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Help with 8080DB

archie2

archie2

Addicted Member
The FM and AM no longer works on my Sansui 8080DB, it just quit. Unit comes out of protection, amplifier works. But no sound, not even a hiss or any needle movement out of the tuner. Probably the Dolby board??? All fuses are good. The unit has a nice new wood case so I'd really like to revive the tuner section. Suggestions most welcome.
 
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archie2 said:
The FM and AM no longer works on my Sansui 8080DB, it just quit. Unit comes out of protection, amplifier works. But no sound, not even a hiss or any needle movement out of the tuner. Probably the Dolby board??? All fuses are good. The unit has a nice new wood case so I'd really like to revive the tuner section. Suggestions most welcome.
Click to expand...

I don't know the particulars about the tuner section.

I think the tuner section should work regardless of the dolby section.:scratch2:

I do have a 8080DB parts unit with a good tuner, if all else fails send me a PM.

Good luck!
 
Check the voltage on the power supply board at the top left front.

I bet you have none.

Rob
 
I see the power board F-2619 and I have a DMM but I know nothing about the 8080DB. Where do I place the DMM probes and do I test with the power on or off? I will send picture.
 
Sansui Power Board Picture

I see the power board F-2619 and I have a DMM but I know nothing about the 8080DB. Where do I place the DMM probes and do I test with the power on or off? I will send picture.
 

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That power board is a known little issue. Re-solder the whole thing, the connections crack around the big transistor. I also had grief with mine until I replaced the capacitors on it. There is also a modification for it that works very well and keeps the whole thing cooler.

It's not a difficult fix.
 
The resistors (large white ones) may need to be resoldered.

I am going by memory. See the solder point at the bottom right in the pic?
With the receiver powered up, test from there to ground. Should be around 12volts DC.

Rob
 
Robisme said:
The resistors (large white ones) may need to be resoldered.

I am going by memory. See the solder point at the bottom right in the pic?
With the receiver powered up, test from there to ground. Should be around 12volts DC.

Rob
Click to expand...

Thanks, I'll test it. The heat sink on the power board is stone cold after the receiver has been running a bit in the FM mode so fair to say it is something on the power board.
 
Solder joint

Just to double check, is this the solder joint that I test to ground?
 

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I think that was it.

Usually the heatsink is hot as hell. So you have a problem. The entire tuner module can be removed from the receiver, so you can flip it over and re-solder ALL the connections first. Do not forget where the black ground wire goes that you will find underneath.
 
I actually have an issue with the same board on my 8080DB. It seams the heat has got the best of it. It is pretty dark under the big resistors, the transistor and a cap that is right next to the heat sink on my board, that was probably relocated to the bottom of your board at the factory because if the proximity to the heat. The pads where the big transistor solders to appear to be lifting because of the heat as well. I am debating whether or not to re-do this board myself or have it "professionally" done. It seams that I may have some extra time on my hands due to a temporary layoff and I am leaning to doing this my self. I'm wondering what replacement transistors the "pros" might recommend if we have to rebuild this board? The rest looks fairly straight forward and I think I could work up a slightly better heat sink as well. If one was to relocate the big resistors, there seams to be plenty of room for a heat sink with fins.
 

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Actually, re-locating the resistors is the mod. It involves using ONE 10watt resistor (not sure of the value right now) and attaching it to the metal frame behind the board. I did this to my 9090db, and it runs much cooler.

Change out those caps!!

I'd have to pop the cover on my 9090db if anyone wants a pic and the resistor value.
 
The pin in the lower right that has the arrow in the earlier picture will give you the output voltage. Measure the DC voltage from that point to a good chassis ground. The specification is 12.5 volts. The little trimmer pot allows you to adjust it.

The two white resistors are wired in parallel. You can replace them with a single 200 ohm 10 to 20 watt. This will drop the temperature of the main power transistor. If you mount the new resistor directly on the steel behind the power board, it will really heat up a lot of the chassis. There is a bundle of wires that passes through a vinyl sleeve in that area that might melt! If you want to mount it there, the best solution I've seen is to mount an aluminum heat sink behind it on the opposite side of the chassis.

As has been mentioned, you need to reflow all the solder joints on that board. Also check the power transistor. They can fail from the heat. This particular board looks like it has the main filter cap mounted on the underside of the board. Sansui moved in in at least three different positions over the production run of this series in an attempt to keep it away from the heat.

- Pete
 
I get zero reading on my DMM test so it's the tuner power supply board as you all suspected. I'll reflow the solder after Christmas. Thanks for all your inputs, I really wanted to get this 8080DB working again. The laminated case was re veneered in wood by Merrylander and looks flawless. Much obliged to you guys.
 
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