New project. Sansui 8080 recap. Advice appreciated.

Ok so instead of answers I somehow have more questions.
That's good.

- About the resistor in series, the previous tech didn't have the resistor's value, so instead he used two resistors in series to get the value. (150Ω according with the schematic).
Now, let's take those resistors in series out and measure them, and please report the values, I think those values are wrong That resistor seems to be R41 150Ω.
The bias problem I would bet is because the lack of 2SC984, although it will be wise to see what output transistors are installed.

VD1212 seems to be fine but they can become noisy.

Those are awesome fellows, Jim (R.I.P) was a contributor of this forum, but those kits are for F-2624 (9090DB/8080DB)
I can help you with the parts, just in case you want to order in mouser. ( Ithink I have a project saved there for 9090 or 8080 that I made for a fellow Aker)

Let me know if you have more question.
 
Ok so the longer I look at this the more asymmetric and crappier it appears so I decided just to measure every resistor.

Should have 120K ohms
R1 119.0k
R2 120.4k

Should have 10k ohms
R3 9.92k
R4 9.98k

Should have 120k ohms
R5 119.8k
R6 121.2k

Should have 68k ohms
R7 66.1k
R8 65.2k

Should have 22k ohms
R9 20.6k
R10 20.6k

Should have 1k ohms
R11 0.994k
R12 0.990k

Should have 22 ohms
R13 22.4
R14 22.4
R15 22.4
R16 22.4

Should have 3.3k ohms
R17 3.285k
R18 3.303k

Should have 8.2k ohms
R19 8.04k
R20 7.97k

Should have 1.8k ohms
R21 1.807k
R22 1.808k

Should have 270k ohms
R23 269.2k
R24 269.5k

Should have 120K Ohms
R25 100 ohms
R26 100 ohms

Should have 390 ohms
R29 0.384k (new)
R30 0.554k (old)


Should have 39 ohms
R31 39.0 ohms
R32 39.7 ohms

Should have 3.3k ohms
R33 3.310k ohms
R34 3.281k ohms

Should have 10 ohms
R39 10.9k ohms
R40 36.2m ohms


Should have 150 ohms
R41 5.96K ohms (Dodgy repair, two resistors in series, 5.50k ohms for one, 0.462k for the other)
R42 7.9k ohms


Should have 22k ohms
R43 22.8 ohms
R44 22.4 ohms

Should have 150 ohms
R45 150 ohms
R46 149 ohms

Should have 4.7ohms
R47 21.0 ohms (+ 17k on the rear of the board)
R48 6.5 ohms (+ 17k on the rear of the board)


Should have 4.7 ohms
R49 6.6 ohms
R50 6.5 ohms


Should have 10 ohms
R51 10.3
R52 10.4​

It's a wonder this receiver is actually working haha. This could this be why the high frequencies are distorting in only the left channel. According to the schematics the side with the dodgy repairs is the left channel.

Also interesting is that R42 (The 'good' side) has also been re-soldered in the past, R41 also does not match R48

Thanks I'd love a link to your parts list on Mouser it'd help a lot, I'm really learning as I go along on this. last time I ordered from RS Components (https://au.rs-online.com/web/) because the shipping is quite a lot less to Australia so I'll compare them.

If it's no hassle are you able to add the resistors and diodes to the Mouser order? I'm still not that knowledgeable on what makes a resistor good or not.

Thanks again for all the help.
 
Should have 150 ohms
R41 5.96K ohms (Dodgy repair, two resistors in series, 5.50k ohms for one, 0.462k for the other)
R42 7.9k ohms

Usually you need to desolder at least one leg to accurately measure them, so lets measure those buggers (two resistors in series) out of the board.

But lets address that 2SC984.
Two options that I'm aware of
- Ebay, but who knows if they are original

- BD137G https://au.rs-online.com/web/p/bipolar-transistors/5452298/
http://www.audiokarma.org/forums/index.php?threads/9090-thermal-run-away.236127/#post-2825991

- Maybe someone will chime in with a better idea, but don't worry....Let me see if I can come up with something.
- As we're learning you probably want one of those atmega328 component tester, they are cheap and works pretty good.
- I know some fellows from NZ and Australia get parts from mouser, but not sure how they charge for shipping, but maybe we can stick with RS.;)
- Remember that caps are just one fifth of the process and I'm sure that this unit will require more than a bunch of caps, but don't worry ...we will fix that bugger. and then we talk about a nice recap/ reconditioning.

Homework:
- Try to get a look of the output transistors. This is important.
- Study the service manual.

I'll let you know what resistors and caps to buy on RS and at least address that pesky board. (is 2am here and time to go to sleep)
 
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The BD137G's look like a good idea instead of taking a chance on the condition of NOS, although one of the comments mentions a TO-92L which might fit better.

I de-soldered the two resistors in series at R41 and got pretty much the same result. (5.62k ohms for one, 0.464k for the other)

I took the heatsink off and it looks like two of the output transistors have been replaced in the past, they don't look like they match either very well either. And here was me thinking all this receiver needed was a new transistor because of some black legs. :rflmao:I'm in too deep now to quit.
They are listed from left to right Sanken 2SC1116 620, Sanken 2SC1116 620 Sanken 2SC1114 71 and Sanken 2SC1114 61. No.3 is quite a lot shallower than the other transistors.

Would I be right in assuming that 4X 9090 Output Transistors, NPN, MJ21194G from http://www.qrxrestore.com/parts/ would be a suitable and necessary replacement?

Also the VU meter lights have been half replaced with LED's and a remaining incandescent bulb has blown, this amp sure lived a hard life, now I realise how easy my AU-719 was haha.



