Fisher 400-left output is odd.....

recently got a this from my grandpa, he was the 1st owner and took great care of it, down to keeping every single receipt, It's perfectly stock, except for the selenium rectifier which was replaced in 73'

the more I've been lessening to it I'm noticing a ton of grain in the left side,enough to that it's getting really annoying, the right side is nearly completely quite, also the left side is just a tinny bit quieter compared to the left, I've checked everything else out, the problem has to be in the receiver, just have teared into it yet as I'm not to familiar with tube amps, only thing I've done was clean the dust off, and open it up to make sure the selenium rectifier was gone.

any idea of where to start looking?

Thanks!

define gain? like when you turn up the volume one channel becomes more distorted as you increase in volume? Or how?

1st off, what's the serial #. Match the serial # with the manual. (there are 3 of them in the AK database.).

Clean with DeOxit D-5, all the pots (Volume, Bass, Treble, Balance) and switches (rotary and slide). Read the thread in the General Audio Forum called "The Idiots guide to DeOxit....Revisited". Follow the directions.

Test. This may do the trick. No guarantees tho. But most of the time it works. At least you can rule out dirty contacts.

Try swapping the Driver tubes (2-12ax7's) in the front of the unit on either side of the middle of the chassis. If it's the tube, then the dullness will change channels. Then swap the pairs of 7868's. Left to right 1-2-3-4 1-2 to 3-4 and 3-4 to 1-2. Same idea. If there is no change in either swap, then you'll need to dig deeper. Take voltage readings at points noted in the schematic. Note that the voltages WILL NOT be exactly whats in the manual, but should all be proportionately off. The test voltages were taken with the input wall voltage @ 117VAC.

You may end up having to recap the unit, (it's due if it hasn't been done before). Some pictures of the inside will tell us a lot...whether it's been worked on or not, etc.

Larry

Thanks for the help guys.

the serial is 14759D but i allready got all the mauals.

I tried swiching out V 10 and V9 but i still have the static/grainy noise. also swiched V 11 and V 12 still the left side static. All of the tube's i just mention are the orginal fisher tube's, but they look perfectly fine.

what happens exactly is that when i fist plug it in i get a bit of static. within the first 10 seconds it dissapers. then i get 2-3 min of perfectly clear music. then randomly at about the 3 min mark thevleft side gets all griany. when i turn it off the right side is perfectly quite while the left makes a few craking noises

any idea? thanks

I can't tell you what the problem is, but I can tell you that it is WELL worth bringing back up to spec.

Those vintage tube pieces are sonic marvels.:thmbsp::thmbsp::thmbsp:

I have a 400, and I will keep it for a very long time.

Cheers

If the amp is all original / stock, its probably needing a refurb. Many components will no longer be up to original spec, and that will affect the sound you get from it. Take a close look at those output tubes and watch for the plates turning red while running. If they do, this indicates a serious problem that needs fixing.

The tubes dont turn red ever. One thing i should probaly point out is how tinny this sound is. I can'thear it on my speakers only on my headphones AKG Q701 whicher are pretty analitical and detailed. on a side note the fisher and akg work great together the fatigueing trebble is cut down and the bass is a little more prominiate. Would be perfect if it wasn't for this tinny little noise

also tubes V4, V5, and V3 all have brownish tops. my grandpa said they were fine. not so sure now, might be the source of all my problems. Was panning on replaceing them after cristmas, when i do any opions on which to get?

thanks again, I' m sure it gets annoying having a total tube idiot bothering you........and my grammer sucks......

You can't tell if tubes are bad by looking at them other than if the silver getter flash has turned white, indicating that the vacuum is lost. Tubes can look fine and be bad or can look awful and be good.

There will be nothing old fashioned about the sound you will get out of that receiver once it has received service and is operating properly.

Is the left channel compromised on all inputs? If you run a CD or other digital source into the aux input, or use a turntable on the phono low input or the tuner?

The left always has a bit if the grainy sound no matter what source. not sure if it happens on my TT, honestly my TT set up is still a work in progress and i wouldn't be able to tell if it was still there.

hippie said:

I can'thear it on my speakers only on my headphones AKG Q701 whicher are pretty analitical and detailed. on a side note the fisher and akg work great together the fatigueing trebble is cut down and the bass is a little more prominiate. Would be perfect if it wasn't for this tinny little noise

also tubes V4, V5, and V3 all have brownish tops. my grandpa said they were fine. not so sure now, might be the source of all my problems. Was panning on replaceing them after cristmas, when i do any opions on which to get?

thanks again, I' m sure it gets annoying having a total tube idiot bothering you........and my grammer sucks......

Click to expand...

I'd love to have a pair of those AKG 701s - bet they sound great.

Too bad about your 400, probably has a few weak tubes. Know anyone with a tester? Most are probably still good but you may have a dud or two in that channel.

...but i still have the static/grainy noise. also swiched V 11 and V 12 still the left side static.

