Another Fisher 400 thread!

So on a whim last weekend I bought a Fisher 400 off of Craigslist. I’d been thinking about getting into tube gear for a while and missed another Fisher 400 a few weeks earlier. I am now able to post in the Fisher forum and the tube audio forum. YAY!

The unit I ended up purchasing worked fine during the demonstration. I think that the tubes are partially original, the 12AX7s are a mixture of “The Fisher by (unreadable)”, RCA, Telefunken and some that the labels have worn off. The 7868s all have the labels worn off as well.

Physical condition is very good. Faceplate is scratch-free, no rust and only minimal oxidation on the chassis. The dials looks very good; the glass is clean and scratch-free and the lights illuminate brightly. There is no wood case with it. I don’t know to what extent this has been restored if it has at all, but I do know that the previous owner listened to it fairly regularly and was selling due to a surplus of equipment.

The issue is when I brought it home was that the left channel is quite weak. I think that it might be (at least partially) a volume control issue. I found that jiggling the volume control caused the left channel to come on briefly. I was listening through headphones at the time so I’m not sure if it does the same thing for the speakers, but I’d assume so. I can’t image why this happened; I didn’t do anything to it! The sound that I get out of the strong channel is undistorted and noise free. I assume that rebuilding the pot as shown in this thread would solve the problem?

Any advice for repair, upgrades, and the like? Those large can caps on the chassis, are there any drop-in replacements for those? I see them replaced a lot. Also, would a full recap using a kit like those purchased on that auction site be a good idea as well?

Also: I’ve heard something about replacing one of the 12AX7s in the tuner section with a 12AU7 or 12AT7 for better selectivity. I swear I read it somewhere here on AK. I have some extra 12AU7/ECC82s and 12AT7/ECC81s lying around somewhere, would this be to my benefit?

Thanks in advance.

Well, a lot of questions here so go slow:

Volume issue with change if you mess with the control?

Sounds like that (and the rest of the controls, switches) could use a cleaning. Deoxit works wonders. $10 or so for a can is good medicine. Before you think rebuilding the pot, think cleaning it and save the pot repair headache for later.

Recap?

Two schools occupying the extremes. One extreme says "if it ain't broke..." Other school says, "Well, it ain't broke, yet..." I like my kids and I don't like fires so I go to the latter school.

There are drop in replacements available. Plug Hayseed Hamfest into your search engine and that'll be the guy many go to. Others restuff the cans, still others do combos of restufffing, drop-ins, and undermounts. Whichever tickles your fancy will do.

Kits? Yet again, different strokes for different folks. The kits available at auction run the gamut. Research Metalbone, Mcshane, and, well, probably stick to those two. Either one is popular.

If you want to know what, if any, work has been done on your new prize, post a few pics of the guts. There are guys here that will be able to tell you that a wire is the wrong color!!!

Lastly: tube selection?

Yeah, 12AT7 swapped in V-100 or V-101, I forget which. Man, it's true but it is so system dependent that I would put that way last on the list. Get the unit up to snuff and running with extreme confidence before you think about swapping tubes around. Otherwise you'll be seeing ghosts and chasing gremlins living upstream which will drive you nuts.

Restoration of your Fisher is a labor of love. Virtually everyone here has a love affair with their respective babies AND the process of fixing them up. Some, on the other hand like the music these things make and prefer to leave the tinkering to someone else. If you're one of the later, then find a good tech and let it be done. On the other hand, if you have DIY inclinations, there is a special reward in restoring your own instrument that you will realize every second you listen to

Congrats and good luck with it!!!! :thmbsp:

Gold -- Congrats on your purchase! It sounds like you found a really nice 400.

Headphone listening usually requires the volume control to operate at a lower setting than listening with speakers does. Therefore, the problem may only be apparent with headphone use versus speaker use. Fisher volume controls are notorious for their tracking issues at very low settings. A good cleaning may help, while in the worst cases (like mine), the volume control must be replaced. Start with a good cleaning and go from there.

Do a search on this site and you will come up with more modifications than you can shake a stick at! You will first need to decide what modifications fit your needs. Some modifications address long term component/tube dependability, some convenience/features, and some sonic/measured performance. With so many options, there's sure to be some that will address your needs.

