MAC 1900 Issues

Hello Mcintosh fans, I have a quick question about my 1900.
I recently had this unit serviced and the tech came across an issue that he wasn't able to correct - the RF transformer in the MPX section has gone bad. Obviously, this doesn't greatly impact the performance of the tuner per se but I'd like to be able to restore it fully.
Does anyone know of a suitable replacement, or of a place to find a replacement?

Also, the volume pot has gone bad on this unit, which I understand is common. There is a rush of sound as I turn the knob off. Can I attach a capacitor to this? Is there any way to modify the switch to keep this from happening?

I am no rush, this unit is a cosmetic disaster and I plan to slowly bring her back to glory over time.

newguytom said:

Hello Mcintosh fans, I have a quick question about my 1900.
I recently had this unit serviced and the tech came across an issue that he wasn't able to correct - the RF transformer in the MPX section has gone bad. Obviously, this doesn't greatly impact the performance of the tuner per se but I'd like to be able to restore it fully.
Does anyone know of a suitable replacement, or of a place to find a replacement?

Also, the volume pot has gone bad on this unit, which I understand is common. There is a rush of sound as I turn the knob off. Can I attach a capacitor to this? Is there any way to modify the switch to keep this from happening?

I am no rush, this unit is a cosmetic disaster and I plan to slowly bring her back to glory over time.

Click to expand...

The reason the volume pots go bad is that the on/off switch is on the volume pot so that every time you turn the unit on or off, you rotate the volume pot causing it to wear out - especially those counterclockwise portions of the rotation near the off position. Last I looked into it, no suitable replacements are available.

So, I use two work-arounds. I use a cheap power strip and use the switch on that to turn the unit on and off and so the only time I have to touch the volume control is when I change the volume. This will substantially reduce continued wear on the pot. I do this for all my older Mc stuff.

Also, when the unit was in to Terry DeWick, I asked him to reduce the gain of the unit. By doing this, you have to rotate the pot further clockwise to get the volume you want so that now most of the use of the pot is in the more-clockwise-rotated portions that aren't as worn and I get less scratchiness when adjusting the volume.

Regarding your MPX transformer, I assume you mean the tuner works but not in stereo, correct?

I don't know about a replacement but will be watching to see if you get an answer on that. I would like to know also if there are more none-replaceable parts besides the volume pot.

Thanks,

newguytom said:

Hello Mcintosh fans, I have a quick question about my 1900.
I recently had this unit serviced and the tech came across an issue that he wasn't able to correct - the RF transformer in the MPX section has gone bad. Obviously, this doesn't greatly impact the performance of the tuner per se but I'd like to be able to restore it fully.
Does anyone know of a suitable replacement, or of a place to find a replacement?

Also, the volume pot has gone bad on this unit, which I understand is common. There is a rush of sound as I turn the knob off. Can I attach a capacitor to this? Is there any way to modify the switch to keep this from happening?

I am no rush, this unit is a cosmetic disaster and I plan to slowly bring her back to glory over time.

Click to expand...

You have two choices and possible third. First choice, contact Ryan at Audio Classics. They cleaned/restored my MA5100 and they are highly recommended by other AKers. Second choice, contact Terry DeWick. The last time I checked his website, there is an 18 week waiting period. If you can do the work, you could contact AC or Tom Manley for the part. Either way, all is not lost and you'll have it up and running in no time.

Good luck!

TSmith8605 said:

The reason the volume pots go bad is that the on/off switch is on the volume pot so that every time you turn the unit on or off, you rotate the volume pot causing it to wear out - especially those counterclockwise portions of the rotation near the off position. Last I looked into it, no suitable replacements are available.

Regarding your MPX transformer, I assume you mean the tuner works but not in stereo, correct?

I don't know about a replacement but will be watching to see if you get an answer on that. I would like to know also if there are more none-replaceable parts besides the volume pot.

Thanks,

Click to expand...

Other than the power/ volume, and the unit works great. It's not a candidate for parting out fortunately. Cosmetics aren't great, but that is fine by me!
The tuner is indeed functional, just not in stereo.

I'll have to employ your power strip idea, until I can manage a suitable long term solution.

newguytom said:

Other than the power/ volume, and the unit works great. It's not a candidate for parting out fortunately. Cosmetics aren't great, but that is fine by me!
The tuner is indeed functional, just not in stereo.

I'll have to employ your power strip idea, until I can manage a suitable long term solution.

Click to expand...

Im fortunate in the sense that this unit doesn't need a complete overhaul, just some minor tweaking. Cosmetics are far from minty but I am fine with the way that it sounds.

Any untouched 1900 is at least 15 years past it's recap date.....

Mac parts offers a volume control, it needs to be tweaked for each unit as it replaces 3 part numbers....shaft needed to be shortened on the last 1900 I did. I believe resistance also needed to be added....

The wrong cleaning solutions destoys volume controls......the solvents eat away the glue that holds the carbon to the pheloic....not uncommon to take one apart and you will find major chunks missing.

c_dk said:

Any untouched 1900 is at least 15 years past it's recap date.....

Mac parts offers a volume control, it needs to be tweaked for each unit as it replaces 3 part numbers....shaft needed to be shortened on the last 1900 I did. I believe resistance also needed to be added....

The wrong cleaning solutions destoys volume controls......the solvents eat away the glue that holds the carbon to the pheloic....not uncommon to take one apart and you will find major chunks missing.

Click to expand...

Thankfully, it's just back from a service that included a recap. The tech also replaced some transistors that were flaky. The only two things that he was unable to correct are the power / volume pot issue and the FM stereo issue

There is no speaker relay......a swooshing sound as the main filter caps discharge at turn off has been common since they were new. Are you saying there is no swooshing sound if you pull the plug with the volume at say 10:00?

c_dk said:

There is no speaker relay......a swooshing sound as the main filter caps discharge at turn off has been common since they were new. Are you saying there is no swooshing sound if you pull the plug with the volume at say 10:00?

Click to expand...

I haven't tried pulling the plug, this happens only when I turn the power knob off thus far. I'll see what happens when I pull the plug, but I'm fairly certain that the issue is in the pot.