-
Feeling lucky? Check out the AK 24th Anniversary Giveaway thread and join in the fun!
Marantz MA500 thread
- Thread starter Bratwurst7s
- Start date
Thanks JD. Hopefully it will be useful for someone sometime.
I have about 30 hours on the amps now and they are giving me some really nice sound, clean and well balanced, don't seem to have any bad habits. You can take them out on a Date and just enjoy being with them for the evening without any complications.
Cheers,
James
I mentioned earlier about using wire and o-rings to stand-off and reposition the main psu filter caps.
If a person has selected caps that are only 50mm tall, or under 60mm, then using this method is the only way that I see a path to using 35mm diameter caps and not having to cut relief space in the bottom frame.
Even then I am a bit skeptical that the space can be found, but it might be worth trying. One would have to shift the upper cap 3mm up and forward, which would allow the lower cap to be shifted up and rearwards.
Doing this might buy enough space for the lower cap to clear the lower mounting frame.
We are talking about very small clearances, a few millimeters, but that is all that there is.
Anyway, here are a few photos of the method that I am talking about, in this case from filter caps mounted in a Yamaha A-520. But the concept is the concept and can be used anywhere.
First some 1.5mm² solid core wire is soldered to the cap leads.
If a person has selected caps that are only 50mm tall, or under 60mm, then using this method is the only way that I see a path to using 35mm diameter caps and not having to cut relief space in the bottom frame.
Even then I am a bit skeptical that the space can be found, but it might be worth trying. One would have to shift the upper cap 3mm up and forward, which would allow the lower cap to be shifted up and rearwards.
Doing this might buy enough space for the lower cap to clear the lower mounting frame.
We are talking about very small clearances, a few millimeters, but that is all that there is.
Anyway, here are a few photos of the method that I am talking about, in this case from filter caps mounted in a Yamaha A-520. But the concept is the concept and can be used anywhere.
First some 1.5mm² solid core wire is soldered to the cap leads.
Then a rubber o-ring is glued to the bottom of the cap to act as a spacer or stand-off. And the leads are bent to whatever position is appropriate.
Cheers,
James
Cheers,
James
Then the new leads are trimmed a bit, but still left a bit longer than needed. This makes it easy to insert the leads in the board.
Cheers,
James
Cheers,
James
Last edited:
Inserted in the board and soldered. Exses lead length is snipped off.
This might work when you have a cap that is short enough. For the 63mm tall caps that I used obviously impossible, there is no room in for the spacer without interference with the case side.
Cheers,
James
This might work when you have a cap that is short enough. For the 63mm tall caps that I used obviously impossible, there is no room in for the spacer without interference with the case side.
Cheers,
James
I have something over 50 hours of use on these amps now. They are surprising the heck out of me.
The sound quality is very good, far better than I ever expected. I am now seriously looking for a 5th one, and a 6th parts unit to source a good circuit board for the '95 unit.
Cheers,
James
The sound quality is very good, far better than I ever expected. I am now seriously looking for a 5th one, and a 6th parts unit to source a good circuit board for the '95 unit.
Cheers,
James
Thanks! Just having some fun.
I spent some time today looking for a 4.7k ohm multi-turn trim pot. Choices are pretty limited and I can't find a side adjust pot in 500mW. I may order some Bourns 3296Y-1472LF and see if I can bend the leads to allow turning the pot 90°.
https://www.mouser.de/ProductDetail/Bourns/3296Y-1-472LF?qs=T%2BU9C%2B7w6dKpLx/xkLRwig==
Cheers,
James
Lavane
Lunatic Member
Very well thought out work. I'll keep in mind the o-ring trick.
I'm a big fan of the Panisonic polypropylene film caps. I use them a lot in the signal path and as bypass caps tube amp builds.
I don't think I've ever read a bad review about how these amps sound.
Running jumpers along the traces and soldering them down was a very good idea. It strengthens the cracked board as well. The way it was originally repaired would scare me every time I connected speaker wire with the repair of the cracked board being so weak.
This thread will be very helpful for others that cone across these amps.
I considered getting a pair when they were so cheap, but bought and restored 70's Marantz power amps instead.
I'm a big fan of the Panisonic polypropylene film caps. I use them a lot in the signal path and as bypass caps tube amp builds.
I don't think I've ever read a bad review about how these amps sound.
Running jumpers along the traces and soldering them down was a very good idea. It strengthens the cracked board as well. The way it was originally repaired would scare me every time I connected speaker wire with the repair of the cracked board being so weak.
This thread will be very helpful for others that cone across these amps.
I considered getting a pair when they were so cheap, but bought and restored 70's Marantz power amps instead.
Thanks for the kind thoughts!
