Hi Maddi, It's been way too long since I've been able to watch one of your videos on receiver maintenance. Thanks for posting this. I saved this video for future reference because I know the day is going to come when this video will prove to be very handy. Regards, Tom
Hi from Argentina again! mate, accordion and vintage electronics maintenance, you certainly are a 1 in a million girl! we here only have mate in winter because we use hot water (hot but not boiling, around 50 or 60 celsius); when u have cold mate (for summer) that's called Tereré and is mostly a Paraguayan beverage (although in northern Argentina is common too); loved the final arrangement of amp+MDs in formation! Big hug!
One thing to watch with bias current is that it will change as the heatsink warms up. It's usually a good idea to adjust to the required voltage, wait 10 minutes or so, and then readjust. Also now you have your 'scope, it's worth feeding some sine waves in and checking for distortion!
@@MsMadLemon Yes, I get "lazy" sometimes to use the oscilloscope, but it is a good idea. When the amplifier has been in my possession for a while and is visually ok and well maintained with no burn marks on the PCB, I usually put on a good headphone and nothing playing at highest volume to hear if there is any "popcorn" noise or 50/60 Hz humming, etc. But after I recap my amps, I do inject the common harmonics one by one: 31.25 Hz, 62.5, 125, 250, 500, 1k, 2k, 4k, 8k, 16kHz on an 8 Ohm (50W) dummy load per channel connected to an oscilloscope just for peace of mind. The service manual usually suggests to test 1kHz only, whatever one decides to do. BTW, some JVC amps (like Class A) suggest to wait only 5 mins to calibrate the bias. Some JVC's w/ the STK Darlington Pack suggest only 2-3 mins wait! That's pretty much what I do. The Marantz tech folks seemed to be more rigid, that's good.
@@kylesmithiii6150 , injecting a clean 400 Hertz tone and rotating the pots and switches will tell you , or Maddy here, if the cleaning solution and technique did its job well or not. Dirty, oxidized pots, or oxidized relay contacts, will make a telltale "scritch scritch" static noise, or cause channel dropouts, or sometimes buzz and whine almost like a mosquito. Easy to see the noise spikes and distortion on an oscilloscope as well.
@@goodun6081 Thanks, it is good to know. BTW, I almost never clean relays (such as those speaker protection relays that can have only a few mOhms of resistance). I prefer to replace them even if I have to do an overlay PCB with pins for the new relay that has different pins. Those relays cost usually less than USD 10 and a new relay will like last for decades.
@@kylesmithiii6150 , I work for a stereo repair shop and we clean and reinstall output relays all the time. Polish them with a pencil eraser shaped to a chisel-lije tip, degrease them, and they should be good for about 10 years. (Do NOT put any kind of residue-leaving switch & control cleaner or so-called contact preservative on them). Often the existing relays in the 30-year old piece of equipment are better quality than what you might replace it with. We have probably a hundred different types of relays on hand, but unless they're visibly pitted or arced, perhaps from high DC offset or a blown up amplifier, we rarely need to replace them. By the way, many of the modern sealed relays end up being intermittent or noisy when installed if they have been sitting around for a few years, which means we have to cut them open and clean them anyway!
NIce, great video ; i just can't believe Marantz notched the heat sink so bad and so off center,just because of that switch control...that was an afterthought,maybe? Also,never saw an amp repair person with red finger nails , looks nice among there.
Thanks! Looking into this amp, I did wonder if some things weren't entirely planned.. Even one of the power transistors underneath is off the PCB and instead screwed onto the heatsink independently, with wires connecting it to the PCB. I did find that odd. And about the red finger nails, there's always a first :o)
Oh, and for DC offset, it's good practice to short out the input to ground before measuring, otherwise various circuit tolerances can give you strange results.
