Sansui 661 HUM problem
- Thread starter Zeus12
- Start date
Zeus12
Active Member
Greetings Audiophiles,
Here´s my update on this epic battle against "windmills"!
1. Removed the 3 ground screws (PSU Board & chassis) and resoldered with fresh solder.
2. Put them back and tighten the **** out of them.
3. Clean the "blue" socket of the PSU board for the driver board, as well as the driver board pins (with alcohol).
Was so excited thinking I discovered America but noooo......fricking HUM is STILL there. NO CHANGE!!
By the way, this is the little Panasonic 0.047uf film cap I used. It wasn´t there to begin with but I tried it (from another Sansui 661 restore video which I saw online). Should I remove it or leave it? Made no difference obviously.
Big thanks for helping me out!!!
Waiting for further instructions!!!
Cheers!!!
Here´s my update on this epic battle against "windmills"!
1. Removed the 3 ground screws (PSU Board & chassis) and resoldered with fresh solder.
2. Put them back and tighten the **** out of them.
3. Clean the "blue" socket of the PSU board for the driver board, as well as the driver board pins (with alcohol).
Was so excited thinking I discovered America but noooo......fricking HUM is STILL there. NO CHANGE!!
By the way, this is the little Panasonic 0.047uf film cap I used. It wasn´t there to begin with but I tried it (from another Sansui 661 restore video which I saw online). Should I remove it or leave it? Made no difference obviously.
Big thanks for helping me out!!!
Waiting for further instructions!!!
Cheers!!!
Get that out of there - it has dangerously long uninsulated leads and could short something out making a hum problem the least of your worries, and as you said 'it made no difference', so why is it still there?
Back to the hum problem.
Ok so you have addressed some of the possible causes, so now you need to look around for things like a regulator transistor not regulating (i.e. same input voltage as output voltage), a cracked joint somewhere - could be anywhere from the rear panel jacks to the PSU. But PLEASE DONT take this as an instruction to re-run every joint in sight !!! Instead LOOK for the cracked joints and ONLY remake those that you can see a problem with - or that look so 'blobby' they could conceal a problem. I use a watchmakers eyeglass for this, you'll be surprised what you can see with one of them.
(a jewellers 'loupe' would do just as well).
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Zeus12
Active Member
@Hyperion
OK! Will remove it!
Will check again for cracked solder joints. I have a jeweler's 'loupe' from my "fountain pen" hobby!
Could it also be that this series, XX1, was "problematic" from the start? Seems to me that this hum is a very common issue on this series---from what I have seen on the net. Shame because the sound is so SWEEEEET!!!
Hope you guys are doing OK in the U.K. They are bombarding us everyday on the news with the "NEW STRAIN FROM THE U.K.",.
Thank God I have this HUM problem. I don´t have to pay attention to the news and immerse myself in the Sansui universe!
As always, thank you for you help!!!
OK! Will remove it!
Will check again for cracked solder joints. I have a jeweler's 'loupe' from my "fountain pen" hobby!
Could it also be that this series, XX1, was "problematic" from the start? Seems to me that this hum is a very common issue on this series---from what I have seen on the net. Shame because the sound is so SWEEEEET!!!
Hope you guys are doing OK in the U.K. They are bombarding us everyday on the news with the "NEW STRAIN FROM THE U.K.",
.Thank God I have this HUM problem. I don´t have to pay attention to the news and immerse myself in the Sansui universe!
As always, thank you for you help!!!
Starbender
Gathering dust...
Don't know how loud is your hum problem.
I remember when I got 661 I noticed low level hum from the start. It was not super annoying. After recap it was still there.
Replaced tone board transistors with ksc1845's. It was still there but receiver started to sound clean.
After cleaning driver board socket it was still there.
At that point I started to replace high value resistors at the tone board and driver board. Replaced adjustment trimpots.
Reflowed all ground lugs and points, also reflowed all driver board socket pins.
Last night I took out 661 from the storage and put it back to my main system and checked. It is dead silent.
Again I do not know which action cured hum problem but it was gone.
I remember when I got 661 I noticed low level hum from the start. It was not super annoying. After recap it was still there.
Replaced tone board transistors with ksc1845's. It was still there but receiver started to sound clean.
After cleaning driver board socket it was still there.
At that point I started to replace high value resistors at the tone board and driver board. Replaced adjustment trimpots.
Reflowed all ground lugs and points, also reflowed all driver board socket pins.
Last night I took out 661 from the storage and put it back to my main system and checked. It is dead silent.