When you begin your work, there are a number of excellent folks on this forum to help you along -- folks with practical experience on a number of Fisher receivers, who can help take you through a good basic cleaning, to assessment, to restoration -- both physically and electronically. Likely then, most questions you have, have already been addressed before. Start with the stickies at the top of the forum. It will answer many of your questions, and also provide a fascinating history of Fisher the man, and his company.

Congrats on your purchase, welcome to the Fisher Forum, and keep us posted on your progress!

Dave

Welcome to the wonderful world of Fisher audio.
You've made the first critical step and on a receiver that's easy to work on. Also, there are multiple options for restoration on a 400, from general maintenance to improved performance to total hot-rodding. These are well documented here in the Fisher forum and out on the web.

Within the last year, the 400 has been noticed as the truly great yet overlooked sleeper that it has always been.

Make haste slowly on restoration. Leaps of faith and making multiple changes at once without checking the results of each change can often lead to service problems. Simple cleanup, as advised already in this thread, is a great way to familiarize yourself with your 400.

Wiring to the headphone jack is often reversed from that of the speakers because there was no standard at the time. In fact, I don't know that I've heard of any that are wired correctly, though you often don't hear good news, only bad.
Try low volume tracking with speakers and see if you can get a sense of mistracking on the same or opposite channel as when using the earphone jack. That will at least help down which channel is mistracking.

Don't overlook the tape monitor switch. These get dirty and need to be cleaned. The volume may come back just by working it in a bit

Most likely scenario is during the ride home, the vibrations from the ride shook some dirt, junk, etc from the inside of the pot and deposited it on another part of the pot. Also like Dave and Don have alluded to headphone listening on these uses the volume pot at a lower setting (unless you like ear bleed volumes thru headphones). So getting a can of DeOxit D-5, and Faderlube F-5 and following the instructions in this thread ----The Idiots Guide to using DeOxit, Revisited!--- is highly recommended.

I'd start off with pictures of the underside. Post them here, so we can tell what's been done. Then doing a baseline restoration is the best place to start with 2 modifications. 1 is the cathode resistors, and 2 is the screen resistors. Neither one changes the sound quality, and both enhance the operational stability of the unit. Then if you want down the road, you can get into "IBAM" (Individual BIAS Adjustment modification), EFB, and other modifications.

The amount of restoration and modification is totally up to you. None of the "mod's" substantially change the 400. But they will enhance the operation of the unit, both in terms of reliability and stability.

So get the pictures up, and we'll let you know what's what on yours. Then sit down and read thru all of the different 400 restoration / modification threads and figure out how you want to attack it.

Thank you all for the warm welcome. I have been a little busy recently, but I have taken some of your advice to heart.

As for DeOxit, I do have a can somewhere. I was a little concerned about using it on the volume pots since they are so close to the power switch. Should I wait some amount of time before powering it on after using DeOxit? I should mention that none of the other pots (treble, bass and balance) scratch, so the previous owner may have already done this. I don’t think that it would hurt to go back over it again though.

I’ll wait on upgrading the caps until I get it functioning properly as is. Same goes with putting a 12AT7 in the tuner section. The tuner sounds fine as is right now and my spare tubes aren’t going anywhere so perhaps I’ll come back to that later.

The wiring on the headphone jack is reversed, thanks for noticing. I used a test record with separate L/R sweeps to confirm this. I think that might be a characteristic of receivers of that era. I have a MAC 1700 (circa ’70-’73) and a Sherwood 7300 (circa ’73) that are also reversed. I don’t remember if my Marantz Twenty-Seven (circa 1970) is the same way. Anyway, I listened to it while moving the volume knob back and forth and I could hear the balance change at lower levels, but still slightly stronger in one channel with the volume high. I was listening through Grado SR-80’s if that helps as a yardstick for my assessment. I hooked up my speakers (Boston Acoustics A40 Series II’s) and left channel is weak in both the headphones and the speakers, and they are roughly equally weak. I was able to crank the volume to about 12 o’clock in the cans and 10 o’clock with the speakers to test this. I wouldn’t want to go louder with the speakers as I am in a small apartment and I’d like to remain friendly with the neighbors. I fiddled with the tape monitor switch but I didn’t notice any difference between before and after.

I’ll post pics soon. I’ve been busy recently and haven’t been able to devote as much time to my music and audio interests.

