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SAE 2400L help needed for rebuild

Goesto11

Goesto11

New Member
So I am working on fixing a couple things, SAE 2400L and them a Marantz 4300. Both were push to the limits since my uncle was the one that owned them! I am starting with the SAE 2400L and going to go thru the unit and I am starting with the main output driver board, the unit calls for 2SD424's and 2SB554's transistors which as we all know are made out of unobtainium. So after reading and looking at transistor specs I narrowed it down to either MJ21196G/95G pair or MJ15024G/25G pairs to replace the originals - any input here on which to select or if there is something better please make a suggestion ?!? Many people on forums mention that using certain transistors can cause oscillations in the amp. As I was also taking apart the amp someone added fuses into the +/- 80vdc supply wires - good idea but a real hack job! They also did this on the audio outputs (I think) - anyone know this? On the bottom of the main output board there are 2 large wire wound inductors, whoever worked on it soldered a fuse into it and ran it thru the inductor - not sure if this is stock or not, any input here would be great - see pictures of what I have! There is also a bias adjustment POT on the same board for each channel, there is 330 ohm resistor soldered in parallel with the POT, not sure if this is stock or not, anyone know? The schematic I have is a bit fuzzy, anyone have a good clean one?
 

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Interesting to say the least. All those fuses were added by someone and that resistor connected to the bias pot.
 
I typically use the MJ21193 & 94’s for outputs, just my preference. If your planning on or need to replace the filter caps as they seemed a little underrated voltage wise.
 
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If your tearing this thing down watch the small transistors that are touching the heat sink as they need to be that way. I believe there bent over at a 90 with a little pad under them to apply pressure to the heat sink.
 
Thank you for the input on the power transistors!
Small transistors touching the heat-sink look to be in good physical condition, have not tested them as of yet, for the power supply filter caps the 16800uf seems to be an odd number now a days, and 17k and 18k seem to be more readily available. Anyone have a picture they took of the underside of the output board - that is how it is supposed to be?
Did not follow "PM if you’d like a good copy" better one would be great!

Pushed to the limits - I remember these amps from when I was a much younger (maybe 13 yo!), my uncle who passed was the one who had the equipment, and never maintained anything, his brother would connect anything to them and turn them up all the way! The Marantz does have a known blown pre-amp card. This SAE2400, most of the fuses that someone else added were gone so I did not try to power up any of it. They have also been sitting in a attic for the last 20 years... I figured I would re-cap at least the power supplies and outputs before giving them a test, I know that the Marantz did work just fine except the channel that went in the past. As far as adding in fuses to the unit (2400L) I like the idea, but it could be done with some class by using some of the open space on the back and adding some fuse holders, not just solder or crimp in an automotive holder - at lease make it look professional even if I am the only one who is going to look at it!!
 
This is a 2400 i bought, refurbed and sold. It had the same fuse thing in the inductors. No parralel resistors on the trim pots tho..
 
If those are speaker fuses use the smallest Fast Blow that allows you to listen at the volume you like. This will afford you the best speaker protection.
 
llwhtt said:
If those are speaker fuses use the smallest Fast Blow that allows you to listen at the volume you like. This will afford you the best speaker protection.
Click to expand...

Your right, I was thinking AC line in not speaker line out. You see 2.5AMP fast blow mentioned at times but I would think you should be looking at what your speakers can take and back track it. Also he needs to consider fuse rating for when they actually should blow which is usually higher than the rating, but for what time and how much.
 
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I guess what I find odd is they have an air-core inductor and then run a wire thru it, that will change the inductance... maybe someone thought it looked cool..
 
Few caps I want to identify, pretty sure the white ones are polyester, and the ones across the output terminals are either mylar or metal film anyone know for sure?
 

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Use some Wima’s for those white jobs or your preference.
Take a look at some Panasonic’s for that other one or your preference.
 
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