Again I do not know which action cured hum problem but it was gone.
Zeus12
Active Member
@Starbender
OK. Going to change the tone board "trannies". By the way, I checked for the 29th time for cracked solder joints (used loupe), reflowed again and AGAIN, NO CHANGE!
Thanks for all your help everyone!!
Cheers!!
OK. Going to change the tone board "trannies". By the way, I checked for the 29th time for cracked solder joints (used loupe), reflowed again and AGAIN, NO CHANGE!
Thanks for all your help everyone!!
Cheers!!
Ronito6
Super Member
A new relay might be the answer. Open it up and clean the contacts and see if the hum disappears.
Even if a relay still mechanically functions, fouled contacts can cause the problem you are chasing down.
The small signal relays on my X1 worked, but intermittently caused a terrible hum. Issue disappeared after replacement.
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I'ce certainly been wrong before but removing TR05 kills power to the tone board so tone board transistors shoul(?)
not be in play. I'd be looking at the unregulated supply and the power amp. Rectifier diodes do rarely fail so more
interested in the power amp...
Ronito6
Super Member
@Ronito6
Big thank you for helping me out.
If I understand you correctly, take it out and clean the contacts? Should I try to open it and clean it inside? First time dealing with relays.
Cheers!!!
Well, it is just easier (and safer) to change the thing out. You have to remove the relay anyway to clean the contacts.
Although, while you wait for a replacement, it will be a reasonable way to test it to make certain the relay is the hum source.
An example of one way to do it is in the following thread.
https://audiokarma.org/forums/index.php?threads/how-to-clean-your-marantz-relay.419394/
ALSO
I don't think I saw this likely helpful thread recommended to you yet. (If it was...apologies.)
https://audiokarma.org/forums/index.php?threads/sansui-661-recap-parts-list-thread.718988/
ALSO ALSO
I forgot the easiest test of all.
Reassemble the amp to a point where you can turn on the amp and do a little listening.
Hopefully you will retain access to the relay in doing this.
Tap on or (not too aggressively) push on the relay.
(Preferably with something not metal. I use chopsticks.)
Tapping the relay jostles the contacts enough to reseat them a little bit for just a moment.
If the hum disappears, it is super likely the relay is the culprit.
Headphones work best to hear the results.
FINALLY
Here is an 881 repair that sought to removed a hum from that amp.
http://conradhoffman.com/Sansui_881_mods.htm
I think you will see a lot there to lead your way forward.
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Zeus12
Active Member
@Ronito6
Big thanks again for ENLIGHTENING ME!! Will order a replacement relay. Never hurts to have a spare one on hand.
In the meantime, I will try the tap (probe) test you mentioned. I use a nylon "MENDA" stick I got from Digi-Key. I found out the hard way not to poke around with a screwdriver, when I saw a BIG FLASH AND BANG that almost made me **** my pants.
Cheers!!!
Big thanks again for ENLIGHTENING ME!! Will order a replacement relay. Never hurts to have a spare one on hand.
In the meantime, I will try the tap (probe) test you mentioned. I use a nylon "MENDA" stick I got from Digi-Key. I found out the hard way not to poke around with a screwdriver, when I saw a BIG FLASH AND BANG that almost made me **** my pants.
Cheers!!!
Ronito6
Super Member
Yikes!
Sounds like you learned the capacitors retain a charge unless drained.
Check circuits with a multi-meter before touching anything.
https://salusengineering.com/technical info_basic electrical_pg5.html
“Safe Voltage Levels
The fundamental approach to protect against electric shock is to prevent contact with voltages that can cause a hazardous current through the body. Voltages above 30 Vrms or 42.2 volts peak or 60VDC are considered great enough to potentially cause a lethal electric shock to humans.”
Zeus12
Active Member
Greetings audiophiles,
Thanks Ronito6 for the nice link on "Safe Voltages Levels".
Yes, I found out and now I take all precautions! I always measure the "big capacitors", especially, before I do anything. I connect the negative of the DMM to the chassis and the positive to the positive lead of the cap. From what I understand, if it´s under 9V it´s OK to work on (same as putting your tongue on a 9V battery). I also keep one hand in my pocket or behind my back and ALWAYS use a nylon or wooden stick to probe around.
Now, regarding the Sansui 661 HUM. This is what I did.
1. I checked for the 339th time ALL solder connections. Touched up a few and they are ALL nice and shiny.
2. I probed the relay to see if that would do anything to the HUM but it had NO effect on it. Tried it with speakers and headphones.
