FT277ZD/FT101ZD doesn't return to rx from tx intermittently - UK Vintage Radio Repair and Restoration Discussion Forum

Meekoblue · 19th Mar 2018, 1:42 pm

Hi. I've been playing with my new acquisition at the moment. Had some nice QSOs central Europe area but noticed after releasing the PTT button I hear a relay click but rx remains muted for a few seconds. I'm unfamiliar with the set so far but it's like part of the relay isn't releasing? I've checked vox is off and isn't activating. Ptt seems to activate relay correctly it's just not returning to rx.

Any thoughts? Will check the circuit diagram, feel it's relay related but any thoughts welcomed.

G6Tanuki · 19th Mar 2018, 2:38 pm

Not familiar with this particular radio but the usual way of muting the RX during transmit is to put a strong negative-bias on the AGC line: this may be adjustable so the receiver isn't totally muted in order to provide sidetone/listen-through.

Stick a meter on the AGC line and see what it does between receive and transmit? A resistor in the AGC time-constant circuitry could have failed/gone-high. Remember that the time-constants are also usually different between AM, SSB and CW.

[Another technique used for muting is to return the normally-earthed end of the RF/IF gain control to earth via a variable resistor: on receive this is shorted so things work normally; on transmit the variable-resistor is unshorted so acts as an 'extension' to the RF-gain control allowing greater gain reduiction. Again, if your radio uses this method meter the RF/IF-gain-control voltages and see if there's something that's not returning to normal fast enough.]

GW3OQK Andrew · 20th Mar 2018, 11:00 am

I had a FT101zd. It's a transistor receiver. The multi-contact tx/rx relay could be worth tapping to see if a contact is sticking, when going to receive.
73, Andrew

Meekoblue · 20th Mar 2018, 9:17 pm

Thanks for the tips I'll go investigate and report back.

HamishBoxer · 21st Mar 2018, 6:18 pm

I think the relays are indeed known trouble spots. Not sure how easy to find replacements though.

Meekoblue · 21st Mar 2018, 10:36 pm

Looks like it is the relay.... a sharp tap to the case returns to receive! As I say it's only intermittent. Might try a spray of contact cleaner.

HamishBoxer · 22nd Mar 2018, 9:57 am

Try the best, De-Oxit from the BVWS.

GW3OQK Andrew · 22nd Mar 2018, 6:10 pm

I have a switched low pass filter with six relays, ex a solid state rig. All relay contacts measure open circuit on a multimeter, but will happily pass 1 Amp when one volt is applied. Good luck with the deoxit. Meanwhile I imagine you saying "over" and giving the rig a good thump. I scrapped my FT101zd when it got too difficult to repair.
73, Andrew

Meekoblue · 24th Mar 2018, 9:50 pm

Exactly "OVER" *thump!*

Meekoblue · 27th Mar 2018, 2:35 pm

On a some what related issue: could someone explain "anti trip" to me please? I'm not sure I understand it's use.

Jon_G4MDC · 27th Mar 2018, 4:03 pm

Usually associated with the VOX circuit.
Stops RX audio being picked up as voice and activating the TX.

Meekoblue · 27th Mar 2018, 9:07 pm

Ah that makes sense. Thanks!

19th Mar 2018, 1:42 pm	#1
Meekoblue Retired Dormant Member Join Date: Mar 2018 Location: Manchester, UK. Posts: 14	FT277ZD/FT101ZD doesn't return to rx from tx intermittently Hi. I've been playing with my new acquisition at the moment. Had some nice QSOs central Europe area but noticed after releasing the PTT button I hear a relay click but rx remains muted for a few seconds. I'm unfamiliar with the set so far but it's like part of the relay isn't releasing? I've checked vox is off and isn't activating. Ptt seems to activate relay correctly it's just not returning to rx. Any thoughts? Will check the circuit diagram, feel it's relay related but any thoughts welcomed.

19th Mar 2018, 2:38 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently Not familiar with this particular radio but the usual way of muting the RX during transmit is to put a strong negative-bias on the AGC line: this may be adjustable so the receiver isn't totally muted in order to provide sidetone/listen-through. Stick a meter on the AGC line and see what it does between receive and transmit? A resistor in the AGC time-constant circuitry could have failed/gone-high. Remember that the time-constants are also usually different between AM, SSB and CW. [Another technique used for muting is to return the normally-earthed end of the RF/IF gain control to earth via a variable resistor: on receive this is shorted so things work normally; on transmit the variable-resistor is unshorted so acts as an 'extension' to the RF-gain control allowing greater gain reduiction. Again, if your radio uses this method meter the RF/IF-gain-control voltages and see if there's something that's not returning to normal fast enough.]

20th Mar 2018, 11:00 am	#3
GW3OQK Andrew Pentode Join Date: Apr 2011 Location: Swansea, Wales, UK. Posts: 144	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently I had a FT101zd. It's a transistor receiver. The multi-contact tx/rx relay could be worth tapping to see if a contact is sticking, when going to receive. 73, Andrew

20th Mar 2018, 9:17 pm	#4
Meekoblue Retired Dormant Member Join Date: Mar 2018 Location: Manchester, UK. Posts: 14	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently Thanks for the tips I'll go investigate and report back.

21st Mar 2018, 6:18 pm	#5
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently I think the relays are indeed known trouble spots. Not sure how easy to find replacements though. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

21st Mar 2018, 10:36 pm	#6
Meekoblue Retired Dormant Member Join Date: Mar 2018 Location: Manchester, UK. Posts: 14	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently Looks like it is the relay.... a sharp tap to the case returns to receive! As I say it's only intermittent. Might try a spray of contact cleaner.

22nd Mar 2018, 9:57 am	#7
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently Try the best, De-Oxit from the BVWS. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

22nd Mar 2018, 6:10 pm	#8
GW3OQK Andrew Pentode Join Date: Apr 2011 Location: Swansea, Wales, UK. Posts: 144	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently I have a switched low pass filter with six relays, ex a solid state rig. All relay contacts measure open circuit on a multimeter, but will happily pass 1 Amp when one volt is applied. Good luck with the deoxit. Meanwhile I imagine you saying "over" and giving the rig a good thump. I scrapped my FT101zd when it got too difficult to repair. 73, Andrew

24th Mar 2018, 9:50 pm	#9
Meekoblue Retired Dormant Member Join Date: Mar 2018 Location: Manchester, UK. Posts: 14	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently Exactly "OVER" thump!

27th Mar 2018, 2:35 pm	#10
Meekoblue Retired Dormant Member Join Date: Mar 2018 Location: Manchester, UK. Posts: 14	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently On a some what related issue: could someone explain "anti trip" to me please? I'm not sure I understand it's use.

27th Mar 2018, 4:03 pm	#11
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently Usually associated with the VOX circuit. Stops RX audio being picked up as voice and activating the TX.

27th Mar 2018, 9:07 pm	#12
Meekoblue Retired Dormant Member Join Date: Mar 2018 Location: Manchester, UK. Posts: 14	Re: FT277ZD/FT101ZD doesn't return to rx from tx intermittently Ah that makes sense. Thanks!