KB5MD
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« on: February 11, 2014, 02:00:22 PM » |
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I've been converting a McGohan 150 watt p.a. amp to a speech amplifier. The original amp used 8417 tubes which are like gold these days, so I converted to 6L6's.
The 24 ohm resistors in the plate leads were toast so I replaced them with new ones from the local supply house. After a time of knashing teeth and pulling hair because
it would not work, I checked the plate voltage and discovered what was to supposed to be new 20 ohm resistors were actually 20,000 ohms. Gotta teach that clerk the difference
between 20 and 20,000.
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W2VW
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« Reply #1 on: February 11, 2014, 02:01:37 PM » |
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You may be met with resistance.
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Jim, W5JO
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« Reply #2 on: February 11, 2014, 02:09:17 PM » |
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Roy that will be a lot like teaching a checkout clerk how to count change without the cash register or calculator.
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Ralph W3GL
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« Reply #3 on: February 11, 2014, 02:35:39 PM » |
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You may be met with resistance.
RESISTANCE IS FUTILE... |
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73, Ralph W3GL
"Just because the microphone in front of you amplifies your voice around the world is no reason to think we have any more wisdom than we had when our voices could reach from one end of the bar to the other" Ed Morrow
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KB2WIG
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« Reply #4 on: February 11, 2014, 03:39:55 PM » |
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The guys' name wasn't Mho, was it?
klc
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What? Me worry?
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W2VW
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« Reply #5 on: February 11, 2014, 04:06:45 PM » |
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Ohm my god this brings out all the cornball stuff.
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KB2WIG
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« Reply #6 on: February 11, 2014, 06:24:17 PM » |
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" this brings out all the cornball stuff"
Well, I can understand your reluctance to get involved.
klc
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What? Me worry?
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Steve - K4HX
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« Reply #7 on: February 11, 2014, 06:31:55 PM » |
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Get series, you guys!
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KB2WIG
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« Reply #8 on: February 11, 2014, 07:01:40 PM » |
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Sorry Steve, I know this board is a drain at times. But don't fet, things will be okay.
klc
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What? Me worry?
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KA8WTK
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« Reply #9 on: February 11, 2014, 07:14:48 PM » |
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... I checked the plate voltage and discovered what was to supposed to be new 20 ohm resistors were actually 20,000 ohms. So, what was your reactance to the discovery? |
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Bill KA8WTK
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Steve - K4HX
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« Reply #10 on: February 11, 2014, 07:26:15 PM » |
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What do you base that on? Sorry Steve, I know this board is a drain at times. But don't fet, things will be okay.
klc
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W2VW
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« Reply #11 on: February 11, 2014, 07:58:08 PM » |
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The source.
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W7TFO
WTF-OVER in 7 land Dennis
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IN A TRIODE NO ONE CAN HEAR YOUR SCREEN
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« Reply #12 on: February 11, 2014, 08:34:45 PM » |
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Be it ever so humble, there's no place like Ohm...  73DG |
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Just pacing the Farady cage...
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w1vtp
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« Reply #13 on: February 11, 2014, 08:38:10 PM » |
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Seriously, I'd like to see a tech... item about converting from 8714's to 6L6 or the like. I have a perfectly functional Bogen M60 amp and I KNOW I won't be replacing them if they ever fail. This is a vy hi performance amp and really sounds good. So, substitution includes good results. Perhaps a tall order
Al
Now. Back to the thread. Thanks for your indulgence
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WU2D
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CW is just a narrower version of AM
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« Reply #14 on: February 11, 2014, 08:42:51 PM » |
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Give us a dogbone and we will chew it...
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These are the good old days of AM
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Patrick J. / KD5OEI
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« Reply #15 on: February 11, 2014, 10:59:47 PM » |
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I'm shocked that you used 6L6s.
I'd use 6550's not 6L6's. It's the current required, and maybe the voltage is higher than the 6L6GC accepts. I assume there are four tubes.
I converted a Bogen MO-200 to 6550's and it worked great. For 6550, EL34, or 6L6, more bias is needed and maybe more plate voltage on the driver as the 8417 needs only a little bias, and also only little drive.
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Radio Candelstein
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KB5MD
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« Reply #16 on: February 12, 2014, 01:13:55 AM » |
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The reason for using 6L6's is because I have quite a few. I used a large resistor to drop the screen and plate voltage. I drive it with a broadcast console, so there is plenty of drive. Works for me.
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flintstone mop
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« Reply #17 on: February 12, 2014, 06:46:42 AM » |
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Be it ever so humble, there's no place like Ohm... 73DG heeeer we go!!!! Good one It's cabin fever setting in and this DAM winter that won't stop!!!!!! |
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Fred KC4MOP
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KA9EGW
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« Reply #18 on: February 12, 2014, 07:29:09 AM » |
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Me like-um EL34's...as long as they're run at lower limits than in my "Scratchy Apache"...
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Steve - K4HX
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« Reply #19 on: February 14, 2014, 07:18:40 PM » |
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I assumed that was bypassed. The source.
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Opcom
Patrick J. / KD5OEI
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« Reply #20 on: February 15, 2014, 02:34:54 AM » |
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The reason for using 6L6's is because I have quite a few. I used a large resistor to drop the screen and plate voltage. I drive it with a broadcast console, so there is plenty of drive. Works for me.
Then it works indeed! Would you mind posting a picture and the schematic for that amp? I've never even seen one of that brand. |
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Radio Candelstein
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