Sansui g-5700 tuner bad

[ghazzer]

Trust, but verify!

I don't have the 6700 open right now, and my memory ain't photographic, so I cannot really answer your question.​

I suggest that you check out this information for yourself, and always assume that your version of this board may not be 'exactly' the same as mine. If you 'ohm' from the input pins to these points and it looks OK then it should work.

Be careful with those single turn trimmers: a small turn goes a long way.

​

 

[Hyperion]

Hi Tomcow, I notice from your pictures (post #17) that you appear to have the wrong orientation trimmers fitted to your driver board, this will give you considerable problems when trying to adjust them. May I suggest replacing them with the 'top adjust' type, (rather than the currently fitted 'side adjust' type) which will make adjustment very much easier?

Here is a link to the correct orientation 100 ohm trimmers:-
https://www.mouser.co.uk/ProductDetail/Bourns/3299Y-1-101LF?qs=sGAEpiMZZMtC25l1F4XBU4/KbyL8DlEzqoVUpFpYhnw=

I have selected 'multi-turn' rather than 'single turn' as I personally prefer them.

(please let me know if you would prefer single turn, and I'll post up the part number for those instead. Also don't worry about the link pointing to the UK Mouser website, clicking on the link will take you to the right place).

 

[Tomcow]

Yea.When I ordered them I thought they were top adjustments.I have a special small screwdriver that will work to adjust them as they are. I just want to be able to get the bias adjusted correctly.This is the F-2980 board.

 

[Hyperion]

Ok, that's fine, just so long as you are happy.

 

[Tomcow]

Could bias be tested by touching each side of the middle bottom wires,( right side blue,left side gray)where the 0.33 resistors appear to make contact on the output transistor board?

 

[Hyperion]

Well, what a complete mess the service manual is! - no wonder you are having trouble finding out where to measure. Let me see if I can help you understand this - but what I really need is a much better copy of the service manual - flying almost blind with the crappy copy I have at the moment...

 

[Tomcow]

I know one side,I can connect to pin 85 and on the other side,I can connect my meter to pin 86.Just need to know where to connect my other probe to get bias readings for the right and left channel.Thanks!

 

[Hyperion]

I just downloaded a better copy of the SM from electrotanya

OK, well it shows in the SM to connect one meter probe to pin 85, and the other meter probe to point 'A' (blue) on the F-2981 board - this isn't marked as 'Point A' on the schematic - but appears to be the Emitter of TR-601, or pin '03' on F-2981 - which will give you the voltage across one 0.33 Ω emitter resistor - this is what you need to measure. Can you find this point? - they mention 'blue' when referring to this point - I think they mean the blue wire at the left of the F-2981 board, this is pin 03.

What kind of meter leads do you have? - do you have 'ordinary probes' or do you have 'mini-grabbers'?

 

[Tomcow]

I have the mini grabbers.

 

[Hyperion]

I have the mini grabbers.

Brilliant! - can you locate the 2 points for your meter leads - Pin 85 on F-2980 and Blue wire pin 03 on F-2981 ? (this is for left channel adjustment ONLY)

You will need to adjust VR03 for this measurement/adjustment - your meter should be set to '200mV DC'

 

[Tomcow]

Are you talking about this(left output board)pin 85 leads to this board.)Which wire is the emitter going to be?This is a picture of the left channel

 

[Tomcow]

Here is a picture of the right channel with terminal 86 leading into it

 

[Tomcow]

So left channel would be pin 85 and the blue wire?

 

[Tomcow]

And the right channel will be pin 86 and????

 

[Tomcow]

Right channel

 

[Hyperion]

And the right channel will be pin 86 and????

Not clear as they say the blue wire on this board too - but I think that is wrong and should be the brown wire.

So, pin 86 and the brown wire is my guess - but set your meter to a higher range - say 200V initially - and see what you get (could be 40 or so volts) ..... if you see a lower voltage, adjust your meter range down to see if the voltage is down in the LOW mV area - then try adjusting the appropriate trimmer.

 

[Tomcow]

Seems blue would make sense,as it connects into the same transistor lead on the right channel as the left channel .The brown wire you suggest seems to be leading into the center transistor terminal.Just wanna make sure.Thanks!

 

[Hyperion]

Just wanna make sure.Thanks!

Ah well in that case - do use the blue wire - and ignore my 'brown wire' suggestion.

I think I have a few extra grey hairs because of Sansui SM's and the mistakes therein.

 

[Tomcow]

Thanks for the help.I will report back later.Hopefully,I won’t blow anything up!!

 

[Hyperion]

Thanks for the help.I will report back later.Hopefully,I won’t blow anything up!!

Happy to help - best of luck with it, please update us with progress.