Fisher 500B - It was working and then...

1scienceguy

1scienceguy

AK Member and E-waver #88
Good evening!

Please help. I purchased a beautiful Fisher 500B from a friend of mine. It was working flawlessly when I went to look at it. Phono, aux, tuner, etc. It was all amazing.

I get it home, wipe it down with water and a washcloth, deox the pots (short burst - not over kill), open up the bottom (all looks good there), and then it sits for 24 hours. When I was cleaning it, I pulled each tube very carefully and made sure they went back into the same slot.

Hooked up the speakers tonight and presto..................the right channel is non-existent. WTF! I wiggle each tube, check everything I can think to check, swap out speakers, cables, tried AUX - nada.

HELP! Please treat me like a newbie on this one. This is my first venture into tubes and I'm already hooked.

Thanks
 
Try DeoxITing the tube pins and the sockets to ensure that you have good connections.
 
I vote for needing a heavier dose of deoxit on one or more of the following: volume pots, balance control, stereo/mono switch, selector switch.

Ofttimes a small dose of deoxit makes things worse than they were and the only cure is a heavy bath of deoxit. I think the little bit of deoxit is enough to loosen some dirt and oxidation and have it move from a benign location into the contact zone of a pot or switch. You need to really flush it out once that happens.
 
The one thing to ALWAYS check on Fisher units from this era (from 1962 on) when you have no sound is the jumpers on the SPACEXPANDER jacks.

If they are in to far- no sound. If they are not in far enough- no sound. If they are missing- no sound.

Lightly wiggle the jumper(s) in and out with a source hooked up (or the tuner) and see what happens- 95% of the time that is the problem.
 
el-37 said:
The one thing to ALWAYS check on Fisher units from this era (from 1962 on) when you have no sound is the jumpers on the SPACEXPANDER jacks.

If they are in to far- no sound. If they are not in far enough- no sound. If they are missing- no sound.

Lightly wiggle the jumper(s) in and out with a source hooked up (or the tuner) and see what happens- 95% of the time that is the problem.
Click to expand...

These are the "U" shaped pieces to the left of the tape rec on the back? About middle of the panel?
 
Here's maybe a dumb question - how will I know (without a measuring device) that a tube has gone bad? All current tubes are lit. Do they "burn-out" or can a bad/dead tube still light up?
 
I forgot to add - THANK YOU to all that have posted!

The right channel plays at a whisper when the vol is allllll the way turned up.
 
Also, the phase inverter pots got bump[ed/turned accidentally during the cleaning process. I take it that it requires equipment I do not have to set.?.?
 
I'm with the call on the U shaped jumpers. Clean them off and reinsert a few times. I have trouble with them at one time. Also see what you get with phones. While off run the selector switches a bit as well. PS, you anywhere near Apex? I can help.
 
sloober said:
I'm with the call on the U shaped jumpers. Clean them off and reinsert a few times. I have trouble with them at one time. Also see what you get with phones. While off run the selector switches a bit as well. PS, you anywhere near Apex? I can help.
Click to expand...

I'll check all suggestions when I get home from work.

I'm in Mooresville, NC. Mind PMing me your phone number? I'd gladly drive there to get this thing right. It's a super nice piece and the friend I bought it from maintained it really well. I just got too aggressive on the cleaning side of things. Do you have the equipment to set the inverter pots?

Thanks for your help.
 
Are you sure the little jumper wires (speaker impedance selectors) are connected? They are the little green and brown jumpers that come out of the back that get screwed into the anticipated speaker impedance on the output connectors.

Also, are you sure your speakers are connected correctly?
 
audiodon said:
Are you sure the little jumper wires (speaker impedance selectors) are connected? They are the little green and brown jumpers that come out of the back that get screwed into the anticipated speaker impedance on the output connectors.

Also, are you sure your speakers are connected correctly?
Click to expand...

The 500B has a black wire that is connected to the 8ohm screw.

Left side plays with two different speaker cables, with two different speaker brands - both 8ohm.
 
Unplug the Spaceexpander jacks and use patch cables to cross left and right channels. If the nonfunctioning side changes sides you know to focus on the preamp side of the amp. If the dead side stays the same, then concentrate on the power amp side....
 
Before you start going crazy chasing down problems that most likely don't exist- just wiggle the U shaped jumper on the right channel in and out while a source is playing- it seriously takes about 25 seconds to do.

They almost always get pushed in to far when picking the unit up, or carrying it around- and cause the problem you are describing.

If it was any other unit besides a post 62' Fisher- I would suspect something else. But believe me 95% of the time, the U shaped jumper(s) are the culprit.

If adjusting the jumper on the right channel does not bring the channel back- then move onto the next step in troubleshooting.
 
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Also- is the remote control shorting plug present on your 500B? If it is missing you will see a 9 pin tube socket on the back of the unit to the left of the reverb (spacexpander) jacks. If it is present it is a black round "cap" with leads on it.

If it is present make sure it is seated properly, and clean the contacts with some de-oxit.

If it missing- you would get no sound at all, but if someone did a poor job of soldering in jumpers (I have seen them NOT soldered in- just leads shoved into the proper socket pins), that would also explain why you have no sound on one channel.

If bad soldering, or just leads shoved into the socket were the culprit- just moving the unit from your friends house to yours could jar them loose.

IF the plug is missing, pins 1 and 3 need to be connected to each other, and pins 6 and 8 need to be connected to each other, in order for the unit to operate correctly.
 
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