Project: Akai AA-1200

[LittleBill]

https://audiokarma.org/forums/index.php?threads/filter-caps-bypassed.336048/

They may not make a difference... but I have seen used by Sansui and some of the Gurus here. I typically use 2.2uF as a standard. Some say ~.01% of filter value.

Thank you for the link to that discussion, very interesting. I think I'll add the bleed resistors and bypass caps to my filter caps.

 

[Reliving.]

Look what just landed in my work room... it’s a monster. Time to start poking around.

Hi there Supernoob, Matt & Dave from the UK , we own a AA 1175 and have changed the four large smoothing Caps and now would like to start changing some more on the power side and the Phono small board for now , but do not know how to discharge the big Caps we changed last year.......you used resistors on your AA1200 ......can I make a discharge tool ?

I'm a little bit out of my depth here and any Help would be great.

cheers Matt UK.

 

[Super Noob]

Matt - you can use 15k 1/4 watt resistors.... they discharge slow. For discharging on the go you can use 5k but I would recommend 1 watt. You can do some calculations online to ensure you are save...

https://www.digikey.com/en/resource...version-calculator-capacitor-safety-discharge

 

[Reliving.]

Matt - you can use 15k 1/4 watt resistors.... they discharge slow. For discharging on the go you can use 5k but I would recommend 1 watt. You can do some calculations online to ensure you are save...

https://www.digikey.com/en/resource...version-calculator-capacitor-safety-discharge

In the house I have a .....8.2k 3 Watt resistor ? off something old , looked up voltage going into the smoothing Cap and its 40.6 V , so not toooo much.

 

[Super Noob]

use the calculator please... what is the capacitance?

 

[Reliving.]

use the calculator please... what is the capacitance?

Thankyou for the fast reply, old one was 4700 uf and new ones 6800 uf.

 

[Super Noob]

Thankyou for the fast reply, old one was 4700 uf and new ones 6800 uf.

yes... at 6800 uf with 8200 ohm = .2 w would work so 3w is plenty. To get the voltage down to 3v = 145 seconds from shutoff.

 

[Reliving.]

Good evening,

Can you advice me on what WILMA CAPACITORS to buy?

Do I need polyester or polypropylene?


We are back on the Akai AA-1175 and finnishing the phono board and tuner board.

Any help would be great!

Cheers Matt.

 

[Super Noob]

Matt... for typical electrolytic capacitors 4.7uF and lower I use MKS for size reasons.

 

[Yamaha5000]

Good evening,

Can you advice me on what WILMA CAPACITORS to buy?

Do I need polyester or polypropylene?
View attachment 2190508

We are back on the Akai AA-1175 and finnishing the phono board and tuner board.

Any help would be great!

Cheers Matt.

Did you see an answer in the response for the polyester or polypropylene question?

 

[Reliving.]

Final Pics:

1st receiver where I set idle current (bias) with meter in-line per the manual... set to 30 mA both channels.

Offset remained similar to start... around 10mV on one channel and 5mV on other.

Sounds like you would expect... strong / tight / like TOTL unit from the late 70s with new guts.

Thanks for viewing!

Did you replace the power switch safety caps? I have looked at mine and they look like they need to be replaced. What ones would you recommend?

 

[Reliving.]

Look what just landed in my work room... it’s a monster. Time to start poking around.

Hi Super Noob, have just finshed complete restorion of this amp and would like to test the bais or idling currant.

Have found the Test point [ small red wire] which you have to discounnect ....but it is wire wrapped .....how to remove professionally ??...........looks like its never been Tested.

Is there any otherway to test idling currant?.

any help wound be great.

0.018m Volts right speaker outlet
0,022m Amps left speaker outlet.

 

[Super Noob]

Let me try…. Offset is measured at speaker terminals / with no input on like AUX, minimum volume, measured in mV (DC)…. Goal is as close to zero as possible after amp warms up.

Bais procedure is in service manual…. mA on this model (likely you could convert to mV dc across output transistor emitter resistor)

Wire wrap pins can typically be desoldered from board with wrap intact on pin.

Snubber cap would go with same type, pF, and voltage (or higher if you like).

Good luck.

 

[Reliving.]

Thank you..0.018 and 0.022 mV on speaker posts…. Not too bad but can you get them lower?.

Would be interested in learning how to test the bias that different way….

 

[Dale G]

Does anyone have an Akai AA-1200 that they may wany to sell?

 

[hogwylde09]

And AA-1175 has been patiently waiting in storage building for a couple of years. Suppose it’s about time to get the old girl out and start some troubleshooting.
@Super Noob, looks like a minimal wire wrap posts may have to be unsoldered from the boards judging from the posted pics? Just an assumption. I’m I anywhere near correct?
It’s still in the storage building.
Also I read somewhere, hifi engine IIRC, this receiver sounds much like a Marantz.
Any truth to this?

 

[Deceders]

Absolutely wonderful job! Well done! I really like the old Akai stuff .... I've yet to experience a 120 wpc model, however.

Super Noob, the dial LEDs in these are AC or DC? If AC did you include a diode rectifier & capacitor on the supply?

LittleBill, I've got an AA-1150 that I'm going to start on. It's got a pretty massive 'thump' on power-up and power-down.

Hi Van_Isle, would you happen to have a decent quality schematic for the aa-1150. Thx