I have this PM 350 which is heating a lot even with zero input. I will watch this video carefully to understand whether there something I can do to avoid burning ;)
next time when you shift or adj idle current , connect speakers on amplifier output-without any input-no signals , then trim and check your sleeping idle current , it s ok 10-15mV
At 5:20, I strongly recommend that you *not* simply spray Deoxit or any other electronic cleaner into any kind of slide fader. This tends to wash away the silicone grease which lubricates the tracks, and the pot will be sticky and never feels quite the same afterwards; it might also be more likely afterwards to fail at some point in the future (the plastics in some pots and faders can react with certain cleaners, or the new cleaner sometimes reacts with the old or original lubricants in the pot, sometimes causing the control to freeze up ). Caig Labs, majer of Deoxit, does make a Fader Lube that they market specifically for slide type faders, but that doesn't work all that well either in my experience, and again, just spraying it into the pot is not a good idea. Anyway, I strongly suggest that you use a small syringe or pipette to put just a couple small drops of cleaner on the actual carbon tracks of the pot, reaching into it from the front (sit the unit on its back panel if you can, so that the fader tracks are facing straight up). That spurt of cleaner from the spray can was probably ten times as much cleaner as you need to use, and that stuff's expensive. Many or most rotary volume controls and tone controls can survive that much cleaner being put inside of them, but slide faders are a special case, and you should always proceed with Extreme Caution, because if you damage them or seize them up, exact replacements are almost certainly not going to be available, and you might have to unsolder the control from the board and take it apart and try to repair it. I have done this from time to time, and trust me when I tell you that it is not fun! Anyway, you should spray some of the Deoxit or other cleaner into a small container and suck it up with a syringe or pipette which will allow you to apply it sparingly to the controls; in fact, you would be better off to clean all switches, controls and potentiometers that way in the future, with a very minimal amount of cleaner, skillfully applied exactly where you want it.! (A small drop or two of pure alcohol directly on the carbon tracks might work as well or better than any electronic cleaner, but again you have to be extremely careful where you apply it and how much you use, as you don't want to flush away lubricant from the tracks, you only want to degrease and de-sludge the connection between the wiper(s) and the track(s). Note that there is actually a metal wiper to metal track connection, as well as the expected metal wiper to carbon track connection).
Check out MsMadLemon's other videos. there's one dedicated completely on how to prepare Yerba Mate, and also one on other blends of tea. i should also get my yerba back out again. i got the straw bombila, but still need to get a decent callabas or something like that to experience the complete sensation. i tried it in a normal cup but that did not work out really good.
I think, sometimes I don‘t have enough respect for the mains voltage :-) I am working with open devices so often. I don‘t touch, but sometimes I just forget the risk. In 24 years of being a hardware developer, I just once burned a little hole into my skin with a backlight inverter of a display. Once, a sales guy came to my lab and put his hand into a computer and got zapped. I still have to laugh, when I think of his face :-)
*Important!* Use a non-metallic, non-conductive screwdriver for your bias adjustments! The best ones are made of ceramic, but plastic tip screwdrivers will work. They have to be kind of wide/thick to fit the slot in that style of trim pot snugly. I also strongly suggest that you build a current-limiter device, an incandescent light bulb *in series* with the input power to the amplifier, that will absorb excess current in case the bias trim pot is intermittent ( a not uncommon occurrence with those flat phenolic wafer trimmers), or breaks as you turn it, or you short something out inside the amp. Look on RUclips for details of how to build a series current limiter. You have easily got the skills oh, it's not difficult at all, and it can make all the difference as to whether or not you let the smoke out of those semiconductor devices, and once you let the magic smoke out, there's no way to put that genie back in the bottle! PS, most well designed amplifiers will have the bias transistor, or some kind of bias-feedback transistor or diode, mounted on or at least pushed up against the heatsink with a dab of silicone heatsink grease so that the device will sense the heat on the heatsinks from the output devices and adjust the bias a little bit accordingly in order to prevent thermal runaway. Sometimes those transistors aren't pushed snugly up against the heat sink, and if they aren't, then you should push them as snuggly or tightly against it as possible, perhaps manipulating the leads or Heating and then resoldering in order to shift it against the heat sink. You could secure it with the dab of Super Glue if you like and then put a dab of silicone grease on the device. This will keep the bias more stable. By the way, sometimes those bias trim pots need to be exercised back and forth a few dozen times with the unit turned off, and maybe with a tiny dab, repeat tiny dab of contact cleaner. You should measure the resistance of the pot in circuit beforehand so that after mechanically exercising it you can set it back to the same resistance it was set to previously, to prevent blowing up the amplifier when you turn it on again. I still strongly suggest that you use a current limiter in line with the power cord of the amplifier for doing this kind of adjustment.
