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  #11  
Old 07-22-2011, 01:33 PM
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Pete.......The copies of the MR78 service manual are not the cleanest. Here is the link to the early MR78 Service Manual. The copy of the underside photo is even worse that the late MR78 manual.

http://www.tubebooks.org/file_downlo...MR78_early.pdf
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STUDIO - McIntosh C1000C/P, MC2301 (2), MR88, Aurender N10, Esoteric K-01X, Shunyata Sigma spdif digital cable, Sonos Connect, PurePower 2000, Stillpoints, Furutech Flux 50, Michell Gyro SE, Michell HR Power Supply, SME 309, Ortofon Cadenza Black, Wireworld, Sonus faber Amati Anniversario
LIVING ROOM - McIntosh C2300, MC75 (2), MR85, Magnum Dynalab 205, Simaudio MOON Neo 260D-T, Schiit Audio Yggdrasil, Aurender N100H, Shunyata Sigma USB cable, Micro Seiki DD40, Ortofon Cadenza Blue, Nakamichi BX-300, Sony 60ES DAT, PS Audio P10, Furutech Flux 50, Sonos Connect, Stillpoints, Wireworld, Kimber, PMC EB1i, JL Audio f113
VINTAGE - McIntosh MA230, Tandberg 3011A tuner, Olive 04HD, Sony DTC-59ES DAT, McIntosh 4300V, JBL 4312A
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  #12  
Old 07-22-2011, 01:58 PM
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Dan....indeed, the service manual photos are not very good. But, I think we have Mike on the right track.

Mike...a simple test to make sure the secondary voltage is adequate (short of using a meter) is to simply touch a jumper wire across the correct resistor (prior to removing it and soldering in the jumper permanently) and see if the lower panel lamps don't brighten up sufficiently.


Pete
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No. 35


Main System: Harmon Kardon T60 TT/Ortofon 2M Black, McIntosh: MR78, MCD1000 Transport on Stillpoint ultra minis, MDA1000 D/A Converter on Stillpoint ultra minis, MS750 Music Server on Rollerblock Jr's, C40, MC501's (3), Soundcraftsmen: DC2215 Eq/AS1000 Real time analyzer, DBX 3BX II, Carver C9, Nakamichi Dragon, Crown SX724, Crown D-75A (as headphone amp), Sony XBR55X900E 4K TV, JBL L220A's, JBL B460, Sumo Delilah active crossover, WireWorld Silver Eclipse audio interconnects, WireWorld Starlight and Silver Starlight Coaxial Digital interconnects, Wireworld SuperNova 7 Toslink digital interconnect, WireWorld Aurora 7 and Silver Electra Power cords, Wireworld Silver Eclipse 8 speaker cables, Terk AF-1 Powered Antenna, PS Audio Direct Stream Power Plant 12, Oppo UDP-205 4K Blu-Ray Player, Bryson BUC-1 USB Converter, Wireworld Gold Starlight XLR Digital interconnect

Florida Room/Art Studio System: Pioneer PL-L1000 TT/Audio Technica ATS52W2, McIntosh: MR77, C32, MC2205; Crown Power Line Four, Wyred for Sound DAC-2 Digital to Analog converter, Soundcraftsmen AE2000 Eq, JBL 4313B's, JBL 2241-based Sub, JBL BX63A Active Crossover, Oppo BDP-105D Blu-Ray Player, Samsung 5500 Series 32" Smart TV, Terk AF-1 Powered Antenna

Master Bedroom System: McIntosh: MX120 Theater processor, MC206 6-channel amplifier; MR74 AM/FM Tuner, Oppo UDP-203 4K Blu-ray player, JVC HM-DH40000U D-Theater Digital VHS, Phase Technology PC80 Towers (now used as stands), (2) JBL 4401's, (1) JBL Studio 6IW speaker, (2) JBL Studio 6IC speakers, Sony XBR-49X900E UHD TV, Panamax 1000 Line Conditioner, (2) JL Audio E110 Subwoofers, Wireworld Solstice speaker cables, Wireworld Aurora Power cords, Wireworld Equinox and Solstice speaker cables and various other flavors of Wireworld and Audioquest cabling

Office System: Marantz 150 Tuner, Crown DL 2, Crown EQ 2, Crown SA 2, Crown D-75A (as headphone amp), McIntosh MCD7009 (as transport), DBX 3BX Series II, Oppo BDP-103 Blu-ray player, JBL 4401's, JL Audio E112 Subwoofer, Samsung 5500 series 32" Smart TV, Wire World Oasis audio interconnects, Wire World Solstice speaker cables, Wyred for Sound DAC-2 DSDse Digital to Analog converter, Wireworld Starlight Coaxial Digital Interconnect, Sennheiser HD800 Headphones, Sennheiser HDVA600 Headphone amp, Wireworld Silver Eclipse Balanced Interconnects, Wireworld Platinum Starlight USB Cable

