McIntosh 1900 Volume Control / On-Off Switch Replacement
- Thread starter bwv1
- Start date
Yet another 1900 with a horrible tracking volume control. Output on the right channel starts out fairly close to the left down low, but gets to around 50% off by 1/2 volume. Looks like I will be using just the amp section in this hooked to an outboard preamp until a suitable replacement control is available. 
Yet another 1900 with a horrible tracking volume control. Output on the right channel starts out fairly close to the left down low, but gets to around 50% off by 1/2 volume. Looks like I will be using just the amp section in this hooked to an outboard preamp until a suitable replacement control is available.
I wonder if it’s original or if it is one of the notoriously awful ones from that ebay seller. Have you had it opened to see if it looks replaced?
It's original, and by reading very common to have this issue over time. That seller has banned me from buying, and blocked me from messaging. I'd pay him a visit if I was to ever end up in his location.
Has anyone tried Mark Opat?
He’s got all kinds of old , vintage pots and switches. Worth a shot.
He’s got all kinds of old , vintage pots and switches. Worth a shot.
Old Radio Parts - Contact Me
oldradioparts.net
I thought I read where that was tried in this thread and not successful.
The seller hifistereo/hifistereorocks/captainfantastic is the seller that I meant, his quality and his “return policy” has been the subject of several threads here, sells pots that he claims work, ...
That is a tough position to be in, several ways to go with that pot but nobody has found a perfect replacement yet. McIntosh Parts and Audio Classics have both sold or rebuilt these, but even at their prices it has been reported that they don’t track perfectly.
Being that far off though, I was expecting you to tell me that the PO had replace it, likely with an ebay quality part from the above notorious seller.
That is a tough position to be in, several ways to go with that pot but nobody has found a perfect replacement yet. McIntosh Parts and Audio Classics have both sold or rebuilt these, but even at their prices it has been reported that they don’t track perfectly.
Being that far off though, I was expecting you to tell me that the PO had replace it, likely with an ebay quality part from the above notorious seller.
I'd settle for not perfect, but the nearly 50% difference at certain positions now is far from acceptable, it's real bad. But one thing is interesting, this old girls amp and preamp sections still perform extremely good when run on test equipment, both channels very equal having 100% original components. But once the signal comes out of the volume control, it's way off.
Well, I'm more interested in keeping things 100% like it should be, meaning functioning correctly as it should. If anything I will run a separate preamp and just use the amp section for now since it has main in / pre out jacks. If it didn't have the on / off switch included on the control, one could replace it with a high quality volume control separate of the on / off switch.
Yet another 1900 with a horrible tracking volume control. Output on the right channel starts out fairly close to the left down low, but gets to around 50% off by 1/2 volume. Looks like I will be using just the amp section in this hooked to an outboard preamp until a suitable replacement control is available.
The normal issue is caused by the need to rotate the volume control from the normal listening position to the off position and back every time the unit is powered on or off. After 40 years, this excessively wears the lower region (say from off up to the 10-o'clock position) of the control.
In your case, it sounds like it tracks correctly at low levels and gets way off when the control gets up around 12-o'clock. Am I reading that right? If so, this sounds like a replacement unit that was bad right out of the box.
perryinva
IS it vintage????
I asked the same in another thread. I ended up finding a matching NOS 500k pot/switch for a Fisher, (I had bought it many years ago, when this whole volume thing was very prominent, and then it got lost in 2 moves, only to resurface unexpectedly when looking for something else) but with the wrong shaft length. So I simply dismantled both, (its all about carefully bending tabs) and installed the NOS wipers and carbon track boards in to the existing original pot and then added 1% 300 & 320k resistors on the output (to match resistance near perfectly) and the results were great. In all the years of owning the 1900 (like 15), I’ve never used the volume full turn. Having 300k on the pot at full turn matched the original resistance at about 85% on the old pot, so I use a better section that tracks much better as well, and still do not get even close to full rotation in use. A minor side benefit is that I felt the Loudness switch was always too much bass when used, and this tamed it as well.
Ironically, the popping noise I mentioned 2 years ago was due to an error in the schematic on the preamp boards on one of the 100uF caps, where polarity is wrong on the picture of the PCB & I apparently missed that when I recapped everything and they had bulged & leaked. So
that was fixed and the hum appeared to be due to the plated shaft of the replacement pot, which tracked perfectly BTW.
Ironically, the popping noise I mentioned 2 years ago was due to an error in the schematic on the preamp boards on one of the 100uF caps, where polarity is wrong on the picture of the PCB & I apparently missed that when I recapped everything and they had bulged & leaked. So
that was fixed and the hum appeared to be due to the plated shaft of the replacement pot, which tracked perfectly BTW.
I see no reason why not if you’re turning it on with an external power strip or similar, just like leaving the switch on.
Just need to ground the shield to the chassis. They have it grounded to the pot itself.
Mcintosh N
Active Member
Anyone had good luck finding a replacement for the mac1900 volume pot?
I am desperately looking one too, called mcintosh and they are selling one for $120, but they said It doesn’t work well! Not sure why McIntosh are selling something that doesn’t work well!!
I am desperately looking one too, called mcintosh and they are selling one for $120, but they said It doesn’t work well! Not sure why McIntosh are selling something that doesn’t work well!!
Here’s a photo off the internet. 500k Balance pot is dual gang wired opposite one another. Lug 1 is the green wire from the audio in, Lug 2 is the 0.22 capacitor, Lug 3 is ground connected to three wires and bridged across to Lug 1 of the other gang. One of the three black wires is loose. Not sure where it goes. There is also a black wire sitting at the bottom of the chassis. It’s grounded wire. Don’t know where that goes. Do they go on each of Lug 3 on the volume pot?
800k log Volume pot also dual gang but wired the same on both gangs. Lug 1 connects to the other leg of the 0.22 capacitor. Lug 2 connects to the coaxial that takes the signal to pin 7 on each respective preamp board. Lug 3? I don’t know what to connect or how on Lug 3. Also the shielding on the coaxial does not seem to be connected to anything on either end.
