Aragon 4004 slow relay problem

[Colin151]

Hi there,
Was hoping someone might be able to give me some advice as to what this problem might be? I have two Aragon 4004 power amps. When I bought them both speaker relays in both amps were pretty slow to kick in, - maybe 5-10 seconds after the power button was pushed. This has got worse in both amps to the stage where it became a minute of two before the speaker relay activates, - you can hear a rasping sound for a long time before the relay activates.

I changed all the old electrolytic caps in the channel cards of both amps and also all the electrolytic caps in the relay section itself (there are 4 caps in the relay section). This made zero difference to the problem. However I have not changed the old big PSU caps yet, - there are 4 large PSU caps in each amp, - each one a blue Aerovox 17000uF caps. I was thinking its possible the problem is being caused by these old PSU caps taking too much time to give power to the relay section, - is this possible?

Unfortunately now in both amps its got even worse and to the stage where the relays don't activate at all! So its a major problem.
I read this could also be down to DC offset problem and possibly some other issues (like bad components in the relay section) but my hunch is that it seems like not enough juice is getting to the relay for it to switch and its down to the old PSU caps. You can slowly hear the rasping sound as the relay tries to active but fails. I should try changing to PSU caps for sure but they are an odd value. I might have to use 8 10,000uF caps instead in parallel pairs.

Any advice on this relay issue would be really appreciated,
Cheers,
Colin

[sakis]

measure and you will find out ...any simple multimeter will do

connect your multimeter to any point in the output before the relay ...you may aswell do that on the relay ....the other lead will have to go to ground

start up the amp ....observe offset ...if ofset takes time to stabilize then its normal for the relay to take time to click

then observe voltage on the main capacitors after the amplifier is switched off and caps are flat empty ( no volts on them )

start up the amp observe voltage first in the one then in the other cap ....if for any reason voltage take time to bulit or there is any diference from rail to rail then the caps are obviously dead ..

State more about the protection circuit is IC based like 1237 or is it descret ? often if a small calculation error is made while designing the amp electrolytics only will not solve the problem an open or a resistor that has a drifted value might cause that .

Often resistors exposed to thermal stress or moisture roll seriously off original value ...you might as welll check that to.

There might be a problem in the relay drive circuit which is more possile than the main capacitors ( simple reason is that relays operate 12-24 volts and amplifier is working much higher ...)

locate if there is a secondary or auxiliary power supply for the protection or voltage comes from a voltage divider from the "big"power that works for the audio ....

it seems that schematic of the 4004 is available but no info arround the protection circuit looking at it though there might be also an issue with the input of the amplifier ...

do any of the above ...post some pictures arround therelay ...might also help