Roland KC 60 amp

[bsco]

Ok. Connected up a set of headphones and ran a guitar through the amp...The current peaked over 100 ma.....so I guess the problem must lie somewhere in this area....I will have to dig further.....the current does not go over mid 60's ma when a speaker is connected....and that is at close to max volume.....
Cheers

[52 Bill]

Ok. Connected up a set of headphones and ran a guitar through the amp...The current peaked over 100 ma.....so I guess the problem must lie somewhere in this area....I will have to dig further.....the current does not go over mid 60's ma when a speaker is connected....and that is at close to max volume.....
Cheers

If I read the schematic correctly, the rated output for the headphone jack is 100 ohms. What type of headphones did you test with? Does the owner use headphones with this amp?

Maybe try connecting 100 ohm resistor dummy loads on the phone jack and see what the maximum current draw is.

[bsco]

Ok.52 Bill.......I will check that out.....
Cheers

[g1]

Hey Bernie! Where you been, digging out from the never ending blizzard? Yikes, that's some amount of snow the maritimes have got this winter, my condolences.

Where are you measuring that 100mA, at the LV supply fuses?

[bsco]

Hey Bernie! Where you been, digging out from the never ending blizzard? Yikes, that's some amount of snow the maritimes have got this winter, my condolences.

Where are you measuring that 100mA, at the LV supply fuses?

Snow???? If I had some way to keep it from melting I could sell it over in the Middlle East somewhere......At one point it was about 10 feet high in the driveway....and the driveway is about 25 feet or more long.....and about 10 or 12 feet wide.....
Yes, I have two dmm's set up to measure current where these LV 100ma fuses go....these fuses are rated for 100ma......and IC4 is the ic that drives the headphones, sub out and line out.....I will have to check the line out to see if the current increases with a load there....any suggestions are always welcome...
By the way....how is the weather out in BC???? too bad you are so far away.......we could crack open a few cold ones.....I got the deck shoveled off and hopefully will have the BBQ ready this weekend....weather permitting!!!
Cheers,
Bernie

[g1]

By the way....how is the weather out in BC????

Very nice, but I'm in Mb.

A couple things to consider, maybe the base current through those fuses is too high from some other cause, and the headphone IC is just putting it over the edge?
Or one of those 3 caps breaking down?
Oscillation?
The 4556 is supposed to be able to deliver 70mA into load, so I would think it would use that much, but the spec. is 12mA max. operating current so that's a bit confusing.

[bsco]

Thanks G1...What caps are you referring to?? the elect??
Cheers
P.S. Sorry about that...thought you were in BC.......

[g1]

The 3 caps at the headphone jack circuit. In the diagram Jazz posted they are labelled C51, C52, & C53.

P.S. Sorry about that...thought you were in BC.......

When I last worked for the company it was in BC, so that's probably what you are thinking of.

[bsco]

actually G1, that was what I was thinking...Anyway, I'll check out those caps later today and let you know what I find....
Cheers

[bsco]

Got tied up with other stuff...I connected two 100 ohm resistors to a TRS plug and used that for the headphones...Then I connected a voltmeter across the resistors to check the voltage drop(AC) and took a jack cord and plugged it into input 1...I turned up ALL the controls to max and placed my finger on the center tip of the jack cord and measured the current flow where the two fuses would be located.....The current rose to about 110mA on each current meter.....there was a voltage drop of about 5V at the resistors which are connected to the headphone jack.....I kept my finger on the tip of the jack cord for a few minutes to see if the current would go higher....it did not.....and I checked the regulators to see how hot they were to the touch.....they felt the same.........so.........according to that, if I was to install two fuses with a slightly higher rating...say 125 or 150mA, then this might work???? the current draw is just slightly above the limit of the original fuse ratings which explains why it will work for awhile before blowing the fuses....any suggestions......the caps checked ok....I did notice that when at idle, on side was drawing about 10mA higher than the other but when I toucked my finger on the tip of the jack cord, the current on both 15V rails didn't go any higher than 110 mA...maybe the slight increase is caused by general aging of the components in general....at idle the positive 15V rail is about 10mA higher(60mA) than the negative 15V rail (50mA)....and the power led is connected to the positive 15V rail...comments.....anyone........

[g1]

Has the customer verified that they are using phones when the fuse blows?
Can you post the power supply schematic?
I see that the KC-350 uses slow-blow fuses for the LV supplies, does this one show fast or slow?

[Jazz P Bass]

Here is the KC 150 PS.

kc-150 pwr supply.pdf

[bsco]

Has the customer verified that they are using phones when the fuse blows?
Can you post the power supply schematic?
I see that the KC-350 uses slow-blow fuses for the LV supplies, does this one show fast or slow?

The schematic shows MRT 100mAL...I will have to check to see what I had installed.......maybe I ordered F/B and didn't realize it......I will check it out and let you know.....Jazz....thanks for the schematic.......much appreciated.......

[Jazz P Bass]

We seem to be at a slight disadvantage here.

I keep posting bits & pieces of the KC150 (as that is the 'closest' one that I have).

Why do you not post the KC60 schematic?

Edit: an NDA was signed by the OP.
I can respect that.

[g1]

The schematic shows MRT 100mAL

Not MRT T100mAL ?