Sansui 8080DB Weak FM

[LBPete]

I have an 8080DB with weak FM. I listen mostly to three college stations at the low end of the dial. The local station comes in strong but the two that broadcast off Mt Wilson on the other side of the LA basin barely register on the signal strength meter. Some days I can't tune in the weaker one at all. My little house is in the shadow of a couple two story houses. That said, when I take the 8080DB out of rotation I replace it with a recapped Sansui 8010 (alternate version of the 771). Using the same antenna, that receiver pulls in those stations like a champ. Strong signal, no issues.

A while back unsoldered the tin cover from the tuning cap then cleaned and lubed it. I've checked the tuner power supply and it's spot on. The tuner isn't flaky at all. No noise and the tuning meter behaves normally. It does receive stereo but for these weak stations I have to turn off the FM muting. The obvious answer here is it needs to be aligned but before I go down that rabbit hole, is there anything short of an alignment I'm missing?

- Pete

 

[TV John]

I have an 8080DB with weak FM. I listen mostly to three college stations at the low end of the dial. The local station comes in strong but the two that broadcast off Mt Wilson on the other side of the LA basin barely register on the signal strength meter. Some days I can't tune in the weaker one at all. My little house is in the shadow of a couple two story houses. That said, when I take the 8080DB out of rotation I replace it with a recapped Sansui 8010 (alternate version of the 771). Using the same antenna, that receiver pulls in those stations like a champ. Strong signal, no issues.

A while back unsoldered the tin cover from the tuning cap then cleaned and lubed it. I've checked the tuner power supply and it's spot on. The tuner isn't flaky at all. No noise and the tuning meter behaves normally. It does receive stereo but for these weak stations I have to turn off the FM muting. The obvious answer here is it needs to be aligned but before I go down that rabbit hole, is there anything short of an alignment I'm missing?

- Pete

I would check the FM Gain/Amp transistor in the tuner as well.

 

[dr*audio]

Alignment is the first step. 99% of the time that fixes it. I can't remember ever having a failed rf component in a Sansui. But if you are in the 1% (lucky you) you'll have to go through the rf chain with test equipment to see where the gain is being lost. I use a high impedance active probe and a spectrum analyzer. You can use an rf detector probe and a scope but then you only see DC, and you don't really know what you are looking at.

 

[LBPete]

you don't really know what you are looking at

In my case, there's a lot of truth to that.

It's hard to check those transistors. You have to remove the whole front end pack and unsolder the tin cage around it to get access to them.

- Pete

 

[dr*audio]

In my case, there's a lot of truth to that.

It's hard to check those transistors. You have to remove the whole front end pack and unsolder the tin cage around it to get access to them.

- Pete

What I do is measure the input at the antenna, using a generator as a source, and then measure the 10.7MHz output from the frontend. You should have at least 30dB of gain. If you do, you can look at the IF. Each stage of the IF should have at least 10dB of gain, usually more because the old crappy filters could have 6dB of loss through each one, so look for 20dB of gain in each IF amp and 6dB loss through each filter.