Good points. BTW, she used the current-limiter device, an incandescent light bulb in series, in her AKAI reel-to-reel restoration a long time ago. IMHO, she did enough of a great job in this small amplifier. I have seen some really complex vintage Sansui Au-X1 and Marantz 2500 restoration videos for instance, which I am incapable to dare to do, that have like 170 VDC rail to rail and 100 W per channel, with complicate tuner stages tuning that require special & expensive lab equipment. Those are really the ones that require more meticulous attention to detail in my opinion.
Non metallic screwdrivers arent that much of a big deal over here, especially if they have plastic handles, its more of an issue when you're dealing with radio. Even still there is no electrical contact between myself and the pot. Thanks for the tips but I had already checked the transistor prior they already have silicon heat sink compound on, I dont wanna take too many unnecessary steps with regarding this, I think the result in the end is a working amp which is well serviced and fixed.
@@MsMadLemon , use of a non-metallic screwdriver for adjusting bias isn't to prevent you from getting shocked, it's to prevent blowing up the amplifier because you slipped with the screwdriver a little bit. I myself have let the smoke out of more than a few transistors in my day, it's not something I care to repeat. I use the current limiter, make my meter-probe connections with the unit turned off, and use a non-conductive screwdriver, always. Glad to see you're using the hook-on type probes, I think the brand name is "EZ-Hook" here in the States. I use them all the time, they work way better than standard "alligator" clips ( AKA crocodile clips to some )......
@@goodun6081 I know it's not to prevent me getting shocked.... I do know about electronics and i'm very careful in my work. You are starting to sound insulting now.
@@kylesmithiii6150 , my boss is a ham radio operator, like most hams he has forgotten more about how radio tuners work than I will ever know. He does the tuner tweaking when I'm finished repairing and refurbishing any vintage receivers. We do a lot of repairs on old Sansui, Pioneer, Marantz, Kenwood, thank you, and so forth. Some of those units have fabulous tuners when they are properly adjusted. I just worked on a Kenwood KR 9600, big heavy receiver with handles, quite the Beast! Nice sounding, very well built, and it has an excellent tuner. Most units we see of that vintage have had multiple klutzy hands and wannabe technicians inside of them, but this one was almost factory stock. Still, in order to make it reliable for the long term we recapped the output amplifier boards and replaced the differential input transistors, which were the old type with beveled edges and badly oxidized leads.
That is how i found your channel years ago with the restoration of the Marantz. Good video (s).
Thank you. Nice to see you are still here!
Hi Maddi,
It's been way too long since I've been able to watch one of your videos on receiver maintenance. Thanks for posting this. I saved this video for future reference because I know the day is going to come when this video will prove to be very handy.
Regards, Tom
Hi from Argentina again! mate, accordion and vintage electronics maintenance, you certainly are a 1 in a million girl! we here only have mate in winter because we use hot water (hot but not boiling, around 50 or 60 celsius); when u have cold mate (for summer) that's called Tereré and is mostly a Paraguayan beverage (although in northern Argentina is common too); loved the final arrangement of amp+MDs in formation! Big hug!
The first amp I ever bought with my own money! Subscribed!!!! :-D
One thing to watch with bias current is that it will change as the heatsink warms up. It's usually a good idea to adjust to the required voltage, wait 10 minutes or so, and then readjust.
Also now you have your 'scope, it's worth feeding some sine waves in and checking for distortion!
