First off.Happy New Year Everyone!! I'm new to this section of Audio Karma but .not new to the site.I read it often and marvel at the wisdom of some,laugh at the antics of others.Now,my problem.I picked up a 1070 Amp off ebay.It arrived today! Problem is the left channel was sounding great then it quit when I pushed the loudness button.I released the button and tried it again.She fired up,played about five minutes and the left channel dropped out again.I looked it over closely but couldn't see any obvious signs of the cause.I recalled reading about a member with a similar problem.He was told to check his output transistors while troubleshooting the cause.Anyway,I swapped my outputs around and got the left side to play.The right side with the suspect transistor in it now doesn't play! Think this may be my fix? If so,where can I purchase new outputs? The part number is;2SD388-S48.Any help that anyone can give will be much appreciated.Thanks!
Newbie Transistor Search.
- Thread starter btus
- Start date
Gigapod
Vintage audio amateur
Changing components around is not a good idea until you have pinned down the cause of a problem. 
Anyways, right now, which channel is playing and which isn't?
Your 1070 has separate power and preamp.
Can you try the Main In input from another source? If so, determine if the power amp or the preamp is the problem.
Then we find a solution. :yes:
Anyways, right now, which channel is playing and which isn't?
Your 1070 has separate power and preamp.
Can you try the Main In input from another source? If so, determine if the power amp or the preamp is the problem.Then we find a solution. :yes:
tim in pa
Active Member
the 2ds-388 equates to a NTE 280 (Si-npn), and the compliment (Si,pnp) would be a NTE-281. avail;able most anywhere. try here: www.nteinc.com
Gigapod
Vintage audio amateur
The NTE280 and NTE281 are just remarked noname TO-3 power transistors and are not an exact substitute for the original transistors 2SD388 and 2SB541 in the 1070. Also Marantz match-paired transistors at the factory and an individual would not have the right equipment to do that nowadaystim in pa said:
(however note that NTE does sell roughly match-paired NTE280 and NTE281's).
Anyways, it's not clear that any transistor needs replacing yet in this amp, is it? :scratch2:
Newbie Transistor Search
Don't know if a new transistor would solve the problem.Do know that when I swapped the rightside transistor for the left that the left channel played.The rightside channel in turn did not.When I first turn it on the left channel played then dropped out after the loudness switch was engaged.I sprayed Deoxit on all switches,turned it back on and the left channel was there for about five minutes,then it was gone.Changing out the transistors gave me sound again out of the left channel.:scratch2:
Don't know if a new transistor would solve the problem.Do know that when I swapped the rightside transistor for the left that the left channel played.The rightside channel in turn did not.When I first turn it on the left channel played then dropped out after the loudness switch was engaged.I sprayed Deoxit on all switches,turned it back on and the left channel was there for about five minutes,then it was gone.Changing out the transistors gave me sound again out of the left channel.:scratch2:
GigaPod,reread your advice for help in solving my problem.If you would ex plain your suggestion and walk me thru connecting a source to the main in and preamp sections.That is what can I hook to the amp other than a CD player? After this is done what do I look for and what should I expect it to do? Thanks for letting me draw on your knowledge.
Gigapod
Vintage audio amateur
Hi btus,
The idea of this test is to determine where the problem lies:
1) In the power amplifier section? or
2) In the preamp section.
If the problem is in the preamp section, then you don't need to touch the output transistors, which is a good thing, because it's practically impossible to get matched replacements for them. It's also good because if the problem is in the preamp, then it's probably an oxidized contact. At worst it's a low power transistor and these have replacements which are cheap and easy to come by.
OK, so how do you proceed? You have two ways to test this:
1) The very simple test: requires just one rca cable.
Find the Pre Out and Main In jacks at the back of your Marantz. They are connected internally or there is a jumper over them. Use you RCA cable to connect them. Test. Which channel is dead? Now just reverse the right and left channels at the Main In jacks. Test. Is it the same channel that is dead? yes -> power amp problem; no-> preamp problem.
2) The more complex test: requires two RCA cables and a second amplifier also with separate Main In Pre Out jacks.
Just do the simple test and report what you get, and we can work on it.
The idea of this test is to determine where the problem lies:
1) In the power amplifier section? or
2) In the preamp section.
