MR-80 Tuner, I found out why I got it so cheap

[Rickey_H]

Folks, I am the new proud owner of a McIntosh MR 80 Tuner that I scored on Ebay, The description indicated that three of the four touch keys were not working. I figured I could fix it and gave the seller a low ball offer which he (to my surprise) accepted. I received it last week and I have looked it over. It is beautiful! Not a scratch or blemish. I got to work studying the schematics. I noticed that this unit uses the same cap touch system that was used on many kitchen microwaves back in the 70's and 80's. It is an obsolete TI part called the TMS1976, Touch Controller. It is so obsolete, that I can't find a data sheet for it. I found a website that has a used solder pull part and they want $12 for it. However, the shipping was $45!!!!!!!!!! I said boo hiss on that. I can pull the MR 80 apart and try adjusting the sensitivity to see if this get the faulty 3 input switches to work, but this requires pulling the panel off which I have never done.
If this simple fix does not remedy this problem, I can build an emulator using a RP Pico and a level shifter mounted on a daughter board that pops onto the 18 pin DIP socket.
Is there anyone out here that has run into this issue before? If so, I would love to find out how you resolved it.

 

[eiraved]

That's beyond my capabilities. Let us know how it works out.

 

[damacman]

Many techs are no longer servicing these units for this very reason. Now, if you developed said emulator there would be a market for that. You won't get rich, but could help get a few MR80s back in service.

 

[clinic-audio]

no,no, don't worried all MR80 are like this and the problem is coming from the pad it self
The problem is the pad become non conductive with the time and replaciing it is the best way to cure the problem
I will try to post some picture to understand why later
I probably refix 20 or 25 MR80 since years

 

[chazix]

I'm just chiming in to reinforce what clinic-audio said.

As much fun as an emulator project might be, I think worrying about the Touch Controller is very, very likely to be a waste of time.

 

[clinic-audio]

Here are some pictures made many years ago to better understand the reason why

 

[Rickey_H]

Here are some pictures made many years ago to better understand the reason why

Thanks for the tech tip, I'll investigate that in detail. At this point I have not taken the front panel off the unit, but I have measured the capacitance of each of the buttons and they appear to be uniformed in value. As I mentioned, I have not attempted to adjust the sensitivity yet, but I am bracing myself for the worst case scenario.

 

[clinic-audio]

I don't think that you will get a worse case scenario
During these last years I never change any IC for any reason . I am pretty sure that you just need to clean "the preset pads"
If you need some TMS IC let me know
Just for your knowledge I work on MCINTOSH units over 45 years long

 

[Rickey_H]

I don't think that you will get a worse case scenario
During these last years I never change any IC for any reason . I am pretty sure that you just need to clean "the preset pads"
If you need some TMS IC let me know
Just for your knowledge I work on MCINTOSH units over 45 years long

Awesome! Thank you. Cleaning those pads should be the low lying fruit. BTW- Do I need to remove the front panel to clean them, or is the cleaning just topical?

 

[clinic-audio]

Do you need to remove the front panel to clean it ? Yes it is more easy for cheking every connection with every pad from presets .
And much more one the front panel is removed you can confim that the system works by touching every spring and you will see it is working !

 

[Rickey_H]

I finally got this tuner on my system and I cannot replicate the problem buttons, as mentioned from the seller. Regardless, I will remove the front panel and clean those buttons/pads to ensure no future surprises. Thanks clinic-audio for your expertise.

 

[62caddy]

Audio Classics no longer will work on MR80s. My Sony XDR-F1HD has replaced it some years ago which is light years better - just as Richard Moderaffi (original designer of the MR78) told me it would compared to the MR78 and by extension the MR80. Neither of which can receive HD FM so standard FM tuners are useless to me now.

 

[Rickey_H]

Audio Classics no longer will work on MR80s. My Sony XDR-F1HD has replaced it some years ago which is light years better - just as Richard Moderaffi (original designer of the MR78) told me it would compared to the MR78 and by extension the MR80. Neither of which can receive HD FM so standard FM tuners are useless to me now.

I was seriously looking into HD radio, but there are only a handful of Hi Fi HD radio tuners available and none made in USA that I know of. I really love the concept of HD Radio, but as with all terrestrial media, the market is shrinking. I have Sirrus/XM which offers commercial free content with comperable audio quality. As for that MR80 it is 45 years old and it has better sensitivity and S/N compared to my Onkyo AV reciever that I purchased in 2010. BTW- I was finally able to replicate the button problems and it appears to be something wrong withe control logic. Obviously a faulty cap or a $.25 CMOS chip. I'll keep you all apprised.

 

[62caddy]

I was seriously looking into HD radio, but there are only a handful of Hi Fi HD radio tuners available and none made in USA that I know of. I really love the concept of HD Radio, but as with all terrestrial media, the market is shrinking. I have Sirrus/XM which offers commercial free content with comperable audio quality. As for that MR80 it is 45 years old and it has better sensitivity and S/N compared to my Onkyo AV reciever that I purchased in 2010. BTW- I was finally able to replicate the button problems and it appears to be something wrong withe control logic. Obviously a faulty cap or a $.25 CMOS chip. I'll keep you all apprised.

I've heard of the limited availability of HD. The irony is that we have quite a few of them despite not being in a particularly dense market. In my case, HD enabled the reception of three classical stations alone which was a godsend in itself. As for standard FM reception, the Sony runs rings around any other FM tuner I've ever had and has the best FM sensitivity of any FM tuner ever made. S/N, background noise and FR is close to CD quality in HD as well. All in a $99.00 (original MSRP) BPC box 1.5x the size of a VHS tape. The outrage and controversy it has generated when compared to highly regarded classic FM tuners of the past, only goes to prove it. As Francis Urquart in House of Cards once said, "One doesn't foam at the mouth when dismissing the jobbing gardener."

 

[Rickey_H]

I've heard of the limited availability of HD. The irony is that we have quite a few of them despite not being in a particularly dense market. In my case, HD enabled the reception of three classical stations alone which was a godsend in itself. As for standard FM reception, the Sony runs rings around any other FM tuner I've ever had and has the best FM sensitivity of any FM tuner ever made. S/N, background noise and FR is close to CD quality in HD as well. All in a $99.00 (original MSRP) BPC box 1.5x the size of a VHS tape. The outrage and controversy it has generated when compared to highly regarded classic FM tuners of the past, only goes to prove it. As Francis Urquart in House of Cards once said, "One doesn't foam at the mouth when dismissing the jobbing gardener."

I'm finding more HD radios in cars now days, the home audio versions are becoming a rarity.