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Author Topic: Help adding Effects Send and Return Loop, need a schematic (example)  (Read 148 times)

smackoj

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I have a 1979 Premier P50R ss amp and I would like to put a fx loop between the preamp and the power amp. Does anyone have a good, working example / schematic they could post?  Here's a picture of the little amp. It only makes about 10 watts so I would like the option of bypassing the preamp and seeing what kind of power and tones I can find using other pedal type preamps. Thanks 
« Last Edit: March 14, 2017, 03:54:09 PM by smackoj »
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g1

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Re: Help adding Effects Send and Return Loop, need a schematic (example)
« Reply #1 on: March 14, 2017, 04:50:55 PM »

If you have a schematic for the amp, post it.  If not, you will need to draw one.
Otherwise, for an example just look at any low power amp schematic that has a loop.
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smackoj

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Re: Help adding Effects Send and Return Loop, need a schematic (example)
« Reply #2 on: March 15, 2017, 02:27:04 AM »

I have not been able to find a schematic for this one anywhere. I'll pull the chassis again and try to draw it.
thanks
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J M Fahey

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Re: Help adding Effects Send and Return Loop, need a schematic (example)
« Reply #3 on: March 16, 2017, 01:11:59 PM »

Mmmmmhhhh, that´s a very old amplifier, your internalpicture shows almost nothing, not even a PCB.

Pull that chassis out in the Sunlight or equivalent and send us a couple sharp and defined pictures (the back one is somewhat unfocused, while the front one is perfect) , *maybe*  we can "detect" where preamp ends and power amp starts, so you can add a couple (or single switching) jack there.

That said, you won´t get more power than what´s available there, you can test different preamp sounds though.

We´ll wait for our friend Galaxiex to chime in, he´s a fan and expert on old weird SS amps like that one ;)
Just warn you that even he had to hand draw the schematics for the ones he bought  :o
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galaxiex

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Re: Help adding Effects Send and Return Loop, need a schematic (example)
« Reply #4 on: March 17, 2017, 01:40:39 AM »

Thanks JM.  :)

I've not seen one of those in person, but have noticed the occasional one on ebay.

Ya, a better picture of the inside would be helpful.
When I saw this thread I googled for a schem.... not much out there.

Depending on the circuit board(s) it could be easy or "hard" to sus out a schem.

It's not actually hard to reverse engineer the circuit, but it can be very labor intense and VERY easy to make a mistake.
I've done that on almost every board I've traced.  ;)

Sometimes the circuit topology is very confusing and it only comes to light once you have the schem complete....
and THEN you notice the mistake and how obvious it is.

The average amp like this takes me a week or 2 or 3, to get a schem drawn up.
That's cuz I have a regular job and only work on the amp in spare time.

Take lots of breaks, especially if you find the going tough and get frustrated with how long and slow it's taking.
I start to get a little cross-eyed after staring at the board and then computer screen for too long when doing this.

Take pics of all connections and label wires and such BEFORE taking stuff apart or un-soldering things,
and you WILL need to un-solder stuff to get the board out so you can trace it.

My best (favorite) tool is an electric vacuum solder sucker.
I could NOT do this without it!

Good luck!  :)
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smackoj

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Re: Help adding Effects Send and Return Loop, need a schematic (example)
« Reply #5 on: March 17, 2017, 01:16:55 PM »

I will gladly pull the chassis and takes some pics. No problem. Thanks for your input.
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