I did that in the video lol ;o))
I adjusted it and said i'll leave it for half an hour, but it was actually 45 minutes lol
Good call on the scope yes!
@@MsMadLemon Yes, I get "lazy" sometimes to use the oscilloscope, but it is a good idea. When the amplifier has been in my possession for a while and is visually ok and well maintained with no burn marks on the PCB, I usually put on a good headphone and nothing playing at highest volume to hear if there is any "popcorn" noise or 50/60 Hz humming, etc. But after I recap my amps, I do inject the common harmonics one by one: 31.25 Hz, 62.5, 125, 250, 500, 1k, 2k, 4k, 8k, 16kHz on an 8 Ohm (50W) dummy load per channel connected to an oscilloscope just for peace of mind. The service manual usually suggests to test 1kHz only, whatever one decides to do. BTW, some JVC amps (like Class A) suggest to wait only 5 mins to calibrate the bias. Some JVC's w/ the STK Darlington Pack suggest only 2-3 mins wait! That's pretty much what I do. The Marantz tech folks seemed to be more rigid, that's good.
@@kylesmithiii6150 , injecting a clean 400 Hertz tone and rotating the pots and switches will tell you , or Maddy here, if the cleaning solution and technique did its job well or not. Dirty, oxidized pots, or oxidized relay contacts, will make a telltale "scritch scritch" static noise, or cause channel dropouts, or sometimes buzz and whine almost like a mosquito. Easy to see the noise spikes and distortion on an oscilloscope as well.
@@goodun6081 Thanks, it is good to know. BTW, I almost never clean relays (such as those speaker protection relays that can have only a few mOhms of resistance). I prefer to replace them even if I have to do an overlay PCB with pins for the new relay that has different pins. Those relays cost usually less than USD 10 and a new relay will like last for decades.
@@kylesmithiii6150 , I work for a stereo repair shop and we clean and reinstall output relays all the time. Polish them with a pencil eraser shaped to a chisel-lije tip, degrease them, and they should be good for about 10 years. (Do NOT put any kind of residue-leaving switch & control cleaner or so-called contact preservative on them). Often the existing relays in the 30-year old piece of equipment are better quality than what you might replace it with. We have probably a hundred different types of relays on hand, but unless they're visibly pitted or arced, perhaps from high DC offset or a blown up amplifier, we rarely need to replace them. By the way, many of the modern sealed relays end up being intermittent or noisy when installed if they have been sitting around for a few years, which means we have to cut them open and clean them anyway!
Awesome =D Nice amp! LOL @ battery delivery!
Cool amplifier! Simple and effective. I like the VU meters also.
NIce, great video ; i just can't believe Marantz notched the heat sink so bad and so off center,just because of that switch control...that was an afterthought,maybe?
Also,never saw an amp repair person with red finger nails , looks nice among there.
Thanks! Looking into this amp, I did wonder if some things weren't entirely planned.. Even one of the power transistors underneath is off the PCB and instead screwed onto the heatsink independently, with wires connecting it to the PCB. I did find that odd.
And about the red finger nails, there's always a first :o)
Oh, and for DC offset, it's good practice to short out the input to ground before measuring, otherwise various circuit tolerances can give you strange results.
It is recommended to ground the signal input before performing the off set adjustment, this prevents noise from interfering with the adjustment
Maddi excellent work wishing you the very best
I have this PM 350 which is heating a lot even with zero input. I will watch this video carefully to understand whether there something I can do to avoid burning ;)
Marantz, good German Tec. Company!
Good for you that are drinking Yerba mate!! Regards from Argentina, the land of mate!
