Alpine 1507 repair

[dhamia]

Hi I have picked up an alpine 1507 that has an issue
With the RCA input terminals.

The terminals have been damaged, looks like it had been dropped and they have
lost 2 gold outer caps.

I decided to pull the whole terminal and replace it with
individual chassis mount type plugs as it was only making sound if you
moved the plugs about- they had worked loose on the board.

The amp seemed to work fine before I fitted the new RCA input plugs
it now produced a very distorted sound.

Any ideas?

 

[dhamia]

The soldering points for the RCA inputs appear to lead into

Integrated Circuit NJM4560L DUAL OPERATIONAL AMPLIFIER

Could it be somehow damaged or shorted?

 

[Perry Babin]

Post a photo of the new jacks showing how you connected them to the amp.

 

[dhamia]

Hi Perry,

I have now removed the new plugs as I had actually wired the earth and positive signal leads the wrong way...... (they looked right when I matched them to the original plug but when I tested the plug with a meter it was obvious I got them the wrong way round)

I have removed the new plugs - there are just 6 wires extending from the board now.

The sound is very loud and distorted when I connect the center pin of my signal rca
( i am using an old sony cd tuner)

The green music light flashes when a sound source is added

I fear I may have caused the distortion issue by wiring the plug the wrong way.

 

[Perry Babin]

You should not have caused any damage connecting the wires incorrectly.

Do you read 0 ohms between the shield grounds and the non-bridging speaker terminals?

Do the center conductors of the two input jacks connect directly to E101 and E102?

 

[dhamia]

Hi Perry
The centre conductors lead to E101 and E102

I did the sheild ohm test with meter set on continuity
and the reading stayed on 1

 

[Perry Babin]

It should read the same as when you touch the probes together.

 

[dhamia]

My meter beeps and shows 000 when the probes
join, when I test the ground shield against the speaker terminals
there is no change or beep

 

[Perry Babin]

Do you find any solder pads in the area of the RCA jacks that read 000 to the non-bridgingg speaker terminals?

 

[dhamia]

Just checked, nothing reads 000

 

[Perry Babin]

The following points (red arrows) should be connected to the non-bridging speaker terminals. I think they connect to the bussbar (green) arrow which connects to the secondary ground near the regulators.

Do you have all wires connected between the two boards?

 

[dhamia]

Tested again with everything connected up
It does measure 000 as you said Perry

The amp is behaving real odd, I connected a speaker
And it makes a loud cracking noise and the cone just moves in and out sl

 

[dhamia]

- Slowly.

 

[dhamia]

I have disconnected the led display board ribbon , would this affect it?

 

[dhamia]

Fixed it,
Cleaned up the solder pads and re soldered the speaker terminals as they had worked loose
All good now

Thanks Perry