Fisher 500b crackle issue

A few weeks ago I bought a fully restored Fisher 500b. While the sound is the greatest thing I've ever heard, I'm having an issue with crackle in the left speaker.

I took it back to the audio tech tonight, and he took everything out and cleaned it inside and out. I brought it home, and the crackle is still there.

Here's what I've tried so far:

1- I swapped the speakers, to make sure it wasn't a speaker issue. The same crackle appeared with a different speaker

2- Installed brand new speaker wire

3- I mostly play vinyl, so I unplugged the TT (RCA plugs) and played the CD player, to see if it was a TT issue

4- I unplugged the TT power cord from the Fisher

Despite all of these actions, I'm still having crackle in the left channel.

Any suggestions? Help please!

 

I had the same issue with my 400 and it seemed to be related to the volume control, specifically from switching on/off. I now have my receiver connected to an Adcom AC conditioner which I use to switch the unit on and off, leaving the Fisher switched on all the time and the crackle in the speaker is gone. If your switching your receiver on/off with the rotary switch, these are problematic. Check eBay or Audiogon for the Adcom, around a hundred bucks.

 

@Ken Clark very interesting. And makes sense. In fact, my volume knob is a bit wonky. When it's off, it's not on the OFF position, it's on 2. It doesn't go down any further. Maybe I should get the Adcom AC. I'm guessing it doesn't affect sound, it's just a switch. But if it's on all the time, doesn't that use a lot of power? Sorry for the silly question as I am unfamiliar with the Adcom.

For those who are interested, here's a link to my speaker crackle so you can hear for yourself....

 

@Ken Clark which Adcom do you recommend and where can I get one? Does it affect sound at all?

 

Could I use a regular surge protector instead, the kind with an on off switch?

 

Does it crackle when you're playing music, or only when you turn the volume control? I'm thinking it might be a loose tube connection, or a loose or dirty IC connection. Try wiggling the various tubes and IC's with the volume up and see if you can recreate the sound.

 

Yes, I do with my Fisher 400

 

To add to the good advice above:

Yes, use a power strip or other device besides the unobtanium (oem) on-off/volume control to turn your Fisher on or off.

Clean tube pins with a small stove brush & deoxit.
If this does not correct the issue, you may need to re-tension the tube sockets. If you re-tension the sockets, unplug the unit or power strip from the wall and let sit overnight before working on it to drain any stored current.

From there you could check/swap individual tubes to track down noise.

Hope this is of some help to you.

Good luck!
Paul

 

Indeed. And bad and old caps stress Avery's best work. As does weak/bad tubes. Service Avery's finest work, it won't give you trouble, and last you years. The Fisher 800-C from a 3 year old estate sale I and Terry DeWick refurbished has been reliable for 16 months of daily use at work. Refurbish it right, you will have reliable music every day without issue. Take no shortcuts.

 

My crackle came from a bad output tube coupling capacitor. In other words, it could be anything.

 

That sounds like a bad coupling cap to me.

But anyway, I do suggest to clean the tube sockets with a round toothpick with 3M "Finesse-it", then flush with electronics cleaner. The "Finesse-it" breaks any petina in there and leaves the pin clean and polished, (do not clean with a file or any harsh abrasive as this will roughen the internal surface leading to future oxidation problems) It's critical to mask the the circuit or flush the 3M residue from the inside/ out.. do not allow the electronics cleaner stream to contact the rest of the components (cleanliness and care required.. that even some experienced techs do not exercise)

The sound I hear is the signature of a bad cap. The tube sockets and pins are not the cause in this instance.

 

@sberger it crackles all the time, music or not. @paul cbc the tech took out all the tubes and cleaned all the pins and slots and whatnot.

So the general consensus here is that it's either a bad cap or the volume knob, right? I'm gonna try the power strip idea today and see if that corrects the issue. If not, we'll know it's a cap.

