Super Noob
Super Member
Look what just landed in my work room... it’s a monster. Time to start poking around.
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Project: Akai AA-1200
- Thread starter Super Noob
- Start date
Look what just landed in my work room... it’s a monster. Time to start poking around.
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NAD80
Super Member
Looks nice. Found the owners manual and schematic here. https://www.vintageshifi.com/repertoire-pdf/Akai.php Also here on HiFiEngine. Manuals https://www.hifiengine.com/manual_library/akai/aa-1200.shtml Good luck with the Akai. Can't wait to hear how it sounds.
Super Noob
Super Member
Thanks = NAD80!
It has dual transformer... kind of weird the boards don't have silk screen or markings = note self even more pictures than typical. The offset is around 3mV on channel and 10mV on the other other = not too bad.
It has dual transformer... kind of weird the boards don't have silk screen or markings = note self even more pictures than typical. The offset is around 3mV on channel and 10mV on the other other = not too bad.
Super Noob
Super Member
Here is the update... few posts to follow.
Pop the lid and noticed two things:
1) 220uF cap replaced with some cheap 100uf caps wired in parallel
2) Relay contracts jumped / bridged.
Here is the deal, the amp board is quite a tightly tucked board on the heat sinks. Was able to suspend heat sink from the chassis and get good access. One thing to note (as well) if anyone ever decides in the future to tackle this thing, there are no bleed resistors on the main filter caps (so you will need to bleed) before working on. I installed some inexpensive 1/4 watt 18K resistors until I got the new filters in. I enjoy the process and the seeing completion of the work, but no markings on the boards made troubleshooting more difficult and errors at least four times more likely.
Okay I am not MTF, Echowars, Kevzep, or any other stud you have read about here, so I took me awhile to track down the reason the relay was jumped out. I checked all the transistors and diodes (a few times) = all checked out fine. Obviously power (voltage) was not in the transistors in the protection area of the relay circuit. After a few hours and night sleep, I found that resistor R48 was open. Print showed this a 27K... found that the bad resistor was 21K. Anyways in this case = I stuffed in 27K per the print, and we were cooking with grease. After that was fixed, the amp board was full recapped, new trimmers, new relay, and fresh Wakefield paste.
Before:
After:
Had to come back in here after I got my filters = was missing two caps (not in stock -some low value high voltage caps), but the last picture shows the proper caps in as well as R48 changed.
Pop the lid and noticed two things:
1) 220uF cap replaced with some cheap 100uf caps wired in parallel
2) Relay contracts jumped / bridged.
Here is the deal, the amp board is quite a tightly tucked board on the heat sinks. Was able to suspend heat sink from the chassis and get good access. One thing to note (as well) if anyone ever decides in the future to tackle this thing, there are no bleed resistors on the main filter caps (so you will need to bleed) before working on. I installed some inexpensive 1/4 watt 18K resistors until I got the new filters in. I enjoy the process and the seeing completion of the work, but no markings on the boards made troubleshooting more difficult and errors at least four times more likely.
Okay I am not MTF, Echowars, Kevzep, or any other stud you have read about here, so I took me awhile to track down the reason the relay was jumped out. I checked all the transistors and diodes (a few times) = all checked out fine. Obviously power (voltage) was not in the transistors in the protection area of the relay circuit. After a few hours and night sleep, I found that resistor R48 was open. Print showed this a 27K... found that the bad resistor was 21K. Anyways in this case = I stuffed in 27K per the print, and we were cooking with grease. After that was fixed, the amp board was full recapped, new trimmers, new relay, and fresh Wakefield paste.
Before:
After:
Had to come back in here after I got my filters = was missing two caps (not in stock -some low value high voltage caps), but the last picture shows the proper caps in as well as R48 changed.
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Super Noob
Super Member
Here are the main outputs pulled and re-pasted:
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Super Noob
Super Member
Front End Boards - Tone Controls, Selector, Input
All boards were recapped and cleaned with De-Oxit.
All boards were recapped and cleaned with De-Oxit.
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Super Noob
Super Member
Large Tuner Board Was Next (pretty sure the phono amp was on the other side of this massive board).
Before (didn't get a entire board shot prior - was so focused on have cap polarity captured):
After:
Before (didn't get a entire board shot prior - was so focused on have cap polarity captured):
After:
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Super Noob
Super Member
Main Filter Caps:
The originals are 4800uf / 80v... went with 6800uf / 100v (snap in - exact same diameter). I pulled the old terminals off the old caps and mechanically fastened them to the new cap snap-in terminals and soldered. Popped on new 1 watt bleed resistors and 2.2uf bypass film caps (like I typically do). This was quite a job, but I think it turned out great.
The originals are 4800uf / 80v... went with 6800uf / 100v (snap in - exact same diameter). I pulled the old terminals off the old caps and mechanically fastened them to the new cap snap-in terminals and soldered. Popped on new 1 watt bleed resistors and 2.2uf bypass film caps (like I typically do). This was quite a job, but I think it turned out great.
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Super Noob
Super Member
Okay Some Shots of the Unit Completed (New LEDs for the dial as well)
74 caps
2 trimmers
1 relay
4 bypass caps & 4 bleed resistors
3 LED dial lamps
74 caps
2 trimmers
1 relay
4 bypass caps & 4 bleed resistors
3 LED dial lamps
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Super Noob
Super Member
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!
