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Author Topic: TR4C uncommanded transmit.  (Read 1232 times)
W9VOX
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Posts: 14




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« on: December 30, 2018, 01:28:07 PM »

Picked up a TR4C with a known t/r relay issue. I was hoping bit was a sticking relay but nothing is ever that simple in my world...
The rig goes into transmit uncommanded...no mic connected or change in any switch state. I’m thinking that the caps are bad. (Original caps are still installed)
Any other thoughts/recommendations are appreciated.
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WA4JQS
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Posts: 280




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« Reply #1 on: December 30, 2018, 08:33:33 PM »

Sounds like a cap has shorted or the relay is welded closed. does it go into transmit as soon as you turn it on ? or does it take a while.
Get on the Drake Tech net 7.238 Sundays at 4:00pm est. or drop Ron Baker WB4HFN an email. it is on his website.
73 Tony WA4JQS
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ZS5WC
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Posts: 715


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« Reply #2 on: December 30, 2018, 11:31:58 PM »

 :)If the rig is turned on, and shortly after goes into transmit when tube emissions are up, check the vox relay tube and associated components.
Those carbon resistors could drift WAY off original values, as well as caps that can become leaky.
73 de William
ZS4L / ZS5WC
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VU2NAN
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« Reply #3 on: December 31, 2018, 12:24:53 AM »

Hi OM Greg,

Here are some tips.

http://www.wb4hfn.com/DRAKE/DrakeArticles/TechTips/TroubleshootingAntRealy.htm

You may also check the custom-built capacitor C145 (4 electrolytic capacitors housed in a can). They may have gone dry and would need to be replaced with individual capacitors.

Good luck!

73,

Nandu.
« Last Edit: December 31, 2018, 12:34:22 AM by VU2NAN » Logged

W9VOX
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Posts: 14




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« Reply #4 on: December 31, 2018, 06:45:49 AM »

Thanks everyone for the recommendations...

I should have mentioned the following:

- T/R relay was inspected and was not stuck but was a little dirty.  I have cleaned it...
- the rig goes into transmit after it warms up a bit.

Nandu, I was on the same page as you and have ordered the can capacitor from Hayseed Hamfest LLC.

I actually tried to check in yesterday to the Drake Net but could not hear Net control. I'll try sending an email to Ron WB4HFN.

73, Greg W9VOX
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WB4SPT
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Posts: 784




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« Reply #5 on: January 04, 2019, 03:08:35 PM »

gassy VOX tube?  total guess at this point.  V19 either of the two sections would be the area I would look into.
« Last Edit: January 04, 2019, 03:11:38 PM by WB4SPT » Logged
W9VOX
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Posts: 14




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« Reply #6 on: January 09, 2019, 07:52:03 AM »

Well replacing the can capacitor did not resolve the issue. Next step is to look at the VOX tube...
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W9VOX
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Posts: 14




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« Reply #7 on: January 10, 2019, 05:35:49 AM »

The VOX tube (V19) was bad. Replaced it and the issue is resolved.

Thanks everyone for the advice.

73, Greg W9VOX
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WA4JQS
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Posts: 280




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« Reply #8 on: January 10, 2019, 09:26:24 PM »

Great news..  Grin
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WB8PFZ
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Posts: 310




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« Reply #9 on: January 12, 2019, 04:24:42 AM »

With a call that ends in VOX. How ironic.
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W9VOX
Member

Posts: 14




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« Reply #10 on: January 13, 2019, 08:36:57 AM »

Yes, very ironic...

As I was troubleshooting the issue I was thinking"wouldn't it be funny if it was the VOX tube"
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