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Need Help! With My MAC 1900 Receiver

E

epuja

New Member
Hi,

I am in process of changing my MAC 1900 volume control knob with the Canadian made replacement I ordered from McIntosh.

I need some help!

Looks like two of the "orange" capacitors broke while I was soldering the new volume control knob into place.

Could someone help me identify what type they are so I can buy replacements?

Here is the picture of what broke:

2516741406_7b40d9ccde.jpg


This is the piece that connects between the balance and volume control knobs.

Thanks a LOT!!! I am new to this so forgive the stupid question.

Best Regards
Shawn
 
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Those color codes on those film caps continue to baffle me. The usual value for a cap in that application is .22 but those stripes don't look like .22 to me. :scratch2:

Someone with a service manual will need to take a peek.

Murray
 
Ok, the sm says that C357/8 are .22µf, 250v. They run between the volume pot and the balance pot.

The original caps are Mylar so a quality polyester cap would be fine there. A 400v cap (which would work fine) might be better there as it would be a little bigger than a current production 250v cap.

If that orange is actually red, the top section would seem to be red, red, making 22. Anyway, the value of that cap in that spot isn't critical.

Murray
 
Skippy, You are awesome... Thanks so much!!!
I will try to go to Frys to get the Cap.

Is there a certain direction the capacitor needs to be installed, between the balance and volume control?

The color is definitely Orange, not red.

On a side note, is a PDF copy of the service manual available anywhere (whether free or for purchase) ?

Thanks again, these forums are great.
 
This style mylar cap sounds very good but is mechanically very weak, if you see one with a crack in the paint near one of the leads or any cracks in the body it needs to be replaced. I never have seen one that had colors that were easy to read and I'm not color blind.
 
LOL Thanks for the info Terry! If this procedure does not pan out I'll be sending it to you if you don't mind!!!
 
Terry/Murray-

Quick Question -- The very slight "crackling" sound in the volume control -- Is it possible it could be caused by the capacitor, and not the actual volume control knob?

As the aftermarket knob I received, is not an exact fit, in particular the positioning (the little notch doesn't seem to be aligned properly), so i'm wondering whether I should drill a notch to accommodate the notch in volume control..

Thanks, as always
 
Yeah, the crackling is more likely to be coming from the volume pot. Anyway, you've got the new one now so solder it in. Caig FaderLube in the balance pot while you have it apart.

Not sure what you mean about the knob but I would modify the knob and leave the pot shaft alone - you may want to put the correct knob on it someday.

Murray
 
Don't quite remember what knob you have but the original can be re clocked by pulling out the insert and rotating it to where you want it the push it back in, you may have to give it a drop of super glue to make sure it stays in place.
 
ok -- got the parts, installed/soldered everything into place.

Now, I'm getting lots of interference noises when I turn it on, like humming noise. Funny thing is, when I move my fingers around the volume control area, the humming increases and decreases. almost some sort of interference?

any ideas?

Thanks!
 
For the hum/noise did you remember to install the jumper between the bottom two tabs? This is the ground and both channels need to be connected.

The knob insert can be twisted while in the knob without removing the insert, needle nose pliers will work. The insert stays in place by friction. I've done this many times with no problems.

David
 
David -

Can u tell me which tabs and insert you are referring to?

Sorry, I think I know what you mean but not sure.

Thanks!
 
The two tabs closest to the chassis are the ground tabs. The center tabs have the coax soldered to them.

On the volume control knob I think you mean the indicator notch does not line up corectly with the front panel off position. If you turn the insert with needle nose pliers the slot on the knob will line after some tinkering. The ones I have changed did not line up correctly. Do you have the same problem?

David
 
yes -- you are correct about the volume knob.. There is a little tab inside the knob that can be turned to correct the alignment, with needle nose pliers..

I will check the ground tabs later today..
I am tempted to take a picture of what i did, just to ensure i didn't screw up anything!

Thanks again..
 
Update:

Thanks everyone for helping. I got the new volume control installed, and it ended up to be a very clean job..

Everything seems fine now, but a minor annoyance is that the new volume control while turning also give a slight 'scratchy' sound, but the sound quality seems to be much better... I tried spraying a bit of deoxit on it, helped a little.

THANKS!!!!
 
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