3. Resolderd again the grounds, tightened those ground screws REALLY TIGHT and also tightened ALL the screws on the chassis. Some of them were not very tight.
4. I checked DC offset and Bias and those trimpots are DEFINETELLY crazy. They need to be changed. Could it be the VR01 and VR02 trimpots that are causing this? From the manual I see that they are 5k Ohm and VR03 & Vr04 are 1k Ohms. Would this be a good replacement for VR01 & VR02? Obviously they need to be "top adjustment" types. Any other suggestions for trimpots?
https://www.digikey.es/product-detail/en/bourns-inc/3329H-1-502LF/3329H-502LF-ND/1088237
Cheers!!!
Thanks Ronito6 for the nice link on "Safe Voltages Levels".
Yes, I found out and now I take all precautions! I always measure the "big capacitors", especially, before I do anything. I connect the negative of the DMM to the chassis and the positive to the positive lead of the cap. From what I understand, if it´s under 9V it´s OK to work on (same as putting your tongue on a 9V battery). I also keep one hand in my pocket or behind my back and ALWAYS use a nylon or wooden stick to probe around.
Now, regarding the Sansui 661 HUM. This is what I did.
1. I checked for the 339th time ALL solder connections. Touched up a few and they are ALL nice and shiny.
2. I probed the relay to see if that would do anything to the HUM but it had NO effect on it. Tried it with speakers and headphones.
3. Resolderd again the grounds, tightened those ground screws REALLY TIGHT and also tightened ALL the screws on the chassis. Some of them were not very tight.
4. I checked DC offset and Bias and those trimpots are DEFINETELLY crazy. They need to be changed. Could it be the VR01 and VR02 trimpots that are causing this? From the manual I see that they are 5k Ohm and VR03 & Vr04 are 1k Ohms. Would this be a good replacement for VR01 & VR02? Obviously they need to be "top adjustment" types. Any other suggestions for trimpots?
https://www.digikey.es/product-detail/en/bourns-inc/3329H-1-502LF/3329H-502LF-ND/1088237
Cheers!!!
Starbender
Gathering dust...
No, adjustment trimpots cannot be the cause.
Get multiturn trimpots and replace them all. After replacement, use dim bulb tester for first bias adjustment. Adjust bias for 10mA first then remove dbt and readjust bias to target value.
Change 470k and above carbon film resistors with metal film.
Zeus12
Active Member
@Starbender
Thanks for the info. Could you tell me which multiturn trimpots you used? Would these for example be OK?
https://www.digikey.com/en/products/detail/bourns-inc/3386P-1-502LF/1088535
I think you also mentioned to change D01-D04 Diodes on Driver Board (F-1499A), correct?
For the DS-430 I have the replacement 1N4148TR. Would that be OK?
Cheers!!
Thanks for the info. Could you tell me which multiturn trimpots you used? Would these for example be OK?
https://www.digikey.com/en/products/detail/bourns-inc/3386P-1-502LF/1088535
I think you also mentioned to change D01-D04 Diodes on Driver Board (F-1499A), correct?
For the DS-430 I have the replacement 1N4148TR. Would that be OK?
Cheers!!
Digikey 3296Y-502-ND
Mouser 652-3296Y-1-472LF, a little cheaper.
Need to be a bit creative with leg spacing/fitting but worth the effort
Mouser 652-3296Y-1-472LF, a little cheaper.
Need to be a bit creative with leg spacing/fitting but worth the effort
Starbender
Gathering dust...
1N4148 is fine for d01-d04.
Zeus12
Active Member
Greetings Audiophiles,
Here´s my "progress report".
1. Changed the D01-D04 diodes (DS-430) on the Driver board with the 1N4148TR Diodes.
(The D01-D03s went in a little crooked
.)
2. Put a little DEOXIT on a "Q-tip" and cleaned all 4 factory trimpots. They improved A LOT! Managed to get the "DC offset" (VR01-VR02) almost spot on 0 (+- 2mV) and the Bias current (VR03-VR04) more or less "on the money" at 19mA.
So, it looks to me that they were "dirty", most likely with residue from the "WD-40 Specialist electrical contact cleaner" spray from my "rookie of rookie" days (spayed the whole board with it). I will change them of course with "multi-turn trimpots", but just wanted to see if it could be improved. Before they would jump up and down just BY LOOKING AT THEM.
Now, I have been advised to "change high value carbon resistors with metal films". Would that change the tonal quality of the Sansui? Can I check them first and if not out of speck, leave them in there?
The HUM is still there. Perhaps a little less???? Maybe the placebo effect?