Gold -- The only way to really put the volume control issue to rest, is to use a known good external preamp with one of its outputs (or both of its outputs connected together) driving the Aux inputs of BOTH channels in the Fisher, with the Fisher's volume control set to MAX. In this scenario, both inputs are receiving the exact same signal, and in the max position, the volume control of the Fisher is out of the circuit, so that any channel balance issues that remain must then be due to the active circuits within the Fisher. If you try this test, let us know what you find!

Dave

dcgillespie said:

Gold -- The only way to really put the volume control issue to rest, is to use a known good external preamp with one of its outputs (or both of its outputs connected together) driving the Aux inputs of BOTH channels in the Fisher, with the Fisher's volume control set to MAX. In this scenario, both inputs are receiving the exact same signal, and in the max position, the volume control of the Fisher is out of the circuit, so that any channel balance issues that remain must then be due to the active circuits within the Fisher. If you try this test, let us know what you find!

Dave

Click to expand...

I hooked up my laptop headphone jack to the aux using a 1/8inch to RCA adapter. I played some frequency sweeps, white noise and some music as well. Not the most glamorous method, but effective. With the volume all the way up, and the signal from the laptop set to even left and right levels, I checked the audio output levels though headphones and speakers. The left channel is still significantly stronger. I pulled out the jumpers from "spacexpander jacks" and used that in case it bypassed the preamp, which it does not appear to as the volume and balance control still works. Still, the left channel remains significantly stronger at all volume levels. In order to get the volume levels even, I need to put the balance knob between 8 and 9 o'clock.

So, I'm not entirely sure what we can infer from this result other than it's not an imbalance with the volume knob at lower levels. However, seeing as how the volume and balance knobs were still in the circuit, I'm not sure that the volume knob can be entirely ruled out. Would it be possible that the levels on the knob drifted drastically out of spec? I understand that it could be the result of some other component(s) going bad as well.

Come to think about it, I didn't check the position of the balance knob when I demoed it. I didn't think to even look at it, I was focused on virtually every other part of the system except that!

GoldSounds said:

I hooked up my laptop headphone jack to the aux using a 1/8inch to RCA adapter. I played some frequency sweeps, white noise and some music as well. Not the most glamorous method, but effective. With the volume all the way up, and the signal from the laptop set to even left and right levels, I checked the audio output levels though headphones and speakers. The left channel is still significantly stronger. I pulled out the jumpers from "spacexpander jacks" and used that in case it bypassed the preamp, which it does not appear to as the volume and balance control still works. Still, the left channel remains significantly stronger at all volume levels. In order to get the volume levels even, I need to put the balance knob between 8 and 9 o'clock.

So, I'm not entirely sure what we can infer from this result other than it's not an imbalance with the volume knob at lower levels. However, seeing as how the volume and balance knobs were still in the circuit, I'm not sure that the volume knob can be entirely ruled out. Would it be possible that the levels on the knob drifted drastically out of spec? I understand that it could be the result of some other component(s) going bad as well.

Come to think about it, I didn't check the position of the balance knob when I demoed it. I didn't think to even look at it, I was focused on virtually every other part of the system except that!

Click to expand...

Hi!
You should listen to what's been said and take care of looking at the basics, FIRST before you go off on a diagnostic goose chase! :yes:

You say that one channel is stronger than the other without saying in what mode, or modes or all the time! :saywhat:

What, if anything, have you done except for getting side tracked by this volume issue? I think the cart may be out in front of the horse already!

DO THE BASICS FIRST! Might just save you a lot of grief (and time! :yes: )

My .02 cents!
Phyllis

GoldSounds said:

I’ll wait on upgrading the caps until I get it functioning properly as is. Same goes with putting a 12AT7 in the tuner section. The tuner sounds fine as is right now and my spare tubes aren’t going anywhere so perhaps I’ll come back to that later.

Click to expand...

THAT may not be possible! (putting off the caps, depending on which ones, if any are bad).

As for swapping tubes in the tuner section? Our friend who did our alignment said don't fool with tuner tubes if the tuner is working well and you are happy with it. He did in fact try a 12AT7 (in the spot suggested in another thread; wrote it down but can't remember it right now either) for me just to see what worked best and on Daddy's 500-C there was no measurable difference in performance.

You also need to have ALL your tubes tested if possible, that should be step one in my opinion (very very HUMBLE opinion).

Save yourself from potentially wasting a lot of time! :yes:

THE BASICS FIRST!