Are all caps created equally? Do they affect sound quality? Would I need specific replacement caps for a Fisher 500b?

 

if it does it all the time, it's not the volume control. If it were, it would only do it when you adjust the volume. I would recommend a power conditioner over a simple surge protector. 90% of them are just junk, until you get into the $30 - $40 range. Something like a Belkin Pure AV PF31 would really help you out more. It would also provide cleaner power to the gear plugged in. Some plugs are always on, and some switched. They can be had for around $75.

Do you have the option to move the speakers at all? If you're digging the Fisher sound now, placing those ADS properly would knock you on your ****!

 

@adamdube a few years ago you recommended the ADS to me and I love them. What placement do you recommend? Also, if it's not the volume switch how would the Belkin help the crackle?

 

That sound could be any number of things, no way to diagnose it from afar or from sound alone. You'll have to bring it in to a tech. However, I will say, the one thing I didn't see on your troubleshooting list, and the first thing I'd try with one channel of crackly type noise, is to swap in known good tubes in the offending channel.

That noise one that video doesn't exactly sound like a typical noise of a preamp tube going bad and I'll defer to others who think it sounds like a bad cap, but in my experience with tube gear, when a crackling appears out of nowhere in one channel only, the most common cause is a noisy preamp tube and they're they easiest thing for a user to troubeshoot -- swap left channel preamp tubes for right channel preamp tubes to see if the noise moves with the tubes, or swap in known good preamp tubes to the left side, or sometimes with a noisy tube if you just gently tap the tube with a chopstick or the eraser of a pencil or something, the noisy one will crackle more and you'll be able to ID it and swap it out.

If in fact the unit has been properly serviced fairly recently -- with bad caps and resistors replaced, pots cleaned, tube sockets properly cleaned (not with anything that is leaving behind a film that's causing intermittance connectivity which also could be a source of crackling), etc, all the things you need to do to a vintage tube amp -- then the most likely thing to fail or go noisy at any given time are the tubes, and preamp tubes do go noisy sometimes. Usually one of the first things to look at when a problem of this sort develops. You should always keep spare known good tubes around.

 

It won't help with the crackle you're experiencing at all. What it would do is provide better power protection for your gear. It will clean up any power/grounding issues that you may have in your home. Appliances and such create noise. It would eliminate them and provide clean power to your stuff. Less noise = better sound. It would also postpone the death or failure of the volume on/off switch. I have one on my Fisher @ work.

On the crackle - does it happen with all inputs? Have you swapped output or input tubes from left to right? Maybe go by a guitar center and grab a cheap JJ or something to test with.

In regards to placement of those ADS, and I LOVE their sound as well, they need to be separated more. You're really narrowing the sound stage with them so close. I also think they are too high, unless the image makes them appear that way. Are the mids and tweet are over you head when sitting? This also may be why you don't think it's loud enough. Is that shelf adjustable? Looks like it is. Maybe push all the storage to the middle and put the speaks on either side. They just need more space to breath.

IMHO, get them more apart and lower to the floor. You might find tilting them back helps as well, but not too much.

 

Two comments:

Find a different way to switch your Fisher on and off. The knob is a notorious weak point, and when it goes bad, you're screwed, because replacements are unobtanium.

I do not recommend using a standard Home Depot/Lowe's power strip with your Fisher, it will degrade its performance. They are very sensitive to whether they are getting clean power or not. One of the hugest improvements I ever made to my hifi was when I bought a proper power conditioner. My Fisher 400 totally came alive and background hum and hiss completely went away. You don't even need to buy a crazy-expensive one either; I'm using a Monster Power Center that I bought used for $40.

 

@adamdube what's a cheap JJ? I don't know if the tubes were swapped L to R to test. Yes it happens with all inputs ...Cd, TT, etc. The speakers are about 5 feet apart, which is about as far as I can separate them given the space. I could lower them a bit, but I'm mostly standing when I am playing music so I kept them high. The top part of the speaker is about 6 ft off the floor.

