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81. [Amps] Soft start, how to determine if needed. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Sun, 28 Feb 2010 17:07:06 -0800
Yes, there is. The most endangered part are the rectifiers. The specification includes a current value called " non repetitive peak current", usually with a time limit of about a cycle or so. Use tha
/archives//html/Amps/2010-02/msg00766.html (10,377 bytes)

82. [Amps] soft start / thermistor (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Mon, 1 Mar 2010 04:45:35 -0800
By the way, an old trick that was used in tube type TV sets was to install a thermistor in series with the mains. It had a cold resistance of a few tens of ohms when cold, dropping to an oh or two af
/archives//html/Amps/2010-03/msg00000.html (6,969 bytes)

83. [Amps] Commander 2500E (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Mon, 1 Mar 2010 07:09:32 -0800
Hello... The above amp is a limited production unit using a pair of 8877s and is in mint condition (new). I am the original owner, and it has been in a non-smoking environment. The amp and Eimac tube
/archives//html/Amps/2010-03/msg00004.html (7,128 bytes)

84. [Amps] Mangian (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Mon, 1 Mar 2010 07:29:50 -0800
Ok .. do you really need the Mangeian Wire from the B- of the Filter board to the shunted amp meter?? CATHODE. I have my amp up and running with a GS-35b now and im sure that my bias isnt working rig
/archives//html/Amps/2010-03/msg00005.html (9,209 bytes)

85. [Amps] Manganin Wire /meter shunts (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Tue, 2 Mar 2010 04:52:11 -0800
The resistance of manganin wire is extremely stable with respect to temperature and this is why it is so useful as a meter shunt. An ammeter is nothing more than a voltmeter that measures the voltage
/archives//html/Amps/2010-03/msg00046.html (7,888 bytes)

86. [Amps] WD-40 (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Tue, 2 Mar 2010 19:58:03 -0800
My buddy, when he worked in the air conditioning field, use to squirt warehouse roaches with freon 12, the first drop froze them, flipped them on their back and turned them all white in the first sec
/archives//html/Amps/2010-03/msg00052.html (9,090 bytes)

87. [Amps] Thermistor's. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Tue, 2 Mar 2010 20:12:29 -0800
No so. I had a RCA CTC-9 (Circa 1959-60) with a 21" round crt that used a ?thermistor? in the transformer's primary and it did open up. Not having a ?replacement handy I just shorted the leads and po
/archives//html/Amps/2010-03/msg00053.html (8,426 bytes)

88. [Amps] MLA-2500 retrofit. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Tue, 2 Mar 2010 20:47:48 -0800
I have a buddy with TWO MLA-2500's..... and both now with flat/bad tubes. I believe one of them has a tuned input, and the 2nd one does not. Is the tube really unavailable ? If so, what are his optio
/archives//html/Amps/2010-03/msg00054.html (6,490 bytes)

89. [Amps] URL for YC-156 / 179 / 12-500pf @ 10 kv ceramic vac caps (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Wed, 3 Mar 2010 04:11:47 -0800
http://www.wa8wzg.net/forsale.htm He has all the tubes tested in the lab.. and guarantee's em. The 12-500 pf @ 10 kv ceramic vac caps are good too. I have several of the 12-500 pf caps... but mine ar
/archives//html/Amps/2010-03/msg00064.html (6,933 bytes)

90. [Amps] 120 hz hum from Henry 2k-4 (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Wed, 3 Mar 2010 23:41:44 -0800
Update to the Henry Hum. Much of the hum was magnetic pickup and moving things and better grounding solved that. It was another operator that first said "That's 120 cycle hum". I don't think it was.
/archives//html/Amps/2010-03/msg00071.html (7,422 bytes)

91. [Amps] Soft start, how to determine... if needed. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Thu, 4 Mar 2010 07:59:35 -0800
Hi Alex, no, I didn't forget what inrush protection is; that is why I suggested the 25 ohm resistor and shorting relay. You are the one suggesting installing a one ohm resistor and leaving it in the
/archives//html/Amps/2010-03/msg00073.html (10,975 bytes)

92. [Amps] snubbing diodes for vac relays / notes. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Thu, 11 Mar 2010 04:20:32 -0800
Most DC relays without indication of "+/-" polarity are non-polarized. For QSK operation, it may be best to add your own snubbing diodes to all relays, including the vacuum relays. It may also be hel
/archives//html/Amps/2010-03/msg00170.html (9,038 bytes)

93. [Amps] reed relay /vac relay (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Thu, 11 Mar 2010 13:16:38 -0800
I'm doing a similar project with my SB-220, but the HF version. I got the reed relay from Richard Measures. He also has things to say about snubbing diodes and resistors. See "High Speed Switching /
/archives//html/Amps/2010-03/msg00174.html (7,878 bytes)

94. [Amps] GI7B Question-Input matching (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Sun, 14 Mar 2010 21:13:18 -0700
I think you will find it's nearer 35ohms.Morrie flywheel action.. as well as Z matching. The tube only conducts for aprx 210 deg, NOT 360 deg. When u drive the cathode POS, you are driving the grid N
/archives//html/Amps/2010-03/msg00272.html (7,828 bytes)

95. [Amps] Teflon dielectric vraiable caps.. another thought. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Wed, 17 Mar 2010 06:55:11 -0700
Carel I am pleased that you checked into this and did the calculations. As you see, the smaller the air gap, the worst off it can become. Its almost better to have a big air gap betwen a big slab of
/archives//html/Amps/2010-03/msg00326.html (9,230 bytes)

96. [Amps] placement of RF choke bypass cap. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Wed, 17 Mar 2010 07:24:00 -0700
REPLY: You also want the cap as close as possible to the (grounded) grid of the tube, which is the common return point for the RF being bypassed. is to install the bypass cap at the base of the plate
/archives//html/Amps/2010-03/msg00332.html (9,240 bytes)

97. [Amps] Xcvr RF delay master list. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Wed, 17 Mar 2010 22:16:43 -0700
I know most rigs employ a delay of some milliseconds between the time when their amp relay closes and RF transmission begins in order to prevent hot keying problems. On some, this is even an adjustab
/archives//html/Amps/2010-03/msg00361.html (8,430 bytes)

98. [Amps] Tuned input for GG 50 mhz amp (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Sun, 21 Mar 2010 22:02:46 -0700
Hi Carl, Thanks. I thought a "Tee" would be easy to tune outside the amp in real time (one cap), and would basically achieve the same result as the "Pi". Someone elsewhere mentioned better harmonic t
/archives//html/Amps/2010-03/msg00457.html (8,328 bytes)

99. [Amps] 2A slo blow in step start (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Sun, 21 Mar 2010 22:19:34 -0700
In the past when I have had similar symptoms it was the plate xmfr shorted. Both of these instances were Henry desktop amps, one a 1KD-5 and the other a 2KD-5. You need to start unloading, ie, unload
/archives//html/Amps/2010-03/msg00458.html (7,729 bytes)

100. [Amps] B+W 800 choke. (score: 1)
Author: "Jim Thomson" <Jim.thom@telus.net>
Date: Mon, 22 Mar 2010 00:07:30 -0700
I used one as a screen choke at 2800 KHz, in a 100 kW amplifier at work. It was fine there, but not sure about 1900. This was 12 years ago. I took data on a B&W 800 using a vector impedance meter and
/archives//html/Amps/2010-03/msg00460.html (7,771 bytes)

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