Please, could you post its schematics? I believe I borrowed its pre-section back in the days, and would love to see it again! thanks
next time when you shift or adj idle current , connect speakers on amplifier output-without any input-no signals , then trim and check your sleeping idle current , it s ok 10-15mV
my pm350 when I turn it on overheats the R809 resistor can you tell me if it's normal or what I should check thanks 1000 a greeting
i had one of those amps- and the mniidisc aswell
New video ! Yes
At 5:20, I strongly recommend that you *not* simply spray Deoxit or any other electronic cleaner into any kind of slide fader. This tends to wash away the silicone grease which lubricates the tracks, and the pot will be sticky and never feels quite the same afterwards; it might also be more likely afterwards to fail at some point in the future (the plastics in some pots and faders can react with certain cleaners, or the new cleaner sometimes reacts with the old or original lubricants in the pot, sometimes causing the control to freeze up ). Caig Labs, majer of Deoxit, does make a Fader Lube that they market specifically for slide type faders, but that doesn't work all that well either in my experience, and again, just spraying it into the pot is not a good idea.
Anyway, I strongly suggest that you use a small syringe or pipette to put just a couple small drops of cleaner on the actual carbon tracks of the pot, reaching into it from the front (sit the unit on its back panel if you can, so that the fader tracks are facing straight up). That spurt of cleaner from the spray can was probably ten times as much cleaner as you need to use, and that stuff's expensive. Many or most rotary volume controls and tone controls can survive that much cleaner being put inside of them, but slide faders are a special case, and you should always proceed with Extreme Caution, because if you damage them or seize them up, exact replacements are almost certainly not going to be available, and you might have to unsolder the control from the board and take it apart and try to repair it. I have done this from time to time, and trust me when I tell you that it is not fun! Anyway, you should spray some of the Deoxit or other cleaner into a small container and suck it up with a syringe or pipette which will allow you to apply it sparingly to the controls; in fact, you would be better off to clean all switches, controls and potentiometers that way in the future, with a very minimal amount of cleaner, skillfully applied exactly where you want it.! (A small drop or two of pure alcohol directly on the carbon tracks might work as well or better than any electronic cleaner, but again you have to be extremely careful where you apply it and how much you use, as you don't want to flush away lubricant from the tracks, you only want to degrease and de-sludge the connection between the wiper(s) and the track(s). Note that there is actually a metal wiper to metal track connection, as well as the expected metal wiper to carbon track connection).
Innit
@@electronscape , huh? What is the meaning of "Innit"?!", AKA "isnt it? ", in this particular context?
Un saludo colegas de chile me encanta sus video 🥰
Great vid, as usual. 👍☕
Hi, there! Do you have any tips to clean the body amp?
Yerba mate? :D the people of Argentina, Uruguay, etc drink liters of mate every day!
Check out MsMadLemon's other videos. there's one dedicated completely on how to prepare Yerba Mate, and also one on other blends of tea.
i should also get my yerba back out again. i got the straw bombila, but still need to get a decent callabas or something like that to experience the complete sensation. i tried it in a normal cup but that did not work out really good.
I think, sometimes I don‘t have enough respect for the mains voltage :-) I am working with open devices so often. I don‘t touch, but sometimes I just forget the risk. In 24 years of being a hardware developer, I just once burned a little hole into my skin with a backlight inverter of a display. Once, a sales guy came to my lab and put his hand into a computer and got zapped. I still have to laugh, when I think of his face :-)
Not many people using MD any more!
4 years all ready 😳 try checking the stk chips 🙂
Marantz good amplifier, good vidieo👍💕💕💕
Where u from lemon?
I always felt different when a girl loves electronics
Subscribing for the background music
I like the delivery truck :-D Do you pay the driver in tea?
hahah indeed :o))
Vraiment très très belle 🌹
Very clean..
*Important!* Use a non-metallic, non-conductive screwdriver for your bias adjustments! The best ones are made of ceramic, but plastic tip screwdrivers will work. They have to be kind of wide/thick to fit the slot in that style of trim pot snugly. I also strongly suggest that you build a current-limiter device, an incandescent light bulb *in series* with the input power to the amplifier, that will absorb excess current in case the bias trim pot is intermittent ( a not uncommon occurrence with those flat phenolic wafer trimmers), or breaks as you turn it, or you short something out inside the amp. Look on RUclips for details of how to build a series current limiter. You have easily got the skills oh, it's not difficult at all, and it can make all the difference as to whether or not you let the smoke out of those semiconductor devices, and once you let the magic smoke out, there's no way to put that genie back in the bottle!
