Hello Jerry, I suggest not to replace that cap. with a similar one
because sooner or later you'll have the same problem. They're prone to
have losses (= lower Resistance) with time. You can try a pair of disk
ceramic capacitors (NP0) or a silver mica one, of not less than 500 V
working voltage (nearly 350V on standby at 12BY7 plate plus some
-60..-80V on final grids, that makes a total V of 430V across this
capacitor).
Glad to help you
Best regards
Guillermo - LU8EYW.
Jerry Pittman wrote:
Hello Guillermo,
Yes, you are right about the finals. I had discovered that one of the
6js6c's had gone shorted on several pins after testing them on my Sencore
tube tester. The driver also showed greatly reduced life test, so I have a
complete set of valves on the way. I'm thankful I got the tip on the C13
cap before the new tubes arrived. I was starting to think their failure
cause the voltage problem and not the other way around.
That cap is an 80pf 1KWV so if they don't have it, I'll try matching up a
couple of 40pf 500v like you suggested. Thanks for the suggestion, since
they probably won't have the original mica cap available.
73 Jerry
----- Original Message -----
From: "GGLL" <nagato@arnet.com.ar>
To: "Yaesu" <yaesu@contesting.com>
Sent: Sunday, February 15, 2004 9:20 PM
Subject: Re: [Yaesu] Problem in FT-101E -100v Circuit (Jerry Pittman)
I've forgotten to add, that you must realign the driver and final
grid section for the upper bands (best if you perform a complete RF
re-alignment as per manual), where you may note the worst tracking
difference after C13 capacitor change.
Good luck
Guillermo - LU8EYW.
GGLL wrote:
Are your final tubes fine after C13 short?; that failure will turn
very positive final tube's grid bias, which causes an indeed high
plate current. Check them before you go to the shop. If I don't miss,
C13 was a 100 pF rectangular old style mica cap. You could replace
them with two 47 pF, 500V NP0 disc ceramics in parallel as I did in
several 101's with good results.
Best regards
Guillermo - LU8EYW.
Jerry Pittman wrote:
Correction!!! Sorry Rick, I spoke to soon. I pulled the C13 cap
from the
circuit and found that it had shorted. You were dead on for the
diagnosis.
Now to go to the electronics shop tomorrow.
Thanks a Million!!
73 Jerry
WD4OIX
----- Original Message ----- From: "Jerry Pittman"
<jerryp49@worldnet.att.net>
To: "R_Davis" <WD8JJA@arrl.net>; <yaesu@contesting.com>
Sent: Sunday, February 15, 2004 5:59 PM
Subject: Re: [Yaesu] Problem in FT-101E -100v Circuit (Jerry Pittman)
Thanks for the tip Rick. I checked that cap and it appears okay, so
the
search goes on.
Jerry
----- Original Message ----- From: "R_Davis" <WD8JJA@arrl.net>
To: <yaesu@contesting.com>
Sent: Saturday, February 14, 2004 12:41 PM
Subject: [Yaesu] Problem in FT-101E -100v Circuit (Jerry Pittman)
Check the coupling capacitor, C13, between the 12BY7A and the finals.
Rick, WD8JJA.
----- Original Message -----
From: <yaesu-request@contesting.com>
To: <yaesu@contesting.com>
Sent: Saturday, February 14, 2004 12:00 PM
Subject: Yaesu Digest, Vol 14, Issue 9
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Today's Topics:
1. Problem in FT-101E -100v Circuit (Jerry Pittman)
----------------------------------------------------------------------
Date: Fri, 13 Feb 2004 12:41:26 -0500
From: "Jerry Pittman" <jerryp49@worldnet.att.net>
To: <yaesu@contesting.com>
Subject: [Yaesu] Problem in FT-101E -100v Circuit
Message-ID: <006e01c3f258$9b485ac0$6101a8c0@JerryPittman>
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Reply-To: Jerry Pittman <jerryp49@worldnet.att.net>
Message: 1
Hello to all,
HELP! I wonder if anyone has run into this problem:
My 101E was just idling along while I was working on the computer
the
=
other evening, when I started smelling something hot. I shot the
rig
=
off immediately and found that the bias control (VR1) on the
voltage =
control board (PB1547B) had over heated, as well as the (2) 10K =
resistors on either side of the control.
When I check the voltage at pin 5 of the 1547 board, I found that it
was
=
getting -160v instead of -100v. I went to the Rectifier board
(PB1076B)
=
and made tests there. When I disconnected the lead from the -100v =
terminal, the voltage shows -60v but with it is connected it shows =
-160v. With the lead disconnected I also tested it for AC voltage
and
=
it shows 125vac as well as -60vdc.
I checked all the components on the 1076B board and found all okay,
but
=
just to be sure I hadn't missed something, I put in a used PB1076B
board
=
and found all of the same readings. I had already checked all of
the
=
other voltages coming and going from the 1076B and all are correct =
except the -100v. The voltages from all of the transformer taps
appear
=
to be within range as well.
Does anyone have an Idea or run into this before?
Thanks in advance for any responses.
Jerry
WD4OIX
jerryp49@att.net------------------------------
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