If the problem is in the preamp section, then you don't need to touch the output transistors, which is a good thing, because it's practically impossible to get matched replacements for them. It's also good because if the problem is in the preamp, then it's probably an oxidized contact. At worst it's a low power transistor and these have replacements which are cheap and easy to come by.
OK, so how do you proceed? You have two ways to test this:
1) The very simple test: requires just one rca cable.
Find the Pre Out and Main In jacks at the back of your Marantz. They are connected internally or there is a jumper over them. Use you RCA cable to connect them. Test. Which channel is dead? Now just reverse the right and left channels at the Main In jacks. Test. Is it the same channel that is dead? yes -> power amp problem; no-> preamp problem.
2) The more complex test: requires two RCA cables and a second amplifier also with separate Main In Pre Out jacks.
Just do the simple test and report what you get, and we can work on it.
OK,with the jumper cable connecting the pre-out and main in both channels played with equal sound for ten minutes.The left channel dropped out,the right one remained.At the main in jacks I swapped the speaker wires and now the left side is playing and the right side is silent.
Gigapod
Vintage audio amateur
Hi btus,
I think you are lucky because it seems the power output stage is OK!
Get yourself a beer, sit down somewhere cosy and relax. Life is good.
:yes:
And you even got both channels to play for 10 minutes. So it seems it's a bad contact somewhere in the preamp/switches/connectors.
Solution: De-Oxit and more De-Oxit of everything in sight.
If that doesn't work then you have a bad solder joint or a bad cap somewhere in the preamp section, sometimes (rarely) they are visible, most of the time they are invisible.
Try cleaning, De-Oxit everything, try all the switches, check if there is something that you do that triggers the channel drop.
(go gently on the pots and switches, they are 30+ years old after all)
I think you are lucky because it seems the power output stage is OK!
Get yourself a beer, sit down somewhere cosy and relax. Life is good.
:yes:
And you even got both channels to play for 10 minutes. So it seems it's a bad contact somewhere in the preamp/switches/connectors.
Solution: De-Oxit and more De-Oxit of everything in sight.
If that doesn't work then you have a bad solder joint or a bad cap somewhere in the preamp section, sometimes (rarely) they are visible, most of the time they are invisible.
Try cleaning, De-Oxit everything, try all the switches, check if there is something that you do that triggers the channel drop.
(go gently on the pots and switches, they are 30+ years old after all)
Fred Longworth
audio fanatic
This thing with swapping transistors around to chase down intermittent signal loss in one channel seems way premature.
Let's return to the switches and controls. You say you "sprayed all the switches with deoxit." If I understand this literally, that is not how DeoxIT is supposed to be used. What you need to do is find small holes in the switches and controls, and then squirt the deox inside these holes.
After I apply the deox so that it gets inside a switch, I immediately operate the switch about a hundred times. If it's a control, I immediately operate it fifty times. The combination of the two actions -- squirting inside followed by exercising the device -- is what constitutes the treatment.
* * * * *
Also, if the 1070 has a protection relay (I'm at my desk at home, so don't have a schematic handy to check) this could also be a source of signal loss.
You can slightly wiggle and tap a protection relay, and if this affects the signal, then a relay service is in order. I will use #1000 sandpaper to lightly resurface the contacts.
* * * * *
Check edge connectors between boards and any wire bundles with plug-ins. Wiggle them and listen to see if the signal changes when you do this. DeoxIT is the treatment for a bad connector. I will squirt deox and then plug and unplug the connector about twenty times.
* * * * *
Hope this is useful.
Fred Longworth
Let's return to the switches and controls. You say you "sprayed all the switches with deoxit." If I understand this literally, that is not how DeoxIT is supposed to be used. What you need to do is find small holes in the switches and controls, and then squirt the deox inside these holes.
After I apply the deox so that it gets inside a switch, I immediately operate the switch about a hundred times. If it's a control, I immediately operate it fifty times. The combination of the two actions -- squirting inside followed by exercising the device -- is what constitutes the treatment.
* * * * *
Also, if the 1070 has a protection relay (I'm at my desk at home, so don't have a schematic handy to check) this could also be a source of signal loss.
You can slightly wiggle and tap a protection relay, and if this affects the signal, then a relay service is in order. I will use #1000 sandpaper to lightly resurface the contacts.