@action pact and @adamdube do you see anything on this list you can recommend that isn't insanely expensive?

http://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias=aps&field-keywords=monster+power++center

 

This is what I have:
http://www.amazon.com/Monster-HTS-5100-MKII-PowerCenter/dp/B000C20YDY

 

I use a Belin PureAv PF30 - like this - shop around, I think I got mine for less than 100

http://www.amazon.com/Belkin-AP2080...qid=1429884378&sr=1-21&keywords=belkin+pureav

 

I'm not terrible familiar with the 500b circuit but based on this layout diagram it looks like there are two 12ax7s in the driver stage and two in the phase splitter that are in use no matter what source or input you're using and that are R/L pairs -- V9, V10, V11, and V12 in the diagram. The diagram is labelled channel A and channel B so I don't know which is right and which is left but what you want to do is swap the 12ax7 so that the ones in the left channel are now in the right channel to see if the sound moves with the tubes. If it does, one or more of the 12ax7s that you've swapped is noisy and should be replaced. You could try the same thing with the pair tube pairs, V13-14 and V15-16.

Can anyone familiar with the unit or better with a diagram or schematic than I am add any more info?

 

Does your crackle change volume as you adjust the volume control or does it always stay the same loudness? If it is independent of the volume setting, then the issue is somewhere in the power amp section.

Have you tried reseating the tubes? I would especially recomment pulling out and reinserting the phase inverter tubes V11 and V12

 

I still think it could be a bad cable connection. Try a different set to AUX. And like I said before, wiggle tubes around when it's on(gently, and they warm so be careful. Just wiggle on top) and see if you're able to find a tube that's making the noise. My bet is on a tube or cable.

 

"bacon frying" or "crinkling of tissue paper"; the classic sound of a noisy pre-amp or phase inverter tube (your 12Ax7s in this case)
Swap the phase inverter tubes and see if the noise changes sides
If not
Swap the first stage tubes (labelled "tone control amp" on the layout diagram in post #21)
If not
Swap output tubes from L to R ONE tube at the time and see if the noise follows
If not?
The problem is in the amp: cold/bad solder joints are fairly common after all these years as are any number of the other suggestions
Fisher used extremely high quality resiters and almost no carbon comps, so they are "probably" "OK"
Look for the easy stuff first
As for tube socket cleaning, you don't need the mess and crap of aerosols; just get some dental/braces cleaning brushes and scrub the sockets using them dipped in some solvent like "DeOxit"
I fill little bottles from the spray can, the 5%; the 100% stuff is a waste of money
If you've got oxidation issues worse than what "D5" can handle you need to be using a petroleum based contact cleaner anyway

"chervokas" already drew you a road map as well as provided you with the layout diagram for the compliment; his advice is the CORRECT procedure to start with in tracking your problem down, take it

My post is merely to re-emphasis the good advice he already took the time to give you

As for the weak AC mains switches on Fishers? Yes, it's true, but it has nothing to do with your current concerns

As for bad coupling caps? Anything is possible, but the failure rate of the ones Fisher used is greatly exaggerated (thanks to the internet) If you do still have the originals they should be changed for safety's sake; you can tell if they are original if they are the "Ero Fol II"s @ 630V and or the little brown/black turd looking dipped polyesters @ 400V
Often they will be mismatched; one of each per side

 

I'll tell you something else that will give you your problem, OFTEN
The "pots" for the inverter adjust
With the amp doing it's thing (making the noise) GENTLY grasp the little plastic tit for adjusting the pot for that side and GENTLY sort of "rock" it (there will be a little play, you'll feel it"
See if that eliminates, changes or exacerbates your noises
Do not turn the pot at this time (you can always index it to do so and we can get to that next) but for now, just rock it and see what happens
Also, gently apply a little pressure to that adjustment tit as well as gently pull up on it (we're looking for that change as described above)