High Resolution Source: HP Omen 17" Gaming Laptop
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  #13  
Old 07-22-2011, 05:44 PM
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Thanks Pete and Dan. I should have no trouble now finding the resistor and trying the lights with it jumpered. I did a lot of homebrew electronics stuff as a teen and feel pretty comfortable inside an electronic chassis and tracing circuits.
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  #14  
Old 07-22-2011, 07:35 PM
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Mike.......You have mine and Pete's interest up, so keep us posted. Maybe a photo or two. We are visual creatures.
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STUDIO - McIntosh C1000C/P, MC2301 (2), MR88, Aurender N10, Esoteric K-01X, Shunyata Sigma spdif digital cable, Sonos Connect, PurePower 2000, Stillpoints, Furutech Flux 50, Michell Gyro SE, Michell HR Power Supply, SME 309, Ortofon Cadenza Black, Wireworld, Sonus faber Amati Anniversario
LIVING ROOM - McIntosh C2300, MC75 (2), MR85, Magnum Dynalab 205, Simaudio MOON Neo 260D-T, Schiit Audio Yggdrasil, Aurender N100H, Shunyata Sigma USB cable, Micro Seiki DD40, Ortofon Cadenza Blue, Nakamichi BX-300, Sony 60ES DAT, PS Audio P10, Furutech Flux 50, Sonos Connect, Stillpoints, Wireworld, Kimber, PMC EB1i, JL Audio f113
VINTAGE - McIntosh MA230, Tandberg 3011A tuner, Olive 04HD, Sony DTC-59ES DAT, McIntosh 4300V, JBL 4312A
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  #15  
Old 07-22-2011, 09:12 PM
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Quote:
Originally Posted by jdandy View Post
Mike.......You have mine and Pete's interest up, so keep us posted. Maybe a photo or two. We are visual creatures.
Yes, that we are!

Pete
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No. 35


Main System: Harmon Kardon T60 TT/Ortofon 2M Black, McIntosh: MR78, MCD1000 Transport on Stillpoint ultra minis, MDA1000 D/A Converter on Stillpoint ultra minis, MS750 Music Server on Rollerblock Jr's, C40, MC501's (3), Soundcraftsmen: DC2215 Eq/AS1000 Real time analyzer, DBX 3BX II, Carver C9, Nakamichi Dragon, Crown SX724, Crown D-75A (as headphone amp), Sony XBR55X900E 4K TV, JBL L220A's, JBL B460, Sumo Delilah active crossover, WireWorld Silver Eclipse audio interconnects, WireWorld Starlight and Silver Starlight Coaxial Digital interconnects, Wireworld SuperNova 7 Toslink digital interconnect, WireWorld Aurora 7 and Silver Electra Power cords, Wireworld Silver Eclipse 8 speaker cables, Terk AF-1 Powered Antenna, PS Audio Direct Stream Power Plant 12, Oppo UDP-205 4K Blu-Ray Player, Bryson BUC-1 USB Converter, Wireworld Gold Starlight XLR Digital interconnect

Florida Room/Art Studio System: Pioneer PL-L1000 TT/Audio Technica ATS52W2, McIntosh: MR77, C32, MC2205; Crown Power Line Four, Wyred for Sound DAC-2 Digital to Analog converter, Soundcraftsmen AE2000 Eq, JBL 4313B's, JBL 2241-based Sub, JBL BX63A Active Crossover, Oppo BDP-105D Blu-Ray Player, Samsung 5500 Series 32" Smart TV, Terk AF-1 Powered Antenna

Master Bedroom System: McIntosh: MX120 Theater processor, MC206 6-channel amplifier; MR74 AM/FM Tuner, Oppo UDP-203 4K Blu-ray player, JVC HM-DH40000U D-Theater Digital VHS, Phase Technology PC80 Towers (now used as stands), (2) JBL 4401's, (1) JBL Studio 6IW speaker, (2) JBL Studio 6IC speakers, Sony XBR-49X900E UHD TV, Panamax 1000 Line Conditioner, (2) JL Audio E110 Subwoofers, Wireworld Solstice speaker cables, Wireworld Aurora Power cords, Wireworld Equinox and Solstice speaker cables and various other flavors of Wireworld and Audioquest cabling

