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Sansui AU 4400 Problems, help/advise needed

Thanks quadmatrix82 for your interest, have new outputs, new drivers and TR's are on my to order list and at least 2 emitter resistors hopefully will do the job. Determined to not hurry and learn all I can along the way
 
Oldsansui441, HepcatWilly, jami w and all others who have showed interest. Have made real progress on the unit donated by way of HepcatWilly and jami w. Have replaced left channel TR07, TR13 and TR15 (all salvaged to restore my original amp) I have replaced TR08, TR10, TR12, TR14 and TR16 on the right channel. R28, R32 and R38 were also replaced. This AM I finished soldering the components in and powered the unit-up. W/O FU01 and FU02 installed, I had 58 VDC on the bottom side of both fuse holders: so far so good !!! Can't tell you how happy I was to NOT have smoke and to measure a good voltage. A real victory !!! Next, I installed the fuses and they did not blow. I was elated !!! Next was speakers and a CD player and I had music !!! Man-o-man, I HAD MUSIC !!! I discovered though that I only had the left channel in mono mode and nothing in stereo mode. Not sure yet what that means just yet ??? Swapped speakers and inputs but still L channel only. Since R channel is not working am I safe in assuming that stereo mode will not work? I have new TR02, 04 and 06 that I did not install and maybe I should start there and just replace them since all the other TR's have been replaced. There are voltage test points too on the schematic that I haven't checked yet. Any other suggestions my patient friends? Today's victories was more than just fun !!!
 
Glad to hear it @dedmonson! My dad was a radio engineer in the Korean War, he could do all of this stuff. I don't have any of it, sadly. I'm happy that you can keep this going!
 
dedmonson said:
Since R channel is not working am I safe in assuming that stereo mode will not work? I have new TR02, 04 and 06 that I did not install and maybe I should start there and just replace them since all the other TR's have been replaced. There are voltage test points too on the schematic that I haven't checked yet. Any other suggestions my patient friends? Today's victories was more than just fun !!!
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Nice to hear you have it up and running. The amplifier section must be working properly, sounds like you have a problem further back, either in the switches or the pre amp etc. Does it do this on all inputs?
 
For what it is worth, I noticed that the donor amp had all the mic input circuits removed. I found it odd, perhaps it's worth noting.
 
Thanks Oldsansui441 and HepcatWilly for your continued interest and encouragement. I am ok not having the mic input since I'm unlikely to ever use it but wondered all the same if it might be causing the right channel not to work ??? So far I have only tried the AUX input but will try the others probably tomorrow. If I might ask a few specific questions of you Oldsansui441 to help me better understand. Do you base your statement "the amplifier section must be working properly" on the fact that FU02 doesn't blow? At what point or component does it cease to be the pre-amp section and become the amp section. I also plan to replace TR02,04 and 06 tomorrow. I plan to pull 06 first and replace it no matter what. My final question is two part: should TR06 measure good does it indicate something directly related to the silent right channel? And conversely, what about a bad TR06? Thanks in advance for your kindness.
 
Hi, the mic input won't be causing your issue. The reason l say your amplifier section is ok is because you stated earlier that both channels work well when the unit is in mono mode? Have you started by cleaning all of the pots and switches thoroughly? The main amplifier board is the F2402 board you have been working on and the pre amp board is the F2400 board up behind where the front controls are. There will be signal wires for each channel that link the pre and main amp boards, you should be able to see where they join into the main amp from underneath the unit.

Ahh, l have just re read your post and l think l may have misunderstood. Are you saying you have no RH channel at all? Yes this could be caused by a problem on the main amp board for sure. See how the remaining transistors in your RH channel check out including FR06.
 
Oldsansui441, HepcatWilly and Jamie w: since my last post I replaced TR06 and cleaned the switches, paying particular attention to the stereo/mono switch. The donor amp fully functions !!!!!!! I borrowed a milliamp meter and set the bias VR's and it sounds amazing !!! I have a sense of accomplishment that I cannot describe !!! It is fully set-up and native Australian, Tommy Emmanuel, sounds just the way he should !!! I made no attempt to fix the mic circuit or even source a mic jack. The headphone jack is also damaged in a way that I can't install it. Down the road I'll attempt to repair both. Sansui Jack's are on Ebay but none yet that will fit. Would the right off the shelf jack be ok? We're unlikely any of us to meet but I feel I've found genuine friendship in all of you. Your generosity and kindness will be long remembered.
 
