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Re: Frankie Confusion [message #13199 is a reply to message #13187] Wed, 17 March 2010 06:25 Go to previous messageGo to previous message
carlc is currently offline  carlc
Messages: 143
Registered: July 2006
Location: Summerville, SC
Senior Member
From my tech:

I just got through doing this testing described and I duplicated the results almost to the letter...there was a few differentials...

I will put my answers in red next to the information supplied...

Here are some results from testing on of my Frank heads last night.

I unsoldered the blue wire on the input side of the driver transformer, and the resistance across that and the red wire was 9.7 ohms 9.6 ohms

I then switched to the output side of it where I unsoldered the tan wire and the orange wire.
The resisteance across the tan and green wire was 5.9 ohms. 6.1 ohms

Resistance read across the orange and brown wire was 6.1 ohms. 6.4 ohms

I then set out to test some A/C drive volatges.
I hooked the amps speaker jack up to a 4 ohm test load and my O-scope. I pumped in a 1k test tone into channel one( really does not matter which channel though) untill I got the output of the amp up its maximum RMS power.

At this point the amp was outputting 19.11 volts, 20.3 volts or 91.2 watts and this was with an A/C line voltage of 118.9. 122.6

With the amp still drivin to this RMS power I took my meter now set for A/C volts and placed it across the red and blue wires on the primary of the driver transfomer where I read 12.85 vac.

Switching to the secondary side I then read 4.93 vac across the tan and green wire, and 4.99 vac across the orange and brown wire.
These voltage test where done with all of the transformers wires hooked back up and with the amp putting out the wattage stated as above.

As you can see the higher output voltage seen across the brown and orange wire confirms the higher resistance reading also seen across those two wires.

Pass this info along to your tech and he should then be able to pin down whats going on with your amp



I once again went through every voltage on each transistor on every board and they were all withing a few decimal points of the schematic...At this point I am at a brick wall in finding what may be going wrong in this amp...every resistor on the driver board checks out and I have changed two of the transistors on this board with no obvious change...This shouldn't be difficult as this is a very basic circuit but I am stumped...unless the transformer , a capacitor or a transistor is breaking down at certain frequency levels I don't know what more to do with this...

Again I am open for any and all suggestions...

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