Good luck with your new toy! :yes:
Phyllis

audiodon said:

Welcome to the wonderful world of Fisher audio.
You've made the first critical step and on a receiver that's easy to work on. Also, there are multiple options for restoration on a 400, from general maintenance to improved performance to total hot-rodding. These are well documented here in the Fisher forum and out on the web.

Within the last year, the 400 has been noticed as the truly great yet overlooked sleeper that it has always been.

Make haste slowly on restoration. Leaps of faith and making multiple changes at once without checking the results of each change can often lead to service problems. Simple cleanup, as advised already in this thread, is a great way to familiarize yourself with your 400.

Wiring to the headphone jack is often reversed from that of the speakers because there was no standard at the time. In fact, I don't know that I've heard of any that are wired correctly, though you often don't hear good news, only bad.
Try low volume tracking with speakers and see if you can get a sense of mistracking on the same or opposite channel as when using the earphone jack. That will at least help down which channel is mistracking.

Click to expand...

Hi Don!
On those headphone jacks, are the CHANNELS actually reversed or just the way the balance control moves them?
Don't have any headphones on hand at the moment or I'd look myself! :yes:

Phyllis

Gold -- With the volume control up at max, it is effectively out of the circuit. Therefore, any imbalance remaining with the control in that position will be due to other issues within the unit. This is basically good news. Good replacement controls are available, but they are second best to a properly operating original device.

Dave

Sorry for the slow reply, busy weekend.

PShuff said:

Hi!
You should listen to what's been said and take care of looking at the basics, FIRST before you go off on a diagnostic goose chase! :yes:

You say that one channel is stronger than the other without saying in what mode, or modes or all the time! :saywhat:

What, if anything, have you done except for getting side tracked by this volume issue? I think the cart may be out in front of the horse already!

DO THE BASICS FIRST! Might just save you a lot of grief (and time! :yes: )

My .02 cents!
Phyllis

Click to expand...

I'll admit that I should DeOxit the pots. They aren't scratchy but it's still probably not a bad idea.

Also, the volume is weak in the left channel regardless of what input is selected.

Getting sidetracked with the volume issue? I have to disagree that this is putting the cart before the horse. After all, isn't taking care of any known issues the first thing you do?

dcgillespie said:

Gold -- With the volume control up at max, it is effectively out of the circuit. Therefore, any imbalance remaining with the control in that position will be due to other issues within the unit. This is basically good news. Good replacement controls are available, but they are second best to a properly operating original device.

Dave

Click to expand...

That's good to know. What would the next steps be to try to remedy it?

I can post images of the interior if that would help. I'm no expert but the parts look original.

GoldSounds said:

Sorry for the slow reply, busy weekend.



I'll admit that I should DeOxit the pots. They aren't scratchy but it's still probably not a bad idea.

Also, the volume is weak in the left channel regardless of what input is selected.

Getting sidetracked with the volume issue? I have to disagree that this is putting the cart before the horse. After all, isn't taking care of any known issues the first thing you do?



That's good to know. What would the next steps be to try to remedy it?

I can post images of the interior if that would help. I'm no expert but the parts look original.

Click to expand...

Hi!
The basics may just take care of a known issue wouldn't you think? That is all I meant. I don't know a whole lot about this (one project) but I don't think there is any rule that says high resistance or oxidation HAS to make scratchy noises in controls and connections to be a problem? :scratch2: I would think too that checking resisters in key locations while scrubbing things might yield (might) an answer as well!
The more know quantities the better!
Just my thoughts! :yes:
Phyllis

Update

Sorry for not posting in quite a while, but I haven't had the opportunity to spend much time with the Fisher due to various other obligations.

Long story short, I looked at the top of the chassis, just poking around tubes to see what went in what place, and try to read the labels on them to see what different brands they are. I noticed that some of them came out more easily than others. So I got an idea. I took out each tube and gently spread all the pins outward so they would fit in more snugly.

I then fired it up for the first time in two weeks and listened to FM through headphones. It was surprisingly balanced! I quickly hooked up a pair of speakers and a turntable. Balanced as well! Not perfectly at low volumes, but once the volume knob gets passed about 8 it's pretty much even.

So did I just get lucky? Or could one of the tubes bounced loose in my car during transport and this fixed it? I did drive >70 miles (or 113 km) with it in my front seat. Either way, I'm listening to my turntable through it now and it's sounding pretty darn good!

More likely that one or more of the tube sockets are dirty, and the tube pins were not making good contact. I would clean them all from info in the stickies above.

Dave