Sansui Seven Receiver intermittent crackling noise

Thread Starter

Roque

Joined Sep 16, 2014
156
Hi Gents,
been working on a Sansui Seven receiver and the right channel crackles intermittently audio is fine just the intermittent pops that at times is loud to disengage the relay for a sec or two and then the relay engages once again ,i have tried swapping the driver boards around and the pop and crackle moves to the left channel ....... i have replaced the three electrolytics also the ceramic caps swapped transistors from the other channel driver board replaced diodes too checked resistance of resistors all ok but something still crackles and pops ......got me pulling my hair out this one will post photos of the boards
any help is very much appreciated
Regards
Roque
 

danadak

Joined Mar 10, 2018
4,057
Do you have a DSO so you can capture a one shot trigger at various
points in the receiver ? Walking down/up the signal chain.

Also cold spray to hit various areas of board/components can be helpful.

Google "cold spray pcb" for vendors.


Regards, Dana.
 

Ylli

Joined Nov 13, 2015
999
I'm looking at the schematic of the Sansui Seven, (got the manual here: https://www.hifiengine.com/manual_library/sansui/seven.shtml) and I see two power amp boards (F-1939) but only one combined driver board (F-1436). Not sure how you "have tried swapping the driver boards around and the pop and crackle moves to the left channel". Which boards did you actually swap?

If you cross the Pre-out/Main-in connections, does the issue move to the other channel?

I leave you with this: https://audiokarma.org/forums/index...ilure-prone-whatever-and-replacements.731653/
 

Thread Starter

Roque

Joined Sep 16, 2014
156
Do you have a DSO so you can capture a one shot trigger at various
points in the receiver ? Walking down/up the signal chain.

Also cold spray to hit various areas of board/components can be helpful.

Google "cold spray pcb" for vendors.


Regards, Dana.
hi Dana,
thank you for your reply ,i dont have an DSO and neither cold spray either just a DM h,will definitely google and keep one handy cheers
 

Thread Starter

Roque

Joined Sep 16, 2014
156
I'm looking at the schematic of the Sansui Seven, (got the manual here: https://www.hifiengine.com/manual_library/sansui/seven.shtml) and I see two power amp boards (F-1939) but only one combined driver board (F-1436). Not sure how you "have tried swapping the driver boards around and the pop and crackle moves to the left channel". Which boards did you actually swap?

If you cross the Pre-out/Main-in connections, does the issue move to the other channel?

I leave you with this: https://audiokarma.org/forums/index...ilure-prone-whatever-and-replacements.731653/
sansui.jpg
I'm looking at the schematic of the Sansui Seven, (got the manual here: https://www.hifiengine.com/manual_library/sansui/seven.shtml) and I see two power amp boards (F-1939) but only one combined driver board (F-1436). Not sure how you "have tried swapping the driver boards around and the pop and crackle moves to the left channel". Which boards did you actually swap?

If you cross the Pre-out/Main-in connections, does the issue move to the other channel?

I leave you with this: https://audiokarma.org/forums/index...ilure-prone-whatever-and-replacements.731653/
 

Thread Starter

Roque

Joined Sep 16, 2014
156
hi Yill,

there are two of these boards that sit in a push in socket which then connects to the output transistors these are easy to swap across ,i have swapped transistors across from the other channel have replaced diodes with 1n4148s swapped across the zener diode too checked the value of all the resistors comparing them withe the other board done all that
Regards
Roque
 

Ylli

Joined Nov 13, 2015
999
OK, I would have called these the output boards or main amp boards. Semantics. Issue moves with the board, and you have swapped all the active components, and replaced the capacitors... well.. It's a simple board, have you tried reflowing all the solder connections? If you haven't already done so, you might want to clean/swap/replace the offset and bias adjust pots.
 

Thread Starter

Roque

Joined Sep 16, 2014
156
OK, I would have called these the output boards or main amp boards. Semantics. Issue moves with the board, and you have swapped all the active components, and replaced the capacitors... well.. It's a simple board, have you tried reflowing all the solder connections? If you haven't already done so, you might want to clean/swap/replace the offset and bias adjust pots.
yes done that swapped the two bias pots still the same ....the cracle is like intermittent might play well for around 1o mins and then a crackle am at my wits end
 

Thread Starter

Roque

Joined Sep 16, 2014
156
You said you swapped the driver pcb, and now it crackles on the Left channel, so that must be the faulty board then...
yeah faulty board definite but swapped all components excluding resistors from thge proper working board to faulty one but the crackle still persists :-(
 

Thread Starter

Roque

Joined Sep 16, 2014
156
Hello,

Are the contacts of the PCB clean?
Dirt can give faulty reactions.

Bertus
done that , didnt realise a little board with probably 25 components would give me that grief hahahaha at times the pop is so loud that it trips the relay and for a sec or two and the relay clicks in again ........
 

SLK001

Joined Nov 29, 2011
1,548
+1 on bad solder joints. IIRC, this is a 70's amp? Cold solder joints, dirty connectors and cracked solder joints are the usual suspects for something like this.
 

Thread Starter

Roque

Joined Sep 16, 2014
156
Hello Gurus sorry for my delay in replying i live downunder Australia) and when its day here might be night elsewhere but my appologies ... goin with all the suggestion you have all kindly given me done that and i guess may have fixed the issue ..used my hot air gun ran it allover the board to make sure all solder joints were good i also found that one of the A640 transistors was the culprit ..crazy as they show good with a DMM butlike you all mentione they go bad so replaced with a BC556 which i had on hand different pinouts but seems like the receiever is working like a dream ...will test it well and keep you all updated thanks you all for your kind support cheers
Kind Regards
Roque
 
Top