Click to expand...

Deoxit is a great tool. Spray everything that you can including the Volume & Balance pots and see where that lands you. Move to cleaning the tube sockets INCLUDING the pins on the tubes. I recently cleared up noise and balance issues on two amps with deoxit. If the unit is stock and not messed with over the years, you'd be surprised over how much havoc oxidation, dirt, and/or smoke can cause.

Know any one with a tube tester :lmao: I don't know anyone who even know what a vacuum tube is.....

Anyways, I'm going to buy some Deoxit later this week hopefully that helps,

Another weird thing happen today, I was listening to some bass heavy dubstep type stuff and the right channel was making a electrical crackling noise, oddly it was happening a millisecond after each sub bass note. Hopefully the deoxit will help.

Just if anyone's curious here's the setup this is all happening on, It my first experiment with vintage equipment.



Thanks again....

Congrats on a great receiver!

You've got to recap it as you risk the transformers! Check resistors also! See the other post today's with another fellows 800C.

Randy

Wasn't really fond of the idea a modifying this. seemd a crime with it so stock.

but i'll start lookin into it. Has anyone wrought up a easy guide to do it?

That's not modifying it, as you won't be changing anything in the circuit design but just replacing mostly caps which can destroy it. You can leave the old can caps in place for looks and put the new ones under the chassis. Some re-stuff the cans or buy new ones.

Randy

hippie said:

Wasn't really fond of the idea a modifying this. seemd a crime with it so stock.

but i'll start lookin into it. Has anyone wrought up a easy guide to do it?

Click to expand...

Man, that is one beautiful 400 :thmbsp:

I wouldn't consider it 'modifying' - just updating the bad with the good/better so it can live for another 50 years or longer. After you're done restoring it, it would have all the appearances of being stock but sound like a million bucks. Keep playing it with the old parts and it will eventually die a slow and agonizing death - I think you're seeing signs of that now.

I don't know about an easy guide to restore it. A lot of folks here have restored Fisher 400s so there's plenty of help if you want to start on your own. If there's some electronics person you know - a friend, or some tech guy nearby - that could be an easier road to have their help.

Though later solid state receivers adapted the user interface of this line of receivers, this is a generation older and is more like an old tube TV in construction than a solid state receiver.

Look at it this way; Unlike a solid state receiver, this unit is hand-wired and uses point-to-point technology to achieve its sonic bliss. When operating, it works by heating things up inside to allow electrons to flow. That heat, while beneficial and necessary, creates opportunity for electrical components to dry out over repeated usage. That's why we advocate a restoration. You're essentially replacing components that have drifted and dried out because of repeated heating over years of use.

Yeah, hopefully you're getting the picture: it's playing now BUT......

The unit is 50 years old and its guts is past its prime. What you should hope to do is bring it back to its former glory and the only way to do that is replacing both the dangerous and worn components. It's really not that much $ if you do it yourself. It might take some time if you're not used to this sort of thing but if you're handy with a soldering iron, it is absolutely possible.

There have been many 400 rebuilds here. Read up on the approach of different folk and the notion will soon gel to something that you'd be comfortable doing. Scary at first but once you get started, it gets easier.

Oh yeah: Those speakers: Uh........might have to recap those as well. Same reason: caps eventually crap out. If I was looking at that array in that room I'd start on the Fisher. There is an excellent Sticky by Larry that you can use as a guide. If nothing else, change out the Selenium Rectifier. I don't think he put it first by accident.

Thanks guys deffently will start researching it.
the selinum rectifyer thing has allready been took out by a hifi shop back in the 70's probaly will put a new silicon one again when i start working on it.
by the sound of it i shouln' t plug it in again before i get this all done?

and the speaker set ups dont have any caps to replace. inside of them its just the positive and negate wires run right to the speaker then right out

I don't look at it as modifying it. I look at it as updating it to original spec or better with new parts. Think of a 40 year old car with the original tires, brakes, crankcase oil, etc. It'll probably run, but it's not going to run optimally. So you change out the dry rotted tires, put new brake pads/shoes on, change the oil and filter, grease the chassis, etc with OEM parts. NOW it'll run like it's suppose to.

There are numerous threads on here (acually too many to count) on restoring the 400. Compared to an 800C or 500C it's fairly easy. But you DO need to learn the difference between a resistor and a capacitor, and how to read a schematic. It's not that hard, but you will learn that the schematic will not look like the unit physically. Electrically, it's the same. It can sometimes be confusing to an untrained person, but you'll get it. Just go for a straight rebuild (caps, resistors as needed, diodes) to get it back to spec. This will get you a baseline sounding / running unit. Then there are upgrades to stabilize output tube screen voltages, bias adjustment upgrades, etc.

For now just rebuild it to original spec. Then you can decide if you want to upgrade or not.

One last thing. Edit your profile and add your city/state in case there is someone near you to give you a hand.

Larry