500c - reform or recap?

specialidiot

specialidiot

Break Glass, Smoke Lucky
I picked up a Fisher 500c this morning, see this thread.

I probably won't keep it, I have enough gear. I'll clean it up a bit, update what needs updating, and move it on.

The seller says it hasn't been powered up for years, and I haven't yet.

I have access to a variac, should I reform or recap? I'll still do the audio path caps with orange drops or better, but I'm sure the filter caps could use some tlc.

If the answer is reform, is there a link to the proper way to do this?
 
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It seems that just a few days ago we had a thread on the same subject.

My take on this topic is to try to reform the capacitor. I have found that many of the old capacitors are fine once they have been reformed. If this was going to be a keeper and used every day, I might go to the trouble and expense to replace the main power supply electrolytic capacitors. And, I would definitely replace the power supply electrolytic capacitors if they were truly bad. i.e. the capacitors could not be reformed.
 
Well, if you recap, and have the time to do it right with an SDS board etc. You could sell it for Big money. By big I mean $600 or more. Are you sure you want to sell that? I have the same amp with AM (800c) and I will never sell it. It sounds that good! John
 
I'd replace the filter cans and the coupling caps at least. Those are for safety reasons and for the protection of the output transformers. If the big filters get hot at all, shut it down.
 
sloober said:
Well, if you recap, and have the time to do it right with an SDS board etc. You could sell it for Big money. By big I mean $600 or more. Are you sure you want to sell that? I have the same amp with AM (800c) and I will never sell it. It sounds that good! John
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huh I never knew those existed. Looks like they include diodes to replace the bridge and everything.

Am I sure I want to sell it? I have pretty good gear that I'm really happy with. My MC225 is a 7591 in PP so I already have that configuration covered, and I have a 45 SET in the works. More amps than I can use. By selling I could cover the cost of the power supply rebuild for the MC225 that is right around the corner.
 
Sounds like you are covered! Well, you may want to keep and try those output tubes if you could use them in the 225. If you have the time, and a couple hundred bucks to invest I would restore it to the hilt, electronically and it's appearance. Looks like you need a couple brights and it has one non-original knob on the tuning dial. Brights are easy, the knob may be tougher. But one is out there somewhere...
A nice looking, FULLY restored unit will sell for good money. But then again you could likely do well as it is.
The SDS is a great little board. Like you said it covers the whole PS section, including rectifier and bias caps. The instructions are lacking, but AK can help there. Then there are a hand full of other caps to do and it is like new!
 
I lost count of the Fisher receivers that I've sent down the line, sold. There were only 2 units where I was forced to change out a can cap. Luckily I had several from units that I'd stripped and parted out so I had originals. I know, awful...

Personally, if I'm just looking to move out a complete unit, I use a cap analyzer like a TO-6 to reform each section. Simply lift a lead, connect, then apply voltage slowly. This isolates the rest of the unit and at the same time uses a low current device to gently reform the cap. This works most of the time. If the caps pass the test, and the B- is still in spec, it's worth it to add the 10 ohm cathode resistors so at least the output tubes can be mixed around to get a decent match. Add a CL-90 inrush limiter at the AC input which will keep the cans from getting pounded upon turn on.

If you're going to use a variac and that's all you have, no ESR meter, multi-meter, etc:

You really should test the output tubes first somehow.
Cycle each tube in and out of it's socket 10-15 times.
Mark the tubes in the tuner section and Multiplex board so that they end up where they started!
Install the lowest value fuse you have on hand.
Connect a load, resistors is if you have them, loudspeakers if you don't, to the unit.
Rotate the selector switch to AUX and short them if possible, not any of the FM modes.
Keep the volume knob at it's lowest setting.
Rest the unit on edge, meaning standing up on edge and stabilze it. This will keep heat that's dissapated by the resistors mounted underneath the can caps from creeping up the can which can lead you to falsely believe that the can is overheating.
Set the Variac to 0 volts and turn the unit on.
Start out at 20VAC, then increase 10 volts per hour.
At 65 to 80VAC you can switch to FM and you should get some tunes if connected to speakers.
After that point watch for redplating of the output tubes as you increase AC volts.
If you get to 120VAC without issues, and it can play at least a day, it's offically saleable. An honest seller might state that all original vintage gear should be refurbished for everyday use.

A dirty dog might snatch all of the TELE 12AX7s out and replace them with new production tubes. A heartless capitalist can end up with 191 smooth plate Teles that way, or so I've heard.
 
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Rocjr said:
If you're going to use a variac and that's all you have, no ESR meter, multi-meter, etc:
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Thanks Rocjr, I think I'll do this. It would be nice to hear it anyway.

A dirty dog might snatch all of the TELE 12AX7s out and replace them with new production tubes. A heartless capitalist can end up with 191 smooth plate Teles that way, or so I've heard.
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I've been called worse but I understand the value of this thing with a full complement of original tubes.

I believe I do have a contact to test the tubes for me.....
 
Jeff, I still have those tubes you sent home with me to test, and I'm embarrassed they are still un-tested. I also have some 6922's that numbdiver (Rick) dropped off for Nate the other day that I need to test for him also.

Maybe we need to sit down and get them all tested at once (including the 500C tubes). I could bring the tester over or you shot over my way :yes:

I picked up a variac also the other day so if everything checks out, you can run with that if you don't want to get the other loaner :thmbsp:

RC
 
The Sprague Tel-Ohmike model TO-6 is a very useful piece of equipment for testing capacitors. One can measure capacitance value, leakage and power factor, the three important measurements that will tell you whether or not your capacitor is good to go. Since Sprague stopped making these years ago, finding one will probably require looking for one in places that sell used test equipment.
 
audiodon657 said:
specialidiot,
Give the 500-C a fair hearing before you decide what to do. You might be surprised.
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I might be, so I will listen to it of course. I've been surprised before. I didn't care for my Pilot 602 so I may be biased against that era of receiver. Still, I love the MC225, and my F5 continues to amaze me. That leaves a Yamaha B-2 as a backup. so....

doucanoe said:
Jeff, I still have those tubes you sent home with me to test, and I'm embarrassed they are still un-tested. I also have some 6922's that numbdiver (Rick) dropped off for Nate the other day that I need to test for him also.

Maybe we need to sit down and get them all tested at once (including the 500C tubes). I could bring the tester over or you shot over my way :yes:

I picked up a variac also the other day so if everything checks out, you can run with that if you don't want to get the other loaner :thmbsp:

RC
Click to expand...

No worries on those tubes I sent home with you - They would still be in the bucket they were in when I gave them to you.

Yeah lets get together during this coming week or weekend. I'm also off on Friday. I'll bring the whole thing along just to be sure I don't get them mixed up.

I may take you up on the variac offer, but I do have one from the lab at work available to me. I just have to sign it out, and I walk by that lab several times a day so it is pretty handy to me.
 
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