Office System: Marantz 150 Tuner, Crown DL 2, Crown EQ 2, Crown SA 2, Crown D-75A (as headphone amp), McIntosh MCD7009 (as transport), DBX 3BX Series II, Oppo BDP-103 Blu-ray player, JBL 4401's, JL Audio E112 Subwoofer, Samsung 5500 series 32" Smart TV, Wire World Oasis audio interconnects, Wire World Solstice speaker cables, Wyred for Sound DAC-2 DSDse Digital to Analog converter, Wireworld Starlight Coaxial Digital Interconnect, Sennheiser HD800 Headphones, Sennheiser HDVA600 Headphone amp, Wireworld Silver Eclipse Balanced Interconnects, Wireworld Platinum Starlight USB Cable

High Resolution Source: HP Omen 17" Gaming Laptop
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  #16  
Old 07-23-2011, 11:13 AM
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Well, Pete's suggestion took care of most of the problem. There is a clear increase in intensity with R508 bypassed, but it looks like I will have to take off the front panel again to see why the light around the volume control is so dim.

Wish I knew why the resistor was there in the first place. My guess is just for longer bulb life, considering the math below.

I also attached a picture of the R508 location with the resistor still in place. It's the one with the green jumper on it.

The voltage drop across the resistor is 2.4 v, and the bulbs are getting 4.2v. Current through the resistor is 1.2 amps, assuming the resistor is really 2 ohms (I haven't cut the lead yet and measured it). So, each of the 5 bulbs is drawing about 240 mA at 4.2 volts. Each bulb must be about 17.5 ohms resistance. That would work out to about 3.5 ohms for the 5 bulbs in parallel, which would give a 4.2 volt drop at 1.2 amps. So, the math is consistent.

At 6.6 volts without the resistor in place the current draw will be 1.9 amps, or 380 mA per bulb, about 50% higher. Each bulb will dissipate about 2 watts at the higher voltage rather than 1 watt with the resistor in place. GE brand 1866 equivalents are rated 2 watts, so they should be okay and match what I am measuring. I saw another brand that had lower current draw of 250 mA at 6.3 volts, so they would put less additional load on the power supply than the ones I have now. Either way, I doubt the additional 700 mA load on the 6 v rail will be a problem, and Pete's experience bears that out.
Attached Images
File Type: jpg With resistor.jpg (58.1 KB, 29 views)
File Type: jpg Bypassed resistor.jpg (59.5 KB, 46 views)
File Type: jpg R508 location.jpg (92.5 KB, 30 views)
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  #17  
Old 07-23-2011, 11:19 AM
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Mike.......Thanks for the photos. Big difference, and nice improvement. It shouldn't take you long to figure out why there is still a light problem behind the volume display. Keep us posted.


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STUDIO - McIntosh C1000C/P, MC2301 (2), MR88, Aurender N10, Esoteric K-01X, Shunyata Sigma spdif digital cable, Sonos Connect, PurePower 2000, Stillpoints, Furutech Flux 50, Michell Gyro SE, Michell HR Power Supply, SME 309, Ortofon Cadenza Black, Wireworld, Sonus faber Amati Anniversario
LIVING ROOM - McIntosh C2300, MC75 (2), MR85, Magnum Dynalab 205, Simaudio MOON Neo 260D-T, Schiit Audio Yggdrasil, Aurender N100H, Shunyata Sigma USB cable, Micro Seiki DD40, Ortofon Cadenza Blue, Nakamichi BX-300, Sony 60ES DAT, PS Audio P10, Furutech Flux 50, Sonos Connect, Stillpoints, Wireworld, Kimber, PMC EB1i, JL Audio f113
VINTAGE - McIntosh MA230, Tandberg 3011A tuner, Olive 04HD, Sony DTC-59ES DAT, McIntosh 4300V, JBL 4312A

Last edited by jdandy; 07-23-2011 at 11:59 AM.
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  #18  
Old 07-23-2011, 11:44 AM
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Mike...glad to hear (and see) that the problem has, for the most part, been remedied. I was nearly certain that this was the problem. As to why the lamp behind the volume knob is still dim...it would be my guess, (and this is only just a guess) that this would be a physical, rather than electrical problem. Sometimes a less than ideal contact between the center electrode of the bulb and the contact point in the socket can be the cause. You could have an oxidized contact in the socket (try cleaning it). Or, try a different bulb. (tolerance variation in the electrode height?) Or, try lightly cleaning the center electrode of the bulb with a piece of fine sandpaper. Or, all of the above. In theory, if you try all that, you should not have a problem. If none of that works, you can try jumpering the connecting wire between the offending socket and the adjacent one. You should, as Dan said, be able to narrow this issue down fairly quickly. Good luck and keep us posted!


