Sansui 7070 no sound

harleyrider

Super Member
I have a friends, Sansui 7070 . From what he says it played fine NO problems . Playing it one night when done powered down for the night . Next time powering it nothing at all ! I do not have a manual on this , but i did check power from plug input to power switch all good there , got some of the lights to come on by wiggling the board that has the 2 molex connectors . Not sure of whats going on but that is all it will do is make those lights go on and off . Any ideas of what to check ? All fused look good and test good on each side for voltage running through . No burn anything that i can see . You can very barely hear audio through a speaker on FM , have not tried anything else . No caps look to be leaking , i know that doesnt mean anything though . Thanks for any suggestions .I will look for broken solder joints too .
 

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Need to start with the power supply-making sure all supply voltages are present and accounted for.
 
On that model sometimes the case will warp down slightly, pushing on top of a PCB, and cracking the main board that is under everything else. Pull off the bottom cover, and closely inspect.
 
Again I am struck by the MASSIVE transformers they put in these receivers, clearly they knew what was/is important.

Thanks for the pics harleyrider.
 
Not sure if its protect or not ? Most of the lights are not working. getting ready to take to garage and try to blow as much dust out of it as i can . Then ill bring it in and inspect more thoroughly. He did say all lights were working before this , so im thinking something has lost power ?
 
Avionic, Thank you very much for the hifiengine web site . Ive downloaded the manual . I have taken and blew it really good and wiped it down . Doesnt look bad after a cleaning. I cant find any bad solder joints yet! Im looking close and a couple times . I did pull a couple of the boards to clean more and have a better look at things . They made this fairly easy to get apart and work on ,thats nice. The only lights im getting on is the one for the tuner pointer and the selector light ,FM,AM, tape etc.... Ill read through this manual and try to locate the points you have mentioned . Thanks
 
Pics of the 7070 inside

A few pics of the inside.
 

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Again I am struck by the MASSIVE transformers they put in these receivers, clearly they knew what was/is important.
Don't forget, Sansui started to build audio equipment to enhance their transformer business. They knew them inside and out.

- Pete
 
Well i have the F-2624 board pulled and have checked several resistors.
R33 124 OHMS
R34 O L (BAD) ?
R35 5.3
R36 5.9
R41 186.7
R42 226.3
R43 171.8
R44 169.3
I may be missing a few on this board.
I been searching here , is there a parts list for the sansui 7070 .
I would like to make a order from digikey or mouser , just not a 100% sure of what to order? I know i would like to recap this as well. Doing one board at a time is ok for me . Any suggestions Thanks for the help
 
This is not intended to be a full restoration .
This is not mine, its a friend of mine and was just hoping to get him up and running.
He doesnt want to spend a ton , ya i know if your gonna do it right then do it .
Well i will do as much as i can for this 7070 , i like the experience of learning as i go.
Thanks again
 
Well i have been to mouser and digikey before and ordered parts . That was when i had part #s given to me . Well i have been trying for some time now to find parts to replace the ones in this F-2624 board . I have tried the original part#s at both sites no good . I tried putting in a (180 ohm 1/2 watt resistor) just to start . I get a ton of stuff , i have a general idea of what i want but cant seem to find it? I dont mind doing the leg work but i am running out of ideas here ???? Things like (series) (temperature coefficient),the size and dimension well i could figure that out . Is the flame retardant coating good for being flame resistant ? I was hoping to get these in the Yageo, i seen that EW uses these a lot in a older thread. Please forgive me if i have mistaken any of this , just trying to learn here .
I am wanting to buy
part# stock#
R33-34 0191181
R35-36 0191479
R37-38 0210392
R39-40 0192100
R41-42 0192151
R43-44 0192151
R47-48 0192479
R49-50 0192479
Im not sure what the zener diodes are ( downloaded manual) is hard to read.(EQA01-24R)?
C07-08 CAPS 330 63v
C05-06 CAPS 470 6.3v
C09-10 CAPS 100 25v
There may be other parts i need to replace as well , please let me know if i have missed something here.
As far as ordering from either one of the 2 places i have mentioned , is there something i need to know about ordering parts ? (other than experience/knowledge loll).
I seen in a thread on here that when you order replacement parts always use the original part #. So that is what i was trying to do . Thanks for any input , please bare with me ......
 
Changed out resistors on F-2626 and F-2624 as mentioned earlier in this thread and what caps i could find this week here in town. Reinstalled the F-2626 aqnd F2624 boards and plugged it in . When i hit the power within about 5 seconds i got a small puff of smoke . Looked to me as if a came from around the F2624 board (near bottom)and the 2 large caps behind the transformer. It was very quick and i unplugged it so when i came back i didnt see any smoke . It was to quick to pinpoint. I pulled both boards back out to look for burnt places and bad solder joints, i also inspected the mother board. I did reflow the solder connection on the mother board for the F2624 board. I have found nothing yet, installed both boards again powered unit back up .
What i have now is
You do hear audio from all four speaker outputs , using am,fm,aux thats all i tried.
You do hear audio through the headphones.
The audio is very faint and distorted ( cracks and pops). In both speakers and headphones.
You have to turn it up all the way to get the VU meters up and moving , at that point they are just starting to bounce. ( not much for having it full volume).
Im not sure were the smoke came from or if i hurt anything . Ill try and do some more testing tomorrow . Im hoping i didnt damage it to bad if any ? Any suggestions at all what i may look for now. I have not did a good cleaning (deoxit) yet i plan on doing that tomorrow as well.. Thanks again for the help.
 
Well ive got all the swithches, controls cleaned with Deoxit D5 and F5 lube. Ill let this set a while to dry .The game is on today so not sure if ill get back on it till later maybe . Any ideas of my problems i found in the last post ?
I did a DC check with my DMM at the speaker outputs today,set in MV (DC).
Speakers A
left 68.8 dc mv
right - o6.5 dc mv
Speakers B
left 69.2 dc mv
right - 07.2 dc mv
I had no sources going into the unit, selector set on Aux and no speakers connected to unit . Basically plugged in , volume down , bass and treble, midrange set in middle.
Thanks for any help .
 

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A and B speaker outputs are the same. No need to check both. 68mv DC offset is too high. The service man has a section for amplifer adjustments that will give you the proceedure to set it correctly.

- Pete
 
A and B speaker outputs are the same. No need to check both. 68mv DC offset is too high. The service man has a section for amplifer adjustments that will give you the proceedure to set it correctly.

- Pete
Could something have went bad causing this ?
I will check them per the manual Thanks
 
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