Fisher 500C power switch

sunrayjack12

Active Member
My power switch went out in my 500c, I had a very good member here offer to fix it for me for a small amount.
I appreciated the offer and it was very reasonable but I wanted to give it ago myself.
Part of this hobby for me is the challenge of learning something new and learning from my mistakes.
Well needless to say I destroyed the cheap switch Fisher put into the 500c, but I was on a mission to find a suitable replacement.
The thought was to search other amps and receivers for a similar switch.
I was on the Bay and saw a nos switch for a Macintosh 1900, it appeared to be almost identical, but a much nicer switch.
I paid a premium for the switch , about 170.00 dollars but well worth it to keep everything as near original as possible.
I put it in last night and it works perfectly, the shaft is a little shorter so I plan on making a new similar knob with an extended hub for it.
I feel like it was a victory in the end ,I learned and have found a suitable replacement power switch for the 500C and can share that with others.
I know that is a tough switch to find also but easier I think than the Fisher switch, It is built like a tank.
I hope this helps others, I knew I would find a suitable solution to the problem with a new part / old part if I just kept looking.
It is nice to have my old friend working again.
 
Thanks. Can you share pictures and specs of the McIntosh switch? Who is the OEM of the switch? The Fisher switch was made by Centralab. How well does the McIntosh switch track (channel balance)?
 
Sunrayjack;

If you have not tossed your old control, you might be able to cut the shaft with a hacksaw, similarly trim back the shaft of the new control enough and use a shaft collar with two set screws to extend the length of the control enough to have it fit correctly.

There are a number of sources for shaft collars including local hardware stores and on the internet. One company I have used frequently is McMaster-Carr on the internet.

Joe
 
Thanks. Can you share pictures and specs of the McIntosh switch? Who is the OEM of the switch? The Fisher switch was made by Centralab. How well does the McIntosh switch track (channel balance)?
I will see if I can find the info on the switch, if all else fails I will open it back up and see if there is a name on the switch.
I have a couple of Macintosh 1900's I will look in one and verify it is the same switch.
I was just happy to find a very good replacement.
 
Sunrayjack;

If you have not tossed your old control, you might be able to cut the shaft with a hacksaw, similarly trim back the shaft of the new control enough and use a shaft collar with two set screws to extend the length of the control enough to have it fit correctly.

There are a number of sources for shaft collars including local hardware stores and on the internet. One company I have used frequently is McMaster-Carr on the internet.

Joe
the shaft is less than a quarter of an inch shorter, I believe a collar would make it too long, but I will look into it.
Thanks for the tip.
 
I just went to eBay and did a search for a Mcintosh 1900 power switch to see if I could still pull up the info.
I guess he has more of them because there is another one on there for 159.00 and 15 shipping or best offer.
I am happy with mine, it seems to work perfectly.
 
Is this the switch on eBay you are referring to? The listing didn't include a brand name or datasheet specs. From the picture below, I can make out the manufacturer name of "CTS." Is this a new old stock switch made for McIntosh by CTS or is it still made today?

s-l1600-9.jpg

s-l1600-7.jpg

s-l1600-6.jpg
 
My concern would be the value of the potentiometer (volume control) sections. In the 500C, each volume control section is 500K, with a loudness tap at about 125K or so. The last tone control stage, balance control, and loudness components of the 500C are all designed to work with a volume control representing these values. I couldn't find a schematic for the Mac 1900, but note that it is a SS design in at least the audio circuits, which invariably use controls of much smaller resistance. I did find a schematic for the 1700 -- assuming it is the forerunner of the 1900 -- and note that the value of the volume control for the SS audio section of that unit is just 75K. If that is the value of the control being offered, while it will certainly "work" in controlling the volume of the 500C, it will also notably reduce the LF response and overall gain of the unit as well due to the additional load such a low value control will place on the circuits it operates with. It would be very helpful to know what the value of the Mac control is to make sure that besides the switch and the shaft, the volume control sections are also appropriate for your Fisher as well.

Dave
 
The value of the loudness tap is not labeled, and it usually isn't. However, the loudness tap is customarily placed at about 20-25% of the total pot value, or in this case, 160-200K. If this is in fact the value of the pot offered , then it should work fine in the 500C -- but it is very odd that a value this large is being specified in a SS unit........

Dave
 
The value of the loudness tap is not labeled, and it usually isn't. However, the loudness tap is customarily placed at about 20-25% of the total pot value, or in this case, 160-200K. If this is in fact the value of the pot offered , then it should work fine in the 500C -- but it is very odd that a value this large is being specified in a SS unit........

Dave

Are there any sonic / performance tradeoffs using a pot with a higher value that specified in the schematic (i.e. using 800K instead of 500K)?
 
I am not as savvy as you guys on the specs so I will just sit back and learn from what you find out about it.
I was just happy to find a decent switch to replace the original one and to get my 500 working again.
 
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