MR80 with problems...worth picking up?

I have line on a MR80 tuner that the owner says can manually tune but the scan and preset buttons don't function. Anyone have an idea what could be wrong? He's asking $250 for it...what do you think?
 
I have line on a MR80 tuner that the owner says can manually tune but the scan and preset buttons don't function. Anyone have an idea what could be wrong? He's asking $250 for it...what do you think?

Yes, these tuners can have all sorts of strange faults and behaviour.....

AK member clinic-audio is an expert on these and he has a fix for those preset problems, in fact I was going to contact him because I need to sort mine out, the presets on mine have gone a bit random on me lately...

But essentially, what a great tuner!! If you are brave, I am sure you could resolve all those problems with the help of the forum.....

250 bucks is a steal for a MR80, is it in nice cosmetic condition?
 
I replaced the front panel glass on an MR80 I bought a while back. Putting it all back together so that all 6 of the front panel touch switches worked took a few tries but I got them all working. It may be that you just need to carefully clean and position everything to make them all functional. Read the later posts in this thread for more on getting the touch switches working.

As kevzep says, the MR80 is a very nice tuner. It probably has more bells and whistles than it really needs but it sounds great. I'd say go for it!
 
Appreciate the thoughts and link! I now have an idea of what it will need. The guy says that it is in excellent cosmetic shape. If it is I will add it to the family. Thanks!
 
Appreciate the thoughts and link! I now have an idea of what it will need. The guy says that it is in excellent cosmetic shape. If it is I will add it to the family. Thanks!

Yeah, grab it, and then all the rest of the help you need is right here....

I will never sell my MR80, they are a great tuner......:thmbsp:
 
MR 80 is an excellent performer but as with all vintage tuners, chances are it'll need a going-over for optimum performance.

Good luck with it.
 
The guy sent some photos and it is in near mint condition, except for the cord that his dog chewed off! :thmbsp: PayPal'd him and will pick it up on Sunday.

Look forward to this project and thanks again to all for chiming in!
 
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The guys sent some photos and it is in near mint condition, except for the cord that his dog chewed off! :thmbsp: PayPal'd him and will pick it up on Sunday.

Look forward to this project and thanks again to all for chiming in!

Cool man!! Good to pick it up too, at least it will be safe in transit....:thmbsp:

Bad Dog! Do not chew the McIntosh!!
 
We sold over a dozen MR-80's as I remember. Mine was the first one. And over the years we saw most of them in the shop for touch button issues. I was very fortunate that my MR-80 worked over 25 years without issues. But finally the button issues caught up with me. As the gentleman at work who repaired the 80's we sold moved on in the 90's to another field of electronics and Audio Classics having a Mcintosh tuner designer on staff I returned mine to Ryan and they tackled the unit. It came back with some hick-ups and shipping issues so back it went. Ryan and the guys at Audio Classics handled everything perfectly and the tuner came back like new and has worked better than new for the last 3 1/2 years. Mine had some IC and small cap issues in addition to the buttons them selves. Plus the digital readout was funkie, .
 
I have line on a MR80 tuner that the owner says can manually tune but the scan and preset buttons don't function. Anyone have an idea what could be wrong? He's asking $250 for it...what do you think?

That's a very low price. It would be best if you could inspect the condition of the tuner in person, but that's not always possible these days. Physical condition is important. If it's good cosmetically... then any electronic issues can be resolved.

My MR80 tuner always had intermittent preset button issues. Some days they all worked, and other days you'd have to press ~5 times. Without being too presumptuous, the MR80 got really flaky a couple years ago. The display started to range erratically even though the station was tuned and stable. Figured I was looking at an expensive shop visit, but instead decided to tackle the problem.

These units need updating

Having a look inside, it was apparent the stock electrolytic caps in the power supply needed to be replaced, also the ROE non-polar caps. IMHO these tuners need to have the PS recapped for reliability.

Here's a look at the original boards. I think we're talkin' 30 years old.

PS_boards.jpg

MR80 power supply boards with original PS filter caps on bench.


Stock NP caps need to come out

Recapping the PS didn't solve the erratic display, but I don't regret doing that update at all. However, after replacing the ROE non-polar electrolytic (dark red in color, pointed out in image below) the display returned to normal. AFAIK the preset buttons aren't any better, but it's always been like that. :)

MR80_new_PS.jpg

PS boards reinstalled with new caps, and two other electrolytics pointed out. Replacing the Red 10uF NP cap fixed the problem. Notice board is double-sided.


Replacing the NP cap above solved the erratic behavior! CAUTION is advised on that PCB. It's double-sided and there are many hidden top-side traces, and yes I did yank the foil off underneath the NP cap.. it was totally hidden underneath!! So.. you must STUDY the board schematics and layout drawings carefully (or have experience) before digging in. There was talk of certain known ICs that were problematic, but I have no specifics to offers.


Maybe I'll get the MR80 reconnected and run it some... and report back on how it's working. :banana:


-Gregory
 
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Within a MR 80 cleanliness is godliness.......the boards must be completely free of any air and humidity borne contaminants.

Patrice, I believe, replaces the contact springs with gold plated springs to combat these contact button issues.

I finally managed to free up from a former employer a Soundtech ST1000, a secore tester, and the old shure cpek I used to set up turntables 36 years ago!
I see complete FM allihnments in my future again assuming i can get the ST1000 to perform correctly.

Good to see you back Gregory.
 
MR80 with problems

Hello !

Patrice, I believe, replaces the contact springs with gold plated springs to combat these contact button issues.

I do it to get improved performances when your finger touch a touch preset pad , 100% efficiency :thmbsp:
 
Picked up the unit today, here's a quick pictorial...

