Sansui BA-3000 No Power

[Rasmu004]

Greetings everyone,

I have a Sansui BA-3000 I bought with issues. I tested it and realized that the RL02 relay was not functioning and decided to replace both relays on the (F-2511) protection board. I then realized the cermet resistors (R01 and R02) were burned up. I replaced them and the new cermets still get incredibly hot. The AC fuse blew after doing that so I followed the manual and tested output transistors to find most all were shot. I then replaced all outputs with their respective matching pairs and put in a new AC fuse. I plugged it into the DBT, and still nothing.
Where should I go from here? I don’t want to turn the unit onto full power as I don’t want to blow anything. What would be heating up the cermets and causing the relays to not pop off? Any input is greatly appreciated.

 

[Hyperion]

What would be heating up the cermets and causing the relays to not pop off?

The reason those resistors are getting hot is because there is a fault in the amplifier - maybe being detected by the protection circuit, or a fault in the protection circuit itself, and preventing RL02 activating and closing it's contacts - when these contacts close they short circuit R01 and R02 (which stops them from heating up), and allows mains power to reach the rest of the amplifier. (This part of the circuit is known as a 'soft start' circuit).

Another possibility
What is the wattage of the incandescent bulb you are using in your DBT ? - if the wattage is too low it could cause the symptoms you are seeing by starving the relay activation circuit of current. The DBT is designed to do this, to limit damage in the event of a high current draw situation, so correct bulb wattage for the unit in question is crucial. It is a fine balancing act between providing protection to the amplifier - but also allowing it just enough power for basic functionality. I would say if you are using a 60 watt bulb that is too low, at a guess I would say 100 watt is about right - the bulb used must be of the 'incandescent' (old style) variety.

Check F04 on F-2511, it should be a quick blow 1A fuse, and also check if you are getting power (approx 25V) to RL02 and TR02. Also be aware that R01 & R02 won't stand that kind of punishment for long, and will open just like the originals if you have the amplifier powered on too long for checks.

Thus far you seem to have approached the repair of this amplifier in a simplistic way, seemingly expecting it to spring to life by replacing a few things you can find that are damaged, you will be extremely lucky to have success with that approach. For example, there was no mention of you testing any of the driver transistors that are directly connected to those faulty output transistors you found. Maybe you did test them, and a lot else too, but you don't say that - I apologise in advance if I have the wrong impression here, I hope you can understand this.

 

[schoenradt]

Greetings everyone,

I have a Sansui BA-3000 I bought with issues. I tested it and realized that the RL02 relay was not functioning and decided to replace both relays on the (F-2511) protection board. I then realized the cermet resistors (R01 and R02) were burned up. I replaced them and the new cermets still get incredibly hot. The AC fuse blew after doing that so I followed the manual and tested output transistors to find most all were shot. I then replaced all outputs with their respective matching pairs and put in a new AC fuse. I plugged it into the DBT, and still nothing.
Where should I go from here? I don’t want to turn the unit onto full power as I don’t want to blow anything. What would be heating up the cermets and causing the relays to not pop off? Any input is greatly appreciated.

First you need to isolate the shorts. If you can remove the power rail supply voltages from the output board and then start troubleshooting the power supply. With the shorts removed the unit should be able to power up provided no damage to the linear supplies have occurred. If the final outputs have shorted it's because their is a problem with loading. Check all your pre drivers and final output transistors. Also verify your low value emitter resistors haven't been stressed out by too much current. I not familiar with your protection circuit, but on my Sansui 8900ZDB the relays will energize without the power rails connected to the main amplifier board. Most protection circuits are looking at the small emitter voltage on the final outputs. Good luck I'm sure you'll find the problem and correct it.

 

[Tina Louise]

Greetings everyone,

I have a Sansui BA-3000 I bought with issues. I tested it and realized that the RL02 relay was not functioning and decided to replace both relays on the (F-2511) protection board. I then realized the cermet resistors (R01 and R02) were burned up. I replaced them and the new cermets still get incredibly hot. The AC fuse blew after doing that so I followed the manual and tested output transistors to find most all were shot. I then replaced all outputs with their respective matching pairs and put in a new AC fuse. I plugged it into the DBT, and still nothing.
Where should I go from here? I don’t want to turn the unit onto full power as I don’t want to blow anything. What would be heating up the cermets and causing the relays to not pop off? Any input is greatly appreciated.

Hi, which replacement relays did you end up using on F-2511?

 

[ivandezande]

Hi, which replacement relays did you end up using on F-2511?

Doesn’t take long to use Google.

Leestereo's Restoration & Upgrade of a Sansui BA-3000

AK member @greymatter 's very nice Sansui BA-3000 power amplifier received a complete restoration and upgrade; the restoration/upgrade of it's companion preamplifier CA-3000 can be found in this separate Leestereo's Restoration and Upgrade of a Sansui CA-3000']thread[/URL]. Part 1: F-2508 Power...

audiokarma.org

It’s a MY4-02-DC24 and a LY2-0-DC24.