Hi Sansui experts! I can't figure out why my G-9000DB is doing this? it has been recapped about a year ago and it was working fine until yesterday. While It powered on and came out of protection fine but if I turned the "Tone" switch on or press one of the "Filters" button then it would go into protection mode. And while in the protection mode if I turned on the "Muting" switch then it would come out of the protection mode again. So I checked the DC offset but the reading is jumping wildly from + hundreds mv to - hundreds mv.,but the Bias is more stable. Any idea where I should be checking ? Thanks in advance!
Sansui G-9000DB protection issue!
- Thread starter stevo1214
- Start date
dr*audio
Fish fingers and custard!
You have a leaky coupling cap somewhere on the preamp board, allowing DC to get through when you press those buttons. Replace all the electrolytic caps on the preamp board. If that was already done, you probably put one in backwards or use a polarized cap where it was supposed to be a non polarized cap.
Hi! Dr* Audio, If I did put one "capacitor" in backward or used a polarized one in the first place. Shouldn't the problem start right then and not waiting for a year later to act up? :scratch2:
Yes, both channels.
Which point/s should I look at?
Darn, there are a lot of them there. I'll pull each of them out to check.
I just did that but there are no reading, my DMM is showing "--OL--"
I just took a look at the tone control board (F-2799), I spotted 4 (220uf 35v) slightly bulging caps (C19,C20) Flat amp unit and (C35,C36) Tone amp unit. I did compare their orientation with the original picture that I took of the board before I installed them, the orientation is correct. So I don't have any idea what caused them to bulge.
JOMARK911
Super Member
Are they really bulged? It looks kind of exaggerated to have these issues from a one year old caps. I'm not saying impossible , but kind of a remote chance. Do you have handy a LCR bridge to check them out?
Also check voltages on them . This will tell you if they run ok , or get overvoltage.
Also check voltages on them . This will tell you if they run ok , or get overvoltage.
I think that those 4 are just slightly bulged. The top is kinda like dome shape not flat like the others. I don't know what is LCR bridge? all I have is a DMM. I also don't have any new caps on hand,so I have to order some new ones. Hopefully that is the problem.
Yes, it does.
I just replaced the 4 bulging caps on the tone control board (F-2799), but it still won't come out of the protection mode, unless I switch to separated mode then It's fine.
So I checked and adjusted the DC offset and Bias with the separated switch is disconnected. Can Any expert tells me with board/s involve in the preamp section ? Is it just the tone control board?
ATM ,I'm using the G-9000DB as poweramp and my Marantz 2285B as preamp and it sounds fine.
So I checked and adjusted the DC offset and Bias with the separated switch is disconnected. Can Any expert tells me with board/s involve in the preamp section ? Is it just the tone control board?
ATM ,I'm using the G-9000DB as poweramp and my Marantz 2285B as preamp and it sounds fine.
It comes out of protection when you separate the amp from the pre amp? That's a little unusual. Does it go back into protection if you drive the amp from another source?
Have you checked the DC offset? You can measure it at the speaker terminals if it's not in protection. It could be borderline high and trips protection when there is a line in.
- Pete
Have you checked the DC offset? You can measure it at the speaker terminals if it's not in protection. It could be borderline high and trips protection when there is a line in.
- Pete
Hi Pete! Yes, once I switch to separated mode then it comes out of protection mode. But not when use the connected mode. If I use the G9000db as poweramp and my Marantz 2285b as preamp then everything works fine.
right now I can only checked the DC offset and Bias when I switched to the separated mode and I can adjust everything to spec with no problem. :scratch2:
Something in the preamp is having problem but I don't know what part/s?
I don't have a scope,I also just found another 2 bulging caps (C37,C38) on the EQ amp circuit board (F-2796). This is a tough problem for me to figure out why these caps are bulging even though I didn't install them backward.
Just out of curiosity, what make are these caps and where did you buy them.
They are Nichicon HE and I got them from mouser.
I was wondering if you bought some cheap caps or may be got counterfeits. Nichicon from Mouser should be good to go, though. I'm also interested in why new caps would bulge. May be look at the voltages to see if they are correct. I've read where running too high a voltage through a cap can make them bulge. I wish I could help but I'm no tech by any stretch. Good luck, and I'm sure the guys who know will chime in.
The first 4 caps that are bulged, I used the exact value. But the later two caps ,I did uprated them a little bit, instead of 470uf 35v I did use 560uf 50v. are they too much? But why only 4 out of 8 exact caps and 2 out of 4 exact caps are bulging? The amp doesn't seem to have a short when using DBT, the light is bright and then dimmed.