PS, most well designed amplifiers will have the bias transistor, or some kind of bias-feedback transistor or diode, mounted on or at least pushed up against the heatsink with a dab of silicone heatsink grease so that the device will sense the heat on the heatsinks from the output devices and adjust the bias a little bit accordingly in order to prevent thermal runaway. Sometimes those transistors aren't pushed snugly up against the heat sink, and if they aren't, then you should push them as snuggly or tightly against it as possible, perhaps manipulating the leads or Heating and then resoldering in order to shift it against the heat sink. You could secure it with the dab of Super Glue if you like and then put a dab of silicone grease on the device. This will keep the bias more stable. By the way, sometimes those bias trim pots need to be exercised back and forth a few dozen times with the unit turned off, and maybe with a tiny dab, repeat tiny dab of contact cleaner. You should measure the resistance of the pot in circuit beforehand so that after mechanically exercising it you can set it back to the same resistance it was set to previously, to prevent blowing up the amplifier when you turn it on again. I still strongly suggest that you use a current limiter in line with the power cord of the amplifier for doing this kind of adjustment.
Good points. BTW, she used the current-limiter device, an incandescent light bulb in series, in her AKAI reel-to-reel restoration a long time ago. IMHO, she did enough of a great job in this small amplifier. I have seen some really complex vintage Sansui Au-X1 and Marantz 2500 restoration videos for instance, which I am incapable to dare to do, that have like 170 VDC rail to rail and 100 W per channel, with complicate tuner stages tuning that require special & expensive lab equipment. Those are really the ones that require more meticulous attention to detail in my opinion.
Non metallic screwdrivers arent that much of a big deal over here, especially if they have plastic handles, its more of an issue when you're dealing with radio. Even still there is no electrical contact between myself and the pot.
Thanks for the tips but I had already checked the transistor prior they already have silicon heat sink compound on, I dont wanna take too many unnecessary steps with regarding this, I think the result in the end is a working amp which is well serviced and fixed.
@@MsMadLemon , use of a non-metallic screwdriver for adjusting bias isn't to prevent you from getting shocked, it's to prevent blowing up the amplifier because you slipped with the screwdriver a little bit. I myself have let the smoke out of more than a few transistors in my day, it's not something I care to repeat. I use the current limiter, make my meter-probe connections with the unit turned off, and use a non-conductive screwdriver, always. Glad to see you're using the hook-on type probes, I think the brand name is "EZ-Hook" here in the States. I use them all the time, they work way better than standard "alligator" clips ( AKA crocodile clips to some )......
@@goodun6081 I know it's not to prevent me getting shocked.... I do know about electronics and i'm very careful in my work.
You are starting to sound insulting now.
@@kylesmithiii6150 , my boss is a ham radio operator, like most hams he has forgotten more about how radio tuners work than I will ever know. He does the tuner tweaking when I'm finished repairing and refurbishing any vintage receivers. We do a lot of repairs on old Sansui, Pioneer, Marantz, Kenwood, thank you, and so forth. Some of those units have fabulous tuners when they are properly adjusted. I just worked on a Kenwood KR 9600, big heavy receiver with handles, quite the Beast! Nice sounding, very well built, and it has an excellent tuner. Most units we see of that vintage have had multiple klutzy hands and wannabe technicians inside of them, but this one was almost factory stock. Still, in order to make it reliable for the long term we recapped the output amplifier boards and replaced the differential input transistors, which were the old type with beveled edges and badly oxidized leads.
Thank you 🎵
I have my own business of sound and light and I wish my wife were like you...kiss
👌🏽👌🏽
Wszysko będzie zalane !!! Tak się nie robi !!!
Nice sound. Not the device. I mean the girl
Sail hawmach
what voice ;)
Красота!👍