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Messages - g1

#706
  Looking again at the schematic, the thermal fuse goes between the 7th tab and one of the 0 taps.  So it can easily be bypassed and the transformer rewired for 120V operation.
#707
Tubes and Hybrids / Re: Peavey Classic VT Blowing Fuses
October 08, 2014, 01:27:05 PM
  Try with power tubes removed.
#708
   Those readings are all good.  Where is the 7th tab on the transformer?
The schematic shows that it is the one with the thermal fuse.  You need to measure resistance from the 7th tab to any of the other 6 on the primary.

The funny thing none of us have mentioned, this transformer can be wired up for any voltage, so it could have been rewired and you would not have needed the external transformer.

Edit:  I think the 7th tab is where the white is connected up on the secondary side (with the orange and black wires).
#709
  The fact that you measure the same voltage on all taps of the primary is precisely the reason we suspect the primary is open.
  As others have suggested, you must check the resistance of the primary winding.
#710
  I also see 19V marked on that transformer.  Aside from the secondaries I don't see what that could possibly refer to.
  Maybe whoever drew up the schematic with the (24VDC listed where it should show AC), specified that the transformer maker also mark it that way?
#711
Amplifier Discussion / Re: De-Soldering Station?
September 25, 2014, 10:53:08 AM
  I think that the one piece unit would turn out to be a major disappointment.
#712
  The piece of wire connecting those 3 pins on the jack must be removed.  The way it is wired all jack contacts are grounded and it can not work.
  Also, the pot you replaced (3rd from jack), it looks like one of the legs is bent over and the solder may be touching the ground trace.  You need to make sure it is only touching the trace it connects to.
#713
Amplifier Discussion / Re: Wharfdale pm700 pa schematic?
September 19, 2014, 11:49:11 AM
  Thrift shops can be very cheap sources of consumer electronic items to be used for parts.
#714
Amplifier Discussion / Re: Wharfdale pm700 pa schematic?
September 11, 2014, 12:23:51 PM
Doc, is that the service manual from elektrotanya ?
#715
Amplifier Discussion / Re: Wharfdale pm700 pa schematic?
September 10, 2014, 10:53:16 PM
 I don't think it will be like the Yamaha:
#716
Tubes and Hybrids / Re: kay model 720 => AB mod
September 10, 2014, 02:00:06 PM
  Just to add a little to what Enzo said, to increase the power supply usually means installing a larger power transfomer, and some amount of re-design.
  So your point about needing a different amp to get (a significant amount of) more power is probably correct.
#717
Amplifier Discussion / Re: Marshal JMP 2099
September 10, 2014, 12:18:28 PM
 :tu:
#718
Amplifier Discussion / Re: DIY amp directions
September 09, 2014, 02:14:37 PM
 Ok, that resistor assortment looks much better than I expected.  I was worried there might just be 500 individual resistors thrown in a bag for you to sort out.  Looks like they are separated by value, with more of the most common values.  Price is reasonable, the only thing to keep in mind is they are 1/4 watt, which is fine for any battery operated device, but may not be useable in some other powered circuits you may build in the future.

Most of those prices you paid are fairly reasonable, except for the very generic individual electronic components, like the caps, led, and battery snaps.
It's fine for a one off project, but if you do more building check an actual electronic supplier such as Mouser, Newark, Digi-key, etc.
  As Roly pointed out, simple items like some of those caps are inflated 10 to 100 times for price.

#719
Tubes and Hybrids / Re: kay model 720 => AB mod
September 09, 2014, 01:59:11 PM
 Ilyaa:  You probably read about it, but I'll mention it for others who may read this thread, the bias circuit you posted with the resistor that connects to the HV AC,
(http://music-electronics-forum.com/attachments/547d1175892694-kscan_0001.gif) that circuit will only work if the PT is center-tapped.
#720
Amplifier Discussion / Re: Marshal JMP 2099
September 09, 2014, 01:37:48 PM
  This is with or without the transformer?