Sansui G-22000 VU meter without Amp stage

U

Utk

New Member
Hello,

I recently restored a G22000 and absolutely blown away by the clarity of the audio. However, the VU meters won’t working.

I did some digging and noticed a burned resistor on the power supply to the VU meter, I patched that and noticed that the VU meters would respond when the unit is turned on and off.

current they move to the very end and come back to zero position when the pre-amp is turned on.

from the schematic it looks like some of the analogue lines from Sony CX silicone goes to the amp stage via the umbilical cord.

I wanted to know if the VU meters are supposed to work when I am just using the pre-amp stage in separated mode with external amp (ROTEL).

I never did any bias correction on the VU board expecting that it should at least move a little bit with Audio.

I checked the reed relay and it seems to be working fine. Does anyone have any suggestions on where to look ?

thanks
 

Attachments

  • image.jpg
    image.jpg
    72.1 KB · Views: 23
Register to hide this ad
The power-amp drives the meters.
I'd have to have a look at the schematic to refresh myself, but what it happening is not normal..
 

Attachments

  • 20221108_083801.jpg
    20221108_083801.jpg
    174.7 KB · Views: 25
  • IMG_20221108_091727.jpg
    IMG_20221108_091727.jpg
    94.9 KB · Views: 23
@LBPete i see. That would mean that the reed relay is always on. I tested it separately and concluded that it works, because I can toggle it.

one interesting thing to note is that when I got this amp the protection circuit won’t flash when the power stage is not connected.

Wonder what the previous owner did to bypass the protection circuit. It probably bothered them as they were just using the pre-amp and it would continuously flash if the power stage is not there.

However this poses an issue where the amp doesn't have enough time to settle all voltage levels before things like the VU meter relay on.

Maybe that could be the reason for the spikes on VU meter on startup?

@kevzep thanks for the feed back
 
Even if the relay clicks it doesn't guarantee that the contacts are making good contact. The larger amps that have the switch that connects or separates the pre amp from the main amp have a reed relay in that circuit. It's purpose is the prevent speaker pops on turn on and turn off. A very similar function to the meter relay.

- Pete
 
Utk said:
one interesting thing to note is that when I got this amp the protection circuit won’t flash when the power stage is not connected.
Click to expand...
This is normal, as the protection circuit is actually located in the Power-amp section, a small part of it, the LED's, the vibrator circuit which makes the protector LED flash and the protection relay are in the Pre-amp section. The timing capacitor which has to charge up before the amp comes out of protection, is located in the power-amp section.
So you have to have the umbilical connected to have the unit power up properly.

There is also another relay on the output of the pre-amp, these can often fail and prevent audio passing out of the pre-amp.

I think that pulse is happening because perhaps you haven't got the umbilical plugged in, the protection circuit will not operate correctly as I have said earlier.

I was thinking the relay that connects/disconnects the meters might be faulty and is stuck on, this needs further investigation.

Can you connect it up with the power amp and so forth then power it on and tell us what it is or is not doing.

I do have rather a lot of experience with these units with all sorts of weird faults, I am sure we can get to the bottom of this quickly.
 
You must log in or register to reply here.
Back
Top Bottom