250 addendum
Be careful on the 250 manual--there are addendum's which you will need. There were issues with the 250s/240s placed into heavy use situations which warrented changes.
You may also need to either find germanium diodes (there are two, one on each amp module) for the earlier 250's. They can be found, contrary to popular belief.
Be careful on the 250 manual--there are addendum's which you will need. There were issues with the 250s/240s placed into heavy use situations which warrented changes.
You may also need to either find germanium diodes (there are two, one on each amp module) for the earlier 250's. They can be found, contrary to popular belief.
Hi Jeff,
Hi torontodude,
I'll also weigh in here. The Marantz 250 is an excellent amplifier. I used to own an authorized warranty depot, but lost all my manuals when I sold the place.
Those axial silver caps that look like electrolytic capacitors ... they are wet tantalum capacitors. Probably good and as expensive as sin to replace. Leave those alone unless you want to check them. There is really no need to replace any transistors unless the are defective. I've rebuilt a few now. Well more than a few really. I'm close to where you are, considering the global nature of this web site.
Are you having any specific problems with it?
Hi RobertinMn,
These were very reliable amplifiers and I have seen many pounding away in bars over the years. I'm a little surprised to hear they had issues. Maybe they were all sorted out by the time they were sold in Canada. Were you authorized warranty as well?
Could you please send me a copy of that manual? The one thing I miss terribly were all my service manuals.
My mail is bhomester at gmail dot com .
Hi Joe,
I wasn't aware of any large changes between the different models. I think I only ever had the 250M (for meters) manual that served for all of them. Of course, it is entirely possible I didn't get them all as well.
How are you doing these days?
-Chris
No, there is a reason for the moderation period, and it works well. The moderating team simply works with the rules that are in place. Allow nature to take it's course.
Hi torontodude,
I'll also weigh in here. The Marantz 250 is an excellent amplifier. I used to own an authorized warranty depot, but lost all my manuals when I sold the place.
Those axial silver caps that look like electrolytic capacitors ... they are wet tantalum capacitors. Probably good and as expensive as sin to replace. Leave those alone unless you want to check them. There is really no need to replace any transistors unless the are defective. I've rebuilt a few now. Well more than a few really. I'm close to where you are, considering the global nature of this web site.
Are you having any specific problems with it?
Hi RobertinMn,
?
These were very reliable amplifiers and I have seen many pounding away in bars over the years. I'm a little surprised to hear they had issues. Maybe they were all sorted out by the time they were sold in Canada. Were you authorized warranty as well?
Could you please send me a copy of that manual? The one thing I miss terribly were all my service manuals.
My mail is bhomester at gmail dot com .
Hi Joe,
I wasn't aware of any large changes between the different models. I think I only ever had the 250M (for meters) manual that served for all of them. Of course, it is entirely possible I didn't get them all as well.
How are you doing these days?
-Chris
marantz 250 schematic need
please email marantz 250 schematic to. [email]vette65.fi@sbcglobal.net [/email]. sorry i can not sent email
yet. thanks in advance
please email marantz 250 schematic to. [email]vette65.fi@sbcglobal.net [/email]. sorry i can not sent email
yet. thanks in advance
anatech said:
Yes, we are VERY close! I used to go to Centennial Middle School in Georgetown!
Anyway...I had no idea those were tantalum caps. Hmmm...
I'd like to change the transistors because they don't match. Someone's had at this amp before me and replaced the original transistors (or at least some of them) with a mix of replacements. They seem to work, but could probably work better.
I am also having a specific problem...you may have run into this in your repair shop. When the amp has been on for a while (somewhat inconsistent, but probably after it's warmed up), I get a "snapping" sound from the speakers once in a while. Sort of sounds like what happens to an LED when you hook up a 12V car battery to them....SNAP! So I figured it might be a cap...or a transistor.
Any ideas?
For anyone asking, I've posted two files on my website for the 250 and 250B. Feel free to download them.
250 Service Manual 250B Schematic
Hi torontodude,
Yes, you must replace those outputs. On Semi makes wonderful transistors these days. I would recommend any pair MJ21195/MJ21196 or MJ21193/MJ21194. Beta is closer these days, but you may as well buy a few extra so you can match the closest ones together. If you need 4 of each, buy at least 6 of each to allow for better matching.
-Chris
Bloody hacks! No shortage of them around here I'm afraid. I've spent over 30 years cleaning up after these people.
Yes, you must replace those outputs. On Semi makes wonderful transistors these days. I would recommend any pair MJ21195/MJ21196 or MJ21193/MJ21194. Beta is closer these days, but you may as well buy a few extra so you can match the closest ones together. If you need 4 of each, buy at least 6 of each to allow for better matching.
I'm on the other side of the tracks from the hospital. Near Hwy #7 and Trafalgar Rd.
Nice! You may have a signal transistor breaking down, or a capacitor. Try to gently warm components up one at a time. If you think you have found the part, try cooling and heating that one part. Leave time for the part to respond thermally. That might be 20 ~ 30 sec. Take your time with this.