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The glass is perfect no bubbles or scratches.

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Just a couple of tiny hairline scratches on top. Notice the dog-chewed power cord.:naughty:

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Her behind is sexy as well!

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Clean as a whistle under the bottom panel. This one was definitely a non-smoker. :D

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She lives! Replaced the cord and it fired right up. :banana:
Pulls in stations well and sounds wonderful through my bench system MC2200 and Yamaha NS10s. The stereo bulb is out and the preset and scan buttons don't function, but I already knew that. I consider this a killer score...a clean, mean tuning machine at a great price!

None of the push buttons move, it's like they are pushed in all the way. Are they supposed to move in and out or are they more like a capacitance switch?

As the great Ren & Stimpy once so blissfully sang, "Happy Happy, Joy Joy!"

Thanks again to all everyone for the advice...I love my Mcs and this supportive community!!!
 

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None of the push buttons move, it's like they are pushed in all the way. Are they supposed to move in and out or are they more like a capacitance switch?

As the great Spongebob once so wisely said, "Happy Happy, Joy Joy!"
The buttons aren't push buttons, just touch based (I assume capacitance).

Happy happy, joy joy was first a Ren & Stimpy thing.

Looks like a great score, congrats!
 
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Removed the glass...

The "Lock" and "Stereo" bulbs are missing, so that's an easy fix.

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Preset 3 & 4 leds are always on. The front panel circuit board has some char marks from what appear to be a smoked and replaced R501 resistor. The etches look fine but something definitely smoked.

Will dig deeper tomorrow.

Thanks Max! You are correct it was Ren & Stimpy and I knew that...memory failed me in my exuberance!
 

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The MR-80 is a sleeper. I've owned the MR 77, the MR 78, and the MR 80. It is the best of the bunch, sound of the MR77 with the DX capability of the MR78.
 
That's the most inexpensive MR80 I have ever seen. Great score. Fantastic deal, and it looks better than I imagined.
 
MR80 Resurrection Update

The half-dead 80 has been fully revived and is now working great!

Here's the resuscitation rundown:

The automatic scanning, presets and digital display features of this tuner were very sophisticated for its time and took many boards and numerous ICs to provide this functionality. This proved to be a challenge in multiple ways because I had to go through the boolean logic and theory of operation to understand how the push button circuits controlled the tuner and indication leds. It also didn't help that there were MANY mistakes in the service manual and on the schematics that came with the tuner. Things like incorrect voltages, wrongly labeled push button inputs to ICs, incorrect connector numbering, wrong high/low logic states and so on made for much frustration and longer hours than necessary. Oh well...such is life right! :yes:

Pre-set buttons didn't respond and preset 3 & 4 LEDs.
These 2 problems were interrelated. IC 301 on board 8 is a NOR R-S latch that determines which preset button has been pressed and feeds this state to downstream circuits that select the preset station circuit and turn on the appropriate LED. The IC had a short on preset 4 causing the BCD Decoder (Board 6 - IC 503) to misinterpret the status of the pushbuttons, this meant none of the downstream preset functions would work.

FIX - Picked up a NOS MC14043B off eBay from a US surplus supplier. All preset circuits and LED indicators work. :D

Up and Down Scan push buttons and LEDs don't work
After repairing the preset problem the Up & Down scan function came partially back to life. But things weren't quite right as no matter which button I pushed it would always scan down and the Down LED stayed on all the time. When the UP button was held the UP led would flicker but the tuner would still scan down.

This turned out to be another shorted chip, IC601 which is used as a voltage comparator to determine when the tuning circuit reaches the top of the FM band. When in automatic scan mode the tuner reverses its scan direction when it reaches up or down limits. So when it hits the top it goes back down and vice versa. The short caused dependent circuits to interpret that the tuner was always at the top of the band.

FIX - Picked up a NOS LF-356 JFET op amp off eBay from a US surplus supplier. Replaced chip and adjusted Scan Up & Down limit pots. All scan functions and LEDs work. :D


Missing Stereo and Lock bulbs.
I was somewhat concerned that there might be problems with these circuits as someone had taken the time to cut the bulbs out but not replace them.

Fix - Replaced with JLK Components 7381 long life 50,000 hr bulbs from Mouser. This was a bit of a pain as it is next to impossible to remove the board. So I left it in place and used an iron on the back and solder sucker from the front to remove most of the solder and then used a sharp bamboo toothpick to enlarge the holes. New lamps work great, circuits function properly. :D

I cleaned the end of the problematic contact springs and back of the pushbuttons with Deoxit and adjusted the touch sensitivity (R509) pot. I found that the service manual sensitivity adjustment did not work and instead adjusted it empirically by turning it in small amounts until all of the buttons responded properly. The buttons now work perfectly on the first press. :banana:

My guess is that cleaning the contacts and adjusting the sensitivity using my method will solve the majority of intermittent button issues many have experienced.

All in all it was rewarding to bring this old girl back to life. For less than $10 in parts and a bunch of heartbeats I now have a beautiful, wonderful sounding, high performance McIntosh tuner! My rooftop Antennacraft 70 Fm Triple Driven-Directional Antenna will be here this week, but that's story for another time. ;)
 
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Great job! Rooftop antenna will definitely allow the tuner to perform its best.

The touch buttons were an elegant touch (I guess they figured the buyer deserved something special for $2,499 - in 1980(!) - they come with a major expense to reliability as it ages.

MR80 also tends to drift from the preset stations as it heats up as - I don't know whether that's related to touch function.

Other than that, it's an excellent performer.
 
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