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MARANTZ 1090 ISSUES

Richs_Trains

Richs_Trains

Well-Known Member
Hey guys, some advice if possible. I bought a beat up 1090 and figured I would try a re-cap and see how I do. I replaced all the electrolytic caps with same value audio grade caps, but did not change any ceramic or film caps. The unit had issues when I bought it and the re-cap did not change the problems so here goes.... The 'tone mode' switch does not seem to work properly, when it is in 'off' mode the channels are pretty close to even, if I switch it to 'on' mode. the right channel drops in volume and if I switch it to 'loudness' there is no change that I can hear, the right channel is still low and the loudness feature doesn't seem to engage. The unit plays about the same as before the re-cap (hard to tell a difference, as I am just using tiny shop speakers) Any thoughts?? Thanks Rich
 
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Deoxit treatment and cleaned as best as I could, one thing I forgot to mention is, the left channel plays softly with the volume all the way down. Thanks , Rich
 
Richs_Trains said:
....The 'tone mode' switch does not seem to work properly, when it is in 'off' mode the channels are pretty close to even, if I switch it to 'on' mode. the right channel drops in volume and if I switch it to 'loudness' there is no change that I can hear, the right channel is still low and the loudness feature doesn't seem to engage....
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Check the solder connections on JN03. Also check the transistors QE05-QE08 (these transistors amplify the tone control signal and are out of the circuit when the tone mode is "off").
 
Leestereo, (thanks for jumping in, you thread on the 1090 got me going on this, but I didn't make any of your mods, just value for value) I changed out QE01 -QE08 and seem to have a working tone selector, but I still have uneven volume (left is louder than right) and the left channel plays with the volume all the way down. I did switch the pre out / amp in with a patch cord and the problem moves when the cord is in place, so I'm thinking it is still some thing in the pre amp section. What about Q401-Q406 ? Thanks for any help.
 
I had a similar issue with a Marantz Thirty amp. One channel was slightly louder than the other and also with the volume knob all the way down you could still hear significant sound on both channels. Im not too good at fixing stereos yet but a friend of mine is, so I gave it to him to fix. Basically he said with this problem taking apart the volume pot and really giving it a thorough cleaning can sometimes fix this issue. But unfortunately in my case it didnt work (but maybe in yours it will) and so he suggested we get a new pot. I was able to get an exact replacement Marantz 2x250k ohm pot that came from a 2270 and low and behold it fixed both issues.
 
So, I have DeoxIT 5 the volume control a couple times and no change at all, anyone know where I might find one? part # RM 05030680 pc mount volume control?
 
Richs_Trains said:
...I did switch the pre out / amp in with a patch cord and the problem moves when the cord is in place, so I'm thinking it is still some thing in the pre amp section. What about Q401-Q406 ?...
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Q401-Q406 are only for the phono stage. Have you cleaned the contacts of the pre-out and main-in jacks?
 
I used DeoxIT 5 and inserted and removed RCA jacks several times on each jack in the Pre out / amp in. It sounds like the left channel is always on and the right channel catches up at about 1/4 volume, so I'm kinda leaning toward the volume control. Any thoughts?
 
No, I sprayed the plugs and then inserted them repeatedly, along the way some suggested I check to see if it was getting hot by playing it for 1/2 hour with no inputs and the volume about 1/3. The right side was noticeably warmer that the left so I tried to read the idle current. The left side was 2.5ma and the right was 45.4ma, but when pulling back the probe I managed to touch between a collector and an emitter and pop, main fuse went and when replaced fuse pops again. Not sure what I did, as I said this is all a learning experience and really didn't think I'd get this far, but I hate to trash this unit (even though is is cosmetically pretty beat up), so if anyone has any advice besides 'don't work on anything else' that might bring this 1090 back, please let me know!
 
It is likely that the transistor to which the emitter was shorted to the collector has failed. Uninstall this transistor and see if the amp powers up, preferably with a DBT, normally.
 
Okay, I pulled the 2SD588 AND 2SB618 from the right channel, installed a 1 amp fuse and took it up slowly on the variac. The 1 amp held at 110v, so do you think all I took out was the output transistors? I found some matched sets on eBay and have two sets on order. If this does fix it, I would like to get the volume control right, finding the exact marantz part is going to be difficult, is there any 50K dual pot I can substitute, even if it doesn't PC mount. Thank you so much Leestereo.
 
Yes, it does sound like removing the output transistors removed the short. With the outputs removed, you can still adequately drive the headphone output and can use this to see if the rest of the channel is OK. I suggest that you try cleaning the pre-out and main in jacks by directly applying DeoxIT to the jacks followed by inserting a RCA plug repeatedly. Note that many obsolete transistors on eBAY are counterfeit, so caveat emptor!
 
That doesn't sound good, any advise on somewhere else to find these. I ordered a pair from New Jersey and another pair from China, I'll try the domestic ones first and cross my fingers. I wish I still had some headphones to try it out. The left channel still produces sound, I hope the transistors are genuine and the right comes to life also. Thanks for your help and advise
 
Post pictures of the output transistors for feedback as to whether they at least look original. Note that with the "clamp bar" arrangement for the output transistors, TO-3P transistors can be used to replace the original "bat-wing" types. For the 1090, you can use 2STA1694 and 2STC4467; these too are obsolete, but Digi-Key still has stock.
 
Update, on Leestereo's advice, I did not install the ebay transistors but ordered the ones he recommended from digikey, 1090 is back working, but still has the uneven volume at low levels. Is there any suitable replacement for the volume control on the 1090? Thanks
 
WP_20160708_11_13_15_Pro.jpg WP_20160708_11_14_15_Pro.jpg so here are the transistors I purchased on eBay, the left are from China and look identical to the originals, the ones on the right are from New Jersey and look vastly different. What do you think?
 
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