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Whats the differnce in outputs?

Thanks onplane! I will have to work on this during winter break since I left that 85lb-beast-of-an-amp at home. My Mc schematic is enroute to me.
I still have a couple questions.
If all goes as planed, will the only none operational thing on the reciever will be the tape-out jack as they were meant to be used? ie. the speaker outputs will still work fine?
Since the outter part of the tape-out jack is currenty connected to the body, is that ok to leave as the ground?
I am trying to locate the power amp board... would that be the one that runs the transistors attached to the big heat sinks?
 
I really think your best bet would be to get one of these, and don't hack on your Mac. This will reduce your speaker level output to a level that will be safe for the inputs of your power amp. No soldering iron required, and they're cheap, too!
PDRM0021.jpg

PDRM0020.jpg
 
Here are some pics to work with. Click for larger version, but they are pretty big.
Top view

Bottom view (cover removed)

back of the RCA outputs

Circut board on the bottom

Circut board on the top(needed to remove cover)
 
FreshMaker said:
Thanks onplane! I will have to work on this during winter break since I left that 85lb-beast-of-an-amp at home. My Mc schematic is enroute to me.
I still have a couple questions.
If all goes as planed, will the only none operational thing on the reciever will be the tape-out jack as they were meant to be used? ie. the speaker outputs will still work fine?
Since the outter part of the tape-out jack is currenty connected to the body, is that ok to leave as the ground?
I am trying to locate the power amp board... would that be the one that runs the transistors attached to the big heat sinks?
Click to expand...


Everything should work as before except the tape output.

Now when you cut the tape output wires, tape them up and leave in place so that you can easily return to the original configuration. Leave the shielded connections to ground intact. No reason to unsolder those.

Your new wires must be shielded cables and yes you must connect the shielded part to ground. The outside part of the tape out jack MUST be grounded, or the signal you send to the power amp will be just loaded with AC hum.

The power amp looks like the board in your 2nd last picture. These boards have wires going to the power transistors mounted on the heat sinks. The tricky part is figuring which wire is the signal in to the power amp. I'd guess the gray wire on the right hand side of the power amp board, but that's just a guess, because I can't see where the wire starts.

Once you find the audio signal in, look at the other side of the board to see where it leads. Usually it will go directly to a blocking cap. You want your signal tap to be on the other side of that cap and naturally, the shield should be soldered to a good ground point.

Regards,
Jerry
 
Ah, I didn't realize the shielding part of a shielded cable required grounding... That was a bit of my confusion. Going off of the shielded cable idea, there is a shielded cable running into the board (noted in the pic). Assuming Mac is taking care of thier signal wire, that should be what we are looking for? It has that white capacitor in its circut after it passes through a 150 resistor.

Here are some more pics
Back of board

Back of board with notes

This is a repost with some notes


This view shows the wires from board to transistors. Most of the wires connect to transistors mounted to the body. I assume that means not as much heat and thus not what we are looking for. The two colors that go to the heatsink transistors would be white and orange/white
Top view
 
Looks like you found the input. To be absolutely safe, however, it would be a good idea to check the schematic.

We just want to make sure no dc component is sent to the power amp.

Regards,
Jerry
 
Good luck.

The whole project scares me, man.

A personal pipedream is to locate a 1700 at an estate sale or something, you're looking to mess with one! :)
 
Mess is a dirty word... Modify sounds better ^^
Besides, It will be an addition of two carfully placed wires. nothing major :)

I am currently just waiting for the schematic to arive and then I will try some tests.
 
Another approach . . .

FreshMaker,
Another approach, one which won't involve cutting into your 1700, would be to make a cable which plugs into the headphone jack, and delivers signal to a pair of RCA plugs to connect into you power amp. Signal levels are generally reduced at the headphone jack so you won't accidentally blow your brain out your nose while listening with 'phones. This reduction should also help protect the two components from each other. Just a thought . . .
 
I had a 1700 here for a while and near as I recall, EW is right about rear panel space. There were pre-amp/tone boards mounted above the chassis and driver boards for the four Motorola outputs mounted under the chassis. My experience with that unit says that I would rather have a root canal than try and modify one.

Rob
 
i want to do this as well

Hello,

i know this is an old thread but i want to do this as well, however the pictures dont show up anymore.

any chance of getting the last pic that shows your work?

Thanks for the great work and onplane is amazing to help you.

Phil
 
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