Rockford Fosgate 750 x

S Merlington · 2012-11-25 2:29 am

If the protection Diodes in a channel are bad would that cause that channel to have no output ??

If so Does anyone know what 2 diodes i need to pull They are the 400 series parts..

If i use the Scope Its saying i have audio all the way up to the Right front positive speaker terminal But i have no output at all out of that channel..

I clean the crossover switch still nothing

Any ideas?

Perry Babin · 2012-11-25 3:17 am

Do you have clean audio on the positive terminal of C412?

It should have the same signal as that on C212 when both channels are set the same.

S Merlington · 2012-11-25 3:39 am

Yes i have clean audio on C412

Perry Babin · 2012-11-25 4:07 am

D401 and D402 are for the protection circuit. It's unlikely that both halves of the protection circuit have failed but anything is possible.

Confirm that you have essentially the same voltage across R417/418 as as you do on the same resistors in the other channels.

S Merlington · 2012-11-25 4:13 am

R417 and R418 Have 0.05 across them ..

All the Other channels measure the same..

Should i lift D401 and D402 to see if i get audio ?

Perry Babin · 2012-11-25 4:16 am

Yes.

Did the outputs fail in this channel?

You mentioned the RF channel but the 400 series parts are in the LR channel according to the diagram. Are you having trouble with 2 channels?

S Merlington · 2012-11-25 4:19 am

Its only 1 channel And your correct Its the LR channel that has the problem..

The outputs failed in this channel and the 0.1 ohm resistors failed and also the drivers and the 10 ohm resistor was also bad

Perry Babin · 2012-11-25 4:21 am

Just to confirm, you say that you have signal up to (on?) the positive terminal for this channel?

S Merlington · 2012-11-25 4:28 am

Now both Channels LR RR have no output

S Merlington · 2012-11-25 4:34 am

I have a bad crossover switch Im going to replace it and see if that solves the problem Ill report back in 5 mins

S Merlington · 2012-11-25 4:40 am

Ok Still no output..

I thought i had audio up to the + terminal but i dont So somewhere Between C412 and the Positive terminal Im losing signal..

seankane · 2012-11-25 5:07 am

Do you have DC off set in any of the 2 problem channels?

S Merlington · 2012-11-25 5:10 am

RR channel works now..

LR channel is still dead..

I Have no DC offset in that channel

Perry Babin · 2012-11-25 5:14 am

Does the bias control function normally?

S Merlington · 2012-11-25 5:19 am

I have D401 and D402 Lifted right now..

If i turn the Bias pot up fully clockwise In the LR channel I get output from that channel but is very distorted...

If i have the bias pot fully counter-clockwise in that channel i get no output..

Perry Babin · 2012-11-25 5:20 am

Does the current draw increase like it should when you turn the pot clockwise?

S Merlington · 2012-11-25 5:22 am

No the amp remains at 1 to 2 amps of current draw

seankane · 2012-11-25 5:31 am

Have you checked the 1A and 2A transistors in that channel?

S Merlington · 2012-11-25 5:39 am

Yes i replaced them

seankane · 2012-11-25 5:46 am

Sounds to me you have the same problem as the punch 360a2 Perry helped me with awhile back, I am not sure if the 4 channel amps are the same as the 2 channel amps and I dont have that schematic in front of me but......if they are the same check RX53-RX59 to see if any of those resistors are out of tolerance.

Rockford Fosgate 750 x

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