Fisher 500C my first tube amp

M

Mcenroe7

Active Member
Hi all..yesterday at an estate sale I was excited to find this. This is my first tube amplifier (I have one tuner I pair with a solid state amp). I want to make sure I bring this back to life safely, and being a novice at electrical..want to know what I can do specifically, to get it up and running? I have not plugged it in yet. It is missing four large tubes that are in the right rear corner. A friend has told me that they are called "7591 tubes". I am wondering should I plug it in and turn it on BEFORE these tubes are in, to see if it even powers up? Im sorry for my ignorance in advance..I am a rookie at solid state gear, so that should tell you where I stand on this one! The serial number, if I am reading correctly (not quite sure of last letter) is: 38319G.
any help or advice, at your convenience will be greatly appreciated!
 
1. Don't plug it in or turn it on WITHOUT the 7591's and speakers (or 50W 8ohm resistors, called dummy loads) connected.

2.)Get the Service Manual that has the schematic in it. Hifiengine.com has it. You have to register, but it's free.

3.) STUDY, STUDY, STUDY the schematic, and correlate the schematic with the parts underneath. Learn the basics of Ohms law and learn how to apply it.

4.) Have the tubes that are there tested. Usually Ham Radio clubs will have guys that have all the testing gear.

5.) Study all of the 500-c and 800-C rebuild threads in the forum. The 800-C is Identical except for having a AM Band on the tuner.

6.) If your level of experience is what i think it is, you'd probably be better served sending it off to Terry DeWick or Mike Urban. Both have banners at the bottom of the page. If you're in the Southeast, send to Terry. If in the Northeast Send to Mike. If you're out west, Fred (can't remember his last name......) in San Diego can fix it. Fred has a shop out there. (need some help here guys).

Edit your profile to show where in the country you are located. There are also AK'ers who do work on these. You might find one local to you.

Larry
 
Thanks Larry. I was fairly certain I should not plug it in..thanks for confirming this!
I am in Central Texas..and do know some AK'ers here who might steer me in the right direction. Meanwhile..I'll just enjoy looking at it!
 
Congrats on a fine Fisher product! Larry is right study study study. Watch out for the lethal high voltages inside it.
 
Thank you, and I have been studying as much as I can during my breaks today. Very excited to see if I can get this going. I have been checking on ebay the 4 tubes that are missing that I need..7591A..and it seems there are many choices. I will continue to research, because I am sure there are other threads that provide more details, but if anybody might have any suggestions/ideas on the type of tubes to get (brand)..and the pro's and con's of choices..I would really appreciate it.
 
Truly one of the great sounding, great looking classics of vintage audio! You might think about a pro rehab, as this is too awesome a machine to experiment with. Fellow AK'er, Audiodon, rebuilt mine....and it was worth EVERY penny.
 
apple_scruff said:
Electro Harminx 7591a's are very popular. Look at my 800c thread for some more information on them.
Click to expand...

Ditto :thmbsp:

A matched quad from Jim McShane will cost you < $100. It's money very well spent and not far off from a NOS quad on performance. It's really a no brainer.

Once you get this thing going, then you can begin assembling a set of vintage tubes to pop in those sockets. True matching will be less of a concern depending on what mods you decide to integrate into your unit. For now, I would spring for the Mcshane quad and, like the others have already stated, READ EVERY FREAKIN' THREAD on 500-c/800-c restores. By the time you get through half of them, you'll have a very good idea on whether you're up to the task yourself, or whether you should just write a check and let a pro do it. Either way, it is very well worth it!
 
notdigital said:
Ditto :thmbsp:

A matched quad from Jim McShane will cost you < $100. It's money very well spent and not far off from a NOS quad on performance. It's really a no brainer.

Once you get this thing going, then you can begin assembling a set of vintage tubes to pop in those sockets. True matching will be less of a concern depending on what mods you decide to integrate into your unit. For now, I would spring for the Mcshane quad and, like the others have already stated, READ EVERY FREAKIN' THREAD on 500-c/800-c restores. By the time you get through half of them, you'll have a very good idea on whether you're up to the task yourself, or whether you should just write a check and let a pro do it. Either way, it is very well worth it!
Click to expand...

