New project. Sansui 8080 recap. Advice appreciated.

Yeah I'll have to look into it, I replaced every capacitor including the big 4 output caps and 'black flag' caps. It doesn't have any fusible resistors but I might measure them all and inspect the relay to see what needs doing, it sounds fine when it does work so not sure what it could be.

 

Open a new thread about it, so the guys with experience in that amp chime in. And I would start measuring voltages on the power supply section.

 

Similar issue with mine not very audiable distortion was caused by the bias on mine all the fine tuning had to be done on everything to bring it back to life. Now I am waiting to get it back as it need new meter bulbs and they are on order so I am waiting for a call to pick it up.

 

Cool glad to hear it. My distortion problem was specifically caused by the fusistors R29 and R30 390ohm on the driver board. now after a recap it sounds phenomenal. The best quality amplifier I have heard so far.

 

I made a thread a years ago I might need to revive, http://audiokarma.org/forums/index....19-protection-mode-help.759837/#post-10343273
I think I'll go through the steps we took in this thread and see if I can find any parts to blame, thanks for the suggestion for the power supply board.

 

Hey I thought Ii'd be good to get your opinion on this, I'm sorely missing my 150hz bass crossover switch from my AU719 on this 8080 which is present on the 9090, I've been looking at the tone control board and schematics and other than the switch and film capacitors C19- C26 and some resistors they're identical.
Could I just bridge the switch connectors and solder in capacitors C20, C22, C24 and C26 and some wire for the 150hz button effect? It's hard to know which points to bridge as I don't know how the 9090 switch operates, as it's a physical switch I assume the down position would operate these capacitors.

8080 Tone Control board


9090 Tone Control board

 

I think it would be fun to do the mod,let us know how it goes.

 

Small update, I filed down the trim as DougBrewster suggested and it came up great! Not as nice as his example as I couldn't draw file the edges properly with the file I bought but it's way nicer looking than before.
I also installed a small switch to change between the stock 8080/9090 light input switching mode and the always on 8080db/9090db look, I couldn't decide what I liked better. The switch is just inside the case for the time being, I'm thinking I might remove the rear Din port and place it there, I'm loathed to cut a hole into the rear panel.

 

Also on the triple tome control board do you know which pads I should bridge to activate the Bass 150hz switch? I've been trying to find a photo of the switch online to figure out how it operates but aren't having much luck. Thanks again.

 

I will have to study the schematic, but if that were my 8080.... I would enjoy it just as it was designed, and grab the next project.
Great work on that one, it looks very nice.

 

Thanks!
Yeah fair point, I primarily use Monitor Audio RX1 bookshelf speakers and love the 150hz mode on my AU719 as the low frequencies tend to trail off a bit too much. The Bass knob makes the mid/low frequencies a little too loud and boomy when turned up above +4. I have an old Kenwood equalizer I could use but the 150hz mode is just perfect for my situation as it turns up just where it's needed most. I'd me making this mod reversible of course.

 

Also these are the best pictures of the switches disassembled I could find online. http://www.sansui-vintage.com/article_info.php?tPath=2&articles_id=6

 

Sorry work has been crazy today... As soon I can, I'll look in to it.

But I think we will need to populate this section, before emulate the switch.

 

No worries take your time!
That's strange, I didn't think the Treble side would have any importance to the bass circuit.

 

I think these are all the parts from the 9090 tone control board Bass frequency switch that are missing in the 8080 excluding the wire and switches.

4X 0.033uf 50V Capacitors 50vhttps://au.mouser.com/ProductDetail/Nichicon/QYX1H333KTP?qs=sGAEpiMZZMv1cc3ydrPrFyoVFLFcIkf0aR2B1Jd06uI%3d
4X 0.012uf 50V Capacitors https://au.mouser.com/ProductDetail...=sGAEpiMZZMv1cc3ydrPrFyoVFLFcIkf0GfaI2S0Txjo=

The Treble end which appears to be in your photo includes Capacitors C11, C12, C13 and C14 as well as Resistors R19, R20, R21 and R22.

Looking at the schematics R09 and R10 could also be related as they lead towards the bass controls.

Any new thoughts on this mod? I'm trying to do this and repair my AU-719 at the same time as to save money when ordering the parts as one order. When I have it all open the new incandescent bulbs are going in too!
Thanks again.

 

Sadly I'm not good enough to modeling the outcome of that circuit, so I think that the best option for you is to test and let us know how it goes.
For that kind of caps I like C0G caps.
Take notice that bumping bass frecuecies on those receivers can lead to trigger the protection circuit.
IMHO, those receives likes laid back speakers. So maybe we are talking about a synergy.

 

That's a shame but thanks anyway, I think I'll order the parts and try the different switch combinations and see what works.
Also cheers for the TDK cap recommendation, they unfortunately both don't come in the correct specifications but I can go with a muRata equivalent of the same type and tolerance.

4X 0.033uf 50V Capacitors https://au.mouser.com/ProductDetail...GAEpiMZZMsh%2b1woXyUXj4dXoCGhcWKpjPFqxQoEPxY=
4X 0.012uf 50V Capacitors https://au.mouser.com/ProductDetail...GAEpiMZZMs7ZEmUmaUL0w8cW9RXEd9xTeScS9Gl%2b04=

I'd like the bass frequencies to be stock for a 9090 150hz switch, not necessarily louder but deeper, mostly due to the size limitations of my speakers and desk setup.

 

Made some progress today, I replaced the VU light bulbs with new bulbs I bought from a guy on eBay with a specific kit for this amplifier, so far they're great! I decided on keeping incandescent bulbs as for me the warm hue was an important factor. One bulb had blown and two had been shoddily replaced with copious hot glue in the past that made it a pain to do, it was easier to remove the whole piece to work on it.
The original bulbs crumbled apart when removing them.

 

I also successfully completed my modification to the bass frequency. Figuring out the schematics took a while especially since it had a few famous Sansui typos.

On the 8080 tone control board F2544 instead of a frequency selector switch and several capacitors the 8080 has these 4 capacitors, they are the same capacitors as the "150HZ" option in the 9090 at 0.033uf, they are C20, C21, C23 and C24.



The schematics for the switch position for S01a is a misprint, it should have the numbers in the reverse order as 3, 2, 1.
In a 9090 0.012uf capacitors alter the bass frequencies at 300HZ and 0.033uf capacitors alter the bass frequencies at 150HZ. I don't think this is entirely correct as my AU719 bass controls at 150HZ sound much deeper.

What I did was solder some 0.012uf capacitors in parallel with the existing 0.033uf capacitors in place. I used MuRata MLCC C0G 50volts 0.012uF capacitors. Part number: RCE5C1H123J1A2H03B
https://au.mouser.com/ProductDetail/81-RCE5C1H123J1A2H3B

I did this on the reverse side of the board as there was more room and it is easily removable if needed in the future.
So far I'm very happy with this mod. With them installed it sounds exactly the same as my AU719 does when in 150HZ mode. For me this really completed the amplifier, it removes the high bass boom and replaces it with a deep curve boosting only the lowest frequencies needed on my Monitor Audio RX1 bookshelf speakers.

 

Cool stuff... thanks for share!