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Robyn T-240D Executive

Shadetree Mechanic

Delaware Base Station 808
Oct 23, 2017
6,597
11,256
798
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The First State (Delaware)
Hey guys,
I just got a Robyn T-240D from eBay. It came with a D104 and it works well except for one strange thing. When I took the coax off of the Sonar and hooked it up to the Robyn, I didn't get any noise in the receive. I found that unscrewing the coax connector and pulling it out a little it would receive. My station and all the equipment is grounded to a ground rod by the antenna. If I unhook the antenna coax from the station and hook it directly to the Robyn then it works like normal. Any ideas why it doesn't like the station ground? Bad capacitor in the power supply on the Robyn maybe? Any help is appreciated.
Chris
IMG_20180906_135142810.jpg
 

Possibly a "spread" center pin connector (SO239) on the not so new (but looks great Robyn!)? Could be that your "main coax" PL259 center pin is a bit fatter from not getting swapped out very often? (A bit easier to swap the coax jumper-More cycles on that PL259?)

Looks Great Shadetree! I'm sure a station ground for the Robyn is imminent as well.

73's
David
 
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Holy cow, I just put the volt meter on it and the radio case to ground has 54vac on it! I thought I felt a little tingle when I laid my arm across it to play with the coax.... I am not sure that I want to tie it to station ground yet. I also noticed that the transformer in the radio hums when I plug it in and its turned off. The cord has no ground and the plug is not polarized. I unplugged it and turned the plug over and now there is 60vac to ground.... with the antenna by itself it works but I got a report that there is a hum in the broadcast audio. 60 HZ? I am looking through the schematic for some clues.
 

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  • robyn_t_240d_om_sch.pdf
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  • robyn_t_240d_om.pdf
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I believe you will find that with the power switch "Off" that the tube filaments are still powered up.(Turn lights off in the room to confirm) This is the "Stand-By" mode for this unit. Turning the power switch to the "On" position should make the unit ready to go with no tube warm up time as is the case with most other tube rigs. Hence, the "tingle" across the arm. It is drawing current even with the switch off.

Teaberry and Gemtronic's radios (Same Panasonic chassis) do not have this feature. They have a switchable "Stand-By" (full clockwise/detent of the Squelch control) and separate "Power" switch (full clockwise/detent of the Volume control).

Regardless, sounds like you have a leaking capacitor. As to isolating it, I would start with the power input bypass disc caps-C31 & C32. You can hook Pin 1 of your Octal socket to ground per the schematic.

Still a great looking classic! Good luck and BE SAFE!!

73's
David
 
Hey guys,
I just got a Robyn T-240D from eBay. It came with a D104 and it works well except for one strange thing. When I took the coax off of the Sonar and hooked it up to the Robyn, I didn't get any noise in the receive. I found that unscrewing the coax connector and pulling it out a little it would receive. My station and all the equipment is grounded to a ground rod by the antenna. If I unhook the antenna coax from the station and hook it directly to the Robyn then it works like normal. Any ideas why it doesn't like the station ground? Bad capacitor in the power supply on the Robyn maybe? Any help is appreciated.
Chris
View attachment 25112
ahh hah now i know who outbided me.haha just kidding but i eyed it couple times . Looked pristine in photos
 
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Teaberry and Gemtronic's radios (Same Panasonic chassis) do not have this feature. They have a switchable "Stand-By" (full clockwise/detent of the Squelch control) and separate "Power" switch (full clockwise/detent of the Volume control).

Correction to the above. That should have said "Full Counter-Clockwise" for the Stand-BY and Power-On. Not "Clockwise"
 
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Man! Glad you're still here to Tell us that ShadeTree...

Live Chassis can kill - glad to know your body resistance was enough for you to feel the tingle.

The chassis, yes, check the output network too - there are several areas in there that can take the final tubes plate voltage into the chassis - that's how my ex-XYL was able to get hers' from the original owner - he got tired of it and sold it off - we sent it to a local tech whom fixed several issues - including a network problem - as he put it, but I can see, how, where and why you got "poked" by it.
 
These Highlighted Chris...could give you the issue...Those tied to ground in PS and or tied to Audio T-windings...
All look to be easy find, common values and should be easy access under chassis. I am thinking Hum in RX and or TX the 350vdc caps...but TX also could be the ones hooked to audio xformer...
I would change these anyway...look at the diodes hooked to these for cracks or damage also.
Those are all 30++ yrs old.
GL
All the Best
Gary
 

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  • robyn_t_240d_om_sch (1)A.pdf
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I found the problem with hooking it to the station coax. I hate to say it but I had it on the station that was disconnected. I had the wrong coax hooked up and stupid me did not realize it until the next day. I took the bottom cover off and started checking the diodes with my DVM. There were some components in one section that looked like the leads might have been touching so I separated them a little.
IMG_20180911_083008348.jpg
 
Otherwise, how's the new arrival doing?

Receive?

Transmit?

That rear plug that kinda looks like a tube socket, any issues since the "live chassis" incident?
 
Otherwise, how's the new arrival doing?

Receive?

Transmit?

That rear plug that kinda looks like a tube socket, any issues since the "live chassis" incident?
I took apart the tube socket plug on the cord and the connections looked correct against the schematic. I measured the chassis voltage with it plugged into the antenna and it was 0v. After I plugged the correct coax into my station, I tried it connected to the station and again 0v. Maybe it is normal to have a floating voltage on the chassis if it is not grounded because there is no ground in the power cord and without coax connected? I will have to disconnect some of my other equipment and check it the same way.

I was able to use it for about a half hour with good reports until the transmit audio quit. It became intermittent then nothing. When I key up I get the carrier but no modulation. Maybe a bad capacitor? I hooked up a speaker to the PA and no audio there either. I cleaned the relay, PA switch and speaker switch with Deoxit. I pulled out the tubes one at a time and wiped them off and cleaned the pins with Deoxit. Still nothing. Maybe a bad audio tube? Like V5a? The tubes V5b and V6 I assume are ok because I get receive audio. Maybe I could swap V5a with V5b just to see if the problem moves? I am open to suggestions.
Chris
 

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  • robyn_t_240d_om_sch.pdf
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