RE: amplifone HV

The "singing" BU406D is caused by a much too high frequency waveform at the
BU. Check your resistors in the 555 circuit - especially R6 and R7. I had
this happen when I had a 47k resistor at R6 instead of a 4.7k.

On the last one, check your over voltage - or disable it temporarily.

JB

-----Original Message-----
From: Curtis H. Wilbar Jr. [mailto:vector@hawkmountain.net]
Sent: Tuesday, April 09, 2002 8:51 AM
To: vectorlist@synthcom.com
Subject: VECTOR: amplifone HV

I have three amlifone HV boards (1 blue, 1 green, 1 beige, all with
resistors and diodes at the regs). With the BU406D removed on each they
all have about the same waveform (one has a bit higher frequency, but all
the same shape) at BU406D's base.

Only 1 has HV... another makes a quite squealy kind of noise, gets the
BU406D
hot (but doesn't blow it), and produces no HV. The last one produces no
HV, makes no noise, doesn't blow BU406D and doesn't produce HV.

I'm guessing I have 1 good red, and 2 dead red hv transformers. Before I
presume that, is there any last things I should check knowing the BU406D
transistors are fine, with good waveform, but no HV ?

Thanks,

-- Curt

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Received on Tue Apr 9 07:30:27 2002