Need help with power supply potentiometer design

[Mike_J]

I have attached the circuit I created to beef up 1/2 watt potentiometers so I can use them to adjust the power supply voltages in my Sluckey inspired Plexi/800 project.  The problem I am having is I am running out of 1K/2W resistors and need to try to use one per pot.  I am also using thin (probably 28 gauge) wire because they are attached to the alligator clips I prefer to use.

Can someone suggest a method that would allow me to use only one of the resistors?  Won't one 2 watt resistor make the potentiometer effectively 2-1/2 watts?  Do you see a problem using such thin wire for a short period of time?

Thanks
Mike

[2deaf]

If you're doing what I think you're doing, you may be able to benefit from a learning experience I had when I was a teenager.  I tried to reduce the E_bb voltage by inserting a series pot after the PI point.  It shorted through the pot and through me.  I didn't like it.
   

[sluckey]

Won't one 2 watt resistor make the potentiometer effectively 2-1/2 watts?

Doesn't work that way. You will need to use a expensive 2 watt pot.

[Mike_J]

If you're doing what I think you're doing, you may be able to benefit from a learning experience I had when I was a teenager.  I tried to reduce the E_bb voltage by inserting a series pot after the PI point.  It shorted through the pot and through me.  I didn't like it.
   

I guess you wouldn't like it.  Thank you for the heads up.

Thanks
Mike

[Mike_J]

Won't one 2 watt resistor make the potentiometer effectively 2-1/2 watts?

Doesn't work that way. You will need to use a expensive 2 watt pot.

Sluckey

Most unfortunate development but glad I found out before I got myself killed doing it the way I was doing it.

Mouser has some one watt trimmers.  Do you think they would work for the short period of time I will need them?  I could make a board out of G10 with all the pots on them like the amp has nodes.  Lift one side of each power supply resistor off the circuit board and connect the relevant pot to that spot using alligator clips.  Would be extra nice to have digital voltage meters for each pot to expedite the process.  Do you know any source of cheap digital DC voltage meters that could be placed next to the trimmer?

My next amp will be the Sluckey inspired JTM45/800 stereo amp and I will be in need of this kind of system again if I am going to do things right.

Thanks
Mike

[shooter]

don't know your Volt drop across your resistor, RS did had like a 10$ palm sized meter, here's a low volt that you can scale to taste;
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2152323_-1

n the smaller the wire the better...AS a fuse n you can smell it!!!!!
keep one hand in your pocket

[DummyLoad]

http://www.ebay.com/itm/Ohmite-Rheostat-RHS25K-25K-25W-25-000-Ohms-25-Watts-25-Kohms-/221584710377?pt=LH_DefaultDomain_0&hash=item33977a5ae9

[sluckey]

I think you're tackling this problem the wrong way. Your amp is built with turret boards. Just remove the particular dropping resistor and use two gator clip leads to connect a different value dropping resistor. For $18 you can have two of every value 3 watt metal oxide resistor that Doug sells.

[Mike_J]

I think you're tackling this problem the wrong way. Your amp is built with turret boards. Just remove the particular dropping resistor and use two gator clip leads to connect a different value dropping resistor. For $18 you can have two of every value 3 watt metal oxide resistor that Doug sells.

Sluckey

That is the way I am going to go.  I just bought five cheap dmm from Harbor Freight for $6 each.  Went to Radio Shack and got the snap on alligator clips to fit the dmms.  Will buy two of every type resistor as you suggested.  By having enough dmms I can tell the impact of each change which hopefully will expedite this little project.

Thanks
Mike

[Mike_J]

don't know your Volt drop across your resistor, RS did had like a 10$ palm sized meter, here's a low volt that you can scale to taste;
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2152323_-1

n the smaller the wire the better...AS a fuse n you can smell it!!!!!
keep one hand in your pocket

Unfortunately I had an abdominal aortic aneurism about five years.  Because of the loss of blood and six weeks in a coma I lost my sense of smell so I would not smell it burning if it was on fire right under my nose.  At the same time my short-term memory was severely impaired which is why I now have to do crazy things like set up seven multi-meters so I can see all of the measurements at the same time.  Otherwise there is no way I would remember what impact making different changes made.  I have to see them all at the same time or I can not process the differences.

Thankfully there are kind people on this forum that provide enough guidance so I can manage.

Thanks
Mike