Thanks..what I am wondering is..can I purchase these four tubes, install them, and then plug it in and power it on to see if it works?..or is that too risky to do before I have somebody check this out? All other tubes are present.
 
At minimum build a dbt and bring it up on that, either way, it's going to need be serviced. These old tube units have 48 year old caps in them that need to be replaced. Simply plugging in the unit and running it for any length of time can do permanent damage and you don't really want to do that.
 
bktheking said:
At minimum build a dbt and bring it up on that, either way, it's going to need be serviced. These old tube units have 48 year old caps in them that need to be replaced. Simply plugging in the unit and running it for any length of time can do permanent damage and you don't really want to do that.
Click to expand...

What he said.

When I got my first 800-c I was a complete greenhorn. I knew zilch about what I had in front of me and zilch minus about what to do about that ignorance. I plugged it in and it went "Whhooommmphhhhhh!!!!" Luckily, it did no damage but I was lucky I didn't cook a transformer. Search around to see how much a replacement transformer will cost you, IF you can find one. Feel lucky? Take the chance.

Most people in the know would play safe and hand it off to someone who will safely do all the sweating for you (for a price) OR you could develop a baseline/working knowledge of the restoration process and get to the stage where you're comfortable and confident it is time to plug it in after implementing what you've learned. Like Bk said, a DBT test is a minimum prerequisite and the second step in that process. The very first step is knowing what, why and how.
 
thanks guys..I will follow this advice for sure, and find someone who can help me with this. I definitely do not want to take any chances!
 
by Notdigital: Most people in the know would play safe and hand it off to someone who will safely do all the sweating for you (for a price)
Click to expand...

That must be why I take a lot of showers!! (JK!!!)
 
Mcenroe7 said:
Thanks Larry. I was fairly certain I should not plug it in..thanks for confirming this!
I am in Central Texas..and do know some AK'ers here who might steer me in the right direction. Meanwhile..I'll just enjoy looking at it!
Click to expand...

Mcenroe, there is a fellow in Manor, TX that works on Fishers. I have not used him personally, but a couple of folks here on AK have. If you are interested, I can look for his contact info. I have seen him run ads on Craigslist occasionally as well.
 
I just spent a couple hundred dollars on mine, and I've built guitar amps and modded St70s and the like. I'm clueless when it comes to tuners, so it wasn't hard to send it off to the tech.

I'm surprised when I run into someone who thinks they can buy a 40 year old amp off e bay and plug it right in. A lot of toasted equipment I suppose.

Have a pro rebuild the Fisher and enjoy it for the next 40 years. I doubt you'll regret it.
 
gguillot said:
Mcenroe, there is a fellow in Manor, TX that works on Fishers. I have not used him personally, but a couple of folks here on AK have. If you are interested, I can look for his contact info. I have seen him run ads on Craigslist occasionally as well.
Click to expand...

That would be great if you can give me his contact info! I have a couple of other leads in the area, but they are busy. I appreciate all the responses on this. I have been heavily into solid state gear the last few years, and really know little about tubes. Cant wait to hear how it sounds, and will have an expert bring this back for me.
 
Welcome to the Fisher family.

You will find that these vintage receivers are somewhat addicting, and once addicted, you're down for the count.

Vinyl and CDs sound fantastic with them.

Cheers
 
Mcenroe7 said:
That would be great if you can give me his contact info! I have a couple of other leads in the area, but they are busy. I appreciate all the responses on this. I have been heavily into solid state gear the last few years, and really know little about tubes. Cant wait to hear how it sounds, and will have an expert bring this back for me.
Click to expand...

Mcenroe, here's what I have been able to find. Here's a link when I asked about this fellow on AK:
http://www.audiokarma.org/forums/showthread.php?t=454395

And here is what I found when searching MV Electronics:
http://www.linkedin.com/pub/mike-ascerno/25/b26/826

I do know that he posted a few times here on AK, I just don't remember what his alias was....it was in regards to doing some requested mods to a Fisher amp.
Anyway, if you contact him, let us know what you find out.
 
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