-Chris
I also have a 250m with one blown channel, as I commented here, missed this thread somehow:
http://www.diyaudio.com/forums/showthread.php?s=&postid=1896272#post1896272
I think that there are design issues with the protection circuitry.
Pete B.
http://www.diyaudio.com/forums/showthread.php?s=&postid=1896272#post1896272
I think that there are design issues with the protection circuitry.
Pete B.
The links above appear no longer to be valid. Is there anyone out there who can re-list, re-post or FTP host the Marantz Model 250 Power Amp Schematic? I have a seriously dead one I'd love to resurrect.
I am interested specifically in the 250 - NOT the 250M, which I have and does not exactly match the circuit I have before me (it's close and may suffice, but the real one is always preferable when repairing).
I am interested specifically in the 250 - NOT the 250M, which I have and does not exactly match the circuit I have before me (it's close and may suffice, but the real one is always preferable when repairing).
I found a copy at MARANTZ 250 SM Service Manual free download, schematics, eeprom, repair info for electronics Lots of advertising junk at this page. Look for the Get Manual link to the right of the picture of the manual, about two thirds of the way down the page. There also is a copy of 250 and 240 manuals in the audiokarma.org data base AK Database PDF Gallery - Marantz/Marantz 250 Service Manual Have to register - but its free.
Ah sregor - thank-you very much! GOT IT! I see the 250M schema I have is in fact more different than even I was aware - particularly around the important area fried on the unit I have.
FYI- guys - The elektrotanya site is sensitive to pop-up blockers, so if you go there you have to disable your blocker first and then the DL link mentioned above appears to the right of the page. (good site BTW!)
Well, now it looks like I need a suitable substitute for the finals (toast), but I found another thread here covering that....
FYI- guys - The elektrotanya site is sensitive to pop-up blockers, so if you go there you have to disable your blocker first and then the DL link mentioned above appears to the right of the page. (good site BTW!)
Well, now it looks like I need a suitable substitute for the finals (toast), but I found another thread here covering that....
Hi Pete,
I don't know how I missed these messages in this thread.
I have fixed a number of these. There are no design issues and they are stable as long as you do your part (and for you, I know you will). Don't try and upgrade the wet tantalum capacitors. You won't find better - yet. They are expensive to replace, really expensive!
I have found one for myself. No meters (darn!), but they do sound good. Today, I would use the MJ21195 / MJ21196 outputs. The MJ1502x parts are too fast. If it was your amplifier I would suggest you change the outputs as the new ones are more linear. So, better performance.
-Chris
I don't know how I missed these messages in this thread.
I have fixed a number of these. There are no design issues and they are stable as long as you do your part (and for you, I know you will). Don't try and upgrade the wet tantalum capacitors. You won't find better - yet. They are expensive to replace, really expensive!
I have found one for myself. No meters (darn!), but they do sound good. Today, I would use the MJ21195 / MJ21196 outputs. The MJ1502x parts are too fast. If it was your amplifier I would suggest you change the outputs as the new ones are more linear. So, better performance.
-Chris
I had to ask..why not the MJ15015 and MJ15016 or MJ15024 and MJ15025? I've used both without any problems? I always thought they were about the same as the perforated emitter transistors. Still got one running fine with 15015's and 15016's.
Well, the MJ1015 / MJ15016 are "economy parts" with really poor performance. The term "economy grade" was used by Motorola in describing these parts. I simplify it to, "The are junk". If I ever saw one of these amps with those in it, they are on the estimate to be replaced.
The MJ1502x TO-3 output transistors are fast, too fast for many designs. You may be on the edge of stability with those. I have been, but you have to look for it instead of just assuming they are fine because the amplifier isn't currently a radio station.
The MJ2119x transistors are slower, but that is a very good thing in the 250. If you look at the collector current vs beta graph, you will see that these are far superior to previous parts. My own testing has shown this to be true.
I have seen people use one Japanese output and a North American number opposite. Just because it functions and doesn't oscillate doesn't mean it's working well. Also, if you match the outputs, the distortion can be reduced.
Doesn't the beta mis-match of those MJ1501x transistors bother you, or do you even measure beta?
-Chris
The MJ1502x TO-3 output transistors are fast, too fast for many designs. You may be on the edge of stability with those. I have been, but you have to look for it instead of just assuming they are fine because the amplifier isn't currently a radio station.
The MJ2119x transistors are slower, but that is a very good thing in the 250. If you look at the collector current vs beta graph, you will see that these are far superior to previous parts. My own testing has shown this to be true.
I have seen people use one Japanese output and a North American number opposite. Just because it functions and doesn't oscillate doesn't mean it's working well. Also, if you match the outputs, the distortion can be reduced.
Doesn't the beta mis-match of those MJ1501x transistors bother you, or do you even measure beta?
-Chris
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