Yeah, I didn't want the 1800, just wanted to see if it had been mickied with.
Another Fisher find, 800-C receiver
- Thread starter RS Steve
- Start date
It looks to be original, not quite as nice as the units I have but not too bad.
I pulled this 800-C out of storage to finally put the finishing touches on it, which included new cans, orange drop capacitors, individual bias adjustment, and a new quad of T.S. output tubes.
I have one issue with it other than not liking how bright the sound is with orange drops installed, I get a pop through the speakers every time the stereo beacon goes on or off. Can anyone suggest what would cause this? Maybe a small capacitor in backwards or something?
I have one issue with it other than not liking how bright the sound is with orange drops installed, I get a pop through the speakers every time the stereo beacon goes on or off. Can anyone suggest what would cause this? Maybe a small capacitor in backwards or something?
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Is it literally an audio popping sound, or an audio overload type sound, where the sound fades momentarily each time the state of the operation changes?
Dave
Dave
It is a audio pop through the speakers, might be only when the light goes off.
Nope, there's not. Likely due to some lead routing issues. Try installing a .01 uF cap across the relay contacts to see if that will dampen it out.
Dave
Dave
I'm pretty sure the pop through the speakers is happening when the relay is switching, never had this before so I'm scratching my head on this one.
P
Probably the leads are too long on the preamp orange drops,
That could do it.
Happy Memorial Day Dave by the way.
It seems this 800-C is a problem child and it's probably why it ended up in a closet without a full restoration. I decided to pull all the orange drop capacitors and install the usual making sure to keep the leads short and shielded. I also checked all my work for anything that might cause these issues. The issues are still there except now less bright sounding than before. Output tubes bias in very well, and main voltage readings all seem within range of usual. I'm hoping I can get pointed in the right direction to rectify these issues, thanks!
voltages
pin 3 412 V
pin 5 all four adjusted to .34 V
pin 6 -18.6 V
pin 8 381 V
negative bias cap reading -23 V
issue #1 - popping in right channel speaker when stereo beacon relay activates or deactivates.
issue #2 - bleed over in right channel in FM only, even in mono FM, no bleed over in any other function.
issue #3 - left channel has less treble or highs than the right, even tried different speakers and wires. But not really noticeable unless you turn balance back and forth.
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I can now call this receiver done, but it took me all day to trace the problem. Turns out a very tiny piece of solder slag was hanging far enough over to make contact with another tube pin in the area of the relay. This was causing the one channel to sound very dull and also act as some type of antenna picking up the relay action and transmitting it. It's always a great feeling when you can figure out the odd gremlins by staying at it, and tracing the path. Glad to have this one sounding and functioning as it should, it has one of the best tuners out of all my collection. Into the done pile it goes! And a special note concerning the new Tung-Sol 7591's, this set really biased nice and has super good sound with balls. Can't say anything positive about the orange drop capacitors, they took away the classic Fisher sound and are now back in their plastic bag.
Steve,
Great work!
So you think that piece of slag was a legacy issue and the cause of it being shelved by the previous owner(s)?
The little yellow ones
https://www.mouser.com/ProductDetai...GAEpiMZZMv1cc3ydrPrF9O2k7r3G2yZFpKzWsYOC%2B4=
Very possible, there were a couple things that looked like some work had been done before. But it wasn't going to get the best of me, I found a way to whoop its ass!
Thanks Dave, it's always a bit worrisome when you encounter a problem that is so different than the norm, especially when the voltages all seem to be good. I started on this receiver over a year ago and initially thought everything was good, but I was just getting my feet wet doing adjustable bias installation. Never followed through on it until recently.