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Hello
I de-soldered the two resistors in series at R41 and got pretty much the same result. (5.62k ohms for one, 0.464k for the other)
Why the muppet use that instead of 150Ω?
Chances of fakes 2sc1114 are high.
https://au.rs-online.com/web/p/bipolar-transistors/5450236/

Caps
https://au.rs-online.com/web/p/products/1082429/
https://au.rs-online.com/web/p/products/7621796/
https://au.rs-online.com/web/p/products/5232606/

I was looking on RS for resistors, but found that It has on big quantities (like 50)
This are the resistors values on 1/2 W (metal films recommended).

150Ω x2
390Ω x 2
10Ω x 2
22Ω x 2
4.7Ω x 4x
1N4148 x 20

maybe you can find them localy
 
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And here was me thinking all this receiver needed was a new transistor because of some black legs
The untold truth of vintage units, I got my 9090 serviced and recapped by great reputation technician for a nice chunk of cash.... Pfffttt..... what a muppet he was, the poor thing was nightmare. It took me like 100 hours of work to proper recondition it.

So it is a good assumption that every unit you get it will need a lot of work.
 
I feel like the resistors used were just what happened to be available on the day haha.

Did you mean to write 1N4148 x 20 or 2? Also are there any other resistors and diodes on the rest of the amp that might need replacing too?

Also I'm a little confused what locations are those capacitors you linked to for?

If you have a link to that Mouser parts list I'll see how much it's cost in Australian Dollarydoos. :thumbsup:
 
About the amount of 1N4148, 20 units was the number, Kind of my way to say that grab a bunch of those, they are dirt cheap and useful.

Also are there any other resistors and diodes on the rest of the amp that might need replacing too?
I think not, it depends of how well the unit performs.

Also I'm a little confused what locations are those capacitors you linked to for?

https://au.rs-online.com/web/p/products/1082429/ C01-C02 on F2436
https://au.rs-online.com/web/p/products/7621796/ C11-C12 on F2436
https://au.rs-online.com/web/p/products/5232606/ C07-C08 on F2436

If you have a link to that Mouser parts list I'll see how much it's cost in Australian Dollarydoos. :thumbsup:

https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=c975bb13b5
 
I updated the project to replace the back ordered items with what looked to be the exact same part with the same brand and specs under a slightly different part number.
Also Mouser looks the way to go, free postage when buying more than AU$60.

https://au.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=118f3b5182


Just a few more questions then I think I'm ready to order.

  1. I noticed that the Nichicon 220μF 80V Capacitors UBT1K221MHD8 for C11 and C12 on 2436 on your parts list is different to what is on my 8080's board. (it has a 100uf 80 cap.) Is this on purpose and is there any benefit to upping this capacitor's rating? I assume the 8080 has the same capacitors as the 9090 on this list.
  2. Should the resistors be 1/2W or 1/4W? The manual said 1/4W as does the parts list but you said 1/2W was the way to go?
  3. I noticed an 8.2Kohm resistor was included instead of the 10ohm in the list you linked to, is this correct? Otherwise is this a good alternative? https://au.mouser.com/ProductDetail...GAEpiMZZMu61qfTUdNhGy8LaROeJAbZP%2bWS/rZ65g0=
  4. Do the output transistors need to be matched like mentioned on the Qrxrestore website or can I just order 4 from Mouser?
  5. Do you know what Diode for D05 and D06 I should also get?
  6. Know of a replacement warm led for the VU meters I could get?

Thanks again heaps for the help and patiently putting up with my endless questions, I swear I'll run out soon! :blah:
 
Hello.
Mouser works great for me.

R1./ - It is a upgrade on capacitance because that capacitor is just for local filtering.
R2./ - I've read that 1/2W works better in that application.
R3./ - I don't remember very well, but maybe it was a different board or typo, go with was is in your board, if is r39,40 on 2436 it is a great choice
R4./ - It is a plus specially on units working at full, If I have dozens of outputs i try to match... then in this case, is not mandatory IMHO.
R5./ - D06, 05 on F2436 are subbed by two 1n4148 in series.(two diodes connected together)
R6./ - https://sites.google.com/site/dgwojocom/ he's a great fellow Aker and have great quality kits.

Questions are a good thing... I'll do my best trying to answer.
Great work with your list.
Cheers!
 
Awesome good to hear on each point, I didn't know diodes worked in series but then again I don't know what a diode does haha.
Here's the updated list with 1/2W Resistors. I went with 1% because I understand they're better, I'd appreciate if you're able to double check it.

https://au.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=ad11886ae3

Also I just read about Wima film capacitors, good idea including them in the parts list.

Do you think replacing the relay is necessary? Mine seems to work fine the the original relay in my AU-719 doesn't have any issues either.
 
Yeah it sure has corrosion issues!
I just placed the order including the relay you recommended. Thanks again very much for the help, I'll have a much better amplifier for years to come as a result.
I'll post more when the parts arrive and the project continues. :thumbsup:
 
I'll post more when the parts arrive and the project continues
I forgot to mention that you will need some ceramic thermal paste for your outputs, I use Ceramique 2, maybe you can find some locally, and 4 mica TO3 pads
The old thermal paste cleans very well with WD40
 
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I used some Noctua NT-H1 PC thermal compound I had left over from when I custom built my PC on my AU-719. The repair shop guy said it was bad to use but it's not electrically conductive and been fine for a year now. I've since run out so I'll grab some Ceramique 2 off eBay.
 
Cool, ordered them both too thanks!

Yeah my Noctua D15 is awesome, after recapping my AU-719 which brought down the hiss the loudest thing in my setup is my secondary storage hard drive haha.

Tackling the rust on the amp now.
 
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