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Fisher 500B First Steps

J

jfalv

New Member
Hello Everyone,

This is my first post, except for my introduction, so if I step out of bounds with our expected behaviors, please let me know.

I bought a Fisher 500B at an estate sale last week. It seems to be a later run with a serial number in the 37,000's. They almost gave it away because someone plugged it in and there was no power. Fuse is intact, but measuring resistance from the plug to two AC outlets on the back shows one side of the power cord not connected. The cord itself looks and feels very good, so I'm hoping the solder point where the cord is connected internally might allow me to use the nice, original, Fisher-branded cord. But- I haven't opened it up yet.

As a complete newbie, I'm looking for insight as to how best approach this project. Especially the first couple of steps with "do's" and "don'ts" equally helpful. I've been asking some AI agents what to do; they lead me to believe that there are a number of internal components that should or must be replaced before running this. I'm also led to believe that I need a variac to slowly power up the receiver, once I stabilize whatever needs to be addressed first.

The unit seems to be fairly complete, but the 7591's are not Fisher branded, and one is physically different than the other three. Two of the brass knob covers are missing, but other that that, it's just sticky dust and my eager ignorance standing between me and this thing singing like Aretha!

I know almost nothing about electronics so please bear with me if I have some follow up questions of a three-year-old.

Thanks in advance for anything and everything!
 
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Tube receivers are not the type of gear you want to learn with, they are complex creatures and have high voltages. Also, they are collectable and their value is dependent upon how well they are restored.

I would set it aside until you have successfully restored a couple of tube power amps or integrated amps which are easier to work on.

Good luck.
 
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Fishers have problems with the power switches failing, so that may be what you're dealing with.

Thats in addition to the usual old tube gear issues. Not going to say it can't be restored by a non-pro but you should have some familiarity with electronics work and tube gear in particular before diving into this. This will have high voltages inside too, easily north of 400 volts. Very easy to be seriously hurt doing this stuff.
 
I'm not big on writing long responses, but I do think the community could do more to encourage instead of dissuade newcomers that would like to learn to repair their own gear so I'm going to weigh in. We all started somewhere, and I don't think that amp is rare or complicated enough for you to shy away from learning on. You're responsible for your own safety and equipment, so learn the fundamentals of safe handling and tube circuit operation before you start plugging things in or sticking your fingers inside. This forum, youtube, and a load of great books exist that can inform you of how these relatively simple systems work. I would suggest you give the AI stuff a rest though - it's a bad approximation of the information you need to learn to be successful at this. I recommend you start by watching Uncle Doug's youtube series "How Tube Amplifiers Work." If you're able to follow along and are still interested in this undertaking, I'd say you're off to a good start and can proceed with care. Good luck, have fun, don't die.
 
I'm hardly trying to dissuade anyone from working on their own stuff. If you look at my post history you'd find I'm probably about the last person who would do such a thing. I'm just trying to dissuade people from going into things without any awareness and possibly killing themselves in the process. Some videos or reading that covers the basics would be a fantastic idea before pulling the cover and diving in head first.
 
SystemError said:
but I do think the community could do more to encourage instead of dissuade newcomers that would like to learn to repair their own gear so I'm going to weigh in.
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Encouragement is one thing, giving real guidance is quite another.

The OP hasn't disclosed their experience, knowledge, equipment, etc.. Unless you're going to guide the OP through the process, start to finish, encouraging a complete stranger to try and tackle a project like this is irresponsible.
 
gadget73 said:
I'm hardly trying to dissuade anyone from working on their own stuff. If you look at my post history you'd find I'm probably about the last person who would do such a thing. I'm just trying to dissuade people from going into things without any awareness and possibly killing themselves in the process. Some videos or reading that covers the basics would be a fantastic idea before pulling the cover and diving in head first.
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I wasn't directing my comment at anyone and certainly not you in particular. It sounds like we're in agreement.
 
malden said:
Unless you're going to guide the OP through the process, start to finish, encouraging a complete stranger to try and tackle a project like this is irresponsible.
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The personal responsibility for OP falls exclusively on OP and cannot become mine just because I suggested on the internet that they could learn how to repair an amplifier. In my comment I acknowledged the risks and personal responsibilities, explained the foundational knowledge OP would need, and even suggested a resource they could explore so they could decide if they want to go further. Did you read my entire comment or did you stop at the sentence you quoted?
 
SystemError said:
Did you read my entire comment or did you stop at the sentence you quoted?
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yes I did, you also suggested staying away from AI.

I'm no fan of AI but I think the op would learn more from it than an AK post suggesting they could learn how to do it without even knowing anything about the OP.
 
malden said:
yes I did, you also suggested staying away from AI.

I'm no fan of AI but I think the op would learn more from it than an AK post suggesting they could learn how to do it without even knowing anything about the OP.
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I can tell we're not going to share the same perspective on this and I'm not here to argue. Good luck to you and to OP with their project.
 
Same, its not fun.

I've also found that I've worked on things while plugged in before. Did whatever I did, then went to plug it back in to test only to find the plug still in the outlet. I quit for the night at that point. A few weeks back I almost reached into something electrical at work without turning it off, only realizing at the last minute that the exhaust fan was running, and it wouldn't be running if the power was locked out. Another one of those deals where I was a little tired and hyper-focused on a specific thing. Realizing that you could have just ended yourself from carelessness is not a great feeling.
 