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!
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Super Noob
Super Member
Here are most under appreciated items of my rebuilds... right tools and mindset which can keep these things going well into the future.
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Reliving.
Active Member
Here is the update... few posts to follow.
Pop the lid and noticed two things:
1) 220uF cap replaced with some cheap 100uf caps wired in parallel
2) Relay contracts jumped / bridged.
Here is the deal, the amp board is quite a tightly tucked board on the heat sinks. Was able to suspend heat sink from the chassis and get good access. One thing to note (as well) if anyone ever decides in the future to tackle this thing, there are no bleed resistors on the main filter caps (so you will need to bleed) before working on. I installed some inexpensive 1/4 watt 18K resistors until I got the new filters in. I enjoy the process and the seeing completion of the work, but no markings on the boards made troubleshooting more difficult and errors at least four times more likely.
Okay I am not MTF, Echowars, Kevzep, or any other stud you have read about here, so I took me awhile to track down the reason the relay was jumped out. I checked all the transistors and diodes (a few times) = all checked out fine. Obviously power (voltage) was not in the transistors in the protection area of the relay circuit. After a few hours and night sleep, I found that resistor R48 was open. Print showed this a 27K... found that the bad resistor was 21K. Anyways in this case = I stuffed in 27K per the print, and we were cooking with grease. After that was fixed, the amp board was full recapped, new trimmers, new relay, and fresh Wakefield paste.
Before:
After:
Had to come back in here after I got my filters = was missing two caps (not in stock -some low value high voltage caps), but the last picture shows the proper caps in as well as R48 changed.
Hi , in this picture you have used a mix of caps ? would you remember what makes you have used because I would love to use one or two makes only ? ....Did you order parts from Mouser ? cheers Matt mattsgpovan69@gmail.com
Super Noob
Super Member
I have plenty of stock on hand...
UKL
UPW
UKA
WIMA Film
Power supply - I like to use UPW (and coupling locations). UKA for general caps on tuner and other positions.
UKL for low leakage where WIMAs don’t fit or larger than 4.7uF.
For Bi-Polar, I use UES.
Honestly - I am doing better lists on more recent builds.
Few Examples Below:
https://audiokarma.org/forums/index.php?threads/project-sx-1250-2nd-take.858276/
https://audiokarma.org/forums/index.php?threads/project-marantz-2275.866240/
https://audiokarma.org/forums/index.php?threads/project-kenwood-kr-8050.882572/
Best of Luck.
Reliving.
Active Member
Wow you’ve done some great amps....
What I did notice on one of your restoration rebuild,s ,is sometimes you upped the capacitance and the volts of a capacitor...!.
Now I know about the volt,s side of things... but did not know about the capacitance upgrade ....
I also have heard that the mains input of today Runs slightly higher than 1970s ! I can remember the power cuts Lol .
If you could explain the basics to me about upping the capacitance with any positive or negative attributes to the Circuit this will give me confidence in buying what’s good for the amp .
Tried last night to order some capacitors... But am finding it a nightmare on Mouser UK ... I think Mouser in the States has a lot more stock .....
Like the capacitor UPW which I struggle to get in the UK .... HELP....
Can you recommend a UK site that is user-friendly .
Cheers Matt... UK .
What I did notice on one of your restoration rebuild,s ,is sometimes you upped the capacitance and the volts of a capacitor...!.
Now I know about the volt,s side of things... but did not know about the capacitance upgrade ....
I also have heard that the mains input of today Runs slightly higher than 1970s ! I can remember the power cuts Lol .
If you could explain the basics to me about upping the capacitance with any positive or negative attributes to the Circuit this will give me confidence in buying what’s good for the amp .
Tried last night to order some capacitors... But am finding it a nightmare on Mouser UK ... I think Mouser in the States has a lot more stock .....
Like the capacitor UPW which I struggle to get in the UK .... HELP....
Can you recommend a UK site that is user-friendly .
Cheers Matt... UK .
LittleBill
New Member
Super Noob, thanks for a great project writeup! I'm pretty new to restoring vintage stereo equipment, and I have a question. What are the bypass caps for, the ones you added to the main filter caps? I understand that the bleeder resistor drains the charge from the filter cap when the receiver is powered down. Do the bypass caps play a part in that?
Btw, I'm currently restoring an Akai AA-1150. Its internal layout is different from the AA-1200, but I picked up a lot of concepts and hints from your writeup.
Btw, I'm currently restoring an Akai AA-1150. Its internal layout is different from the AA-1200, but I picked up a lot of concepts and hints from your writeup.
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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.
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.
Super Noob
Super Member
Looks like T10 style LEDs used. I believe they were AC (9V)... but the T10 LED 12V will run on AC / DC no worries.
Best of Luck.
Best of Luck.
Super Noob
Super Member
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.
LittleBill
New Member
Van_Isle, my AA-1150 produces a big speaker pop on power-down too. Power-up is nice and quiet though. I wonder if the pop is a common issue (or is it normal?) for the AA-1150. I'm trying to figure out how to eliminate the power-down pop. If one of us figures it out, we should let the other know!