Very glad to hear it @dedmonson! That amp found the right home. I'm so happy, because the faceplate was so pristine silver, I always wanted to see it get fixed up. Funny, because it really took a beating internally, but looked great outside.
 
That is excellent news dedmonson, l bet when you started this venture that you didn't think you would end up with two fully functioning AU-4400's, great work on your part indeed. I saw Tommy Emmanuel live about 15 years ago locally, he was terrific, a real magician with the guitar.

Would something like this do for the headphone jack if you desoldered it from it's little board? No affiliation with this seller, l was just having a look around.
https://www.ebay.com/itm/SANSUI-D-X...597030?hash=item48a1f164a6:g:jOIAAOSwDMhZsBle

Here's one that may work also, l believe the faceplate on your Sansui has a headphone jack hole diameter that may not allow for a threaded section right to the front though.
https://au.mouser.com/ProductDetail/Amphenol-Audio/ACJS-MIV-3?qs=sGAEpiMZZMuaKyt/jIB/pkrxID7dl753

Friends indeed :thumbsup:, thank you again for your very kind words. This has been a great thread of yours with an excellent outcome.
 
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Thanks Oldsansui441 !!! I think the Mouser jack may work. I have boxed and stored the original 4400 and daily play the donated unit (thanks again HepcatWilly and Jamie w) on a daily basis. I plan to see the jack repairs through and consider someone locally who will love it as much as I do. I am actively on the search for it's companion 2200 to make repairs to. After a look at the schematic for the AU 5500/5900 I think I would like to take a shot at it as well. Where does it stop I wonder !!! LOL
 
dedmonson said:
I am actively on the search for it's companion 2200 to make repairs to
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I had an AU-2200 a while ago, quite a different little amp as it uses IC chips for the pre amp section and STK modules for the main amplifier section, no discrete components. The available aftermarket STK modules are questionable at best.

dedmonson said:
After a look at the schematic for the AU 5500/5900 I think I would like to take a shot at it as well. Where does it stop I wonder !!! LOL
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LOL, yes very true, it is a never ending hobby. I haven't had an AU-5900 but have had about 9 of the AU-2900 through AU-4900 units and they are great little performers.
 
dedmonson said:
Old sansui441, jami w and HepcatWilly: time for an update. With the donated AU 4400 (kind regards to HepcatWilly and jami w and the generous help of Oldsansui441),ORIGINAL outputs and needed TR's were salvaged and installed and the idled Sansui sings again !!! The amazing dobro of Jerry Douglass delights my ears as I type. Bob Dylan, ZZ Topp, Led Zeppelin and CCR have never sounded better !!! I must confess though that once I'd done all I felt comfortable doing, and not wanting to risk trashing the amp, I enlisted the paid help of a local technician. I am confident it would not sound as good were it not for the donated original 2SC1444's .I have begun troubleshooting the power board of the donated unit and want to continue learning. I have identified 3 bad TR's and 3 bad resistors and putting together a parts list. Distinguishing good from bad resistors is proving difficult for my limited skills and I suspect the related caps affect my meter readings. As it is, nearly every res on both channels (on the lower 1/2 of the board) read open after a flash that is gone before I can read it. The few that do read seem out of tolerance. Are the caps drawing my Meter? NOS 2SC1445"s I bought on e-bay and was afraid to be counterfeit are thought to be genuine by the technician who helped me and I plan using them on the donated unit. More to follow. Blessings to all !!!
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thats really great to hear well read rather, im glad it all worked out for you my friend!!
 
HepcatWilly said:
Very glad to hear it @dedmonson! That amp found the right home. I'm so happy, because the faceplate was so pristine silver, I always wanted to see it get fixed up. Funny, because it really took a beating internally, but looked great outside.
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whats really odd is that i never even opened up the hood on that amp. the only thing i remember? is i bought it home and sat on a shelf.
 
That is too funny! I remember cleaning it up and playing it once or twice, it sounded great! But, I remember at least one resister flaming out and so I put it aside and other things got in the way.
 
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