Pete
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No. 35


Main System: Harmon Kardon T60 TT/Ortofon 2M Black, McIntosh: MR78, MCD1000 Transport on Stillpoint ultra minis, MDA1000 D/A Converter on Stillpoint ultra minis, MS750 Music Server on Rollerblock Jr's, C40, MC501's (3), Soundcraftsmen: DC2215 Eq/AS1000 Real time analyzer, DBX 3BX II, Carver C9, Nakamichi Dragon, Crown SX724, Crown D-75A (as headphone amp), Sony XBR55X900E 4K TV, JBL L220A's, JBL B460, Sumo Delilah active crossover, WireWorld Silver Eclipse audio interconnects, WireWorld Starlight and Silver Starlight Coaxial Digital interconnects, Wireworld SuperNova 7 Toslink digital interconnect, WireWorld Aurora 7 and Silver Electra Power cords, Wireworld Silver Eclipse 8 speaker cables, Terk AF-1 Powered Antenna, PS Audio Direct Stream Power Plant 12, Oppo UDP-205 4K Blu-Ray Player, Bryson BUC-1 USB Converter, Wireworld Gold Starlight XLR Digital interconnect

Florida Room/Art Studio System: Pioneer PL-L1000 TT/Audio Technica ATS52W2, McIntosh: MR77, C32, MC2205; Crown Power Line Four, Wyred for Sound DAC-2 Digital to Analog converter, Soundcraftsmen AE2000 Eq, JBL 4313B's, JBL 2241-based Sub, JBL BX63A Active Crossover, Oppo BDP-105D Blu-Ray Player, Samsung 5500 Series 32" Smart TV, Terk AF-1 Powered Antenna

Master Bedroom System: McIntosh: MX120 Theater processor, MC206 6-channel amplifier; MR74 AM/FM Tuner, Oppo UDP-203 4K Blu-ray player, JVC HM-DH40000U D-Theater Digital VHS, Phase Technology PC80 Towers (now used as stands), (2) JBL 4401's, (1) JBL Studio 6IW speaker, (2) JBL Studio 6IC speakers, Sony XBR-49X900E UHD TV, Panamax 1000 Line Conditioner, (2) JL Audio E110 Subwoofers, Wireworld Solstice speaker cables, Wireworld Aurora Power cords, Wireworld Equinox and Solstice speaker cables and various other flavors of Wireworld and Audioquest cabling

Office System: Marantz 150 Tuner, Crown DL 2, Crown EQ 2, Crown SA 2, Crown D-75A (as headphone amp), McIntosh MCD7009 (as transport), DBX 3BX Series II, Oppo BDP-103 Blu-ray player, JBL 4401's, JL Audio E112 Subwoofer, Samsung 5500 series 32" Smart TV, Wire World Oasis audio interconnects, Wire World Solstice speaker cables, Wyred for Sound DAC-2 DSDse Digital to Analog converter, Wireworld Starlight Coaxial Digital Interconnect, Sennheiser HD800 Headphones, Sennheiser HDVA600 Headphone amp, Wireworld Silver Eclipse Balanced Interconnects, Wireworld Platinum Starlight USB Cable

High Resolution Source: HP Omen 17" Gaming Laptop
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  #19  
Old 08-04-2011, 05:15 PM
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Default Mystery solved

Well, son is married, visiting family have gone home and life is back to a semblance of normal, so I finally got back to this project. As it turns out, whoever worked on it before had the diffuser in backwards:

Backward diffuser.jpg

You can see it is flipped left to right, with the white mask for the markings around the volume control on the right in this picture, which is the left from the front (volume control is on the right on frontal view)

Here is the way the diffuser was oriented against the bulbs. The poorly drawn red circles show where bulbs and holes for the bulbs do not line up:

Diffuser as it was.jpg

And flipping the diffuser over makes the bulbs and holes line up:

Diffuser as it should be.jpg

I couldn't include the last pic in this post so will show the final result in the next. I see I still haven't got the hang of placing full size images in the text of a post.

Last edited by altbrewer; 08-04-2011 at 05:21 PM. Reason: Don't know my left from my right
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  #20  
Old 08-04-2011, 05:18 PM
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Default Mystery solved

And here is the faceplate installed with the diffuser in the correct orientation and the resistor bypassed. Much better.

Diffuser fixed and resistor bypassed.jpg

Turns out I couldn't upload the picture to the previous post because my Macintosh let me save the file without the .jpg at the end.

Anyhow, thanks for your help, Pete and Dan.

Last edited by altbrewer; 08-04-2011 at 05:19 PM. Reason: Title post
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