Gutting Out An Bose 1801 Amp

[Cambe]

Hello Everyone,
I have been reading the posts and have decided to attempt to build a Aleph or Zen.I have a Bose 1801 amplifier that fried one channel and the sub that was connected to it.I want to use the chassis and heatsinks and junk box the rest.Any suggestions on what amp Aleph or Zen I could build in the chassis?
Sincerely,
Cambe

 

[dshortt9]

Tell us the size of the heatsink.

 

[Cambe]

1801 Haetsink Size

Hello dshortt9,
I will send a picture as soon as I can figure out how to. The heat sink is an L shape.
l l l l l l l
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The short leg is 6" long 6.375" tall and the height of the fins are1.25" with base of heatsink 2".The long leg 14.25" Long,6.375" high and same fin depth.The fin spacing is.625"and where the L forms a right angle theirs a fin at a 45 degree angle that looks like trees that I use to draw in the first Grade.I hope this helps.
Thank you,
Cambe

 

[woody]

If one channel still lives you might fire the amp up look at the
rail voltage and measure the bias in the chanel that still lives.
Then if you can find the bias adjustmant pot you might raise the bias till the heatsink starts to get hot and get an idea about
the thermal capacity from there.

regards bob12345678

 

[Cambe]

1801 voltage / bias measurements

Hello bob 12345678,
I am a newbie in true sense of the word. Remembering,how powerful the amp sounded driving Bose 901 series ones listening to Egar Winter's, Frankenstien at listening levels I dare not today.Plus, that awful sound I heard the Sunday morning while having breakfast and listening to FM radio,along with "what's that smell"I ran to the den where my rig is and my right channel sub's woofer was sticking out like a zit.I have just taken the cover off of the beast and confirmed my earlier suspicsions.The transformer is 7.5" in dia. and about the same in height.Their is 2 -14,000 mF/ 100v capacitors 3"x 5.375".It still smells.It would have set the house on fire if I hadn't pull the plug when I did.I don't trust plugging the thing in.
Cambe

 

[Nelson Pass]

A Bose 1801 should support 200 watts rms, which is
OK for 60+ watts total of Zen or Aleph. (1 X 60 or 2 X 30 )

 

[Cambe]

Hello Everyone,
And thank you very much,Mr. Pass.I now know that I can at least get to try one of your designs.Now which one should be suitable following your guidelines,Zen or Aleph?
Sincerely,
Cambe

 

[dshortt9]

My suggestion would be an Aleph 3 as you could make a stereo amp on one chassis. PCB available here. http://web.vip.hr/pcb-design.vip/ matched FET's here: http://www.diyaudio.com/forums/showthread.php?threadid=5015

Good luck!

 

[Nelson Pass]

If you can tap the Bose transformer to 240 V input and
operate it at 120V, you might be able to use it.

 

[Peter Daniel]

Any drawbacks to such use of transformer Mr Pass? I was thinking about using trafo from A75 for Aleph X in that way. High power, low voltage is hard to get without going custom.

 

[Cambe]

Bose 1801 Remod

Hello Everyone,
I am very pleased to hear from you dshortt9 and Mr. Pass!This is very good news, indeed!I have already e-mailed the gentleman a-
bout the semi's.And will be proceeding with quickness to order the
the PCB's.I'm in the process buying a used Tek 475 or 465 oscilloscope,a signal generator and ac milli-amp meter.I don't know,right now if the transformer is in good operating condition or
not,I am still learning.I will pull the transformer out and let a friend of mine check it.If it checks out ok I'll try what you recommended,Mr. Pass.
Sincerely,
Cambe

 

[Nelson Pass]

Running 240V primaries at lower voltages works just fine,
and I do it whenever I feel like it. Typically they run a
bit warmer, but they tend to buzz less.

 

[Cambe]

Hello Mr. Pass,
Thank you,may not sound like alot but its what I mean.You have planted many seeds.And they are producing lots of good fruit.I really had not thought about using the exsisting transformer.Now,I will be extra careful taking it out,so I can have some room to work with.Are the
0.47 ohm resistors 5w or 10w ? Also,where can they be bought?
Thanks For Your Support,
Cambe

 

[trigon]

Hi

5W is ok.

Trigon

 

[Peter Daniel]

You can buy 3W Panasonic resistors here http://www.digikey.com/. They OK instead of 5W.

 

[Cambe]

Hello Everyone,
Thank you,trigon and Peter Daniel.What is the ratings for the 9.1v
zeners and the 1 nF capacitor?I am ready to order the parts.
Sincerely,
Cambe

 

[Peter Daniel]

Some people commented that 0.5W zener sounded better than 1W and you can use any. As for cap any rating is good, they usually start at 63V.

 

[Cambe]

Hello Peter Daniel,
I really appreciate yours and everybody who has helped me get this project under way.
I'll keep everyone informed on my progress.
Sincerely,
Cambe

 

[djk]

Nelson's idea about the transformer is excellent, it is about +/- 85V at 1.5KVA .With the primary wired for 240V and run on 120V it should give you about +/- 42V .Or you could consider trading someone if you need a different voltage.

 

[Cambe]

Hello Everyone,
From just looking at the left channel PCB which is the damaged side of the amp.I took the board out and all the components under the output transistors is charcoal.I'm still working on getting the transformer out of the chassis I need a very large hex
wrench,to remove it which I don't have right now.Isn't the42 volts
+/- going to be to much for the Aleph 3?What voltage and current rating do I actually need for a stereo amp?
Sincerely,
Cambe