Today I got some cooling fans installed behind the amps on my stand.
https://audiokarma.org/forums/index.php?threads/new-diy-system-stand.1047211/page-2#post-16846294
This evening I will check out what they do, the amps do run somewhat hot after a couple of hours and this will get a bit of air movement across them.
Cheers,
James
Well, I went and did it. Bought a 5th one of these today. I guess that I'm going to have to make another Mouser order.
Cheers,
James
Cheers,
James
I have no idea how this will work out in the summer, or if I even have these amps in the system then, as I am hoping to have the Denon monoblocks working by then, but, (yes, another comma), what with the massive increase in heating costs in the last year, (comma), adding the fans to my system stand has been a great success in terms of helping cool the amps and keeping my living room warm while it is sub freezing outside.
Cheers,
James
Cheers,
James
BTW, there is a listing on ebay for a replacement protection relay for these amps. As usual for these listings the photo carefully shows an upside down part with no nomenclature visible.
If you look at the photo carefully it shows a single pole relay. That would be a downgrade from the original double pole part and I would not touch it.
Cheers,
James
edit: Concerning the Finder relays that I am using.
I have extensive experience using these relays in an industrial environment. Mainly in the parking garage gates at the hospitals where I used to work. They were used in the motor controller, so a fairly heavy load, in all weather, temps and humidity. Generally they did degrade over time and I had to replace them after about 3 years.
We had on average through the year about 6000 cars a week going into the garage. That is 312,000 cycles per year. Which is 936,000 cycles by the time the contacts were burnt/degraded enough that they needed to be changed.
They have silver/nickle contacts and are rated at 8 amps, compared to 5 amps for the original parts. I am completely confidant that one of these relays will last the rest of my lifetime in my amps (well, I am 66 now.
)
If you look at the photo carefully it shows a single pole relay. That would be a downgrade from the original double pole part and I would not touch it.
Cheers,
James
edit: Concerning the Finder relays that I am using.
I have extensive experience using these relays in an industrial environment. Mainly in the parking garage gates at the hospitals where I used to work. They were used in the motor controller, so a fairly heavy load, in all weather, temps and humidity. Generally they did degrade over time and I had to replace them after about 3 years.
We had on average through the year about 6000 cars a week going into the garage. That is 312,000 cycles per year. Which is 936,000 cycles by the time the contacts were burnt/degraded enough that they needed to be changed.
They have silver/nickle contacts and are rated at 8 amps, compared to 5 amps for the original parts. I am completely confidant that one of these relays will last the rest of my lifetime in my amps (well, I am 66 now.
)
Last edited:
My brother-in-law in Arizona has been helping me with finding an inexpensive parts unit that we can cannibalize for a replacement main circuit board. Yesterday he found one and bought it for me, so after we get it shipped over here my damaged amp will get an upgrade.
So what with the 5th amp that I bought I will have one spare amp that I can use for modding. Stand by for more fun in the near future.
So what with the 5th amp that I bought I will have one spare amp that I can use for modding. Stand by for more fun in the near future.
Actually, I get to say thanks. Your thread and those from the other members prepared me for the project.
I am enjoying the amps a lot. I never actually expected such great results from them. The 5th one should be here early this week.
Yesterday I bought a Kenwood L-1000C pre-amp. It will be my first experience with Kenwood. I will start a thread when I start on that project.
Cheers,
James
Yeah! Amp number 5 arrived today. Other than that the power cord is only 23cm/9" long 
rolleyes it looks like it is in decent condition and first look shows it to be all original inside. I can see one cap with a date code of 9340, so a '93 model made sometime after week 40.
After the condensation from shipping in the cold dries up I will test it. Also my Mouser order, speaker binding posts and replacement RCA jacks arrived.
Cheers,
James
rolleyes it looks like it is in decent condition and first look shows it to be all original inside. I can see one cap with a date code of 9340, so a '93 model made sometime after week 40.After the condensation from shipping in the cold dries up I will test it. Also my Mouser order, speaker binding posts and replacement RCA jacks arrived.
Cheers,
James
The things that people do.
Drudgery work first. Time to replace that power cable.
Cheers,
James
Drudgery work first. Time to replace that power cable.
Cheers,
James
Amazingly, when I looked through my spare power cord stash I found one that is exactly the same name and part number as the ones on the other amps. So I just had to cut off the female end and go from there.
For reasons that I can't explain I measured the interior length of the old wire. Total length = 85mm. 55mm of mantle, 15mm of exposed insulated wire and 15mm of stripped wire wrapped around the posts. Just in case anyone would want to know.
Anyway, the power cable is now replaced.
Cheers,
James
For reasons that I can't explain I measured the interior length of the old wire. Total length = 85mm. 55mm of mantle, 15mm of exposed insulated wire and 15mm of stripped wire wrapped around the posts. Just in case anyone would want to know.
Anyway, the power cable is now replaced.
Cheers,
James