v. All of the gate resistors are fine, reading 10ohm.

With remote and ground only, getting +5v on pins 9 and 10 of U1, and +5v on the gates of the 3205s.

With the power supply connected, voltage drops to 8.5

[seankane]

Originally Posted by Jat40

All read 5.4m, in diode mode, 0.6v. All of the gate resistors are fine, reading 10ohm.

With remote and ground only, getting +5v on pins 9 and 10 of U1, and +5v on the gates of the 3205s.

With the power supply connected, voltage drops to 8.5

I set my meter in ohms mode range in M ohms. For example one that is not shorted will read like .680 or .534 etc..etc... one that is shorted will read like 1.9 or 2.9 etc...etc.. try it in that mode. Did you turn the bias pots all the way counter clockwise to see if your current draw went away?? Sometimes the output fets can be partially shorted. So the power supply wont completely short but can draw alot of current.

[seankane]

I dont have the schematic or a used board of that type so I dont know locations on the board.

[seankane]

I am going to have to assume that U1 is the PWM chip from the readings you posted? Like a TL494C or something??

[Perry Babin]

Email me for a schematic diagram that's supposed to be close to this amp.

babin_perry@yahoo.com

[seankane]

Originally Posted by Perry Babin

Email me for a schematic diagram that's supposed to be close to this amp.

babin_perry@yahoo.com

I have the schematic for the H500a2 which is supposed to be the same, keep us posted on your progress.

[Jat40]

Well, been working on this one for a little while, and here are the parts that are replaced and found to be defective;

- Q104, 105, 204, and 205, replaced with MMBTA56
- Q109 and 209, with MMBTA56
- R123, 124, 223, 224. These are 300ohm, did not have, subing with 330
- Q125, 115, and 127, replaced with IRF540

The amp will turn on, getting +-HV, but after 3 or 4 seconds the output measures high levels of DC; right channel jumps from 1v to 35v, left channnel, 1v to -18v. I can here my power supply start to drag down. Not seeing anything get hot, pulling the remote connection off after 4 seconds.

I have went back through the amp again, can't find any problems at this point. All of the parts listed above are still intact. Any suggestions?