Several years ago the Fisher forum was a hotbed of activity and I got hooked. I read every post about the 400-500-800 family and decided I must have one. I consider myself to be an "advanced beginner" when it comes to electronic repair. Armed with the forum knowledge, enthusiasm to learn more, and the willingness of fellow members to help, I bought a 500B. I bought a Jim McShane rebuild kit. I planned the rebuild for months. My unit never saw power until everything had been replaced. I only made one mistake and fortunately there were no sparks or smoke. Then I added IBAM. Again no surprises.

I suggest reading the following Fisher sticky and then deciding if tackling your 500B is something you feel comfortable with.


larryderouin

Thread 'Most Common Parts Needed For Fishers!'

I think we need a Sticky of the most "COMMON" or "UNIVERSAL" parts used in the 400-500C-800 or basically ANY FISHER, the same questions being asked over and over again after it being posted on a similar thread in the past few days to a week. Think of items common to all or most of them, items that can be had quite easily by going to Home Depot, RatShack, the local TV Shop.

I'll start off.

EDIT 08-06-2015. With the Demise of Radioshack (Don't everyone clap and cheer all at once!) Part #1 is not available. An equivalent (actually better) part is available from MOUSER.
1.)...
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Welcome to AK and regardless of which way you perceive to take this first page of post, I find the members here and those over in the Fisher threads to be very helpful and a wealth of knowledge regardless of your level of experience.

And with that congratulations on your nice Fisher, I own a few myself, and I sort of broke in on a Fisher KX200, which is considerably less complex than the 500b. But it gave me satisfaction and courage to progress on more complex gear. I don't know your level of experience and others might not know either so starting with the real and potential dangers is understandable, don't take their advice without regard, just as you take their advice that is helpful because it is all based on real concerns.

Now not knowing your experience level, and mine being best at keeping limited to mine own gear as my knowledge level is limited, the likelihood that your power cord has come unsoldered and that is the extent of what is wrong is wishful thinking at best. Even if the unit had never been used and was still in its original box, due to years it would need some work to be dependable, and even prior to power up I think limiting the power voltage and using a dim bulb tester would be wise to keep from possible damage due to old components within the unit. but don't plug it in, pull the cover and look inside take some photos and then post them. Others might be able to give you helpful advice on what and where to advance using measures to protect both your life, and the health of your future Fisher.
 
jfalv said:
Hello Everyone,

As a complete newbie, I'm looking for insight as to how best approach this project.
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Welcome to the site! :thumbsup:

The first thing I would do is find the best tube tech near you. You have one of the more complex tube receivers that was built in numbers. If you try to DIY this puppy as the first rodeo, you're likely to get frustrated and fail.

The other thing to consider is that most good techs that I know do not like working on "basket cases." Units that are torn apart with all kinds of mods, and may have parts in boxes.

Don't rush to get this unit working. Take your time and think about things before whipping out the soldering iron and wire cutters.

Here's a link to download the schematic. Do this first to get a better feel for what you may be tackling.

Just a little public service announcement. ;)
 
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I have to agree with some of the others here that the 500B is a heck of a first project to try to tackle, especially if you have absolutely no previous experience with tube equipment. There's a LOT that probably needs to be done and it needs to be done expertly if the unit is 1) going to work properly and 2) retain its considerable value. Even if you were able to get it running, it's not going to sound the way it should until it has some restoration work done.

If you are in the Mid-Atlantic region, contact Bruce Wenger at BWS Tube (bwstube.com). He's in VA. He has repaired, restored and/or upgraded dozens of 500's. He can give you a choice of just getting it working or upgrading the unit.

If you are not in that area, ask in the Fisher forum for the location of a skilled tech near you.
 
I second the recommendation of Youtube/Uncle Doug for explanation and demonstration of tube electronics ... sometime I would watch same video a few times to really get the concept (like the cathode-bias one) .. nuts and bolts concrete demonstration of the concepts .. reminds me of a chemistry teacher I had in HS ..

I haven't done much with my 400 which I got from a neighbor ..my biggest challenge currently is time, but I am making progress... certainly not on the scale of some of the complete and detailed restorations you will find here (yes - I bookmarked all of them)... but what little I have done has given positive results, and so I am satisfied with the process. Still plenty work to do, but it really is an enjoyable hobby.

But - safety first always.
 
Mr Boochie said:
The other thing to consider is that most good techs that I know do not like working on "basket cases." Units that are torn apart with all kinds of mods, and may have parts in boxes.
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This is a very good point. If you bring a non-working receiver to a shop and it has been "recapped" by inexperienced hands, either the cost to repair goes up or it won't be accepted at all.

I have a few amps and receivers I bought on ebay that were listed as "recapped" but do not work.
 
malden said:
This is a very good point. If you bring a non-working receiver to a shop and it has been "recapped" by inexperienced hands, either the cost to repair goes up or it won't be accepted at all.

I have a few amps and receivers I bought on ebay that were listed as "recapped" but do not work.
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Yeah sometimes I take a gamble and will buy those when they get to the point of unloading them for parts. They get cheap enough that if I can't get if fixed the parts are worth it.
 
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