Maybe I´m overanalyzing it? It is DEFINETELLY louder then my other Sansuis, FOR SURE!
Maybe I should just leave it the way it is? It is sounding SWEEEEEEET, CLEAN, and A LOT BETTER than before all the changes (recap, "trannies", diodes").
Thanks for all your help fellows!!! I´ve been dragging this "epic windmill battle" for 4 pages and counting now...
Here´s my "progress report".
1. Changed the D01-D04 diodes (DS-430) on the Driver board with the 1N4148TR Diodes.
(The D01-D03s went in a little crooked
.) 2. Put a little DEOXIT on a "Q-tip" and cleaned all 4 factory trimpots. They improved A LOT! Managed to get the "DC offset" (VR01-VR02) almost spot on 0 (+- 2mV) and the Bias current (VR03-VR04) more or less "on the money" at 19mA.
So, it looks to me that they were "dirty", most likely with residue from the "WD-40 Specialist electrical contact cleaner" spray from my "rookie of rookie" days (spayed the whole board with it). I will change them of course with "multi-turn trimpots", but just wanted to see if it could be improved. Before they would jump up and down just BY LOOKING AT THEM.
Now, I have been advised to "change high value carbon resistors with metal films". Would that change the tonal quality of the Sansui? Can I check them first and if not out of speck, leave them in there?
The HUM is still there. Perhaps a little less???? Maybe the placebo effect?
Maybe I´m overanalyzing it? It is DEFINETELLY louder then my other Sansuis, FOR SURE!
Maybe I should just leave it the way it is? It is sounding SWEEEEEEET, CLEAN, and A LOT BETTER than before all the changes (recap, "trannies", diodes").
Thanks for all your help fellows!!! I´ve been dragging this "epic windmill battle" for 4 pages and counting now...
Zeus12
Active Member
@moefuzz
"I save the Wd-40 products for loosening the blade on the neighbors lawn mower and that's about it."
Hilarious!!! Made me laugh!! You are absolutely right!!! Learned the hard way!!
Thank you for the link. Yes, I read it a long time ago and as he says:
"The fix isn't for the faint of heart, the owner who values originality over all else, or the electronic neophyte who hasn't done this type of rework, but it isn't terribly difficult or time consuming. You have to decide if you want a hum-free receiver, or if the idea of cuts, jumpers and parts mounted with a single lead is too horrible, and the small amount of hum is tolerable. There's nothing wrong with either answer."
I´m still a newbie and I don´t feel comfortable doing "brain surgery" on the receiver. Unfortunately this series (XX1), from what I´ve seen and my own experience, has HUM problems. I can tell you that the AU-2900, AU-2200, AU-5500 (my newest toy) have NO HUM.
I think I will live with the "small amount of hum" -- which is NOT audible unless it is DEAD SILENT and you put your ear 5 inches or closer to the speaker. I know it sounds like the "fox and sour grapes story from Aesop" but I would rather have a working receiver with a little hum than a non working receiver with no HUM and NO SOUND. As I´ve said before, the sound is AMAZING!! So warm and musical. Can listen to it ALL DAY long with no listening fatigue!!
Big thanks for your help, as always!!!
Cheers!!!
"I save the Wd-40 products for loosening the blade on the neighbors lawn mower and that's about it."
Hilarious!!!
Made me laugh!! You are absolutely right!!! Learned the hard way!! Thank you for the link. Yes, I read it a long time ago and as he says:
"The fix isn't for the faint of heart, the owner who values originality over all else, or the electronic neophyte who hasn't done this type of rework, but it isn't terribly difficult or time consuming. You have to decide if you want a hum-free receiver, or if the idea of cuts, jumpers and parts mounted with a single lead is too horrible, and the small amount of hum is tolerable. There's nothing wrong with either answer."
I´m still a newbie and I don´t feel comfortable doing "brain surgery" on the receiver. Unfortunately this series (XX1), from what I´ve seen and my own experience, has HUM problems. I can tell you that the AU-2900, AU-2200, AU-5500 (my newest toy) have NO HUM.
I think I will live with the "small amount of hum" -- which is NOT audible unless it is DEAD SILENT and you put your ear 5 inches or closer to the speaker. I know it sounds like the "fox and sour grapes story from Aesop" but I would rather have a working receiver with a little hum than a non working receiver with no HUM and NO SOUND. As I´ve said before, the sound is AMAZING!! So warm and musical. Can listen to it ALL DAY long with no listening fatigue!!
Big thanks for your help, as always!!!
Cheers!!!