* * * * *
Check edge connectors between boards and any wire bundles with plug-ins. Wiggle them and listen to see if the signal changes when you do this. DeoxIT is the treatment for a bad connector. I will squirt deox and then plug and unplug the connector about twenty times.
* * * * *
Hope this is useful.
Fred Longworth
Thanks for chiming in Mr.Longworth.Gigapod has been graciously helping me find my way to that light at the end of the tunnel.No I don't spray Deoxit everywhere and hope it works.I try to get down inside if I see moving contacts by using the small tube supplied with the can.When I can't do this I try to cover any areas I don't want to get wet and spray it sparingly.Anyway the 1070 does have a protection switch.When I turn it on there is a delay and then I hear a click.Thank you very much for your input,it opens another avenue that I can try in our efforts to bring back this amp to its glory.
Newbie Transistor Search
Hello Mr.Longworth,thanks for chiming in! When I apply Deoxit I use it sparingly.I look for a point that I can squirt the Deoxit on the contact areas of switch,controllers etc.If and when I can I will protect those areas that I beleive won't benefit by its use.The 1070 does have a protection relay.Well,when it's powered on there is a delay and then a click before any music is heard.I will try what you suggest.I appreciate another helping hand in the effort to rid this amp of its' ghosts! Gigapod has been both great and patient in his quest to tutor me! Thanks again Guys,we will get this rascal exorcised and you :yes: can take that to the Bank!!
Hello Mr.Longworth,thanks for chiming in! When I apply Deoxit I use it sparingly.I look for a point that I can squirt the Deoxit on the contact areas of switch,controllers etc.If and when I can I will protect those areas that I beleive won't benefit by its use.The 1070 does have a protection relay.Well,when it's powered on there is a delay and then a click before any music is heard.I will try what you suggest.I appreciate another helping hand in the effort to rid this amp of its' ghosts! Gigapod has been both great and patient in his quest to tutor me! Thanks again Guys,we will get this rascal exorcised and you :yes: can take that to the Bank!!
Newbie Transistor Search
Here's back at you Guys!! I apologize for making to many posts.I kept dropping off line and had to log back in each time. Didn't know that my posts were being seen.BINGO!! The problem is in the protection relay! I went back to amp and carefully Deoxited my switches and controls.Then I worked them at least 50 times each (fingers are crapping)and tried putting sound thru unit.Left channel was still out.I then tapped on relay and great goobly goop!! left channel came in with a vengence!!
.We had sweet music for about an hour until I shut her down.:thmbsp: My next step is to take care of that pesky relay.Many thanks and praises to you Guys,for your SAGE ADVICE!!:tresbon: :tresbon:
Here's back at you Guys!! I apologize for making to many posts.I kept dropping off line and had to log back in each time. Didn't know that my posts were being seen.BINGO!!
The problem is in the protection relay! I went back to amp and carefully Deoxited my switches and controls.Then I worked them at least 50 times each (fingers are crapping)and tried putting sound thru unit.Left channel was still out.I then tapped on relay and great goobly goop!! left channel came in with a vengence!! .We had sweet music for about an hour until I shut her down.:thmbsp: My next step is to take care of that pesky relay.Many thanks and praises to you Guys,for your SAGE ADVICE!!:tresbon: :tresbon:Newbie Transistor Search
Hello Mr.Longworth,Cheers Gigapod.Rallied on because of the progress made in the repair of my amp,I tackled that relay today.Glad to report that after much patience and perserverence ,its working fine! . My problem was being caused by poor contact.Only one side of the relay was making contact and holding in place.Adjustments were made and after a lot of fun games it decided to cooperate!:thmbsp: .Gigapod ,as soon I can figure out how to post pictures I will have a few of my new toy and the other equipment in my humble collection! Thanks again Guys !!
Hello Mr.Longworth,Cheers Gigapod.Rallied on because of the progress made in the repair of my amp,I tackled that relay today.Glad to report that after much patience and perserverence ,its working fine!
. My problem was being caused by poor contact.Only one side of the relay was making contact and holding in place.Adjustments were made and after a lot of fun games it decided to cooperate!:thmbsp: .Gigapod ,as soon I can figure out how to post pictures I will have a few of my new toy and the other equipment in my humble collection! Thanks again Guys !!
